Showing papers in "Journal of Animal Science in 1994"

Microbial attachment and feed digestion in the rumen.

Abstract: Direct microscopic examination of the rumen and its contents shows microbial populations largely attached to feed particles in the digesta Most feeds contain a surface layer that is resistant to attachment and therefore to digestion Infiltration of these recalcitrant epidermal layers through damage sites or through focused enzymatic attack is essential for initiation of the digestive process Proliferation of primary colonizing cells produces glycocalyx-enclosed microcolonies Secondary colonizers from the ruminal fluid associate with microcolonies, resulting in the formation of multispecies microbial biofilms These metabolically related organisms associate with their preferred substrates and produce the myriad of enzymes necessary for the digestion of chemically and structurally complex plant tissues Upon accessing the internal, enzyme-susceptible tissues, microbial "digestive consortia" attach to a variety of nutrients, including protein, cellulose, and starch and digest insoluble feed materials from the inside out Substances that prevent microbial attachment or promote detachment (eg, condensed tannins, methylcellulose) can completely inhibit cellulose digestion As the microbial consortium matures and adapts to a particular type of feed, it becomes inherently stable and its participant microorganisms are notoriously difficult to manipulate due to the impenetrable nature of biofilms Properties of feed that place constraints on microbial attachment and biofilm formation can have a profound effect on both the rate and extent of feed digestion in the rumen Developments in feed processing (ie, chemical and physical), plant breeding, and genetic engineering (both of ruminal microorganisms and plants) that overcome these constraints through the promotion of microbial attachment and biofilm formation could substantially benefit ruminant production

Prediction of net energy value of feeds for growing pigs

Abstract: Digestible (DE), metabolizable (ME), and net (NE) energy values of 61 diets were measured in 45-kg growing Large White boars. Net energy was calculated as energy retained at an average ME intake equivalent to 540 kcal/kg BW.60 plus fasting heat production estimated from data of the present experiment as 179 kcal/kg BW.60. Retained energy was measured as the difference between ME intake and heat production obtained in respiration chambers. The amounts of DE digested before the end of the ileum (DEi) and in the hindgut (DEh) were also measured for each diet. Regression equations for predicting dietary NE content from digestible nutrient levels or from DE or ME and chemical characteristics or from chemical composition only were calculated. Efficiencies of utilization of ME for NE (k, %) were also obtained. The mean k value for the 61 diets was 74% (range: 69 to 77). Digestible nutrients were used differently for NE: k values varied from approximately 60% for digestible CP or digestible cell wall fractions to 82% for starch and 90% for digestible ether extract. Accordingly, k for ME associated with DEh was lower than ME from DEi (58 vs 76%). Equations for predicting NE content are proposed. Their applicability, the comparison with other available NE prediction equations, and the effects of energy system on diet formulation are discussed.

Kinetics of fiber digestion from in vitro gas production.

Abstract: In vitro gas production, measured by computer-interfaced pressure sensors, was used to follow the digestion of a crystalline processed cellulose, a bacterial cellulose, and mixtures of these substrates by mixed ruminal bacteria. A first-order, substrate limited model (simple exponential with lag) and two bacterial growth models (logistic, Gompertz) were tested to fit these data. No single pool model gave an optimal fit to all substrates, but dual pool versions of both the logistic and Gompertz models fitted the data extremely well. Derivations of these models in the context of gas production are presented. The dual pool version of the exponential model commonly used to analyze fiber digestion was not able to reproduce the slope variations seen with mixed substrates. A modified dual pool logistic equation, with a single lag value, was selected to model the in vitro digestion of these substrates. The model was able to predict adequately both the input composition and the kinetic parameters for a defined mixture and gave a good fit (r2 > .995) to data from all the single and mixed substrates tested. This model may be useful for interpreting gas accumulation from natural feedstuffs.

Wet corn distillers byproducts compared with dried corn distillers grains with solubles as a source of protein and energy for ruminants.

Abstract: Five trials investigated the feeding value of wet and dried corn distillers byproducts as a source of protein and energy for growing and finishing cattle and investigated the effect of heat damage on the feeding value of dried distillers byproducts. In a calf growth trial, no differences in rate of gain or protein efficiency were observed among calves fed wet distillers byproducts (wet distillers grains + thin stillage; WDB) or one of three composites of dried distillers grains + solubles (DDGS) having a low, medium, or high concentration of ADIN. A finishing trial compared the energy value of dry-rolled corn (DRC) with WDB or the three DDGS composites, fed at 40% of the diet DM replacing DRC. Cattle consuming WDB or DDGS gained faster ( P .lo). In a lamb finishing trial, the addition of 5 or 10% ethanol did not affect (P > .lo) daily gain, DMI, or feed efficiency. In two metabolism trials with steers, grain byproducts (wet distillers grains, dry distillers grains plus solubles, wet corn gluten feed, dry corn gluten feed, hominy feed) and DRC had similar effects on ruminal pH and total VFA. Feeding thin stillage or condensed solubles reduced (P < .lo) ruminal pH and tended to reduce acetate:propionate. Wet corn distillers byproducts, fed at 40% of the diet DM, contain more NE, than did DRC and drying WDB reduces its NE, content. Acid detergent insoluble N is a poor indicator of protein and energy value in distillers grains.

