Showing papers in "Journal of Animal Science in 1988"

Carcass Composition in Mature Hereford Cows: Estimation and Effect on Daily Metabolizable Energy Requirement During Winter

Abstract: Seventy-two mature, nonpregnant, nonlactating Hereford cows (400 kg) were utilized in a comparative slaughter trial to investigate the effects of carcass composition on the metabolizable energy (ME) required for maintenance in winter. Body condition score (CS), live weight (LW) and weight:height ratio (WTHT) were evaluated and compared as estimators of carcass composition in cows. Cows ranged in LW, CS and WTHT from 275 to 595 kg, 2.0 to 8.0 units and 2.29 to 4.62 kg/cm, respectively. Live weight, CS and WTHT predicted total carcass energy (TMCAL, r2 = .81, .85 and .83), carcass fat (FAT, r2 = .78, .82 and .80), carcass protein (PRO, r2 = .71, .74 and .70) and carcass water (WAT, r2 = .78, .71 and .77) with similar accuracy. When composition was expressed on a per unit weight basis, CS was superior to LW and WTHT as predictors of TMCAL/hot carcass weight, TMCAL/LW and FAT/hot carcass weight (r2 = .82, .60 and .64; .83, .58 and .62; and .82, .64 and .68, respectively). Forty-seven cows were individually fed a complete diet (2.50 Mcal ME/dry matter) in drylot for 114 d in yr 1 and 115 d in yr 2. Daily feed intakes were adjusted each week to maintain constant LW throughout the winter. Data were analyzed by fitting the model: ME intake = k-1 (carcass energy change) + f(CS)LW.75, where k = efficiency of ME use for carcass energy change and f(CS) = function of CS. Year as a class variable and the expression .1028 + .0234(CS) - .0025(CS)2 accounted for 41% of the variation in Mcal ME for maintenance/LW.75. Condition score was more closely related to carcass composition in mature cows than was LW or WTHT and cows in either a thin (CS = 3) condition or a fat (CS = 7) condition required less (4.4% and 8.9%) Mcal ME/LW.75 for maintenance than cows in moderate (CS = 5) condition.

Effect of age, weaning and postweaning diet on small intestinal growth and jejunal morphology in young swine.

Abstract: The effect of age, weaning and postweaning diet on small intestinal growth and morphology were investigated in young swine Small intestine weight and villus height, measured at the midpoint of the small intestine (ie, jejunum), were determined in suckling and weaned pigs Scanning electron microscopy was performed on jejunal specimens from suckling pigs killed at 2, 10, 21, 28 and 35 d of age and in 21-d and 35-d weaned pigs at various ages postweaning A 2 X 2 factorial arrangement of postweaning diets also was used to investigate jejunal morphological measurements in a 21-d-old weanling pig group These dietary treatments evaluated the effects of 0 or 25% added dried whey and 0 or 6% added corn oil The morphology results demonstrated that jejunal villus height declined during the suckling period, with a marked reduction at 3 and 7 d postweaning for both 21-d-old and 35-d-old weaned pigs Transmission electron microscopy also demonstrated long, uniform microvilli on the jejunal villi in suckling pigs at 2 and 21 d, with markedly reduced lengths upon weaning Jejunal villi were shorter in weaned compared with suckling pigs at the same approximate chronological age Scanning electron microscopy in suckling pigs at 2 and 10 d of age demonstrated long, thin, fingerlike villi with subsequently reduced heights and larger diameters by 35 d of age At weaning, villi were in close apposition, resulting in an overall smoother villus luminal surface Villus height subsequently increased by 14 d postweaning, coinciding with the appearance of morphologically tongue-shaped villi Starter diet composition initially did not influence the villus height reduction response postweaning Dietary corn oil addition was subsequently associated with shortened villus length (P less than 05) during the starter phase

A review of lipoprotein cholesterol metabolism: importance to ovarian function.

Abstract: Cholesterol utilized for steroid synthesis by ovarian tissue may be derived from de novo synthesis or cellular uptake of lipoprotein cholesterol The majority of blood cholesterol is transported by either low (LDL) or high (HDL) density lipoproteins, depending on the animal species Prior to vascularization, only HDL are in follicular fluid and contribute sterol to granulosa cells because other lipoproteins are unable to transverse the basement membrane due to their molecular masses Following vascularization, both LDL and HDL bathe luteal cells Most species preferentially use LDL cholesterol as a precursor for ovarian steroid synthesis The LDL uptake by ovarian tissue occurs by receptor-mediated endocytosis The receptor recognizes apolipoprotein B of LDL and apolipoprotein E found on some, but not all, HDL Within a species, a positive relationship may exist between HDL apolipoprotein E content and importance of HDL cholesterol as a precursor for steroidogenesis A "HDL pathway" exists for uptake of sterol from HDL void of apolipoprotein E The HDL receptor exhibits broad binding specificity Unlike LDL, the HDL particle is not internalized, and cholesterol preferentially is taken up relative to other HDL constituents In most species, lipoproteins, rather than de novo synthesis from acetate, contribute the majority of cholesterol used for steroid production Trophic hormones increase lipoprotein binding, internalization, degradation and conversion of lipoprotein-derived sterol to steroids, effects that are mediate through cyclic adenosine monophosphate Knowledge recently acquired regarding lipoprotein sterol utilization by the ovary may be useful in developing nutritional, pharmacological or endocrine manipulations that may positively affect cholesterol clearance by the ovary, steroidogenesis and reproductive performance

