Showing papers in "Journal of Animal Science in 2008"

Use of phytogenic products as feed additives for swine and poultry.

Abstract: This article summarizes the experi- mental knowledge on efficacy, possible modes of action, and aspects of application of phytogenic products as feed additives for swine and poultry Phytogenic feed additives comprise a wide variety of herbs, spices, and products derived thereof, and are mainly essential oils The assumption that phytogenic compounds might im- provethe palatabilityof feedhas notyetbeen confirmed by choice-feeding studies Although numerous studies have demonstrated antioxidative and antimicrobial ef- ficacy in vitro, respective experimental in vivo evidence is still quite limited The same applies to the supposi- tion that phytogenic compounds may specifically en- hance activities of digestive enzymes and nutrient ab- sorption Nevertheless, a limited number of experimen- tal comparisons of phytogenic feed additives with antibiotics and organic acids have suggested similar

Board-invited review: Recent advances in biohydrogenation of unsaturated fatty acids within the rumen microbial ecosystem.

Abstract: Recent advances in chromatographic identification of CLA isomers, combined with interest in their possible properties in promoting human health (e.g., cancer prevention, decreased atherosclerosis, improved immune response) and animal performance (e.g., body composition, regulation of milk fat synthesis, milk production), has renewed interest in biohydrogenation and its regulation in the rumen. Conventional pathways of biohydrogenation traditionally ignored minor fatty acid intermediates, which led to the persistence of oversimplified pathways over the decades. Recent work is now being directed toward accounting for all possible trans-18:1 and CLA products formed, including the discovery of novel bioactive intermediates. Modern microbial genetics and molecular phylogenetic techniques for identifying and classifying microorganisms by their small-subunit rRNA gene sequences have advanced knowledge of the role and contribution of specific microbial species in the process of biohydrogenation. With new insights into the pathways of biohydrogenation now available, several attempts have been made at modeling the pathway to predict ruminal flows of unsaturated fatty acids and biohydrogenation intermediates across a range of ruminal conditions. After a brief historical account of major past accomplishments documenting biohydrogenation, this review summarizes recent advances in 4 major areas of biohydrogenation: the microorganisms involved, identification of intermediates, the biochemistry of key enzymes, and the development and testing of mathematical models to predict biohydrogenation outcomes.

BOARD-INVITED REVIEW: Use of distillers by-products in the beef cattle feeding industry.

Abstract: The ethanol industry is expanding rap- idly. This expansion in production of renewable energy also increases production of by-products. These by- products, primarily distillers grains plus solubles (DGS), are utilized very efficiently by ruminants. When the starch in corn is fermented to produce ethanol, the remaining nutrients (protein, fat, fiber) are concen- trated about 3-fold. Whereas DGS is an excellent pro- tein source for ruminants, the large supply and the price relative to corn make DGS an attractive energy source as well. This is especially important with re- duced availability and higher price of corn because of demand by the ethanol industry. A meta-analysis of 9 experiments, where various levels of wet DGS were fed to feedlot cattle, shows that wet DGS produced higher ADG and G:F compared with cattle fed corn-based diets

Mammary tissue damage during bovine mastitis: causes and control.

Abstract: Mastitis, an inflammatory reaction of the mammary gland that is usually caused by a microbial infection, is recognized as the most costly disease in dairy cattle. Decreased milk production accounts for approximately 70% of the total cost of mastitis. Mammary tissue damage reduces the number and activity of epithelial cells and consequently contributes to decreased milk production. Mammary tissue damage has been shown to be induced by either apoptosis or necrosis. These 2 distinct types of cell death can be distinguished by morphological, biochemical, and molecular changes in dying cells. Both bacterial factors and host immune reactions contribute to epithelial tissue damage. During infection of the mammary glands, the tissue damage can initially be caused by bacteria and their products. Certain bacteria produce toxins that destroy cell membranes and damage milk-producing tissue, whereas other bacteria are able to invade and multiply within the bovine mammary epithelial cells before causing cell death. In addition, mastitis is characterized by an influx of somatic cells, primarily polymorphonuclear neutrophils, into the mammary gland. With more immune cells migrating into the mammary gland and the breakdown of the blood-milk barrier, damage to the mammary epithelium worsens. It is well known that breakdown of the extracellular matrix can lead to death of the epithelial cells. Meanwhile, polymorphonuclear neutrophils can harm the mammary tissue by releasing reactive oxygen intermediates and proteolytic enzymes. In vitro and in vivo studies suggest that the use of antioxidants and other protective compounds in mastitis control programs is worth investigating, because they may aid in alleviating damage to secretory cells and thus reduce subsequent milk loss.

Food animal-associated Salmonella challenges: pathogenicity and antimicrobial resistance.

Abstract: Salmonellosis is a worldwide health problem; Salmonella infections are the second leading cause of bacterial foodborne illness in the United States. Approximately 95% of cases of human salmonellosis are associated with the consumption of contaminated products such as meat, poultry, eggs, milk, seafood, and fresh produce. Salmonella can cause a number of different disease syndromes including gastroenteritis, bacteremia, and typhoid fever, with the most common being gastroenteritis, which is often characterized by abdominal pain, nausea, vomiting, diarrhea, and headache. Typically the disease is self-limiting; however, with more severe manifestations such as bacteremia, antimicrobial therapy is often administered to treat the infection. Currently, there are over 2,500 identified serotypes of Salmonella. A smaller number of these serotypes are significantly associated with animal and human disease including Typhimurium, Enteritidis, Newport, Heidelberg, and Montevideo. Increasingly, isolates from these serotypes are being detected that demonstrate resistance to multiple antimicrobial agents, including third-generation cephalosporins, which are recommended for the treatment of severe infections. Many of the genes that encode resistance are located on transmissible elements such as plasmids that allow for potential transfer of resistance among strains. Plasmids are also known to harbor virulence factors that contribute to Salmonella pathogenicity. Several serotypes of medical importance, including Typhimurium, Enteritidis, Newport, Dublin, and Choleraesuis, are known to harbor virulence plasmids containing genes that code for fimbriae, serum resistance, and other factors. Additionally, many Salmonella contain pathogenicity islands scattered throughout their genomes that encode factors essential for bacterial adhesion, invasion, and infection. Salmonella have evolved several virulence and antimicrobial resistance mechanisms that allow for continued challenges to our public health infrastructure.

