Showing papers in "Journal of Animal Science in 1998"

Statistical analysis of repeated measures data using SAS procedures.

Abstract: Mixed linear models were developed by animal breeders to evaluate genetic potential of bulls. Application of mixed models has recently spread to all areas of research, spurred by availability of advanced computer software. Previously, mixed model analyses were implemented by adapting fixed-effect methods to models with random effects. This imposed limitations on applicability because the covariance structure was not modeled. This is the case with PROC GLM in the SAS® System. Recent versions of the SAS System include PROC MIXED. This procedure implements random effects in the statistical model and permits modeling the covariance structure of the data. Thereby, PROC MIXED can compute efficient estimates of fixed effects and valid standard errors of the estimates. Modeling the covariance structure is especially important for analysis of repeated measures data because measurements taken close in time are potentially more highly correlated than those taken far apart in time.

Acidosis in cattle: a review.

Abstract: Acute and chronic acidosis, conditions that follow ingestion of excessive amounts of readily fermented carbohydrate, are prominent production problems for ruminants fed diets rich in concentrate. Often occurring during adaptation to concentrate-rich diets in feedyards, chronic acidosis may continue during the feeding period. With acute acidosis, ruminal acidity and osmolality increase markedly as acids and glucose accumulate; these can damage the ruminal and intestinal wall, decrease blood pH, and cause dehydration that proves fatal. Laminitis, polioencephalomalacia, and liver abscesses often accompany acidosis. Even after animals recover from a bout of acidosis, nutrient absorption may be retarded. With chronic acidosis, feed intake typically is reduced but variable, and performance is depressed, probably due to hypertonicity of digesta. Acidosis control measures include feed additives that inhibit microbial strains that produce lactate, that stimulate activity of lactate-using bacteria or starch-engulfing ruminal protozoa, and that reduce meal size. Inoculation with microbial strains capable of preventing glucose or lactate accumulation or metabolizing lactate at a low pH should help prevent acidosis. Feeding higher amounts of dietary roughage, processing grains less thoroughly, and limiting the quantity of feed should reduce the incidence of acidosis, but these practices often depress performance and economic efficiency. Continued research concerning grain processing, dietary cationanion balance, narrow-spectrum antibiotics, glucose or lactate utilizing microbes, and feeding management (limit or program feeding) should yield new methods for reducing the incidence of acute and chronic acidosis.

The biology of leptin: a review.

Abstract: Leptin, a 16-kDa protein secreted from white adipocytes, has been implicated in the regulation of food intake, energy expenditure, and whole-body energy balance in rodents and humans. The gene encoding leptin was identified by positional cloning and is the mutation leading to the profound obese phenotype of the ob/ob mouse. Exogenous administration of leptin to ob/ob mice leads to a significant improvement in reproductive and endocrine status as well as reduced food intake and weight loss. The expression and secretion of leptin is highly correlated with body fat mass and adipocyte size. Cortisol and insulin are potent stimulators of leptin expression, and expression is attenuated by beta-adrenergic agonists, cAMP, and thiazolidinediones. The role of other hormones and growth factors in the regulation of leptin expression and secretion is emerging. Leptin circulates specifically bound to proteins in serum, which may regulate its half-life and biological activity. Isoforms of the leptin receptor, members of the interleukin-6 cytokine family of receptors, are found in multiple tissues, including the brain. Many of leptin's effects on food intake and energy expenditure are thought to be mediated centrally via neurotransmitters such as neuropeptide Y. Multiple peripheral effects of leptin have also been recently described, including the regulation of insulin secretion by pancreatic beta cells and regulation of insulin action and energy metabolism in adipocytes and skeletal muscle. Leptin is thought to be a metabolic signal that regulates nutritional status effects on reproductive function. Leptin also plays a major role in hematopoeisis and in the anorexia accompanying an acute cytokine challenge. The profound effects of leptin on regulating body energy balance make it a prime candidate for drug therapies for humans and animals.

Overview of the effects of beta-adrenergic receptor agonists on animal growth including mechanisms of action

Abstract: The beta-adrenergic receptors (beta-AR) are present on the surface of almost every type of mammalian cell. These receptors are stimulated physiologically by the neurotransmitter, norepinephrine and the adrenal medullary hormone, epinephrine. There are three subtypes of beta-AR, namely, beta1-AR, beta2-AR, and beta3-AR; the pharmacological and physiological responses of an individual cell result from the particular mixture of the three beta-AR subtypes present on that cell. Species-specific structure (amino acid sequence) also causes modification of the function of a given beta-AR subtype. Knowledge of the beta-AR subtypes present in various cell types, coupled with knowledge of receptor structure (sequence), will allow an understanding of the complexity of physiological function regulated by beta-AR. Oral administration of some beta-AR agonists increases muscle and decreases fat accretion in cattle, pigs, poultry, and sheep. The large number of physiological functions controlled by beta-AR suggests that the mechanism(s) for the observed changes in carcass composition may be extremely complex. Any proposed mechanism must begin with the possibility of direct effects of the agonist on skeletal muscle and adipocyte beta-AR. However, many other mechanisms, such as modification of blood flow, release of hormones, or central nervous system control of feed intake may contribute to the overall effects observed with a given beta-AR agonist in a given species. Furthermore, the pharmacodynamic properties of a particular agonist are complex and expected to vary among species as well as within the same species at different ages or when fed different diets.