Genotype and Sex Effects on the Relationship Between Energy Intake and Protein Deposition in Growing Pigs

Abstract: Seventy-two crossbred (Large White X Landrace) pigs were used in a 3 X 7 factorial experiment to investigate the response of two strains of boars (strains A and B) and of castrated male pigs (strain B) to seven levels of intake of a single diet (ranging from 5.3 Mcal digestible energy [DE]/d to ad libitum) between 45 and 90 kg live weight. All aspects of growth performance and body composition were affected to different degrees by both strain and sex. At all levels of energy intake strain A boars grew faster, had a lower feed to gain ratio and contained less fat and more water in the empty body than strain B boars, which in turn exhibited faster live weight gain and more efficient and leaner growth than castrated males. The magnitude of the differences in growth performance between strain A and strain B boars and castrates increased with increased energy intake above 7.88 Mcal DE/d, and these differences were associated with concomitant strain differences in their respective capacity for protein growth and in the relationship between energy intake and protein deposition. For strain A boars the rate of protein deposition increased linearly from 92 to 188 g/d with increased energy intake from 5.3 Mcal DE/d to ad libitum. For strain B boars and castrates the rate of protein deposition increased linearly with increased energy intake up to 7.88 Mcal DE/d, but thereafter it remained constant at 128 and 85 g/d, respectively. For castrates protein deposition was depressed (P less than .01) when the diet was offered ad libitum. Strain A boars had a higher energy requirement for maintenance (3.55 Mcal DE/d) than strain B boars (2.77 Mcal DE/d) or castrates (2.60 Mcal DE/d). Strain A boars also contained less protein and more water in the fat free empty body than the other two pig types.

Researching the Plant-Animal Interface: The investigation of Ingestive Behavior in Grazing Animals

Abstract: Profitable livestock production from forages largely depends on efficiency of converting forages into products. Efficient grazing management systems require an understanding of the roles of system components. However, experimentation should be conducted with regard to the system as a whole rather than on the systems components in isolation. This may necessitate development of computer models. The short-term intake of forage by grazing animals is controlled both by the structure of the forage and by effects of the ingested forage on gut fill as moderated by the hunger-satiety complex. Intake can be defined as the product of bite size, rate of biting and grazing time. Measurement of these variables is facilitated by the use of esophageally fistulated animals and automatic recording devices. Bite size has the greatest influence on intake, with rate of biting and grazing time being compensatory variables. Sward structure influences bite size to varying degrees. In temperate grass swards, leaf surface height appears to be the dominant influence on bite size. But in tropical grass swards, leaf density and leaf:stem ratio have a greater influence on bite size than does leaf surface height. Alternative techniques to conventional grazing trials are described. Diversity of environments and forages in the U.S. requires further research into the development of grazing systems. In the future, small-scale trials and computer simulation techniques likely will be used to a greater extent.

Relationship among weight change, body condition and reproductive performance of range beef cows.

Abstract: A 5-yr study involving 45 to 78 pregnant Hereford range cows each year evaluated relationships among prepartum nutrition, body condition scores, BW changes and reproductive performance. Four prepartum nutritional treatments were imposed. One group of cows were fed to maintain (M) their November BW until calving in March and April. The other three groups of cows were fed to lose about 5% of their November BW by 8 wk before parturition, then to maintain BW (LM), lose an additional 5% of their BW (LL) or gain 5% of their BW (LG). After calving, all cows were fed to maintain BW. Body condition scores and BW were recorded every 14 d throughout the trial. Linear regression analyses were conducted to examine treatment effects on BW, body condition score and measures of reproductive performance. A discriminant analysis was performed on pregnancy rate and percentage of cows with ovarian luteal activity by 85 d after parturition. The M cows had a greater pregnancy rate (71%) than cows on other treatment groups. The LL cows had a reduced pregnancy rate (42%) compared with LM (51%) and LG (58%) cows. Prepartum nutritional treatment did not affect the days from parturition to conception. Precalving body condition score and November to January BW changes influenced pregnancy rate (P less than .001). A cubic response curve described the relationship between pregnancy rate and precalving body condition score for cows with condition scores of 3 through 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicity and metabolism of pyrrolizidine alkaloids