A new heat load index for feedlot cattle

Abstract: The ability to predict the effects of extreme climatic variables on livestock is important in terms of welfare and performance. An index combining temperature and humidity (THI) has been used for more than 4 decades to assess heat stress in cattle. However, the THI does not include important climatic variables such as solar load and wind speed (WS, m/s). Likewise, it does not include management factors (the effect of shade) or animal factors (genotype differences). Over 8 summers, a total of 11,669 Bos taurus steers, 2,344 B. taurus crossbred steers, 2,142 B. taurus x Bos indicus steers, and 1,595 B. indicus steers were used to develop and test a heat load index (HLI) for feedlot cattle. A new HLI incorporating black globe (BG) temperature ( degrees C), relative humidity (RH, decimal form), and WS was initially developed by using the panting score (PS) of 2,490 Angus steers. The HLI consists of 2 parts based on a BG temperature threshold of 25 degrees C: HLI(BG>25) = 8.62 + (0.38 x RH) + (1.55 x BG) - (0.5 x WS) + e((2.4-WS)), and HLI(BG<25) = 10.66 + (0.28 x RH) + (1.3 x BG) - WS, where e is the base of the natural logarithm. A threshold HLI above which cattle of different genotypes gain body heat was developed for 7 genotypes. The threshold for unshaded black B. taurus steers was 86, and for unshaded B. indicus (100%) the threshold was 96. Threshold adjustments were developed for factors such as coat color, health status, access to shade, drinking water temperature, and manure management. Upward and downward adjustments are possible; upward adjustments occur when cattle have access to shade (+3 to +7) and downward adjustments occur when cattle are showing clinical signs of disease (-5). A related measure, the accumulated heat load (AHL) model, also was developed after the development of the HLI. The AHL is a measure of the animal's heat load balance and is determined by the duration of exposure above the threshold HLI. The THI and THI-hours (hours above a THI threshold) were compared with the HLI and AHL. The relationships between tympanic temperature and the average HLI and THI for the previous 24 h were R(2) = 0.67, P < 0.001, and R(2) = 0.26, P < 0.001, respectively. The R(2) for the relationships between HLI or AHL and PS were positive (0.93 and 0.92 for HLI and AHL, respectively, P < 0.001). The R(2) for the relationship between THI and PS was 0.61 (P < 0.001), and for THI-hours was 0.37 (P < 0.001). The HLI and the AHL were successful in predicting PS responses of different cattle genotypes during periods of high heat load.

Methane output and diet digestibility in response to feeding dairy cows crude linseed, extruded linseed, or linseed oil.

Abstract: This experiment studied the effect of 3 forms of presentation of linseed fatty acids (FA) on methane output using the sulfur hexafluoride tracer technique, total tract digestibility, and performance of dairy cows. Eight multiparous lactating Holstein cows (initial milk yield 23.4 +/- 2.2 kg/d) were assigned to 4 dietary treatments in a replicated 4 x 4 Latin square design: a control diet (C) consisting of corn silage (59%), grass hay (6%), and concentrate (35%) and the same diet with crude linseed (CLS), extruded linseed (ELS), or linseed oil (LSO) at the same FA level (5.7% of dietary DM). Each experimental period lasted 4 wk. All the forms of linseed FA significantly decreased daily CH(4) emissions (P 0.05) but was decreased with ELS and LSO (-3.1 and -5.1 kg/d, respectively; P < 0.001). Milk yield and milk fat content were similar for LSO and ELS but less than for C and CLS (19.9 vs. 22.3 kg/d and 33.8 vs. 43.2 g/kg, on average, respectively; P < 0.01 and P < 0.001). Linseed FA offer a promising dietary means to depress ruminal methanogenesis. The form of presentation of linseed FA greatly influences methane output from dairy cows. The negative effects of linseed on milk production will need to be overcome if it is to be considered as a methane mitigation agent. Optimal conditions for the utilization of linseed FA in ruminant diets need to be determined before recommending its use for the dairy industry.

Nitrogen recycling through the gut and the nitrogen economy of ruminants: an asynchronous symbiosis

Abstract: The extensive development of the ruminant forestomach sets apart their N economy from that of nonruminants in a number of respects. Extensive pregastric fermentation alters the profile of protein reaching the small intestine, largely through the transformation of nitrogenous compounds into microbial protein. This process is fueled primarily by carbohydrate fermentation and includes extensive recycling of N between the body and gut lumen pools. Nitrogen recycling occurs via blood and gut lumen exchanges of urea and NH(3), as well as endogenous gut and secretory N entry into the gut lumen, and the subsequent digestion and absorption of microbial and endogenous protein. Factors controlling urea transfer to the gut from blood, including the contributions of urea transporters, remain equivocal. Ammonia produced by microbial degradation of urea and dietary and endogenous AA is utilized by microbial fermentation or absorbed and primarily converted to urea. Therefore, microbial growth and carbohydrate fermentation affect the extent of NH(3) absorption and urea N recycling and excretion. The extensive recycling of N to the rumen represents an evolutionary advantage of the ruminant in terms of absorbable protein supply during periods of dietary protein deficiency, or asynchronous carbohydrate and protein supply, but incurs a cost of greater N intakes, especially in terms of excess N excretion. Efforts to improve the efficiency of N utilization in ruminants by synchronizing fermentable energy and N availability have generally met with limited success with regards to production responses. In contrast, imposing asynchrony through oscillating dietary protein concentration, or infrequent supplementation, surprisingly has not negatively affected production responses unless the frequency of supplementation is less than once every 3 d. In some cases, oscillation of dietary protein concentration has improved N retention compared with animals fed an equal amount of dietary protein on a daily basis. This may reflect benefits of Orn cycle adaptations and sustained recycling of urea to the gut. The microbial symbiosis of the ruminant is inherently adaptable to asynchronous N and energy supply. Recycling of urea to the gut buffers the effect of irregular dietary N supply such that intuitive benefits of rumen synchrony in terms of the efficiency of N utilization are typically not observed in practice.

Salmonella challenges: prevalence in swine and poultry and potential pathogenicity of such isolates.

Abstract: Salmonellosis is the second leading cause of bacterial foodborne illness in the United States, and the great majority of these infections are associated with the consumption of products such as meat, poultry, eggs, milk, seafood, and fresh produce contaminated with Salmonella. The per capita consumption of meat and poultry in United States has increased significantly over the past century. This increase is especially evident with poultry products, where there has been a nearly 6-fold increase in chicken consumption and 17-fold increase in turkey consumption since 1909. The per capita consumption of pork has also increased over this time from 18.7 to 21.7 kg/yr. With this increase in meat and poultry consumption, the dynamics of animal production and consumer exposure have changed leading to new challenges in limiting salmonellosis. To meet the demands of consumers, more intensive agricultural practices have been adopted, which has likely changed the population characteristics of Salmonella present among poultry flocks and swine populations. In Salmonella isolated from swine in the United States, S. Typhimurium has replaced S. Choleraesuis as the predominant serovar in recent years. Among isolates from turkeys collected in 2004, serovars S. Senftenberg and S. Hadar were most common overall; however, S. Heidelberg was most common from clinical diagnostic sources, potentially indicating increased virulence. Salmonella Heidelberg was also the most commonly detected serovar among chicken isolates from clinically ill birds and Salmonella surveillance samples. Overall among the 10 serovars most commonly associated with human infections, 6 are also found in the top serovars of swine and poultry. These include S. Typhimurium, S. Enteritidis, S. Heidelberg, S. Montevideo, S. Saintpaul, and S. I 4,[5],12:i:-.

Board-invited review: Peptide absorption and utilization: Implications for animal nutrition and health.