Effect of marbling degree on beef palatability in Bos taurus and Bos indicus cattle

Abstract: This study was designed to evaluate the relationship between marbling score and breed-type (Bos taurus vs .05) from Modest or Moderate marbling. In addition, variation in shear force was lower (P .05) by marbling score in either Bos taurus or Bos indicus cattle. Percentage yield of retail product decreased (P .05) to shear force or tenderness rating.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of free amino acids and vitamins on cleavage and developmental rate of bovine zygotes in vitro.

Abstract: Due to the complicated media used for culturing bovine embryos, most of the nutrient requirements are unknown. Recently, we developed a simple, serum-free medium (CR1) that allows bovine embryos to develop in vitro. Therefore, our objective was to determine whether development of bovine embryos would be improved by the addition of free amino acids and vitamins to CR1. Oocytes were recovered from slaughterhouse ovaries and matured 22 +/- 2 h, following which the oocytes were randomly allotted to treatment. The experiment was a randomized block design with a 2 x 5 factorial treatment structure. The oocytes were fertilized with or without cumulus cells intact. The five fertilization media were 1) Control (CR1 +/- 10 micrograms/mL of phenol red); 2) control + basal medium Eagle (BME) essential amino acids (EAA) + minimum essential medium (MEM) nonessential amino acids (NEA) + MEM vitamins (VIT); 3) control + EAA + NEA; 4) control + EAA + VIT; and 5) control + NEA + VIT. Cleavage rate was greater (P < .001) when cumulus cells remained on the oocytes during fertilization (51.7 vs 73.2% without and with cumulus cells, respectively). The frequency of blastocysts was increased (P < .001) when EAA or NEA were added to CR1; however, adding VIT had no effect or tended (P = .12) to decrease the frequency of embryos attaining the blastocyst stage. This experiment demonstrates that development of bovine embryos in vitro can be improved by the addition of free amino acids to a simple medium. Contrary to work in rodents, the mixture of vitamins in MEM was not beneficial for bovine embryos.

Heritabilities and phenotypic and genetic correlations for bovine postrigor calpastatin activity, intramuscular fat content, Warner-Bratzler shear force, retail product yield, and growth rate

Abstract: To estimate the heritability (h2) of postrigor calpastatin activity (CA), 555 steers were reared and processed conventionally. Breed-types included purebreds (Angus [A], Braunvieh [B], Charolais [C], Gelbvieh [G], Hereford [H], Limousin [L], Pinzgauer [P], Red Poll [RP], and Simmental [S]), composite populations (MARC I [1/4 C, 1/4 B, 1/4 L, 1/8 H, 1/8 A], MARC II [1/4 S, 1/4 G, 1/4 H, 1/4 A], and MARC III [1/4 RP, 1/4 H, 1/4 P, 1/4 A]), and F1 crosses (H, A, C, G, P, Shorthorn, Galloway, Longhorn, Nellore, Piedmontese, or Salers x H or A). Steers were serially slaughtered on an age-constant (across breed groups) basis. Heritability estimates for CA, i.m. fat content (IMF), Warner-Bratzler shear (WBS) force, retail product yield (RPY), and ADG were .65 +/- .19, .93 +/- .02, .53 +/- .15, .45 +/- .18, and .32 +/- .26, respectively. The genetic correlations (rg) of CA with WBS, RPY, and ADG were .50 +/- .22, .44 +/- .25, and -.52 +/- .37, respectively. The rg of IMF with WBS, RPY, and ADG were -.57 +/- .16, -.63 +/- .15, and -.04 +/- .11, respectively. These h2 and rg estimates indicate that it should be possible to select for improvements in CA, IMF, and WBS. However, selection against CA may be a more suitable approach for improving meat tenderness than selection for increased IMF because the level of genetic antagonism between CA and RPY was not as great as that between IMF and RPY.

The influence of maternal nutrition on muscle fiber number development in the porcine fetus and on subsequent postnatal growth

Abstract: In the pig, undernutrition in utero causes low birth weight, a decrease in muscle fiber number, and a reduction in postnatal growth rate. The effect on fiber number is mediated via a reduced secondary fiber population. Within a litter of pigs, lighter-weight pigs have probably suffered some deficit in muscle fiber number. In an attempt to improve the number of fibers in the lighter-weight pig fetuses, four maternal feeding regimens were used, one serving as the control. Maternal feed intake was doubled for one of three time periods during pregnancy: 1) d 25 to 50 (HE) immediately before fiber hyperplasia; 2) d 50 to 80 (HL) during fiber hyperplasia; or 3) d 25 to 80 (HT) covering both developmental events. Controls were fed at levels routinely used for pregnant sows on the farm. Sows farrowed normally and pig birth weights were recorded. Estimates were made of total myofiber number, total primary fiber number, and mean secondary:primary fiber number ratio (S:P) for the semitendinosus of each pig at 5 wk postnatal or 80 kg (HT and two control litters only). The progeny of all supplemented sows had a significantly greater mean S:P ratio (P < .05), and the HE pigs tended to have a greater number of muscle fibers than control pigs (403,840 +/- 8,197 vs 370,970 +/- 12,720). Postnatal growth rate to 80 kg was also investigated for the HT group of pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