Biochemical Identification and Biological Origin of Key Odor Components in Livestock Waste

Abstract: Animal production results in conversion of feeds into valuable products such as meat, milk, eggs, and wool as well as into unavoidable and less desirable waste products. Intensification of animal numbers and increasing urbanization has resulted in considerable attention to odorous gases produced from animal wastes. It is clear that animal manure was, and still is, a valuable resource. However, it may be a major obstacle to future development of the animal industry if its impact on the environment is not properly controlled. Poor odor prevention and control from animal wastes is related to a lack of knowledge of the fundamental nature of odor and its production by farm animals. Odor, like noise, is a nuisance or disturbance and there is no universally accepted definition of an objectionable odor. Thus, regulation and control of odors in the environment is difficult because of the technical difficulties of defining odor limits and their measurement and evaluation. A variety of direct (sensory) and indirect (analytical instruments) methods for measuring odor intensity and determination of individual or key odor components are discussed. The biological origins of the four principal classes of odor compounds, namely branched- and straight-chain VFA, ammonia and volatile amines, indoles and phenols, and the volatile sulfur-containing compounds, are reviewed. Because more than 50% of N from animals is excreted as urea, one strategy to conserve N in waste is to inhibit the urease enzyme that converts urea to ammonia. Laboratory studies to evaluate di- and triamide compounds to control urea hydrolysis in slurries of cattle and swine wastes are presented. Finally, a brief overview of various intervention strategies is provided. Multiple combinations of nutritional management, housing systems, treatment options as well as storage and disposal of animal wastes will be required to reduce environmental pollution and provide for long-term sustainable growth.

Liver abscesses in feedlot cattle: a review.

Abstract: Liver abscesses in slaughtered beef cattle result from aggressive grain-feeding programs. The incidence, averaging from 12 to 32% in most feedlots, is influenced by a number of dietary and management factors. Liver abscesses represent a major economic liability to producers, packers, and ultimately consumers. Besides liver condemnation, economic impacts include reduced feed intake, reduced weight gain, decreased feed efficiency, and decreased carcass yield. Fusobacterium necrophorum, a member of the ruminal anaerobic bacterial flora, is the primary etiologic agent. Actinomyces pyogenes is the second most frequently isolated pathogen. Ruminal lesions resulting from acidosis generally are accepted as the predisposing factors for liver abscesses. F. necrophorum possesses or produces a number of virulence factors that participate in the penetration and colonization of the ruminal epithelium and subsequent entry and establishment of infection in the liver. However, only a few virulence factors have been characterized well. Control of liver abscesses in feedlot cattle generally has depended on the use of antimicrobial compounds. Five antibiotics (i.e., bacitracin methylene disalicylate, chlortetracycline, oxytetracycline, tylosin, and virginiamycin) are approved for prevention of liver abscesses in feedlot cattle. Tylosin is the most effective and the most commonly used feed additive. Tylosin feeding reduces abscess incidence by 40 to 70%. The mode of action of antibiotics in preventing liver abscesses is believed to be via inhibition of ruminal F. necrophorum. Protective immunity against F. necrophorum induced by a variety of antigenic components has ranged from ineffectual to significant protection.

Standardization of in situ techniques for ruminant feedstuff evaluation

Abstract: Over the last two decades, in situ techniques have been used extensively for measuring ruminal degradation of feedstuffs. Current predictive models put renewed emphasis on the need for quantitative information regarding rates and extents of ruminal degradation. However, in situ techniques suffer from tremendous variation, both within and among laboratories. A considerable number of studies have evaluated the influence of various factors on in situ-derived estimates of ruminal degradation. Factors that should be addressed in a standardized procedure include bag and sample sizes; bag material and pore size; sample processing; animal diet, feeding level, and frequency; bag insertion and removal procedures; location of bags within the rumen and containment procedures for the bags; rinsing procedures; microbial correction; incubation times; mathematical models; and numbers of replicate animals, days, and bags required to obtain repeatable estimates of ruminal degradation. Several recommendations that should increase the precision of in situ measurements are presented. Currently, the lack of standardization in rinsing techniques and the failure or inability to correct for microbial contamination of in situ residues seem to be the major sources of variability with in situ procedures.

Expression of steroidogenic enzyme and gonadotropin receptor genes in bovine follicles during ovarian follicular waves: a review

Abstract: Ovarian follicular development in cattle is characterized by waves of growth during the prepubertal and postpartum periods and during estrous cycles. Each wave of follicular growth is characterized by recruitment of a cohort of follicles 4 to 5 mm in diameter. From the cohort, one follicle is selected for continued growth and becomes dominant. If luteolysis occurs during the growth phase of dominant follicles, final maturation and ovulation occurs. If luteolysis does not occur during the growing and maintenance phase of follicles, the fate is atresia. Changes in mRNA expression for the gonadotropin receptors (FSHr and LHr), key steroidogenic enzymes (cytochrome P450 side chain cleavage [P450scc], cytochrome P450 17alpha-hydroxylase-[P450c17], cytochrome P450 aromatase [P450arom], and 3beta-hydroxysteroid dehydrogenase [3beta-HSD]), and growth factors (IGF-I and -II) and their binding proteins (IGFBP) have been associated with different stages of follicular growth and atresia. In general, expression of mRNA for the gonadotropin receptors, steroidogenic enzymes, and steroidogenic acute regulatory protein (StAR) increase with progressive follicular development and is highest when dominant follicles approach maximum size. Expression of mRNA declines rapidly and becomes low or undetectable in atretic follicles. The IGF-I (granulosal cells) and IGF-II (thecal cells) are increased, whereas IGFBP-2 (granulosal cells) is reduced, in dominant follicles. Recruitment of a cohort of follicles is associated with initiation of expression of mRNA for P450scc and P450arom in granulosal cells. Selection of dominant follicles is associated with expression of mRNA for LHr and 3beta-HSD in granulosal cells. Thus, changes in gene expression likely are important to recruitment, selection, dominance, and atresia in ovarian follicles.