Abstract: Pyrrolizidine alkaloids (PA) are found mainly in plants of three families: boraginaceae, Compositae and Leguminosae. In North America, PA poisoning of livestock is caused primarily by consumption of Senecio and Crotalaria spp. The PA of Senecio spp. cause irreversible hepatic damage; toxicity signs are a consequence of impaired liver function. Crotalaria intoxication leads to pulmonary damage as a primary effect; hepatic effects are less prominent. Large species differences exist in susceptibility to PA toxicosis. Small herbivores such as sheep, goats, rabbits, guinea pigs and other herbivorous laboratory animals are highly resistant to PA toxicity, associated with a low rate of hepatic production of reactive metabolites (pyrroles) and(or) a high rate of activity of detoxifying enzymes. Diester PA common to Heliotropium and Echium spp. are metabolized in the ovine rumen to 1-methyl metabolites, whereas the macrocyclic ester PA of Senecio spp. are not. Exposure to PA results in high concentrations of liver Cu, reduced liver Zn, and abnormal Fe metabolism with hematopoiesis markedly impaired. Pyrrolizidine alkaloid toxicity alters vitamin A metabolism in rats, depressing plasma and liver levels of vitamin A. Synthetic antioxidants in the diet confer protective activity in laboratory animals (e.g., rats, mice) against PA toxicoses. The PA and their metabolites are secreted in the milk of lactating animals, but this probably does not represent a significant human health hazard.

Development of Dietary Choice in Livestock on Rangelands and its Implications for Management

Abstract: Plant species that constitute forage for a given species of livestock vary tremendously throughout the diverse environments inhabited by domestic livestock. Within neurological, morphological and physiological constraints, learning early in life enables herbivores to develop preferences for or aversions to available plants and to acquire the motor skills necessary to harvest and ingest those forages efficiently. Hence, the foraging experiences of young herbivores undoubtedly affect their dietary habits as adults. Three mechanisms help young herbivores to learn efficiently to select appropriate foods: 1) food imprinting, 2) social models and 3) trial and error. Dietary habits of adults apparently are more stable than those of young herbivores. Adults accept new foods less readily, avoid foods that cause gastrointestinal distress to a greater degree, and are influenced less in choice of diet by social models than young animals are. The ability of livestock to learn dietary habits early in life presents both problems and opportunities for managers. Livestock that forage efficiently in the environment where they are reared may not forage as efficiently in a new environment. Diet training may enable managers to create a foraging group more suited to management goals. Additional research is needed to determine how age at which exposure occurs, as well as how duration, intensity, variability and complexity of exposure early in life affect dietary habits of adults. These v~riables affect the efficiency of learning and the persistence of dietary habits and thus are crucial to the development of cost-effective management based on diet training.

Comparative feeding value of supplemental fat in finishing diets for feedlot steers supplemented with and without monensin.

Abstract: Two comparative slaughter trials and a metabolism trial were conducted. Treatments consisted of: 1) 0 fat, 0 monensin; 2) 4% yellow grease, 0 monensin; 3) 0 fat, 33 mg/kg monensin and 4) 4% yellow grease, 33 mg/kg monensin. Trial 1 involved 104 crossbred beef steers (267 kg) in a 140-d comparative slaughter trial. There were no interactions (P greater than .20) between supplemental fat and monensin on steer performance. Monensin supplementation decreased rate of weight gain (P less than .10) and feed intake (P less than .05) with no effect on energy value of the diet (P greater than .20). Fat supplementation increased (P less than .01) rate of weight gain 12.5% and increased the net energy for maintenance (NEm) and net energy for gain (NEg) value of the diet 8.5 and 9.4%, respectively. Trial 2 involved 154 Holstein steers (290 kg) in a 94-d comparative slaughter trial. There were no interactions between supplemental fat and monensin (P greater than .20). Monensin supplementation did not affect rate or composition of gain (P greater than .20), but supplementation reduced (P less than .05) feed intake and feed required per unit weight gain 3.6%. Fat supplementation increased (P less than .01) fat and energy gain 12.5 and 10.3%, respectively, and the NEm and NEg content of the diet 7.5 and 8.4%, respectively. Trial 3 utilized four crossbred beef steers (220 kg) with cannulas in the rumen, proximal duodenum and distal ileum. There were no interactions between supplemental fat and monensin with respect to site of digestion (P greater than .20). Supplemental fat did not affect (P greater than .20) organic matter, starch, fiber or N digestion. Intestinal digestibility of fat averaged 77.3%. Monensin increased (P less than .10) intestinal digestibility of fat 7.4%. There were negative associative effects between supplemental fat and monensin on ruminal acetate:propionate ratios and estimated methane production. It was concluded that the feeding value of feed fat is underestimated in tables of feed standards currently in use, and that the net effects of monensin on these estimates are additive.

Pituitary porcine growth hormone (pGH) and a recombinant pGH analog stimulate pig growth performance in a similar manner.