Apparent digestibility and retention of nutrients bound to phytate complexes as influenced by microbial phytase and feeding regimen in pigs

Abstract: Five barrows of approximately 45 kg BW, fitted with post-valvular T-cecum cannulas at the ileo-cecal junction, were assigned randomly to five treatments (5 x 5 Latin square design) to assess the effect of microbial phytase and feeding regimen (frequency and level) on the apparent digestibilities (total tract [ATTD] and ileal [AID]) and retention of nutrients. A corn-tapioca-soybean meal diet of low intrinsic phytase activity, containing no added inorganic P, was fed either without or with microbial phytase from Aspergillus niger var. Van Tieghem (800 phytase units/kg of diet) at different feeding frequencies (once, twice, or seven times per day) and feeding levels (2.3 vs 2.8 times the maintenance requirement for ME, i.e., 418 kJ ME/BW.75). Microbial phytase enhanced significantly the ATTD of DM, OM, CP, Ca, total P, and amino acids (except for cystine and proline). Also, the AID of total P, phytic acid, methionine, and arginine was increased (P < .05 or .01). As a consequence of adding this enzyme, the retention (grams/day) of N, Ca, and P was greater (P < .01) and their daily excretion was diminished by 5.5, 2.2, and 1.9 g/d, respectively. The feeding level exerted a minor effect on the ATTD and AID (except for methionine and cystine), although the retention (grams/day) of N, Ca, and P was greater (P < .01) at the higher level of feeding. The feeding frequency influenced significantly the ATTD of Ca, tryptophan, and isoleucine and the AID of phytic acid, cystine, arginine, isoleucine, and phenylalanine. Also, N retention (grams/day) was reduced in pigs fed once daily (P < .01).

Mechanisms associated with corpus luteum development

Abstract: The transition of a preovulatory follicle into a corpus luteum is a complex process involving mechanisms similar to wound healing and tumor formation. The objective of this review is to focus on mechanisms associated with corpus luteum development with specific attention to the follicular lineage of luteal cells, mechanisms associated with luteinization, and neovascular changes during luteal development. Corpora lutea are a continuation of follicular maturation and form from granulosal and theca interna cells. There is morphological and immunological evidence in ruminant species for the differentiation of granulosal and theca interna cells into large and small steroidogenic luteal cells, respectively. Different morphological, physiological, and biochemical characteristics of large and small luteal cells may reflect different follicular lineages with separate embryological origins. Following the preovulatory gonadotropin surge, follicular cells begin morphological, endocrinological, and biochemical changes associated with luteinization. Luteinization involves the transition of a preovulatory follicle into a highly vascular corpus luteum capable of secreting large quantities of progesterone. In addition, various cell types undergo hyperplasia, hypertrophy, and(or) migration during corpus luteum formation. An essential component of corpus luteum development is the recruitment of a blood supply. The development of a new microcirculatory bed involves breakdown of the follicular basement membrane, endothelial cell migration, endothelial cell proliferation, and development of capillary lumina. This process is regulated by the interaction of angiogenic and antiangiogenic substances. Further clarification of the preceding mechanisms may result in the development of improved methodologies for controlling the time of ovulation and(or) increasing pregnancy rates.

Function of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system in models of acute stress in domestic farm animals.

Abstract: In response to stressors, the central nervous system of livestock (and other mammalian species) evokes physiological responses that ultimately result in activation of the hypothalamo-pituitary-adrenocortical (HPA) axis and the sympatho-adrenal axis. The responses of these major systems are presumed to have adaptive and homeostatic value during periods of stress. The major hormone regulating the synthesis and secretion of adrenal glucocorticoids is ACTH. In sheep, cattle, and pigs, both corticotropin-releasing hormone (CRH) and vasopressin (VP) participate in the regulation of secretion of ACTH, and the two peptides seem to interact to enhance that secretion. In cattle and pigs, CRH is the more potent peptide, whereas VP is the more potent in sheep. In addition to its better-known role in regulating pituitary function, CRH also may participate as a neurotransmitter acting centrally to enhance sympathetic activation of the adrenal medulla. Many experimental models of stress have been evaluated that reliably activate the HPA axis and the sympatho-adrenal medullary axis, and some of these model systems also reduce functions of cells of the immune system. Recent data support an important role of stressor-activation of the sympathetics rather than increased glucocorticoids per se in modulating some measures of immune function in response to stress. Thus, current dogma of glucocorticoids as the primary mediator of stressor-associated alteration in immune function of domestic livestock may require reevaluation.

Effects of dietary fiber on intestinal growth, cell proliferation, and morphology in growing pigs.