Abstract: Over the last 50 yr, the study of intesti- nal peptide transport has rapidly evolved into a field with exciting nutritional and biomedical applications. In this review, we describe from a historical and cur- rent perspective intestinal peptide transport, the im- portance of peptides to whole-body nutrition, and the cloning and characterization of the intestinal peptide transporter, PepT1. We focus on the nutritional signifi- cance of peptide transport and relate these findings to livestock and poultry. Amino acids are transported into the enterocyte as free AA by a variety of AA transport- ers that vary in substrate specificity or as di- and trip- eptides by the peptide transporter, PepT1. Expression of PepT1 is largely restricted to the small intestine in most species; however, in ruminants, peptide transport and activity is observed in the rumen and omasum. The extent to which peptides are absorbed and utilized is still unclear. In ruminants, peptides make a contri- bution to the portal-drained visceral flux of total AA and are detected in circulating plasma. Peptides can be utilized by the mammary gland for milk protein synthesis and by a variety of other tissues. We discuss the factors known to regulate expression of PepT1 in- cluding development, diet, hormones, diurnal rhythm, and disease. Expression of PepT1 is detected during embryological stages in both birds and mammals and increases with age, a strategic event that allows for the immediate uptake of nutrients after hatch or birth. Both increasing levels of protein in the diet and dietary protein deficiencies are found to upregulate the peptide transporter. We also include in this review a discus- sion of the use of dietary peptides and potential alter- nate routes of nutrient delivery to the cell. Our goal is to impart to the reader the nutritional implications of peptide transport and dietary peptides and share dis- coveries that shed light on various biological processes, including rapid establishment of intestinal function in early neonates and maintenance of intestinal function during fasting, starvation, and disease states.

Genomic selection using different marker types and densities

Abstract: With the availability of high-density marker maps and cost-effective genotyping, genomic selection methods may provide faster genetic gain than can be achieved by current selection methods based on phenotypes and the pedigree. Here we investigate some of the factors driving the accuracy of genomic selection, namely marker density and marker type (i.e., microsatellite and SNP markers), and the use of marker haplotypes versus marker genotypes alone. Different densities were tested with marker densities equivalent to 2, 1, 0.5, and 0.25Ne markers/morgan us- ing microsatellites and 8, 4, 2, and 1Ne markers/mor- gan using SNP, where 1Ne markers/morgan means 100 markers per morgan, if effective size (Ne) is 100. Marker characteristics and linkage disequilibria were obtained by simulating a population over 1,000 genera- tions to achieve a mutation drift balance. The marker designs were evaluated for their accuracy of predicting breeding values from either estimating marker effects or estimating effects of haplotypes based upon combin- ing 2 markers. Using microsatellites as direct marker effects, the accuracy of selection increased from 0.63 to 0.83 as the density increased from 0.25Ne/morgan to 2Ne/morgan. Using SNP markers as direct marker effects, the accuracy of selection increased from 0.69 to 0.86 as the density increased from 1Ne/morgan to 8Ne/morgan. The SNP markers required a 2 to 3 times greater density compared with using microsatellites to achieve a similar accuracy. The biases that genomic selection EBV often show are due to the prediction of marker effects instead of QTL effects, and hence, ge- nomic selection EBV may need rescaling for practical use. Using haplotypes resulted in similar or reduced accuracies compared with using direct marker effects. In practical situations, this means that it is advanta- geous to use direct marker effects, because this avoids the estimation of marker phases with the associated errors. In general, the results showed that the accu- racy remained responsive with small bias to increas- ing marker density at least up to 8Ne SNP/morgan, where the effective population size was 100 and with the genomic model assumed. For a 30-morgan genome and Ne = 100, this implies that about ~24,000 SNP are needed.

Myofibrillar protein turnover: The proteasome and the calpains

Abstract: Metabolic turnover of myofibrillar proteins in skeletal muscle requires that, before being degraded to AA, myofibrillar proteins be removed from the myofibril without disrupting the ability of the myofibril to contract and develop tension. Skeletal muscle contains 4 proteolytic systems in amounts such that they could be involved in metabolic protein turnover: 1) the lysosomal system, 2) the caspase system, 3) the calpain system, and 4) the proteasome. The catheptic proteases in lysosomes are not active at the neutral pH of the cell cytoplasm, so myofibrillar proteins would have to be degraded inside lysosomes if the lysosomal system were involved. Lysosomes could not engulf a myofibril without destroying it, so the lysosomal system is not involved to a significant extent in metabolic turnover of myofibrillar proteins. The caspases are not activated until initiation of apoptosis, and, therefore, it is unlikely that the caspases are involved to a significant extent in myofibrillar protein turnover. The calpains do not degrade proteins to AA or even to small peptides and do not catalyze bulk degradation of the sarcoplasmic proteins, so they cannot be the only proteolytic system involved in myofibrillar protein turnover. Research during the past 20 yr has shown that the proteasome is responsible for 80 to 90% of total intracellular protein turnover, but the proteasome degrades peptide chains only after they have been unfolded, so that they can enter the catalytic chamber of the proteasome. Thus, although the proteasome can degrade sarcoplasmic proteins, it cannot degrade myofibrillar proteins until they have been removed from the myofibril. It remains unclear how this removal is done. The calpains degrade those proteins that are involved in keeping the myofibrillar proteins assembled in myofibrils, and it was proposed over 30 yr ago that the calpains initiated myofibrillar protein turnover by disassembling the outer layer of proteins from the myofibril and releasing them as myofilaments. Such myofilaments have been found in skeletal muscle. Other studies have indicated that individual myofibrillar proteins can exchange with their counterparts in the cytoplasm; it is unclear whether this can be done to an extent that is consistent with the rate of myofibrillar protein turnover in living muscle. It seems that both the calpains and the proteasome are responsible for myofibrillar protein turnover, but the mechanism is still unknown.

A decade of developments in the area of fat supplementation research with beef cattle and sheep.

Abstract: Supplementing ruminant animal diets with fat has been investigated as a means to influence a variety of physiological processes or to alter fatty acid composition of food products derived from ruminant animals. Several digestion experiments have been conducted with beef cattle and sheep to elucidate the effects of supplemental fat on utilization of other dietary components. Negative associative effects are not likely to be observed in ruminants consuming forage-based diets with supplemental fat at < or = 2% of DMI. Inclusion of supplemental fat at < or = 3% of DM is recommended to obtain the most benefit from the energy contained within the fat and other dietary components in high-forage diets. For ruminants fed high-concentrate diets, supplementing fat at 6% of diet DM is expected to have minimal impacts on utilization of other dietary components. Although there is greater potential to supply the ruminant animal with unsaturated fatty acids from dietary origin if fat is added to high-concentrate diets, incomplete ruminal biohydrogenation of C18 unsaturated fatty acids results in an increase in duodenal flow of 18:1 trans fatty acids regardless of basal diet consumed by the animal. The biohydrogenation intermediate 18:1 trans-11 (trans-vaccenic acid) is the likely precursor to cis-9, trans-11 CLA because the magnitude of increase in CLA content in tissues or milk of ruminants fed fat is much greater than the increase in CLA presented to the small intestine of ruminants fed fat supplements. Duodenal flow of trans-vaccenic acid is also substantially greater than CLA. Increasing unsaturated fatty acids status of ruminants imparts physiological responses that are separate than the energy value of supplemental fat. Manipulating maternal diet to improve unsaturated fatty acid status of the neonate has practical benefits for animals experiencing stress due to exposure to cold environments or conditions which mount an immune response. Supplementing fat to provide an additional 16 to 18 g/d of 18:2n-6 to the small intestine of beef cows for the first 60 to 90 d of lactation will have negative impacts on reproduction and may impair immune function of the suckling calf. Consequences of the suckling animal increasing its intake of unsaturated fatty acids because of manipulation of maternal diet warrants further investigation.