Abstract: This study was conducted to establish the extent to which different doses of pituitary porcine growth hormone (ppGH) increase pig growth performance. Pigs were treated daily for 11 wk with 0, 35 or 70 micrograms ppGH/kg BW. In addition, these effects were compared with those produced by treating pigs with 0, 35, 70 or 140 micrograms.kg BW-1.d-1 of a recombinantly derived analog of porcine growth hormone (rpGH). This analog lacks the first seven amino acids at the NH2 terminus. Growth rate was increased similarly by ppGH and rpGH (the maximal increase was 19%). Feed efficiency was improved by ppGH and rpGH (the maximal response was 25%). This improvement in feed efficiency was associated with a decrease in feed intake (17% with the largest dose of rpGH). Both ppGH and rpGH decreased adipose tissue growth and increased muscle mass. Carcass lipid was decreased by 68% in pigs treated with the largest dose of rpGH. The recombinant pGH analog appeared to be less potent than ppGH in decreasing adipose tissue growth rate. All other parameters measured, however, indicated that rpGH mimicked the biological effects of ppGH (including binding to pig liver membranes and induction of insulin-like growth factor I production). Sensory panel evaluations indicated that neither ppGH nor rpGH affected pork palatability. Larger doses of pGH (greater than 70 micrograms/kg BW) adversely affected pig mobility. This impairment in mobility appears to be due to osteochondrosis. Our findings establish that the rpGH analog is equipotent to ppGH in stimulating growth performance and that pigs can be treated without any significant adverse effects when they are treated with less than 70 micrograms of pGH.kg BW-1.d-1.

Nycterohemeral patterns of acid-base status, mineral concentrations and digestive function of lactating cows in natural or chamber heat stress environments.

Abstract: Effects of heat stress on multiparous lactating Holstein cows were evaluated in a continuous design in natural environments (a shade management system vs no shade, n = 6/treatment, early- to mid-lactation cows) and in a single-reversal design in climatic chambers (thermoneutral vs thermal stress, n = 4/treatment, mid- to late-lactation cows). Objectives were to compare effects of nycterohemeral heat stress vs nonheat stress environments on acid-base status, mineral concentrations and rates of ruminal liquid dilution and solid phase digesta turnover. In the shade vs no shade experiment, the complete mixed diet consisted of 38% corn silage and 62% corn-based concentrate mix. In the chamber experiment, the diet consisted of 40% alfalfa haylage and 60% corn-based concentrate mix. In both experiments, respiration rates, rectal temperatures, blood and urine were sampled hourly for 26 h. Measurements of rectal temperature, respiration rate and blood gas composition indicated that chamber heat stress simulated natural heat stress. In both experiments, cows exhibited signs of respiratory alkalosis only during hours of heat stress. Ruminal turnover rates of liquid were measured with chromium-ethylenediaminetetraacetate and solid turnover rates with ytterbium-marked fecal fiber, both dosed through the ruminal cannula. Turnover rates of liquid and solid digesta and total volatile fatty acids were lower in the heat stress vs the thermoneutral environment. The results illustrate the necessity of frequent sampling to characterize nycterohemeral patterns of physiological measurements during heat stress.

Interrelationships between energy intake and endogenous porcine growth hormone administration on the performance, body composition and protein and energy metabolism of growing pigs weighing 25 to 55 kilograms live weight

Abstract: Thirty-six barrows were used in a 2 X 3 factorial experiment to investigate the effects of porcine growth hormone (pGH) administration (USDA-pGH-B1; 0 and 100 micrograms.kg body weight-1.d-1) and three levels of feeding of a single diet (EI; ad libitum, 1.64 and 1.38 kg/d) on the performance, body composition and rates of protein and fat deposition of pigs growing over the live weight phase 25 to 55 kg. Raising EI resulted in linear increases in growth rate and in protein and fat accretion but had no effect on the feed to gain ratio (F/G). Carcass fat content and carcass fat measurements also increased with EI, whereas carcass protein and water decreased (P less than .01). Growth hormone administration resulted in improvements in growth rate (16 to 26%), F/G (23%), protein deposition (34 to 50%) and increases in carcass protein and water at each level of feeding, but reduced ad libitum feed intake (P less than .01), carcass fat content (P less than .01) and carcass fat measurements (P less than .01). Estimated maintenance energy expenditure was increased by pGH administration (2.02 vs 1.72 Mcal digestible energy/d). Results indicate that the effects of pGH on growth performance and energy and protein metabolism were largely independent of, and additive to, the effects of energy intake.

Adipose tissue, longissimus muscle and anterior pituitary growth and function in clenbuterol-fed heifers.

Abstract: The present study was conducted to determine the effects of feeding clenbuterol on adipose tissue and longissimus muscle growth in heifers. For 50 d, 14 heifers were fed either a sucrose-based, clenbuterol supplement or a placebo in which the clenbuterol had been omitted. The heifers were slaughtered in two groups, based on initial weight. Adipose tissue from several anatomical sites and longissimus muscle (depending on slaughter group) were obtained fresh at slaughter. Changes in carcass characteristics elicited by clenbuterol were similar to those reported by others for steers and sheep. Subcutaneous (sc) and intramuscular (im), but not perirenal, adipocytes were smaller and there were more cells per g tissue in the adipose tissue depots of the clenbuterol-fed heifers. Clenbuterol decreased lipogenic enzyme activities, fatty acid-binding protein activity, basal lipolysis and acetate incorporation into glyceride-fatty acids (P less than .05) in sc adipose tissue, but had no effect (P greater than .05) on lipogenesis or lipolysis in im adipose tissue. Clenbuterol elicited a 20% increase in type II myofiber diameters (P less than .05) but had no effect on type I myofiber diameters. In vitro growth hormone release by perifused anterior pituitaries was not affected significantly by long-term in vivo exposure to clenbuterol. These data indicate that a depression in lipogenesis is the mechanism by which clenbuterol decreases subcutaneous fat accretion in cattle.