Abstract: Growing pigs (initial BW 14.3 +/- 1.2 kg) were fed isocaloric (3.26 Mcal of ME/kg) and isonitrogenous (16% CP) diets containing either 0 (low fiber, LF; n = 4) or 10% (high fiber, HF; n = 4) wheat straw for ad libitum intake for 14 d. On d 14, each pig was injected i.v. with bromodeoxyuridine (BrdU, a thymidine analog; 5 mg/kg) and was slaughtered 1 h later. Visceral organs (liver, pancreas, and intestines) were weighed, and tissue samples were obtained. Feed consumption, daily gain, gain: feed, and final BW did not differ between treatments. Neither visceral weights nor visceral weights per unit of eviscerated BW were affected by diets. Tissue concentrations of DNA (milligrams/gram of tissue) were lower (P < .03) in HF than in LF only for jejunum, ileum, and liver. Contents of DNA and protein (milligrams) did not differ between LF and HF for intestinal segments or liver. Content of RNA (milligrams) was greater (P < .04) in HF than in LF only for colon. The number of crypt cell nuclei that were labeled with BrdU (indicating DNA synthesis and thus cell proliferation) was increased (P < .03) in HF relative to LF for jejunum and colon. The number of epithelial cells exhibiting DNA fragmentation (indicating programmed cell death) was greater (P < .07) in the HF than in the LF group for jejunum and ileum. Width of intestinal villi was increased (P < .10) in HF vs LF for jejunum and ileum. Depth of intestinal crypts was increased (P < .08) in HF vs LF for jejunum, ileum, and colon.(ABSTRACT TRUNCATED AT 250 WORDS)

Ruminal microbiology, biotechnology, and ruminant nutrition: progress and problems.

Abstract: Present methods for manipulating ruminal fermentation that involve microbial biotechnology include dietary ionophores, antibiotics, and microbial feed additives. Developments in recombinant DNA technology mean that future methods will have a much wider scope. It has been suggested that genetically engineered ruminal microorganisms will be used in future to improve ruminal fermentation. Several technical objectives must be achieved before that will be possible. First, methods for inserting foreign or modified genes into ruminal microorganisms and ensuring their efficient expression must be developed. Broad host range plasmids and transposons have been used successfully to introduce new DNA into ruminal bacteria, as have shuttle vectors constructed as chimeras of plasmids from ruminal species and Escherichia coli. Although so far only antibiotic resistance markers have been transferred, the prospects for introducing other genes into selected ruminal bacteria are excellent. Second, the expression of the gene product(s) should be known to be nutritionally useful in vivo. A few examples of this type of benefit have been demonstrated, and many more proposed, including polysaccharidases for improving fiber digestion, methods for improving the amino acid composition of ruminal bacteria, and breakdown of plant toxins. Third, the difficulty that has been examined least, yet may prove most difficult to overcome, is that mechanisms have to be found for introducing and maintaining the new strain in the mixed ruminal population. Factors governing the survival of new strains in vivo are ill-understood, and attempts to select in favor of added new organisms have so far been unsuccessful. Because of the last obstacle, it may be advantageous, at least in the short term, to use nonruminal organisms, such as Saccharomyces cerevisiae, rather than indigenous ruminal species as a vehicle for implementing the benefits of recombinant DNA technology to ruminal fermentation. Yeast is already in widespread use as a feed additive, so no enrichment is necessary; and its genetics are already well known. Alternatively, adding particular enzymes to the diet may achieve some of the objectives described above, with the advantage that the manipulation could be achieved without the release of a recombinant microorganism.

Estimation of variance components for lamb weights in three sheep populations.

Abstract: Variance components were estimated for lamb weight at birth, 50 d, and 100 d of age. Data from the Canadian flock recording program for lambs born in 1977 to 1991 for Hampshires (n = 6,395) and Polled Dorsets (n = 29,204) and 1982 to 1991 for Romanovs (n = 3,432) were studied. Observed weights were pre-adjusted for the effects of age of dam, sex of lamb, birth-rearing type, month or quarter of year of birth, parity-lambing interval, and age of dam at first lambing, using estimates derived from a fixed effects model including contemporary groups plus these factors. Pre-adjusting for nuisance variables reduced the number of equations in the model for variance component estimation. A single-trait animal model with derivative-free restricted maximum-likelihood procedures was used. Random effects were additive direct and maternal genetic, litter (common environmental), and error. An alternate model excluded maternal genetic effects. Estimates of litter variance as a proportion of phenotypic variance were of moderate size (.12 to .43) and consistent across breeds and models. The mean correlation between direct and maternal genetic effects, across traits and breeds, weighted by the number of animals, was -.40 (SE = .15). The maternal genetic variance or direct-maternal genetic covariance component, or both, was different from zero (P < .05) for all traits in Hampshires and Polled Dorsets, suggesting that maternal effects were important for weight of lambs even at 100 d of age. Estimates of direct heritability ranged from .05 to .45, varying across traits, breeds, and models.(ABSTRACT TRUNCATED AT 250 WORDS)

Prerigor and postrigor changes in tenderness of ovine longissimus muscle

Abstract: A novel approach was used to measure the tenderness of prerigor ovine longissimus thoracis et lumborum by avoiding the confounding effects of heat-induced shortening resulting from cooking prerigor meat. The objective was to determine the tenderness of the muscle at the time of slaughter and to monitor changes in tenderness during rigor development and postmortem aging. Nine Romanov and 12 Finnsheep rams were slaughtered at 49.3 kg live weight. Samples of longissimus thoracis et lumborum were removed at 0, 3, 6, 9, 12, 24, 72, or 336 h after exsanguination. Five of the eight sample times were represented in each carcass and all carcasses were sampled at 0, 12, and 24 h. Prerigor muscle samples (0, 3, 6, 9, and 12 h) were clamped between two metal plates before excision to prevent shortening. The samples were frozen at -30 degrees C then stored at -5 degrees C for 10 d to allow glycolysis to proceed to completion, and thus ultimate pH and complete rigor mortis were attained. The longissimus thoracis et lumborum was then cut into chops and cooked and shear force was determined. Sarcomere length decreased through 24 h postmortem, then increased slightly through 336 h postmortem. Warner-Bratzler shear force values were 5.1 kg at 0 and 3 h, increased to 8.3 kg from 3 to 9 h, and then declined to 3.1 kg from 24 to 336 h postmortem. These data imply that longissimus thoracis et lumborum at slaughter is intermediate in tenderness, rigor shortening toughens the meat, and proteolysis tenderizes the meat, resulting in more tender meat after 14 d of aging than at slaughter.