Selection response and genetic parameters for residual feed intake in Yorkshire swine.

Abstract: Residual feed intake (RFI) is a measure of feed efficiency defined as the difference between the observed feed intake and that predicted from the average requirements for growth and maintenance. The objective of this study was to evaluate the response in a selection experiment consisting of a line selected for low RFI and a random control line and to estimate the genetic parameters for RFI and related production and carcass traits. Beginning with random allocation of purebred Yorkshire littermates, in each generation, electronically measured ADFI, ADG, and ultrasound backfat (BF) were evaluated during a approximately 40- to approximately 115-kg of BW test period on approximately 90 boars from first parity and approximately 90 gilts from second parity sows of the low RFI line. After evaluation of first parity boars, approximately 12 boars and approximately 70 gilts from the low RFI line were selected to produce approximately 50 litters for the next generation. Approximately 30 control line litters were produced by random selection and mating. Selection was on EBV for RFI from an animal model analysis of ADFI, with on-test group and sex (fixed), pen within group and litter (random), and covariates for interactions of on- and off-test BW, on-test age, ADG, and BF with generations. The RFI explained 34% of phenotypic variation in ADFI. After 4 generations of selection, estimates of heritability for RFI, ADFI, ADG, feed efficiency (FE, which is the reciprocal of the feed conversion ratio and equals ADG/ ADFI), and ultrasound-predicted BF, LM area (LMA), and intramuscular fat (IMF) were 0.29, 0.51, 0.42, 0.17, 0.68, 0.57, and 0.28, respectively; predicted responses based on average EBV in the low RFI line were -114, -202, and -39 g/d for RFI (= 0.9 phenotypic SD), ADFI (0.9 SD), and ADG (0.4 SD), respectively, and 1.56% for FE (0.5 SD), -0.37 mm for BF (0.1 SD), 0.35 cm(2) for LMA (0.1 SD), and -0.10% for IMF (0.3 SD). Direct phenotypic comparison of the low RFI and control lines based on 92 low RFI and 76 control gilts from the second parity of generation 4 showed that selection had significantly decreased RFI by 96 g/d (P = 0.002) and ADFI by 165 g/d (P < 0.0001). The low RFI line also had 33 g/d lower ADG (P = 0.022), 1.36% greater FE (P = 0.09), and 1.99 mm less BF (P = 0.013). There was not a significant difference in LMA and other carcass traits, including subjective marbling score, despite a large observed difference in ultrasound-predicted IMF (-1.05% with P < 0.0001). In conclusion, RFI is a heritable trait, and selection for low RFI has significantly decreased the feed required for a given rate of growth and backfat.

Effects of conventional and grass feeding systems on the nutrient composition of beef

Abstract: The objectives of this study were to determine the nutrient composition of grass-fed beef in the United States for inclusion in the USDA National Nutrient Database for Standard Reference, and to compare the fatty acid composition of grass-fed and conventionally fed (control) beef. Ground beef (GB) and strip steaks (SS) were collected on 3 separate occasions from 15 grass-fed beef producers that represented 13 different states, whereas control beef samples were collected from 3 regions (Ohio, South Dakota, and Texas) of the United States on 3 separate occasions. Concentrations of minerals, choline, vitamin B 12 , and thiamine were determined for grass-fed beef samples. Grass-fed GB samples had less Mg, P, and K (P < 0.05), and more Na, Zn, and vitamin B 12 (P < 0.05) than SS samples. Fat color, marbling, and pH were assessed for grass-fed and control SS. Subjective evaluation of the SS indicated that grass-fed beef had fat that was more yellow in color than control beef. Percentages of total fat, total cholesterol, and fatty acids along with trans fatty acids and CLA were determined for grass-fed and control SS and GB. Grass-fed SS had less total fat than control SS (P = 0.001), but both grass-fed and control SS were considered lean, because their total fat content was 4.3% or less. For both GB and SS, grass-fed beef had significantly less (P = 0.001 and P = 0.023, respectively) content of MUFA and a greater content of SFA, n-3 fatty acids, CLA, and trans-vaccenic acid than did the control samples. Concentrations of PUFA, trans fatty acids, n-6 fatty acids, and cholesterol did not differ between grass-fed and control ground beef. Trans-vaccenic acid (trans-11 18:1) made up the greatest concentration of the total trans fats in grass-fed beef, whereas CLA accounted for approximately 15% of the total trans fats. Although the fatty acid composition of grass-fed and conventionally fed beef was different, conclusions on the possible effects of these differences on human health cannot be made without further investigation.

Polymorphisms and haplotypes in the bovine neuropeptide Y, growth hormone receptor, ghrelin, insulin-like growth factor 2, and uncoupling proteins 2 and 3 genes and their associations with measures of growth, performance, feed efficiency, and carcass merit in beef cattle.

Abstract: Genes that regulate metabolism and energy partitioning have the potential to influence economically important traits in farm animals, as do polymorphisms within these genes. In the current study, SNP in the bovine neuropeptide Y (NPY), growth hormone receptor (GHR), ghrelin (GHRL), uncoupling proteins 2 and 3 (UCP2 and UCP3), IGF2, corticotrophin-releasing hormone (CRH), cocaine and amphetamine regulated transcript (CART), melanocortin-4 receptor (MC4R), proopiomelanocortin (POMC), and GH genes were evaluated for associations with growth, feed efficiency, and carcass merit in beef steers. In total, 24 SNP were evaluated for associations with these traits and haplotypes were constructed within each gene when 2 or more SNP showed significant associations. An A/G SNP located in intron 4 of the GHR gene had the largest effects on BW of the animals (dominance effect P < 0.01) and feed efficiency (allele substitution effect P < 0.05). Another A/G SNP located in the promoter region of GHR had similar effects but the haplotypes of these 2 SNP reduced the effects of the SNP located in intron 4. Three SNP in the NPY gene showed associations to marbling (P < 0.001) as well as with ADG, BW, and feed conversion ratio (FCR; P < 0.05). The combination of these 3 SNP into haplotypes generally improved the association or had a similar scale of association as each single SNP. Only 1 SNP in UCP3, an A/G SNP in intron 3, was associated with ADG (P = 0.025), partial efficiency of growth, and FCR (P < 0.01). Three SNP in UCP2 gene were in almost complete linkage disequilibrium and showed associations with lean meat yield, yield grade, DMI, and BW (P < 0.05). Haplotypes between the SNP in UCP3 and UCP2 generally reduced the associations seen individually in each SNP. An A/G SNP in the GHRL gene tended to show effects on residual feed intake, FCR, and partial efficiency of growth (P < 0.10). The IGF2 SNP most strongly affected LM area (P < 0.01), back fat, ADG, and FCR (P < 0.05). The SNP in the CART, MC4R, POMC, GH, and CRH genes did not show associations at P < 0.05 with any of the traits. Although most of the SNP that showed associations do not cause amino acid changes, these SNP could be linked to other yet to be detected causative mutations or nearby QTL. It will be very important to verify these results in other cattle populations.