Selection on individual phenotype and best linear unbiased predictor of breeding value in a closed swine herd.

Abstract: Computer simulation of a closed 100-sow and 4-boar swine herd was used to analyze effects of selection method on genetic change, inbreeding and genetic variance over 10 yr for traits with heritabilities (h2) of .10, .30 and .60. Selection of replacement animals was either on individual phenotype or best linear unbiased predictor (BLUP) of breeding value using an animal model. For both methods, culling of existing breeding animals was at random on age and reproductive performance. The effect of additional culling of existing breeding animals when a replacement with better individual phenotype or BLUP of breeding value was available also was evaluated. Genetic gain was greater for selection on BLUP than on individual phenotype, but relative differences narrowed with increasing heritability. At yr 10 the relative advantage of selection on BLUP was 55% for h2 = .10, 25% for h2 = .30 and 10% for h2 = .60. Culling when a replacement with better individual phenotype or BLUP of breeding value was available resulted in considerably increased genetic progress (34% to 57%). The proportional effect of culling on rate of genetic gain was relatively independent of heritability and type of selection. Inbreeding (F) was higher with selection on BLUP (F = .27 to .38 at yr 10) than on individual phenotype (F = .17 to .22 at yr 10). As heritability increased, rate of inbreeding increased for selection on individual phenotype, but rate of inbreeding tended to decrease with increasing heritability for selection on BLUP.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of glycerol concentration, equilibration time and temperature of glycerol addition on post-thaw viability of boar spermatozoa frozen in straws.

Abstract: Experiments were conducted to study the effect of glycerol concentration, equilibration time and temperature of glycerol addition on post-thaw viability of boar spermatozoa after cryopreservation in straws. Semen (split ejaculate) in maxi-straws (6 mm o.d.) was frozen using a programmable freezing chamber. Three methods for in vitro sperm evaluation were used: motility (MOT), acrosome integrity (NAR) and flow cytometric analysis of sperm treated with carboxyfluorescein diacetate and propidium iodide to assess sperm plasma membrane integrity (PMI). No interactions were found among the three variables evaluated. Length of prefreeze exposure to glycerol, ranging from .5 min to 75 min, had no effect on post-thaw sperm viability. Exposure of sperm to a glycerol-containing extender medium at 5 degrees C gave improved post-thaw viability over that exposed at 0 degree C (P less than .05). Glycerol at a concentration of 3 or 4% resulted in maximum post-thaw MOT. Acrosome integrity values were greatest for 2 and 3% glycerol, whereas PMI was greatest when glycerol concentration was 4 to 6%. The primary cryoprotective effect of glycerol on boar semen may be extracellular. It is concluded that 3 or 4% glycerol gives maximum viability of frozen-thawed spermatozoa when the present methods are employed.

Maintenance requirements and energetic efficiency of cows of different breed types.

Abstract: Dry, nonpregnant, mature cows (greater than 10 yr) of five breeds (Angus, A; Brahman, B; Hereford, He; Holstein, Ho; and Jersey, J) and their crosses (n = 60) were used in a 428-d experiment to determine maintenance energy requirements and efficiency of energy exchange. Cows were fed individually (via Calan electronic gates) a 70% cottonseed hull diet for four consecutive periods (127, 105, 97 and 99 d) at each of four levels (50, 83, 117 and 150% of each animal's estimated maintenance requirement). Each of four cows/breed group was assigned to one of the four feeding levels each period, with one cow fed each level each period. Body composition was measured initially and following each period in all cows via D2O dilution with a two-pool kinetics model procedure. Average ending live weight and empty body weight, protein and fat were similar to beginning values, indicating that cows began and ended in similar body composition. Dry matter digestibility (DMD) following the last period averaged 54.7%. Average DMD was 53.5, 57.8, 52.0, 55.0 and 51.7% (standard error of mean [SE] = 2.1) for A, B, He, Ho and J; values for He and J were lower (P less than .05) than for B. Diet digestible energy (DE) was similar for all breed types and averaged 62.4% of gross energy (GE). A small decrease in DE with increasing GE intake was noted for all breed types. The daily metabolizable energy requirement for weight equilibrium for A, B, He, Ho and J differed (P less than .01) and was 100, 98, 108, 119 and 152 kcal/kg.75 (SE 4.8), respectively, with an overall mean of 107. The ME for maintenance (MEm) was 91.6, 93.8, 95.3, 115.7 and 140.4 kcal/kg.75 for A, B, He, Ho and J (SE 6.0), respectively, with an overall mean of 101.9. Efficiency of weight change for A, B, He, Ho and J differed (P less than .01) and was 116, 135, 80, 116 and 58 g/Mcal ME intake, respectively, with an overall mean of 96. The respective efficiency of ME use for tissue energy gain or loss was 80.6, 66.8, 66.0, 36.5 and 36.2% for A, B, He, Ho and J, with an average energetic efficiency of 60.1%. In general, maintenance requirements for weight and energy equilibrium were lower in beef breeds and their crosses than in dairy breeds and their crosses. Efficiency of ME use also favored the beef breeds over the dairy breeds.(ABSTRACT TRUNCATED AT 400 WORDS)

Relationships between nutritive quality and fiber components of cool season and warm season forages: a retrospective study.