Ruminal Microbial and Fermentative Changes Associated with Experimentally Induced Subacute Acidosis in Steers

Abstract: We used six ruminally cannulated steers in a two-period crossover design to study ruminal fermentative and microbial changes as- sociated with induced subacute acidosis. Steers were adapted to either an 80% alfalfa hay (hay-adapted)- or corn grain (grain-adapted)-based concentrate diet. After feed was withheld for 24 h, steers were overfed with an all-grain diet at 3.5 × NEm daily for 3 d. Ruminal contents and jugular blood samples were collected before withholding feed and at 0 and 12 h daily for 3 d during the overfeeding period. Ruminal samples were analyzed for pH, lactate, VFA concen- trations, and counts of total anaerobic, amylolytic, lactic acid-producing and -fermenting bacteria, and ciliated protozoa. Blood samples were analyzed to assess acid-base status. Ruminal pH declined to a range of 5.5 to 5.0 with increased VFA concentrations, but normal lactate concentrations (<5 mM) were indicative of subacute acidosis. Total viable and amylolytic bacterial counts were higher ( P < .05) in grain-adapted than hay-adapted steers. Anaerobic lactobacilli counts increased over time ( P < .01) in both groups and were generally higher in grain- adapted than hay-adapted steers. Lactate-utilizing bacteria were initially greater in grain-adapted than hay-adapted steers and increased over time in both groups following grain challenge. Total ciliates were initially higher ( P < .05) in grain-adapted than hay- adapted steers and decreased after 48 h in both groups. Blood acid-base changes were minimal. Bac- terial changes associated with subacute acidosis resemble those reported during adaptation to grain feeding, and the decline in ciliated protozoa may be the only microbial indicator of a potentially acidotic condition in the rumen.

The role of pH in regulating ruminal methane and ammonia production

Abstract: When steers (n = 4) were fed increasing amounts of concentrate (0, 45, or 90% of DM) and decreasing amounts of forage, the VFA concentration increased (P .05) rates of ammonia production at pH 6.5 to 5.7 (approximately 12 nmol x mg protein(-1) x min(-1)). These results indicated that ruminal pH affected ruminal methane production, acetate:propionate ratio, deamination, and ammonia concentration.

Environmental concerns about animal manure

Abstract: The structure of swine production has changed dramatically in the last four decades. Raw materials for swine feeds are often grown in regions other than where swine production takes place. Swine manure is mostly spread in the neighborhood of the facilities, which may lead to soil accumulation of minerals such as P, Cu, and Zn. Moreover, soil nitrate may leach and result in enhanced nitrate levels in ground and surface water. Large swine units generate odors, ammonia, and dust that can exceed tolerable levels. Negative effects of swine production on the environment have already led to new legislation that limits the use of animal manure or the expansion or localization of pig operations in some countries. The consequences of intensive swine production on the environment and possible solutions by means of nutrition are outlined. Also, discussed are experiences from the Dutch situation, forthcoming legislation, and environmental constraints on pig production in the future. Our approach centers more on the system level.

Technical note: a technique for inserting a T-cannula into the distal ileum of pregnant sows

Abstract: Our objective was to develop a technique for cannulating the terminal ileum in pregnant sows and to evaluate the usefulness of this procedure in digestibility studies in pregnant and lactating sows A simple T-cannula was inserted into the terminal ileum approximately 15 cm cranial to the ileo-cecal valve in a total of 15 multiparous sows at d 40 (+/- 5 d) of pregnancy All cannulated sows recovered quickly after the surgery and within 3 d they were eating normally Elevated body temperatures were not registered in any sows, and clinical problems related to the surgery were not observed At farrowing, normal litters were born, and number of stillborn pigs, number of live born pigs, and daily litter weight gain were not affected by the cannulations (P > 05) Of the 15 sows originally cannulated, 11 sows were used for collection of digesta during gestation and the following lactating period Eight sows were rebred after weaning, and five sows were rebred after the second lactation period and kept for another cycle Blockage of the cannulas never occurred, and no serious problems were associated with digesta collections The experiment demonstrated that pregnant sows can be prepared with a simple T-cannula in the distal ileum and that the cannula can be maintained in sows throughout the reproductive cycle Hence, the procedure provides a tool for obtaining digesta from pregnant and lactating sows for nutrition studies

An evaluation of ruminally degradable intake protein and metabolizable amino acid requirements of feedlot calves.