Gastrointestinal microbial ecology and the safety of our food supply as related to Salmonella.

Abstract: Salmonella causes an estimated 1.3 million human foodborne illnesses and more than 500 deaths each year in the United States, representing an annual estimated cost to the economy of approximately $2.4 billion. Salmonella enterica comprises more than 2,500 serotypes. With this genetic and environmental diversity, serotypes are adapted to live in a variety of hosts, which may or may not manifest with clinical illness. Thus, Salmonella presents a multifaceted threat to food production and safety. Salmonella have been isolated from all food animals and can cause mor- bidityandmortalityinswine,cattle,sheep,andpoultry. The link between human salmonellosis and host ani- mals is most clear in poultry. During the early part of the 20th century, a successful campaign was waged to eliminate fowl typhoid caused by Salmonella Galli- narum/Pullorum. Microbial ecology is much like ma- croecology; environmental niches are filled by adapted and specialized species. Elimination of S. Gallinarum cleared a niche in the on-farm and intestinal microbial ecologythatwasquicklyexploitedbySalmonellaEnter-

Effects of chito-oligosaccharide supplementation on the growth performance, nutrient digestibility, intestinal morphology, and fecal shedding of Escherichia coli and Lactobacillus in weaning pigs

Abstract: A total of 50 weaning pigs (16 d of age; 4.72 ± 0.23 kg of BW) were selected to investigate the effect of dietary chito-oligosaccharide (COS) supple- mentation on growth performance, fecal shedding of Escherichia coli and Lactobacillus, apparent digestibil- ity, and small intestinal morphology. Pigs housed in individual metabolic cages were assigned randomly to 5 treatments (n = 10), including 1 basal diet (control), 3 diets with COS supplementation (100, 200, and 400 mg/kg), and 1 diet with chlortetracycline (CTC) supple- mentation (80 mg/kg). Fresh fecal samples were col- lected to evaluate shedding of E. coli and Lactobacillus on d 0, 7, 14, and 21 postweaning. Fresh fecal samples collected from each cage from d 19 to 21 were stored frozen for determination of apparent total tract digest- ibility. On d 21, all pigs were killed to collect the middle sections of the duodenum, jejunum, and ileum for de- termination of mucosa morphology. Supplementation of COS at 100 and 200 mg/kg and supplementation of CTC improved (P < 0.05) overall ADG, ADFI, and G:F in comparison with the control. Supplementation of COS at 200 mg/kg as well as supplementation of CTC increased (P < 0.05) apparent total tract digestibility of DM, GE, CP, crude fat, Ca, and P, whereas COS at 100 mg/kg increased (P < 0.05) the digestibility of DM, Ca, and P in comparison with the control diet. Pigs re- ceiving diets supplemented with COS or CTC had a de- creased (P < 0.05) incidence of diarrhea and decreased diarrhea scores compared with control pigs. Fecal sam- ples from pigs receiving diets supplemented with COS had greater (P < 0.05) Lactobacillus counts than those from control pigs and pigs receiving diets supplement- ed with CTC on d 14 and 21. However, supplementa- tion of COS at 200 mg/kg and supplementation of CTC decreased (P < 0.05) E. coli counts in the feces on d 21 compared with the control diet. Dietary supplementa- tion of COS at 200 mg/kg and of CTC increased (P < 0.05) the villus height and villus:crypt ratio at the ile- um and jejunum, and COS at 100 mg/kg also increased (P < 0.05) the villus height in the ileum compared with the control diet. The current results indicated that di- etary supplementation of COS at 100 and 200 mg/kg enhanced growth performance by increasing apparent digestibility, decreasing the incidence of diarrhea, and improving small intestinal morphology.

Effects of commingling beef calves from different sources and weaning protocols during a forty-two-day receiving period on performance and bovine respiratory disease

Abstract: The study objective was to determine health and performance of ranch calves from different preconditioning strategies during a 42-d receiving period when commingled with calves of unknown health histories from multiple sources. Steer calves from a single source ranch (RANCH) were weaned and immediately shipped to a feedlot (WEAN, initial BW = 247 +/- 29 kg); weaned on the ranch for 45 d before shipping, but did not receive any vaccinations (WEAN45, initial BW = 231 +/- 26 kg); or weaned, vaccinated with modified live viral vaccine, and held on the ranch for 45 d before shipping (WEANVAC45, initial BW = 274 +/- 21 kg). Multiple-source steers were purchased through auction markets (MARKET, initial BW = 238 +/- 13 kg), and upon receiving, a portion of ranch-origin steers from each weaning group was commingled with a portion of MARKET cattle (COMM). The experimental design was completely randomized with a 2 x 3 +1 factorial arrangement of treatments. Factors were RANCH vs. COMM and weaning management (WEAN vs. WEAN45 vs. WEANVAC45) as the factors; MARKET cattle served as the control. Calves of WEAN, WEAN45, and MARKET were vaccinated on arrival at the feedlot. Ranch-origin calves tended (P = 0.06) to have greater ADG than COMM or MARKET calves, although ADG was not affected (P = 0.46) by weaning management. Across the 42-d receiving period, DMI was not affected (P = 0.85) by cattle origin. However, MARKET, WEAN45, and WEANVAC45 calves consumed more (P or = 0.11) by treatment. Ranch-origin calves were less (P < 0.001) likely to be treated for bovine respiratory disease than MARKET calves; COMM calves were intermediate. Calves that were retained on the ranch after weaning (WEAN45 and WEANVAC45) were also less likely to be treated (P = 0.001) than MARKET or WEAN calves. As expected, differences in morbidity related to differences in health costs. Calves of WEAN45 and WEANVAC45 had less (P < 0.001) health costs than MARKET and WEAN calves. On arrival, serum haptoglobin concentrations were greater (P < 0.001) in MARKET and WEAN compared with WEAN45 and WEANVAC45 calves. Calves from a single source that are retained on the ranch for 45 d after weaning exhibit less morbidity and less health costs during the receiving period at the feedyard than when cattle are commingled or trucked to the feedyard immediately after weaning.

Transportation of young beef bulls alters circulating physiological parameters that may be effective biomarkers of stress.