Abstract: Feeding trials were conducted with 428 forages in three forage classes (C3 grasses, legumes, C4 grasses) fed ad libitum to sheep and with 170 forages fed to cattle over a 20-yr period. Of this total, 153 forages were fed concurrently to sheep and cattle. Where the same forages were fed, mean dry matter digestibility (DMD) and dry matter intake (DMI) were lower (P less than .01) for sheep than for cattle, with significant effects of forage class. With the main population of forages, the regression of DMI on DMD was positive and curvilinear (P less than .01) for sheep, with no effect of forage class, and positive and linear (P less than .0001) for cattle, with a significant effect of class. For all forages, correlations between DMI and neutral detergent fiber (NDF) concentration were -.57 for sheep and -.41 for cattle; regressions differed (P less than .05) with class and animal species. Correlations of DMD with NDF and acid detergent fiber (ADF) concentrations were -.45 and -.59 (P less than .01), respectively, for sheep, and -.32 and -.39 (P less than .01) for cattle; again, regressions differed significantly with class and animal species. Within forage class, regressions of DMD and DMI on fiber components generally were linear. Intake of NDF (NDFI) was related to NDF percentage for all forages by a quadratic regression, with significant differences due to animal species and forage class. Results indicate that relationships between DMD, DMI and fiber fractions differ between forage classes and animal species, that C4 grasses are consumed at levels higher than would be expected from their DMD and fiber concentrations and that ruminants increase NDFI in response to higher NDF concentrations in the forage.

Local and general anesthetic effects on behavior and performance of two- and seven-week-old castrated and uncastrated piglets

Abstract: Four experiments were conducted to examine the effects of general and local anesthetics given prior to castration on piglet behavior and weight gain. The first experiment showed that use of general anesthesia by xylazine, ketamine hydrochloride and glyceryl guaiacolate for 2-wk-old piglets resulted in the death of 28% of the piglets and, for those that survived, suppressed nursing behavior. In the second experiment, using 2-wk-old piglets, local anesthesia by lidocaine hydrochloride prevented the slight (30 min) castration-induced nursing behavior suppression. In the third and fourth studies, using 7-wk-old pigs, local or general anesthetic did not overcome castration-induced changes in behavior. Castration affected behavior of 7-wk-old pigs for 6 to 8 h. None of the treatments in any of the studies influenced weight gain. We conclude that castration is painful for 2-wk-old and 7-wk-old pigs. The 2-wk-old pig seems behaviorally less affected by castration than does the 7-wk-old pig. Local anesthetic prevented pain-induced behavior changes for 2-wk-old, but not for 7-wk-old, pigs. At present, the FDA does not permit use of these anesthetics in meat-producing animals.

Effect of dietary fiber on young adult genetically lean, obese and contemporary pigs: body weight, carcass measurements, organ weights and digesta content.

Abstract: Twenty-one genetically lean, obese or contemporary barrows (6 mo old; seven of each genotype) were assigned to individual tether stalls and fed a control diet (low-fiber) or a diet containing 80% alfalfa meal (high-fiber) at 1.50% of initial body weight for 71 d (1.75% for d 1 to 4). Backfat thickness was recorded ultrasonically at 2-wk intervals, and body weight was recorded at the beginning and end of the 10-wk experiment. Pigs were slaughtered after a 24-h fast, and carcass weight, length and backfat thickness and cross-sectional area of the longissimus muscle were measured. Weights of cecum, heart, liver and kidney and of full and empty stomach and colon and empty small intestine were recorded. Volume and weight of colon and cecum contents were determined. Restriction of digestible energy reduced weight gain to zero or below in pigs fed alfalfa meal compared with 220 g daily in pigs fed the low-fiber diet. Restriction of energy reduced backfat in all three genotypes. Liver, kidney and empty segments of the gastrointestinal tract as a percentage of body weight were increased by high fiber. Obese pigs had smaller longissimus muscle area, more backfat and smaller liver, heart, empty stomach and colon than lean or contemporary pigs, but there were no diet X genotype interactions for any of these traits. Obese pigs consistently had smaller digesta volumes and dry matter weights than the other genotypes. The increased relative organ weights and the associated disproportionate contribution of these organs to body energy expenditure have important implications for effects on basal metabolic rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Losses to internal parasites in swine production.