Abstract: Ruminally degradable intake protein (DIP) and metabolizable indispensable amino acid (MIAA) requirements of feedlot steers were evaluated Dietary treatments consisted of isocaloric 80% concentrate steam-flaked corn-based diets containing either 8% urea, 15% fish meal (FM), 30% FM, 45% FM, or 45% soybean meal (SBM) Treatment effects on characteristics of ruminal and total tract digestion were evaluated using four Holstein steers (249 kg) with cannulas in the rumen and proximal duodenum Ruminal digestibility of OM (RDOM; P 10) on DOM As the level of FM was increased, MIAA increased linearly (P 10) for urea- and SBM-supplemented diets Treatment effects on 56-d growth performance were evaluated using 100 medium-framed crossbred steers (231 kg) Daily weight gain (linear effect; P < 01), DM intake (linear effect; P < 10), feed efficiency (linear effect; P < 05), and diet NE (linear effect; P < 05) increased with level of FM supplementation Daily weight gain (P < 10) and DM intake (P < 05) were greater for urea- than for SBM-supplemented diets Using bovine tissue as the reference protein, the biological value (based on chemical score) of the intestinal chyme protein averaged 73%; methionine was first-limiting There was a close association (R2 = 99) between methionine supply to the small intestine and observed/expected dietary NE The metabolizable methionine requirement (MMETR, g/d) of medium-framed feedlot steers can be reliably predicted from measures of BW and ADG (MMETR = 1565 + 0234ADG[268 - (294 x 0557BW(75)ADG(1097))/ADG] + 0896BW(75)) There was a very close association (R2 = 89) between DIP and MNF (MNF = 137DIP - 66DIP(2) + 259) At maximal observed synthesis, DIP accounted for 76% of the MNF A minimum of 100 g DIP/kg of total tract digestible OM was required to maximize RDOM and MNF

Behavioral, endocrine, immune, and performance measures for pigs exposed to acute stress.

Abstract: Weanling pigs (n = 132) were used to investigate the effects of three common stressors (and a control) and differing social status on behavior, immunity, plasma cortisol, blood chemical, and performance measures. Eleven blocks of 12 pigs each were evaluated. Each pen contained three pigs of dominant (DOM), intermediate (INT), or submissive (SUB) social status. Two weeks later, random pens of pigs experienced either a control treatment (CON) or they were stressed for 4 h by shipping (SHIP), heat-stressed (HEAT) with overhead heat lamps in their home pens, or cold-stressed (COLD) by direct application of water and an air current. Treatments did not influence body weights; however, percentage weight loss during SHIP was greater than for other treatments. Body weights were heavier for DOM pigs than for INT and SUB pigs. Social status had large effects on plasma cortisol, globulin, acute-phase proteins, body weight, and weight changes. Only acute shipping stress resulted in weight loss. Many immune and blood measures were not changed among acutely stressed pigs; however, the relationship between social status and mitogen-induced lymphocyte proliferation and natural killer cell cytotoxicity was disrupted during acute stress. Pig behavior was significantly changed by each stress treatment in a unique manner. During acute stress, behavioral changes seem to be the most consistent and reliable indicators.

Impact of disease on feedlot performance: a review

Abstract: Morbidity and mortality of feedlot cattle have a variety of causes. Compared to respiratory disease, metabolic and digestive disorders generally are less prevalent and occur later in the feeding period. In addition to the obvious costs related to animal death and medication, subsequent performance of sick cattle often is depressed substantially. Closer coordination between veterinarians, nutritionists, and feedlot managers should help reduce the incidence of morbidity and mortality of feedlot cattle.

Methane output and lactation response in Holstein cattle with monensin or unsaturated fat added to the diet

Abstract: We measured effects of continuous vs twice-daily feeding, the addition of unsaturated fat to the diet, and monensin on milk production, milk composition, feed intake, and CO2-methane production in four experiments in a herd of 88 to 109 milking Holsteins. Methane and CO2 production increased with twice-daily feeding, but the CO2:CH4 ratio remained unchanged. Soybean oil did not affect the milkfat percentages, but fatty acid composition was changed. All saturated fatty acids up to and including 16:0 decreased (P < .01), whereas 18:0 and trans 18:1 increased (P < .001). The 18:2 conjugated dienes also increased (P < .01) when the cows were fed soybean oil. Monensin addition to the diet at 24 ppm decreased methane production (P < .01); the CO2:CH4 ratios reached 15, milk production increased (P < .01), and milkfat percentage and total milkfat output decreased (P < .01), as did feed consumption, compared with cows fed diets without monensin (P < .05). Milk fatty acid composition showed evidence of depressed ruminal biohydrogenation: saturated fatty acids (P < .05) decreased and 18:1 increased (P < .001); most of the increase was seen in the trans 18:1 isomer. As with soybean oil feeding, addition of monensin also increased (P < .05) the concentration of conjugated dienes. The monensin feeding trial was repeated 161 d later with 88 cows, of which 67 received monensin in the diet in the first trial and 21 cows were newly freshened and had never received monensin. Methane production again decreased (P < .05), but this time the CO2:CH4 ratio did not change and all other monensin-related effects were absent. The ruminal microflora in the cows that had previously received monensin seemed to have undergone some adaptive changes and no longer responded as before.

Effects of forage vs grain feeding on carcass characteristics, fatty acid composition, and beef quality in Limousin-cross steers when time on feed is controlled.