Abstract: Transportation causes stress in cattle that may alter numerous physiological variables with a negative impact on production and health. The objectives of the current study were to investigate the physiological effects of truck transportation and to characterize a pattern of phenotypes in the circulation that may aid in the early identification of stress-susceptible animals that often succumb to severe respiratory disease. Thirty-six young beef bulls (Aberdeen Angus, n = 12; Friesian, n = 12; and Belgian Blue x Friesian, n = 12) were subjected to a 9-h truck transportation by road. Blood (10 mL) was collected at -24, 0, 4.5, 9.75, 14.25, 24, and 48 h relative to the initiation of transportation (0 h). Plasma was collected for the assay of various metabolic, inflammatory, and steroid variables, and total leukocyte counts were determined in whole blood at each time point. Body weight and rectal temperature were recorded at -24, 9.75, and 48 h. Transportation decreased measures of protein metabolism in the plasma, including albumin (P = 0.002), globulin (P < 0.001), urea (P = 0.006), and total protein (P < 0.001), and increased creatine kinase (P < 0.001). The energy substrate beta-hydroxybutyrate was not changed (P = 0.27). Acute phase proteins haptoglobin and fibrinogen were both decreased (P < 0.001), whereas total leukocyte counts were elevated (P = 0.002). Circulating steroid concentrations were altered, because a classical acute increase in plasma cortisol was observed with the onset of transit (P < 0.001), in association with a decrease in dehydroepiandrosterone (P = 0.07), resulting in a profound increase in cortisol:dehydroepiandrosterone ratio (P < 0.001). Plasma testosterone was decreased, whereas plasma progesterone was increased (P < 0.001) in association with the increase in cortisol (P < 0.001). There was also an effect of breed for all variables except plasma urea, creatine kinase, and testosterone, perhaps indicating that a genetic component contributed to the physiological response to transportation stress, although without any clear trend. Taken together, this profile of physiological variables in the circulation of transportation-stressed bulls may aid in the future detection of disease-susceptible cattle after transportation. Further research to validate these potential biomarkers is necessary.

Changes in rumen microbial fermentation are due to a combined effect of type of diet and pH.

Abstract: Low ruminal pH may occur when feeding high-concentrate diets. However, because the reduction in pH occurs at the same time as the amount of concentrate fed increases, the changes observed in rumen fermentation may be attributed to pH or the type of substrate being fermented. Our objective was to determine the contribution of pH and type of substrate being fermented to the changes observed in rumen fermentation after supplying a high-concentrate diet. Eight dual-flow, continuous culture fermenters (1,400 mL) were used in 4 periods to study the effect of pH and type of diet being fermented on rumen microbial fermentation. Temperature (39 degrees C), solid (5%/h), and liquid (10%/h) dilution rates, and feeding schedule were maintained constant. Treatments were the type of diet (FOR = 60% ryegrass and alfalfa hays and 40% concentrate; CON = 10% straw and 90% concentrate) and pH (4.9, 5.2, 5.5, 5.8, 6.1, 6.4, 6.7, and 7.0). Diets were formulated to have similar CP and ruminally undegradable protein levels. Data were analyzed as a mixed-effects model considering the linear, quadratic, and cubic effects of pH, the effects of diet, and their interactions. Semipartial correlations of each independent variable were calculated to estimate the contribution of each factor to the overall relationship. True digestion of OM and NDF were affected by pH, but not by type of diet. Total VFA were reduced by pH and were greater in CON than in FOR. Acetate and butyrate concentrations were reduced by pH but were not affected by diet. Propionate concentration increased as the pH decreased and was greater in CON than in FOR. Ammonia-N concentration decreased with decreasing pH and was lower in CON than in FOR. Microbial N flow was affected by pH, diet, and their interaction. Dietary N flow increased as pH decreased and was greater in CON than in FOR. The degradation of CP followed the opposite pattern, increasing as pH increased, and was less in CON than in FOR. The efficiency of microbial protein synthesis (g of N/kg of OM truly digested) was slightly reduced by pH and was less in CON than in FOR. These results indicate that the effects of feeding a high-concentrate diet on rumen fermentation are due to a combination of pH and substrate. Furthermore, the digestion of OM in high-concentrate diets is likely limited by the pH-induced effects on the microbial population activity.

Use of mannanoligosaccharides and zinc chelate as growth promoters and diarrhea preventative in weaning pigs: Effects on microbiota and gut function.

Abstract: The efficacy of a commercial source of mannanoligosacharides (BM), organic zinc (BP), or their combination to enhance performance, gastrointestinal health, and immune response in weaned pigs was evaluated. A total of 128 piglets, weaned at 20 +/- 2 d, were housed in 32 pens. Animals received 1 of 4 dietary treatments: a control diet (CT) to which 0.2% of BM, 80 mg/kg of Zn as BP, or both additives (BMP) were added. The experiment lasted for 5 wk including a prestarter period of 2 wk and a starter period of 3 wk. Body weight was recorded and daily feed intake was calculated. Fecal consistency was monitored for the first 21 d. After 2 wk, 32 animals were killed, digesta samples from the stomach, ileum, and cecum were collected, and pH and the short-chain fatty acid profile were determined. Microbiological counts for enterobacteria and lactobacilli were evaluated using quantitative PCR. Histological parameters in the jejunum and immunoglobulin concentrations in serum and ileal digesta were also measured. Both additives improved G:F during the starter period (0.63, 0.69, 0.67, and 0.68 for CT, BM, BP, and BMP, respectively; P < 0.04). Mean fecal score values for the first 21 d were improved by BM and BP, showing decreased values compared with the CT diet (1.22, 0.89, 0.87, and 1.06 for CT, BM, BP, and BMP, respectively; P = 0.002). The addition of BM decreased enterobacteria counts in the jejunum (9.13, 8.05, 8.87, and 7.89 log 16S rRNA gene copies/g of matter for CT, BM, BP, and BMP, respectively; P = 0.05). Empty ileal weight, defined as the segment including the continuous Peyer's patch, tended (P = 0.08) to increase with BP treatment (8.9, 9.6, 11.9, and 10.3 g/kg of BW for CT, BM, BP, and BMP, respectively). Crypt depths in the jejunum were lower in animals fed the combination of the additives (BPM) compared with those fed the control diet (281 vs. 235; P < 0.03). No significant differences were registered in pH, short-chain fatty acids, or serum and ileal immunoglobulin concentrations. The results suggest that the use of BM or BP can improve the efficiency of gain during the starter period.

Model for estimating enteric methane emissions from United States dairy and feedlot cattle.