Abstract: Experimental infections of pigs with Strongyloides ransomi, Stephanurus dentatus, Ascaris suum, Oesophagostomum spp. or Trichuris suis at increasing levels generally decrease daily gain and increase feed to gain ratio linearly. At lower, subclinical levels of infection, the feed to gain ratio typically is increased 3% to 6% by an infection. Based on low-level experimental infections with A. suum, the economic loss to producers in the U.S. from increased feed to gain ratio is estimated at $155 million annually.

Large Particle Breakdown by Cattle Eating Ryegrass and Alfalfa

Abstract: The proportion of large particles (LP) broken down to small, insoluble particles by primary mastication (eating), rumination, digestion and detrition (rubbing) was determined for separated leaf and stem fractions of perennial ryegrass (Lolium perenne) and alfalfa (Medicago sativa) fed to cattle cannulated at the esophagus. Large particles were defined as those particles retained during wet sieving on a screen with an aperture of 1.18 mm. Reduction in weight of particles caused by solubilizing or digestion was not considered to be particle breakdown per se, and particles were corrected for this loss in weight. The proportion of LP in the forage broken down by primary mastication was 25 +/- 1.9% (means +/- SE). Breakdown of LP by rumination was calculated from the weight of total particles regurgitated and the proportion of LP in the regurgitated and swallowed remasticated material. The weight of LP regurgitated was corrected for the dry matter lost by digestion using lignin ratio in the LP entering the rumen and of the regurgitated digesta. Rumination accounted for 50 +/- 1.5% of LP breakdown. Fecal loss accounted for 8 +/- .8% of the LP in forage. Breakdown of LP by digestion and detrition was calculated as 17 +/- 1.3% from the difference between the LP eaten and those broken down by primary mastication, rumination and passing out in the feces. The significance of these results for predicting voluntary intake from laboratory analysis is considered.

Effect of dietary energy source and level on serum growth hormone, insulin-like growth factor 1, growth and body composition in beef heifers.

Abstract: Effects of fiber vs starch energy supplements on endogenous growth hormone (GH), insulin-like growth factor (IGF-1) and animal performance from weaning to breeding age were evaluated in 18, 9-mo-old beef heifers. Heifers had ad libitum access to wheat silage plus an average daily supplement intake of 1) 4.08 kg corn-soybean meal (SBM) (high energy-starch, HS), 2) 4.54 kg soyhulls (SH)-SBM (high energy-fiber, HF) or 3) 1.36 kg SH-SBM (low energy-fiber, LE). Serum samples were collected via jugular puncture every 10 d and were analyzed for IGF-1 by RIA. On d 45 and d 176, four heifers per treatment were fasted 18 h and serial blood samples collected via jugular cannulas every 15 min for 6.5 h. Arginine (.5 g/kg BW) was administered intravenously (ARG) to induce release of GH, and four additional samples of blood were collected. Samples were analyzed by RIA for GH. Mean fasted GH (6.4 +/- .4, 8.3 +/- .4 and 13.8 +/- .4 ng/ml for HS, HF and LE, respectively) varied with energy source and level (P less than .01). Mean GH following ARG was higher (P less than .01) in heifers receiving LE (46.2 +/- 4.7) than in those receiving HS and HF (23.5 +/- 4.4 and 24.1 +/- 4.6 ng/ml). Basal GH concentration and peak amplitude were higher (P less than .05) in LE than in HS and HF treatments. Diet did not influence number or frequency of GH peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

Weekly digestibilities of diets supplemented with corn oil, lard or tallow by weanling swine.

Abstract: Two experiments were conducted to evaluate supplementation of diets with 8% corn oil, lard or tallow. In Exp. 1, 36 barrows weaned at 21 d of age were used to evaluate the effects of these three diets on digestibilities of fat and dry matter and subsequent N retentions from wk 1 to 4 postweaning. In Exp. 2, 147 weanling pigs in six replicates were used to evaluate weekly growth and feed performance measurements when fed these same diets for a 4-wk postweaning period. A large quantity of fat was absorbed (P less than .01) during wk 1 postweaning by pigs fed the corn oil diet, with the quantity absorbed similar for the three sources of fat from wk 2 to 4. Diets with corn oil had a higher apparent fat digestibility than diets supplemented with lard or tallow during each week postweaning (P less than .05). Apparent digestibility of fat increased (P less than .01) for each fat source each week postweaning but appeared to reach a plateau by wk 3 postweaning. Differences in apparent digestibility of fat between fat sources narrowed from wk 1 to wk 4, with digestibility of corn oil increasing from 79 to 89% and of animal fat sources increasing from 67 to 84%. Apparent digestibility of dry matter tended (P less than .10) to be highest when corn oil was provided during the initial 2-wk postweaning period. Although N retention was highest during wk 1 postweaning when the corn oil was fed, this response was attributed to the higher feed intakes of pigs fed this diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of Cornual Insemination on Conception in Dairy Cattle