Heat and social stress effects on pig immune measures

Abstract: Forty-eight domestic pigs were used to evaluate the effects of heat and social stress on immune indices. Pigs were brought together in groups of three per pen and video-taped for the first 72 h. Video tapes were viewed to determine time spent in aggressive and submissive behaviors. Social status of each pig was determined from outcomes of agonistic interactions. Pens of pigs were housed in either a thermoneural (control, 24 degrees C) or heat-stress (33 degrees C) air temperature. Immune measures were determined from blood samples obtained on d 0, 7, 14, 21, and 28 after grouping. Social status had an effect (P < .05) on lymphocyte proliferation in response to pokeweed mitogen: socially intermediate pigs had a higher proliferative response than socially dominant or subordinate pigs. Many immune measures showed a significant interaction between heat and social stress over days of the study. Generally, socially dominant or submissive pigs had alterations in immune function (elevated numbers of neutrophils, decreased antibody production) compared with socially intermediate pigs. In conclusion, heat and social stress interact in their effect on the pig's immune system. Although one might have predicted immunosuppression among submissive pigs, there also seemed to be immunological costs to dominant pigs as well. These data also have implications in design of stressor research in that social behavior should be measured or controlled.

Breed differences and genetic parameters for body composition traits in beef cattle.

Abstract: The recent scientific literature was reviewed to summarize breed differences and genetic parameters for carcass traits in beef cattle. Heritability estimates were generally moderate to large, suggesting good potential for accurate genetic selection for a given individual carcass characteristic. However, effectiveness of multiple-trait selection for some trait combinations could be slowed by genetic antagonisms between traits, suggesting the use of terminal breeding systems with complementary sire and dam genetic types. Individual and maternal heterosis estimates from age-constant analyses were numerically positive for most carcass traits, although estimates from weight-constant analyses were generally nonsignificant. Potential contributions to improved carcass composition from crossbreeding would primarily result from genetic complementarity rather than heterosis. Considerable variation exists between breeds for body composition, and breed rankings vary across different traits. Studies have consistently indicated reduced meat tenderness for Bos indicus compared with Bos taurus breeds. Some differences in breed rankings for marbling vs tenderness were noted. If the U.S. beef industry shifts toward a more value-based marketing system, some genetic concerns will include 1) an apparent antagonistic relationship between marbling and cutability across breeds and within some breeds, 2) inconsistency of beef tenderness, particularly in Bos indicus cattle, 3) the effect of increased leanness on female reproductive performance, and 4) the extent to which terminal breeding systems can be used.

Effect of level of dietary neutral detergent fiber on ileal apparent digestibility and ileal nitrogen losses in pigs.

Abstract: A study was conducted with 20 barrows (average BW 25 kg) to determine the effect of various levels of neutral detergent fiber (NDF) in the diet on the apparent ileal nutrient digestibility and ileal diaminopimelic acid (DAPA) content, and consequently on the amount of ileal endogenous nitrogen. The pigs were fitted with a post-valvular T-cecal cannula. They were fed .8 kg/d of a corn starch-based semisynthetic diet formulated to contain equal amounts of protein and starch and 0, 60, 120, or 180 g of purified NDF/kg of diet, included at the expense of glucose. The purified NDF (pNDF) was isolated from wheat bran using an incubation procedure with pancreatin. Ileal digestibility of NDF was approximately 17% and was independent of the pNDF level in the diet. By increasing the amount of pNDF in the diets, apparent ileal digestibilities of dry matter (DM), nitrogen (N), neutral detergent insoluble N (NDF-N), and ash decreased linearly (P < .05). The DAPA content of the ileal digesta (g/d) was not affected by the percentage of pNDF in the diets. Calculation of the ileal bacterial N excretion indicated that more than 50% of the ileal N was of bacterial origin. With increased percentage of dietary pNDF, both endogenous and exogenous N in ileal chyme were linearly increased (P < .05). Thus, an increase in the dietary fiber content leads to a decreased apparent ileal protein digestibility due to increased ileal losses of both endogenous and exogenous protein.

Determination of apparent ileal amino acid digestibility in pigs: effect of dietary amino acid level.