Abstract: Methane production from enteric fer- mentation in cattle is one of the major sources of an- thropogenic greenhouse gas emission in the United States and worldwide. National estimates of methane emissions rely on mathematical models such as the one recommended by the Intergovernmental Panel for Climate Change (IPCC). Models used for prediction of methane emissions from cattle range from empirical to mechanistic with varying input requirements. Two empirical and 2 mechanistic models (COWPOLL and MOLLY) were evaluated for their prediction ability us- ing individual cattle measurements. Model selection was based on mean square prediction error (MSPE), concordance correlation coefficient, and residuals vs. predicted values analyses. In dairy cattle, COWPOLL had the lowest root MSPE and greatest accuracy and precision of predicting methane emissions (correlation coefficient estimate = 0.75). The model simulated dif- ferences in diet more accurately than the other models, and the residuals vs. predicted value analysis showed no mean bias (P = 0.71). In feedlot cattle, MOLLY had the lowest root MSPE with almost all errors from ran- dom sources (correlation coefficient estimate = 0.69). The IPCC model also had good agreement with ob- served values, and no significant mean (P = 0.74) or linear bias (P = 0.11) was detected when residuals were plotted against predicted values. A fixed methane con- version factor (Ym) might be an easier alternative to diet-dependent variable Ym. Based on the results, the 2 mechanistic models were used to simulate methane emissions from representative US diets and were com- pared with the IPCC model. The average Ym in dairy cows was 5.63% of GE (range 3.78 to 7.43%) compared with 6.5% ± 1% recommended by IPCC. In feedlot cat- tle, the average Ym was 3.88% (range 3.36 to 4.56%) compared with 3% ± 1% recommended by IPCC. Based on our simulations, using IPCC values can result in an overestimate of about 12.5% and underestimate of emissions by about 9.8% for dairy and feedlot cattle, respectively. In addition to providing improved esti- mates of emissions based on diets, mechanistic mod- els can be used to assess mitigation options such as changing source of carbohydrate or addition of fat to decrease methane, which is not possible with empirical models. We recommend national inventories use diet- specific Ym values predicted by mechanistic models to estimate methane emissions from cattle.

The effects of feeding sericea lespedeza hay on growth rate of goats naturally infected with gastrointestinal nematodes

Abstract: Goat production is increasing in the United States due to high ethnic demand, but infection with gastrointestinal nematode (GIN) parasites is a major constraint to the industry Increasing GIN resistance to chemical anthelmintics worldwide has led to the development of alternative control strategies, including use of forages containing condensed tannins (CT) An experiment was designed using infected and dewormed male kids (Kiko x Spanish, 6 mo old, 189 +/- 325 kg) fed diets containing 25% concentrate and either 75% sericea lespedeza [SL; Lespedeza cuneata (Dum-Cours) G Don], a high CT forage (87 to 181 g of CT/kg), or 75% bermudagrass [BG; Cynodon dactylon (L) Pers] hay (n = 10/treatment) The kids were weighed every 14 d, and fecal and blood samples were taken weekly for fecal egg counts and packed cell volume determination, respectively Fecal cultures were processed every 14 d to determine CT effect on larval development At slaughter, adult GIN were collected from the abomasum and small intestines for counting and speciation Blood samples were also analyzed for plasma urea-N, and ruminal VFA and pH were determined The infected SL-fed kids had consistently lower (P < 005) fecal egg counts than the infected BG goats throughout the trial and greater (P < 005) packed cell volume beginning by d 77 Average daily gain was greater (P < 0001) in kids fed SL- than BG-based diets, regardless of infection status (1043 +/- 50 and 755 +/- 48 g/d, respectively) Total VFA and acetate concentrations were greater (P < 0001) in the BG- than in SL-fed goats, whereas propionate levels were unaffected by diet Acetate:propionate ratio (P = 001) and plasma urea-N (P = 003) levels were greater in BG-fed goats, whereas rumen pH was greater (P < 0001) in the SL-fed goats Feeding SL hay can reduce GIN infection levels and increase performance of goats compared with BG hay

Insulin resistance induced by tumor necrosis factor-alpha in myocytes and brown adipocytes.

Abstract: Insulin resistance is an important contributor to the pathogenesis of type 2 diabetes, and obesity is a risk factor for its development, in part because adipose tissue secretes proteins, called adipokines, that may influence insulin sensitivity. Among these molecules, tumor necrosis factor (TNF)-alpha has been proposed as a link between obesity and insulin resistance because TNF-alpha is overexpressed in adipose tissues of obese animals and humans, and obese mice lacking either TNF-alpha or its receptor show protection against developing insulin resistance. Direct exposure to TNF-alpha induces a state of insulin resistance in terms of glucose uptake in myocytes and brown adipocytes because of the activation of proinflammatory pathways that impair insulin signaling at the level of the insulin receptor substrate (IRS) proteins. In this regard, the Ser(307) residue in IRS-1 has been identified as a site for the inhibitory effects of TNF-alpha in myotubes, with p38 mitogen-activated protein kinase and inhibitor kB kinase being involved in the phosphorylation of this residue. Conversely, Ser phosphorylation of IRS-2 mediated by TNF-alpha activation of mitogen-activated protein kinase was the mechanism found in brown adipocytes. Protein-Tyr phosphatase (PTP)1B acts as a physiological, negative regulator of insulin signaling by dephosphorylating the phosphotyrosine residues of the insulin receptor and IRS-1, and PTP1B expression is increased in muscle and white adipose tissue of obese and diabetic humans and rodents. Moreover, up-regulation of PTP1B expression was recently found in cells treated with TNF-alpha Accordingly, myocytes and primary brown adipocytes deficient in PTP1B are protected against insulin resistance induced by this cytokine. Furthermore, down-regulation of PTP1B activity is possible by the use of pharmacological agonists of nuclear receptors that restore insulin sensitivity in the presence of TNF-alpha. In conclusion, the lack of PTP1B in muscle and brown adipocytes increases insulin sensitivity and glucose uptake and could confer protection against insulin resistance induced by adipokines.

Digestible and metabolizable energy of crude glycerol for growing pigs.

Abstract: The apparent DE and ME values of crude glycerol for growing pigs were determined in 5 experiments using crude glycerol (86.95% glycerol) from a biodiesel production facility, which used soybean oil as the initial feedstock. Dietary treatments were 0, 5, or 10% glycerol addition to basal diets in Exp. 1; 0, 5, 10, or 20% glycerol addition to basal diets in Exp. 2; and 0 and 10% crude glycerol addition to the basal diets in Exp. 3, 4, and 5. Each diet was fed twice daily to pigs in individual metabolism crates. After a 10-d ad- justment period, a 5-d balance trial was conducted. Dur- ing the collection period, feces and urine were collected separately after each meal and stored at 0°C until anal-

Evaluation of alternatives to antibiotics using an Escherichia coli K88+ model of piglet diarrhea: effects on gut microbial ecology.