Abstract: Limousin-cross steers (n=135; 258+/-26 kg) were used to compare forage vs grain feeding on carcass composition and palatability attributes of beef when time on feed was controlled. Diets included a 95% alfalfa silage ration (AS) or a 68% high-moisture corn, 25% alfalfa silage ration (HMC). These were incorporated into six treatments to allow comparisons of end points based on similar days on feed or backfat finish. Dietary treatments included 1) HMC (4 mm), or cattle allowed ad libitum intake of HMC until slaughter at 4 mm ultrasound backfat; 2) AS (HMC-4), or cattle allowed ad libitum intake of AS until slaughter, regardless of finish, when HMC (4 mm) cattle were slaughtered; 3) AS (4 mm), or cattle allowed ad libitum intake of AS until slaughter at 4 mm backfat; 4) HMC (AS-4), or cattle allowed ad libitum intake of HMC until slaughter, regardless of finish, when AS (4 mm) cattle achieved 4 mm backfat; 5) HMC (RES), or cattle fed HMC at restricted intakes until slaughter at 4 mm backfat with feed offered at 75% of intake achieved by HMC (4 mm) and HMC (AS-4) cattle; and 6) AS (8 mm) or cattle allowed ad libitum intake of AS ration until slaughter at 8 mm backfat. Grain feeding generally increased (P .10) by diet with the exception of slightly less beef flavor and more off-flavor in forage-fed vs grain-fed beef. Higher (P < .01) concentrations of linolenic acid and lower (P < .10) concentrations of oleic acid in forage-fed beef may be partially responsible for diet differences in flavor.

Illegal use of beta-adrenergic agonists: European Community

Abstract: The use of veterinary medicinal products within the European Community is governed by a series of directives and regulations that describe the requirements for safety, quality, and efficacy of these products. Veterinary therapeutic use of β-agonists has only been approved in the case of clenbuterol for bronchodilatation in horses and calves and for tocolysis in cows. No β-agonists have been permitted in the European Community for growth-promoting purposes in farm animals. Surveillance for the presence of residues of veterinary agents in food-producing animals and meat is regulated by the Directive 86/469/EEC containing specific guidelines for sampling procedures on farms and in slaughterhouses. The level and frequency of sampling is dependent on the category of compounds and animal species. When positive samples have been identified (above certain action levels), sampling intensity is increased. Results of monitoring programs in EU member states during 1992 and 1993 for the occurrence of residues of β-agonists in food-producing animals vary substantially with respect to the percentages of positive samples, ranging from 0 to 7%. The variability is partly explained by differences in sampling strategies, detection methods, and action levels applied. Identification of the proper matrices for sampling and detection of β-agonists is important. In the case of clenbuterol, hair and choroid retinal tissue are appropiate tissues because clenbuterol accumulates in these matrices. A clear decrease in the use of clenbuterol in cattle has been observed in The Netherlands, Germany, Northern Ireland, and Spanish Basque Country over the last 3 yr. This is partly due to intensified surveillance activities at farms and slaughterhouses by governmental agencies and production sector organizations. There are data on human intoxication following consumption of liver or meat from cattle treated with β-agonists. At the concentrations of clenbuterol measured in contaminated liver and meat samples, pharmacological effects may be expected in humans after consuming 100 to 200 g of product. The use of highly active β-agonists as growth promoters is not appropriate because of the potential hazard for human and animal health, as was recently concluded at the scientific Conference on Growth Promotion in Meat Production (Nov. 1995, Brussels).

Effects of birth weight and postnatal nutrition on neonatal sheep: I. Body growth and composition, and some aspects of energetic efficiency.

Abstract: We investigated the effects of birth weight and postnatal nutrition on growth characteristics of neonatal lambs. Low- and high-birth-weight male lambs were individually reared on a high-quality liquid diet to grow rapidly (ad libitum access to feed) or slowly (ADG 150 g) to various weights up to 20 kg live weight (LW). Average daily gain tended to be greater in the high- (mean+/-SE 345+/-14 g) than in the low- (329+/-15 g) birth-weight lambs given ad libitum access to feed owing to slower growth by the small newborns during the immediate postpartum period. At birth, on a weight-specific basis, small newborns contained 6.4% less nitrogen and tended to have more ash (8.9%) than the high-birth-weight newborns. Daily rates of fat, ash, and GE accretion were greater, and nitrogen accretion tended to be greater in the rapidly grown large newborns than in their small counterparts. At any given empty body weight (EBW) during rearing, low-birth-weight lambs contained more fat and less ash, resulting in slowly and rapidly grown small newborns containing 39.3 and 42.7 Mcal GE, respectively, at completion of the study (17.5 kg EBW), compared with 34.8 and 40.5 Mcal in their large counterparts. The differences in fatness and energy content between the birth weight categories are attributed to energy requirements for maintenance that were approximately 30% lower, coupled with higher relative intakes in the low-birthweight lambs, during the early postnatal period. At this time, the ability to consume nutrients in excess of lean tissue growth requirements was apparently more pronounced in small than in large newborns, which resulted in lower efficiency of energy utilization for tissue deposition. Furthermore, body composition differences between the slowly and rapidly reared lambs support the notion of a priority of lean tissue over fat when nutrient supply is limited.

Livestock odors: implications for human health and well-being.