Abstract: Studies were carried out to investigate the effect of dietary amino acid level on apparent ileal amino acid digestibility. Six barrows, average initial BW 35 kg, were fitted with a simple T-cannula at the distal ileum and fed six diets according to a 6 x 6 Latin square design. Six cornstarch-based diets containing six levels of CP from SBM (4, 8, 12, 16, 20, and 24% CP, respectively) were formulated. Chronic oxide was included as a digestibility marker. Each experimental period consisted of 8 d. After a 6-d adaptation period, ileal digesta were collected for 24 h during d 7 and 9 at 2-h intervals. The pigs were fed twice daily, equal amounts, at 0800 and 2000. The dietary allowance was 1,600 g/d during the first period and increased by 100 g each following period. There was a quadratic increase (P < .05) in apparent ileal amino acid digestibility as the dietary CP content was increased from 4 to 24%. Initially, the apparent ileal amino acid digestibilities increased sharply then gradually reached their plateaus, after which there were no further increases and the digestibility values became independent of the dietary amino acid levels. The lower end points of 95% confidence intervals of the plateau ileal digestibility values were defined to be the initial plateau digestibilities. The dietary CP and amino acid contents, corresponding to the initial plateau digestibility values, represent the dietary threshold levels.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of regrouping on behavioral and production parameters in finishing swine.

Abstract: Three trials involving 396 pigs were conducted to determine the effects of regrouping finishing swine (83.8 +/- .69 kg) on weight gain and behavior during the subsequent 2-wk period. The methodology between Trials 1, 2, and 3 differed primarily in the total number of pigs tested (72, 144, and 180, respectively) and the number of pigs per pen (3, 3 or 5, and 5, respectively). In all trials, like-sexed pigs were moved into a new pen location and allotted to one of three treatments: 1) a group of familiar pen mates (Control), 2) a group composed of unfamiliar pigs (Mixed), and 3) pigs mixed with strangers for 24 h and then reunited with original pen mates for the duration of the trial (Mixed 24 h). In the pooled analysis, control pigs gained faster (P < .01) than Mixed pigs (.87 and .77 kg/d, respectively) over the 2-wk period. Mixed 24-h pigs were intermediate in gain (.80 kg/d), indicating that the most severe aggression normally observed during the first 24 h accounts for only a portion of the setback. Apparently the negative social stress associated with being in the presence of unfamiliar pigs persisted beyond the first 24 h and was sufficient to limit weight gain over the 2-wk period. Time spent fighting was reduced from 1.72 min/h during a 6-h period on d 1 to .39 min/h during a 3-h period by d 2 in the Mixed group. Fighting was still observed in the Mixed pens 8 d after regrouping (.23 min/h), indicative of ongoing social conflicts.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipopolysaccharide-induced sickness behavior in pigs is inhibited by pretreatment with indomethacin

Abstract: Many of the behavioral responses following acute bacterial or viral infection are now considered important for maintaining homeostasis during inflammation. In the present study, we extend this concept to pigs (16 crossbred barrows) by demonstrating that lipopolysaccharide (LPS, .5, 5, or 50 micrograms/kg BW) from Escherichia coli injected i.p. reduces feed intake, decreases activity, and elevates body temperature. To determine whether any of these effects could be mediated via a prostaglandin (PG)-dependent mechanism, a second experiment with 16 crossbred barrows was conducted. Barrows were pretreated with indomethacin (IND, 5 mg/kg BW [a cyclooxygenase inhibitor]), and their behavior and body temperature following a challenge i.p. injection of LPS (5 micrograms/kg BW) were assessed. Pretreatment with IND inhibited the anorexia and inactivity caused by LPS, suggesting that the behavioral effects of LPS are dependent on activation of a PG system. Lipopolysaccharide alone, however, did not elevate body temperature in this case; thus, the involvement of PGs in this response was not determined. Collectively, these data indicate that pigs respond to LPS by reducing feed intake, decreasing activity, and becoming febrile. The ability of IND to inhibit behavioral effects of LPS is consistent with the hypothesis that a PG system is involved in mediating sickness behavior. Perhaps, by altering the activity of cyclooxygenase it is possible to enhance or inhibit the behavioral symptoms of sickness in pigs.

Prepartum body condition and weight influences on reproductive performance of first-calf beef cows.

Abstract: Data were collected on 476 spring-calving, primiparous cows at six locations in Louisiana over a 2-yr period. Objectives of the study were to evaluate changes in prepartum body condition score (BCS) and BW of heifers when fed varying energy levels and to determine the influences of prepartum BCS and BW changes and BCS at calving on postpartum traits. Heifers were allocated to one of three energy levels from approximately 90 d prepartum to parturition. The diets were formulated to provide low, recommended, and high energy levels based on TDN requirements. After calving, cows were placed on annual ryegrass pasture and managed similarly at each location. Weight and BCS at calving were greater (P .05) by IBCS, energy level, prepartum changes in BCS and BW, or BCS at calving. Prepartum changes in BCS and BW regulated by varying energy levels had no effect (P > .05) on postpartum reproduction; however, BCS at calving influenced (P or = 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium level affects the efficacy of supplemental microbial phytase in corn-soybean meal diets of weanling pigs.