Abstract: Enterotoxigenic Escherichia coli is a major problem in the swine industry and results in scouring, increased mortality, and poor performance in the period immediately postweaning. The traditional way to control this problem is to include subtherapeutic antibiotics in the feed, but this is no longer acceptable to consumers; thus, alternatives to antibiotics are needed. One of the supplements that has been effective in reducing scouring in the absence of antibiotics is animal blood products produced from the rendering process. This is also becoming a problem because of concerns regarding the transfer of transmissible spongiform encephalopathies to humans from animals. In this research, we investigated the effects of spray-dried porcine plasma (SDPP), a Bacillus subtilis direct-fed microbial (DFM), a blend of organic acids, and sweeteners on E. coli-induced scouring. A total of 108 pigs of approximately 17 d of age were assigned to 6 treatments, with 3 pigs per pen, in 2 blocks, with each block having 3 replicates. The 2 blocks were initiated approximately 2 mo apart, because a sufficient number of pigs were not available that met our inclusion criteria in the first block. Diet 1 was a negative control containing no antibiotics (NC). Diet 2 was the positive control and included the same ingredient composition as NC except that antibiotics (110 mg/kg of chlortetracycline, 110 mg/kg of sulfamethazine, and 55 mg/kg of penicillin) were added (PC). Diet 3 was equal to the NC, but with a B. subtilis probiotic (DFM). Diet 4 was the NC to which SDPP was added. Diet 5 was the NC plus a combination of SDPP and DFM (SDPP + DFM). Diet 6 was the NC plus a combination of supplements, including SDPP and a blend of organic acids, DFM, and a sweetener (Blend). At 24 d of age, the pigs were experimentally infected with 6.3 x 10(9) cfu/mL of E. coli K88. All pigs were euthanized 7 d after infection and tissues were obtained for analysis. There were no significant differences among treatments for ADG, ADFI, G:F, plasma urea nitrogen, alpha-acid glycoprotein, tumor necrosis factor-alpha, intestinal ammonia, pH, or VFA. However, the PC and DFM treatments showed decreased (P < 0.05) scours at 24 h postinfection compared with the NC, SDPP, and SDPP + DFM diets. Mortality in the NC treatment, which did not contain antibiotics, was greater (P < 0.05) than in the other treatments. Terminal restriction fragment length polymorphism analysis of the 16S rDNA genes of digesta showed a greater incidence (P < 0.05) of Bacteroidetes in the PC and DFM diets than in the NC diet. When SDPP and DFM were included in the diet, the incidence of Bacteroidetes was also greater than in the NC diet (P < 0.05).

Defining the transcriptional signature of skeletal muscle stem cells.

Abstract: Satellite cells, the main source of myoblasts in postnatal muscle, are located beneath the myofiber basal lamina. The myogenic potential of satellite cells was initially documented based on their capacity to produce progeny that fused into myotubes. More recently, molecular markers of resident satellite cells were identified, further contributing to defining these cells as myogenic stem cells that produce differentiating progeny and self-renew. Herein, we discuss aspects of the satellite cell transcriptional milieu that have been intensively investigated in our research. We elaborate on the expression patterns of the paired box (Pax) transcription factors Pax3 and Pax7, and on the myogenic regulatory factors myogenic factor 5 (Myf5), myogenic determination factor 1 (MyoD), and myogenin. We also introduce original data on MyoD upregulation in newly activated satellite cells, which precedes the first round of cell proliferation. Such MyoD upregulation occurred even when parent myofibers with their associated satellite cells were exposed to pharmacological inhibitors of hepatocyte growth factor and fibroblast growth factor receptors, which are typically involved in promoting satellite cell proliferation. These observations support the hypothesis that most satellite cells in adult muscle are committed to rapidly entering myogenesis. We also detected expression of serum response factor in resident satellite cells prior to MyoD expression, which may facilitate the rapid upregulation of MyoD. Aspects of satellite cell self-renewal based on the reemergence of cells expressing Pax7, but not MyoD, in myogenic cultures are discussed further herein. We conclude by describing our recent studies using transgenic mice in which satellite cells are traced and isolated based on their expression of green fluorescence protein driven by regulatory elements of the nestin promoter (nestin-green fluorescence protein). This feature provides us with a novel means of studying satellite cell transcriptional signatures, heterogeneity among muscle groups, and the role of the myogenic niche in directing satellite cell self-renewal.

Pros and cons of automatic milking in Europe.

Abstract: During the last several decades, new milking management systems have been introduced, of which development of automatic milking (AM) systems is a significant step forward. In Europe, AM has become an established management system and has shown to be much more than milking management. Factors such as milking, milk quality, feeding, cow traffic, grazing, and animal behavior are essential elements of AM. This system offers possibilities for more frequent milking and can be adapted to lactational stage. Increased milk yield with AM has been observed, but lack of increased production has also been reported from the field, probably due to less attention paid to the total management system. The AM system provides consistent milking routines, with those for teat stimulation and feeding during milking giving an adequate oxytocin release and milk ejection. Initially, reduced milk quality, such as increased FFA, total bacteria count, and somatic cell count (SCC), was observed. Increased FFA could be due to increased milking frequency or handling of the milk, although this has not yet been determined. The elevated total bacteria count was probably due to mismanagement because later studies indicated that teat cleaning in AM is sufficient to reduce spores and dirt on the teats. Significant positive effects on udder health and teat treatment were observed in some studies, possibly as an effect of quarter milking, a procedure whereby an individual teat cup is detached when milk flow is below the preset level for detachment. Well-functioning cow traffic is a prerequisite for successful AM system performance to obtain an optimal number of visits to the feeding area and the milking parlor for all cows. Technical stoppages in the AM system (i.e., the milking unit) increased milk SCC, and the variation and length of the milking interval seem to contribute to elevated SCC. Grazing is a common management routine in many countries. Different ways to motivate the cows to visit the milking parlor, such as shorter distance between barn and pasture, supplement feeding, access to water, and use of acoustic signals, have been tested. It was concluded that use of AM and grazing systems together is possible as long as the distance from the milking parlor to pasture is short. With proper management routines, it is possible to achieve a production level and animal well-being in AM systems that are at least as good as in conventional milking systems.

Effects of dietary arginine supplementation during gestation and lactation on the performance of lactating primiparous sows and nursing piglets.

Abstract: A2 × 2 factorial arrangement of treat- ments in a randomized block design was used to deter- mine the effects of dietary Arg supplementation during gestation and lactation on the lactation performance of 38 first-parity sows. At 30 d of gestation, pregnant gilts were allotted based on BW to 1 of 2 diets supplemented with 1% L-ArgHCl or 1.7% L-Ala (isonitrogenous con- trol). After farrowing, sows were further allotted based on BW within previous gestation treatment groups to 1 of 2 lactation diets supplemented with 1% L-ArgHCl or 1.7% L-Ala (isonitrogenous control). All gestation diets contained 3.1 Mcal/kg and 12.2% CP (as is) and were fed 2 kg/d in 2 equally sized meals, whereas all lactation diets contained 3.2 Mcal/kg and 18.6% CP (as is) and were fed ad libitum. Litter size was standardized to 10 piglets by cross-fostering within 24 h postfar- rowing. On a weekly basis, BW and backfat (BF) thick- ness of sows, as well as piglet BW were measured, and blood and milk samples were obtained from the sows. Number of days from weaning to estrus and ADFI were also recorded. There were no differences in BW, BF thickness, ADFI, or days until return to estrus among treatment groups. There was no effect of the gestation diet or a gestation × lactation diet interaction on any parameter measured. On d 7 of lactation, plasma con- centrations of Arg and insulin in sows, as well as con- centrations of most AA in milk, were greater (P < 0.05) in response to Arg supplementation during lactation compared with the control. Weight gain of piglets from sows fed the Arg-supplemented diet during lactation was greater betwee nd0a nd 7( P < 0.01) and between d 0 and 21 (P < 0.05) of lactation compared with piglets from sows fed the control diet. Collectively, results from this study indicate the potential beneficial effects of dietary Arg supplementation in improving the lactation performance of first-parity sows.