Abstract: The purpose of this paper is to examine the potential effects of livestock odors on the health and well-being of neighbors. Complaints of odor nuisance have become more frequent in communities surrounding areas with high concentrations of livestock. This increase in complaints from livestock odors parallels increased complaints of odor in general, including ammonia, diesel exhaust, beauty products, cleaners, and paints. Persons who report symptoms from odors generally find problems with many different types of odorous compounds. A review of recent studies suggests that the main complaints of health symptoms from odors are eye, nose, and throat irritation, headache, and drowsiness. Sensory irritation (pungency) can be produced by a broad range of odorous volatile organic compounds from trees, flowers, foods (pepper and ginger) as well as emissions from livestock operations. Odors can also potentially affect mood and memory. Further research is required to assess fully the health impact of odors in order to establish recommendations for air quality guidelines based on scientific data.

Dietary carbohydrates alter the fecal composition and pH and the ammonia emission from slurry of growing pigs.

Abstract: We investigated the effects of dietary carbohydrates on the composition and pH of fecal material and on the ammonia emission from the slurry of growing pigs. Thirty-four barrows (BW approximately 40 kg) were randomly allotted to 1 of 10 diets. A basal diet was formulated to meet all requirements for protein, amino acids, minerals, and vitamins. The control diet was composed of the basal diet plus heat-treated cornstarch. In the other diets, the cornstarch in the control diet was replaced with three levels of either coconut expeller, soybean hulls, or dried sugar beet pulp. Feces were collected separately from urine in a balance experiment. Feces were mixed with a standardized urine (ratio of 1:2.5, wt/wt) to form a slurry. A sample of this slurry was placed in an in vitro system to determine the pH and the ammonia emission for 16 d at 20 degrees C. The fecal and slurry DM contents decreased (P < .001) and the total VFA concentrations increased (P < .001) when the level of dietary carbohydrates increased. The pH and the ammonia emission decreased as the level of carbohydrates increased (P < .001). The addition of soybean hulls to the diet had the greatest effect on reducing the pH and ammonia emission (P < .001), and the effects of sugar beet pulp and coconut expeller were approximately the same. A linear relationship was found between the intake of dietary nonstarch polysaccharides (NSP) and the ammonia emission (P < .001). For each 100-g increase in the intake of dietary NSP, the slurry pH decreased by approximately .12 unit and the ammonia emission from slurry decreased by 5.4%. We conclude that replacing cornstarch in the diet with components that have a high concentration of fermentable carbohydrates increases the VFA concentration of feces and slurry and reduces the pH and ammonia emission from the slurry of growing pigs.

Identification of quantitative trait loci affecting carcass composition in swine: I. Fat deposition traits.

Abstract: One of the major determining factors in the price of market hogs today is backfat depth. Therefore, identification of regions of the genome affecting this trait could be very useful to the swine industry. A large resource population (n = 540) was developed by backcrossing F 1 Meishan-White composite females to either Meishan or White composite boars. A genomic scan was conducted by genotyping all animals with microsatellite markers spaced at ∼20-cM intervals across the entire porcine genome. Breed of origin for all chromosomal segments was determined using multipoint linkage procedures, and a least squares regression analysis was conducted. Nominal P-values were converted to a genome-wide level of significance to adjust for the numerous tests conducted. Traits analyzed were backfat depths at the first rib (FRIB); 10th rib (10th); last rib (LRIB); last lumbar (LLUM) vertebra; the average of FRIB, LRIB, and LLUM (AVBF); and weight of leaf fat (LEAF). Significant quantitative trait loci (QTL) were detected on chromosomes 1, 7, and X. Suggestive evidence for QTL was present on chromosomes 5, 8, 9, 10, 13, and 14. Genotypic means for the loci detected indicated a predominantly additive mode of inheritance. Meishan alleles produced fatter pigs for all loci except those on chromosomes 7 and 10. Additional research should be conducted to refine the estimated position of each QTL and its effect and determine epistatic interactions. These loci should be evaluated in other germplasms to determine whether allelic variation at the QTL exists in other breeds.

Changes in the calpains and calpastatin during postmortem storage of bovine muscle.

Abstract: Changes in activity and protein status of μ-calpain, m-calpain, and calpastatin in bovine semimembranosus muscle during the first 7 d of postmortem storage were monitored by using assays of proteolytic activity, SDS-polyacrylamide gel electrophoresis, and Western blot analysis. Extractable m-calpain activity changed slightly during the first 7 d after death (decreased to 63% of at-death activity after 7 d), whereas extractable calpastatin activity decreased substantially (to 60% of at-death activity after 1 d and to 30% of at-death activity after 7 d of postmortem storage) during this period. Extractable μ-calpain activity also decreased rapidly (to 20% of at-death activity at 1 d and to less than 4% of its at-death activity at 7 d after death) during postmortem storage. Western blot analysis showed that the 80-kDa subunit of m-calpain remained undegraded during the first 7 d after death but that the 125- to 130-kDa calpastatin polypeptide was gone entirely at 7 d after death. Hence, the calpastatin activity remaining at 7 d originates from calpastatin polypeptides that are 42 kDa or smaller. The 80-kDa μ-calpain subunit was almost entirely in the 76-kDa autolyzed form at 7 d after death; this form is proteolytically active in in vitro systems, and it is unclear why the postmortem, autolyzed μ-calpain is not active. Over 50% of total muscle μ-calpain is tightly bound to myofibrils 7 d after death; this μ-calpain is also nearly inactive proteolytically. Unless postmortem muscle contains some factor that enables μ-calpain in this muscle to be proteolytically active, it is not clear whether μ-calpain could be responsible for any appreciable postmortem myofibrillar proteolysis.