Abstract: A 2 x 2 x 2 factorial experiment was conducted with 64 pigs (4 wk old, 804 +/- 50 kg BW) to determine the effect of various dietary concentrations of Ca, vitamin D, and microbial phytase (Aspergillus niger) on phytate-P utilization A low-P, corn-soybean meal diet was supplemented with two levels of phytase (unit/gram), 750 (suboptimal) and 1,200 (optimal); of vitamin D (international unit/kilogram), 660 (normal) and 6,660 (high); and of Ca (percentage), 4 (low) and 8 (normal) Pen feed consumption and individual pig weights, plasma inorganic P and Ca concentrations, and plasma alkaline phosphatase (AP) activity were measured at d 10, 20, and 30 The normal dietary Ca concentration had an adverse effect (P < 05) on all the response measures The depressive effect of the normal dietary Ca on performance was greater (P < 05) at the normal vitamin D level or at the optimal phytase level than at the other levels of these two factors The elevation in plasma AP activity in pigs fed the normal dietary Ca was greater (P < 05) at the suboptimal than at the optimal phytase level The decreases in plasma inorganic P concentration and increases in plasma Ca concentration associated with the normal dietary Ca were substantial In conclusion, the normal level of Ca in the diet greatly reduced the efficacy of supplemental phytase Raising vitamin D in the diet partially offset this adverse effect but did not produce further improvement when the Ca level was low

Effects of restricted feeding of growing steers on performance, carcass characteristics, and composition

Abstract: Two experiments were conducted to determine the effects of restricted feeding on performance, carcass characteristics, and composition. In Trial 1, 36 individually penned steer calves (280 +/- 13 kg BW) were fed all-concentrate diets at intake levels of ad libitum and 90 and 80% of ad libitum. Trial 2 used 36 individually penned steer calves (298 +/- 14 kg BW) fed corn silage-based growing diets for 84 d followed by 91% concentrate finishing diets. Intakes were as described for Trial 1. Compared with steers with ad libitum intake, ADG was reduced (P < .005) .15 and .25 kg for steers fed 90 and 80% of ad libitum intake, respectively, in Trial 1. In Trial 2, growing phase ADG was reduced (P < .005) .15 and .24 kg for the 90 and 80% of ad libitum feed intake, respectively. Finishing phase ADG was reduced (P < .005) .12 and .21 kg for the 90 and 80% of ad libitum intake, respectively. Feed efficiency was not affected by intake when all-concentrate diets were fed in Trial 1, or when a corn silage-based diet was fed in the growing phase of Trial 2. During the finishing phase of Trial 2, feed efficiency was increased when intake was restricted. Carcass quality grade and 12th rib backfat were reduced (P < .04) with decreases in daily feed intake when all-concentrate diets were fed. However, no effect on carcass characteristics was observed in Trial 2. Liver and heart weights were not affected by daily feed intake. Serum triiodothyronine (T3) concentrations tended (P = .11) to decrease for cattle receiving restricted intakes of all-concentrate diets and were decreased (P < .04) with intake restriction in Trial 2. Carcass fat content was reduced (P < .02), whereas carcass protein and water were increased (P < .06) with reductions in daily feed intake in both trials. We concluded that restrictedly feeding growing-finishing steer calves does not decrease feed efficiency and actually may improve feed efficiency. Restrictedly fed steers had reduced maintenance requirements, and lean tissue accretion represented a greater percentage of their total gain.

Bioavailability of zinc from inorganic and organic sources for pigs fed corn-soybean meal diets.

Abstract: Two experiments were conducted with pigs 1) to determine the effect of supplemental Zn on growth performance, bone Zn, and plasma Zn in pigs fed Zn-unsupplemented, corn-soybean meal diets and 2) to assess bioavailability of Zn from inorganic and organic Zn sources. In both experiments, weanling pigs were fed a diet with no supplemental Zn for 5 wk to deplete their Zn stores. In Exp. 1, 192 pigs were fed a corn-soybean meal diet (growing diet, 32 mg/kg of Zn; finishing diet, 27 mg/kg of Zn) supplemented with feed-grade ZnSO4.H2O to provide 0, 5, 10, 20, 40, and 80 mg/kg of supplemental Zn. Supplemental Zn did not affect weight gain, feed intake, or gain/feed during either the growing or the finishing period (P > .05). However, bone and plasma Zn concentrations increased linearly (P ZnMet > ZnO > ZnLys.

Optimum particle size of corn and hard and soft sorghum for nursery pigs.

Abstract: A total of 240 weanling pigs (22 d of age and 5.3 kg average BW) were used to determine the effects of particle size of corn and two sorghum hybrids on diet processing, growth performance, apparent digestibility of nutrients, and morphology of the stomach and intestines in weanling pigs. Treatments were corn, hard endosperm sorghum, and soft endosperm sorghum milled to particle sizes (geometric mean) of 900, 700, 500, and 300 microns, in a 3 x 4 factorial arrangement. All diets were pelleted and the pigs were allowed to consume feed and water on an ad libitum basis. As particle size was reduced, production rate (tons/hour) decreased and energy required to mill (kilowatt hours/ton) increased. Corn required more energy to mill and had a lower production rate than the sorghums. For d 0 to 14, ADG and gain/feed increased linearly (P < .009 and P < .002, respectively) as particle size was decreased to 300 microns. However, there was a grain source x particle size interaction; pigs fed corn responded to particle size reduction more than pigs fed the sorghums (P < .04). For d 0 to 35, pigs fed diets with corn grew 23% faster and were 6% more efficient (P < .001) than pigs fed diets with sorghum. Gain/feed responded quadratically to reduction of particle size (P < .01), with maximum gain/feed at 500 microns for all grains. Lowest cost of gain (including milling and ingredient costs) was achieved at 500 to 700 microns for corn and 500 microns for the hard and soft sorghums. These data suggest that response to reducing particle size is greatest during the first 2 wk postweaning and that optimal particle size for corn and sorghums increases with age of nursery pigs.