Beef color update: the role for vitamin E

Abstract: Dietary supplementation of livestock with vitamin E results in improved quality of meat subsequently obtained from these animals. The effect is especially noteworthy in cattle, in which the primary effects are delayed discoloration and lipid oxidation. A threshold level of alpha-tocopherol in muscle ensures a detectable effect; dietary strategies for attaining this threshold must consider tocopherol status of cattle arriving at the feedyard and duration and level of supplementation. The alpha-tocopherol concentration in muscle must be determined before proper interpretation of experimental results can be made. Muscles vary in their color stability, and this relative difference is not changed by vitamin E supplementation. Several in vitro models have been used to characterize the interaction between alpha-tocopherol, lipid oxidation, and oxymyoglobin oxidation. Alpha-tocopherol seems to exert its color-stabilizing effect by indirectly delaying oxymyoglobin oxidation via direct inhibition of lipid oxidation. However, recent results demonstrating a protective effect of alpha-tocopherol toward oxymyoglobin in low-oxygen atmospheres indicate that additional mechanisms may exist. A better understanding of the fundamental bases for protection of water-soluble myoglobin by lipid-soluble alpha-tocopherol is needed to optimize this beneficial effect.

Growth performance of pigs subjected to multiple concurrent environmental stressors.

Abstract: The effects of many single stressors have been reported, but how pigs perform when subjected to more than one or two stressors at a time, as is common in commercial swine production, has not. To study this, 256 Yorkshire x Hampshire or purebred Duroc pigs (34.7+/-.5 kg) were subjected to one of the eight treatment combinations (2 x 2 x 2 factorial) of ambient temperature (constant thermoneutral [24 degrees C] or high cycling temperature [28 to 34 degrees C]), stocking density (.56 or .25 m2/pig), and social group (static group or regrouped at the start of wk 1 and 3) during a 4-wk experiment. The temperature regimens were imposed in two adjacent mechanically ventilated rooms, and each temperature was imposed in each room across two trials. Four barrows and four gilts were assigned to each of the eight pens in the two rooms, and they always had free access to water and a corn-soybean meal-based diet. Treatments were imposed after a 7-d acclimation period at 24 degrees C and .56 m2/pig. Weight gain and feed intake were measured weekly. The main effects of each of the stressors for 4-wk ADG and ADFI were significant (P < .05). The stress of high temperature, high stocking density, and regrouping depressed 4-wk ADG by 12, 16 and 10% and ADFI by 7, 6, and 5%, respectively. Of the possible 60 stressor interactions for ADG, ADFI, and gain:feed (G:F), there were no significant three-way interactions and only six two-way interactions, suggesting that the effects of the individual stressors were additive. Accordingly, the growth rate of pigs subjected to the single stressor of high cycling temperature, restricted space allowance, or regrouping was depressed 10, 16, and 11%, respectively, and ADG of pigs subjected to all three stressors simultaneously was depressed by 31%. Stressor additivity was further corroborated by examining the effect of stressor order, or the number of stressors imposed simultaneously. As the number of stressors increased from 0 to 3, ADG, ADFI, and G:F decreased linearly. These data suggest that multiple concurrent stressors affect growth performance of pigs in a predictable fashion (i.e., additively) and indicate that avoidance or removal of a given stressor is advantageous even when other uncontrollable stressors persist.

Manipulation of ruminal fermentation with organic acids: a review

Abstract: The dicarboxylic acids aspartate, fumarate, and malate stimulate lactate utilization by the predominant ruminal bacterium, Selenomonas ruminantium. Malate stimulates lactate uptake by S. ruminantium more than does aspartate or fumarate, and it seems that malate and sodium are involved in stimulating lactate utilization by this bacterium. Based on the ability of S. ruminantium to grow on malate in the presence of extracellular hydrogen and produce succinate, malate may be acting as an electron sink for hydrogen in the succinate-propionate pathway used by S. ruminantium. Incorporation of DL-malate into soluble starch and cracked corn fermentations with mixed ruminal microorganisms changed final pH, CH4, and VFA in a manner analogous to ionophore effects. When compared with either dicarboxylic acids or monensin alone, dicarboxylic acid plus monensin addition to cracked corn incubations stimulated the mixed ruminal microorganism fermentation to produce more propionate, less lactate, and increased final pH. Reduced lactate concentrations in dicarboxylic acid- and monensin-treated incubations most likely represents an additive effect of decreased lactate production by monensin-sensitive bacteria (i.e., Streptococcus bovis) and increased lactate utilization by the monensin-resistant S. ruminantium. The inclusion of malate as a feed additive into the diets of ruminants is currently not economically feasible; however, forages rich in organic acids might serve as vehicles for providing malate to ruminants. When five alfalfa varieties and three bermudagrass hay varieties were surveyed for malate content, the concentration of malate in both plant species declined as maturity increased. However, after 42 d of maturity, the concentration of malate in both forages ranged between 1.9 and 4.5% of the DM. These results suggest that the incorporation of forage varieties that are high in malate may include malate economically into the diet and reduce losses associated with ruminal acidosis.