Influence of chromium picolinate on glucose usage and metabolic criteria in growing Holstein calves.

Abstract: Holstein calves, 10 steers (98 +/- 16 kg; Exp. 1) and 14 heifers (122 +/- 7 kg; Exp. 2), were fed either corn-cottonseed hull basal diets (CON; 15.1 and 13.2% CP, respectively) or CON plus 370 micrograms/kg of Cr as Cr-tripicolinate (CrP). After either 58 (Exp. 1) or 56 (Exp. 2) days of ADG and DMI measurement, calves were individually fed 1.4% of their BW every 12 h through the end of each experiment. Nitrogen balance, i.v. glucose tolerance tests (IVGTT), i.v. insulin challenge tests (IVICT), baseline growth hormone (GH) measurements, and GH-releasing hormone challenges were then performed on calves in split groups on d 70 through 87 in Exp. 1. In Exp. 2, all challenges began on d 78 and N balance was not determined. Inclusion of CrP did not affect (P > .10) ADG, DMI, or ADG/DMI of pooled data from Exp. 1 and 2 or N balance criteria in Exp. 1. Plasma glucose, insulin, and NEFA concentrations were not affected (P > .10) by CrP. Total plasma cholesterol was lower (P < .05) for CrP- than for CON-fed calves at wk 4 in Exp. 1 and wk 6 in Exp. 2. During IVGTT, calves fed CrP vs CON had higher (P < .05) clearance rates for glucose in Exp. 1 (2.68 vs 1.88%/min) and in Exp. 2 (2.64 vs 2.08%/min). During IVICT, calves fed CrP vs CON had higher clearance rates for glucose in Exp. 1 (2.98 vs 2.34%/min; P = .12) and in Exp. 2 (2.89 vs 2.00%/min; P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of mastication on digestion of whole cereal grains by cattle.

Abstract: A study was conducted to evaluate the effects of mastication on the physical breakdown and ruminal digestion of whole cereal grains by cattle. Three Hereford cows (initial BW 557 kg; SD, 17) surgically fitted with ruminal and esophageal fistulas were fed 5.5 kg/d (as-fed basis) of whole barley, corn, or wheat in an experiment designed as a 3 x 3 Latin square. Eating time and chews per kilogram of DM were greater (P < .10) for corn than for barley or wheat. Whole corn was substantially damaged after ingestive mastication, and the majority of kernels were broken into small pieces. Many barley and wheat kernels showed signs of dentition, but most kernels remained intact. Less saliva (P < .10) was added to whole wheat than to barley or corn during ingestive mastication. Cattle fed whole barley spent twice (P < .10) as long ruminating per kilogram of DM as those fed corn, with intermediate times for wheat. Less than 30% of the DM disappeared from unmasticated whole grains during 96 h of ruminal incubation. Ingestive mastication increased DM digestion to 53, 69, and 66% for barley, corn, and wheat, respectively. Mastication alters the kinetics of ruminal digestion of unprocessed cereal grains. Combined with the inherent protein and starch digestibilities of the grain, mastication affects the type and extent of processing required to optimize the utilization of cereal grains by cattle. Unlike barley and wheat, corn kernels are extensively damaged during ingestive mastication, reducing the need for physical processing.

Effect of dietary copper, iron, and molybdenum on growth and copper status of beef cows and calves.

Abstract: A study was conducted to determine the effects of copper (Cu) depletion by feeding diets high in either iron (Fe) or molybdenum (Mo) on performance and Cu status of beef cows and calves. Thirty-eight 2-yr-old beef heifers, entering the last one-third of gestation, were randomly assigned by expected calving date to one of four diets: 1) control (CON; corn silage-soybean meal-based diet, 4 mg of Cu/kg), 2) control + 600 mg of Fe (as FeCO3)/kg, 3) control + 5 mg of Mo (as Na2MoO4)/kg, and 4) control + 10 mg of Cu (as CuSO4)/kg. From d 28 until after the end of the calving season (d 125), heifers receiving supplemental Cu had higher (P < .05) plasma Cu levels and ceruloplasmin activities than heifers fed the other diets. By d 224, plasma Cu concentrations of heifers fed the CON and Fe diets had increased to levels similar to those observed in the Cu-supplemented heifers, whereas the Mo heifers exhibited the lowest (P < .05) plasma Cu of the four treatments from d 168 through the remainder of the 280-d trial. Plasma Cu concentrations and ceruloplasmin activities were greater (P < .05) in Cu-supplemented than in non-Cu-supplemented calves (diets 1, 2, and 3) from d 168 onward, and the Fe- and Mo-supplemented calves did not differ in either measurement at any time during the trial. Rate of gain did not differ among calves fed the CON, Fe- or Cu-supplemented diets, whereas the Mo-supplemented calves gained at a much slower (P < .05) rate.(ABSTRACT TRUNCATED AT 250 WORDS)