Manipulating ruminal fermentation: a microbial ecological perspective

Abstract: The essential role of ruminal microflora in ruminant nutrition provides the potential for improvement in animal production via altering the numbers or activities of specific classes of microorganisms. Successful alterations will be facilitated by an understanding of the microbial ecology of the rumen based on its mechanistic underpinnings. Demonstrated improvements in ruminal fermentation can be traced to their consonance with well-established principles of microbial ecology (niche occupancy, selective pressure, adaptation, and interactions) and the thermodynamics and kinetics of substrate utilization. Application of these principles to several proposed alterations of the ruminal bacterial population allows a prediction of their relative feasibility. Improving fiber digestion, decreasing protein degradation, and detoxifying feed components that are present in low concentrations will be difficult to achieve in the rumen and are best approached by altering the feed, either genetically or with postharvest treatment. By contrast, the detoxification of feed components present in high concentration, and redirection of electron disposal away from methanogenesis, are more productive targets for microbiological research.

Beef customer satisfaction: role of cut, USDA quality grade, and city on in-home consumer ratings.

Abstract: An in-home beef study evaluated consumer ratings from moderate-to-heavy beef users as influenced by cut (top loin, top sirloin, and top round steaks), USDA quality grade (Top Choice, Low Choice, High Select, and Low Select), and city (Chicago, Houston, Philadelphia, and San Francisco). Consumers (n = 2,212) evaluated each steak for overall like (OLIKE), tenderness (TEND), juiciness (JUIC), flavor desirability (DFLAV), and flavor intensity (IFLAV) using 23-point hedonic scales (23 = like extremely, extremely tender, extremely juicy, like extremely, and an extreme amount of flavor; 1 = dislike extremely, not at all tender, not at all juicy, dislike extremely, and no flavor at all). A USDA grade x cut interaction existed for OLIKE (P .05) able to distinguish OLIKE differences between Low Choice and High Select or between High Select and Low Select. For OLIKE, top sirloin was rated intermediate (P .05) USDA quality grade differences. For OLIKE, top round was the lowest-rated (P < .05) cut. However, consumers preferred (OLIKE, P < .05) Top Choice to the other USDA grades offered. Grade and city interacted to affect TEND, JUIC, DFLAV, and IFLAV. The cut x city interaction was significant for all palatability attributes. Cut and city affected customer satisfaction more than USDA quality grade. Tenderness and flavor were important and equal contributors to OLIKE, r = .85 and r = .86, respectively.

The pharmacokinetics, metabolism, and tissue residues of beta-adrenergic agonists in livestock.

Abstract: Since the early 1980s the usefulness of dietary beta-agonists to improve the efficiency of feed utilization and(or) to enhance carcass leanness in livestock species has been well documented. Less well documented are the pharmacokinetic properties, biotransformation pathways, and tissue residue profiles of beta-agonists used to enhance leanness in experimentally or illegally treated animals. Pharmacokinetic data for clenbuterol, cimaterol, fenoterol, L-644,969, ractopamine, salbutamol, and terbutaline have been published but biotransformation and tissue residue studies for these compounds in livestock species are sparse. In general, beta-agonists having halogenated aromatic ring systems are metabolized by oxidative and conjugative pathways and have long plasma half-lives, whereas beta-agonists having hydroxylated aromatic rings are metabolized solely by conjugation and have relatively short plasma half-lives. Beta-Agonists having high oral bioavailabilities, long plasma half-lives, and relatively slow rates of elimination have high oral potencies in humans. Residues of such illegally used compounds in edible tissues of livestock represent a genuine risk to consumers. Conversely, beta-agonists having low oral bioavailabilities, short plasma half-lives, and rapid rates of elimination have low oral potencies in humans. Residues of such compounds in edible tissues of properly treated animals would not likely represent a credible risk to consumers of such products. The reviewed data indicate that the development of a safe and effective beta-agonist for use in livestock is possible.

Illegal use of beta-adrenergic agonists in the United States.

Abstract: Clenbuterol (CBL) is a member of the class of drugs called beta-agonists, which have powerful desirable and undesirable effects. Clenbuterol has the ability to increase muscle mass and residues in tissue of treated animals but can cause symptoms of acute poisoning in people. Symptoms, but no deaths, from CBL residue-induced food poisoning have been reported from investigations of separate events in Spain and France. In 1991, FDA sent letters to all states and USDA/FSIS advising them of the possibility of illegal CBL use in domestic animals and of our concern about adverse effects on public health if residue was present in food. The FDA asked U.S. Customs to be alert to attempts at illegal importation and to advise that we were prepared to investigate distribution, sale, or use of the drug. Analytical methods are available to assay for CBL residue in edible tissues and in the retinal tissues of the eye. Methods are being developed for assay of noninvasive samples such as hair. Residues of CBL have been found in one sample of edible tissue and several samples of retinal tissues from show animals and in some classes of commercial meat-producing animals. Several individuals have been found guilty of distributing CBL, cases are pending, and investigations are continuing. It is possible that CBL will be approved for safe conditions of use. The scenario of ultimately one or more beta-agonist drugs approved for legal use in food-producing animals and the probable continued availability of several illegal analogs will be a challenging containment task for regulators and the leaders of the meat-producing livestock industries.