Abstract: The objective of this study was to compare conception to artificial insemination (AI) services in dairy cattle when semen was deposited into the uterine body or into both uterine horns (cornual insemination). Nine herdsman inseminators (HI) in four commercial dairy herds in Washington constituted the experimental units. Herds ranged in size from 393 cows to 964 cows. The duration of the experiment was 12 mo in three herds and 18 mo in the fourth herd. At the beginning of the experiment all inseminators were trained to deposit semen in the body of the uterus. Inseminators were instructed to use this method for 6 mo. Following employment of body deposition, the same inseminators were retrained to deposit one-half of the semen into the right uterine horn and one-half into the left uterine horn. Cornual inseminations were performed for 6 mo. A total of 4,178 services constituted the data set. Milk samples were collected from cows on the day of insemination and later were assayed for progesterone (P4). There was variation (P less than .01) in conception associated with month of insemination and insemination method (P less than .001). The monthly variation was not associated with season of the year. Least squares means for conception when semen was deposited in the uterine body was 44.7%, compared with 64.6% when cornual insemination was employed. The insemination treatment X inseminator interaction was not significant. Results suggest that cornual insemination provides an alternative to deposition of semen in the uterine body.

Effects of additives on in vitro ruminal fermentation: a comparison of monensin and bacitracin, another gram-positive antibiotic.

Abstract: Mixed ruminal bacteria (n = 4) were incubated in anaerobic media for 24 h in vitro with either hay, corn meal, protein hydrolyzate or hydrogen gas as the substrate. The ionophore monensin and the polypeptide antibiotic bacitracin were added to the incubation flasks at concentrations ranging from 0 to 10 or 40 mg/liter. As was expected, monensin decreased methane production, increased the ratio of propionate to acetate and decreased the deamination of amino acids. Monensin had little effect on methane production, however, if hydrogen gas was the fermentation substrate. Bacitracin, another gram-positive antibiotic with a distinctly different cellular target, was somewhat less potent than monensin, but it produced strikingly similar responses. This similarity of fermentation patterns suggested that monensin action in the rumen is probably due to its activity as a gram-positive antibiotic, and that any gram-positive antibiotic not suppressed by resistance may produce fermentation effects similar to those of monensin. The cellular action of monensin as an ionophore in membranes is probably little more than a means of inhibiting sensitive species. Many gram-positive antibiotics have little affect on ciliate protozoa or coccidia.

Fumaric and citric acids as feed additives in starter pig diets: effect on performance and nutrient balance.

Abstract: The effect of dietary citric acid (CA) and fumaric acid (FA) on pig weight gain (ADG) and gain/feed (G/F) was studied in two trials using 192 crossbred, 4-wk-old weaning pigs. Three dietary levels (0, 1.5 or 3.0%) of either FA (Trial 1) or CA (Trial 2) with or without an antibiotic supplement (110 mg chlortetracycline, 110 mg sulfamethazine and 55 mg penicillin/kg diet) formed six treatment combinations in each trial. These six diets were fed to two replicate pens of eight pigs each for a 4-wk period. In Trial 1, ADG was improved (P less than .01) during wk 1, and G/F was improved during wk 1 (P less than .01) as well as during wk 1 to 2 (P less than .05) for pigs consuming FA-supplemented diets. In Trial 2, CA had no beneficial influence on ADG during the 4-wk trial. However, feed intake during wk 1 was depressed (P less than .05) by adding CA, as was G/F during wk 1 to 2 (P less than .05). Based on these results, FA was selected to be used in a nutrient balance study. Twelve 4-wk-old weanling pigs were fed one of three diets: control (C), C + 1.5% FA, or C + antibiotic supplement (A). Diet digestible energy (DE), ME and N-corrected ME (MEN) were not different among treatments. Nitrogen balance, percentage N retained and apparent N digestibility were not affected by dietary treatment. Calcium balance and percentage of Ca retained were unaffected by diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of transport stress on concentrations of cortisol, corticosteroid-binding globulin and glucocorticoid receptors in pigs with different halothane genotypes.

Abstract: Effects of stress on concentrations of cortisol and corticosteroid-binding globulin (CBG) in blood plasma and on glucocorticoid receptor concentrations in muscle cytosol were studied in pigs representing three Halothane (Hal) genotypes (NN, Nn, nn). At 12 wk of age, animals were divided into four groups: pigs subjected to transport (5 h in a truck), pigs treated with amperozide prior to transport, pigs not transported but treated with amperozide and pigs neither transported nor given amperozide. Animals were slaughtered the week they reached 100 kg live weight (3 mo later). The Hal gene showed no major influence on the variables studied except for cortisol concentrations (P = .06) measured directly after transport at 12 wk of age (NN = 66.8 nM, Nn = 61.4 nM, nn = 69.4 nM). However, the response in each Hal genotype differed, depending on whether or not the pigs had been exposed to transport. Two weeks after transport, NN pigs developed higher cortisol concentrations than untransported animals, whereas the response was reversed in nn animals; Nn pigs showed no difference in this regard. At slaughter, the effect of transport (12 wk of age) on cortisol and CBG was still apparent. In NN pigs cortisol and CBG concentrations were elevated (P less than or equal to .05, P = .08, respectively), whereas concentrations tended to be lower in nn pigs (P = .17, P = .07, respectively) when compared with untransported pigs. Transported pigs had lower receptor concentrations at slaughter (P less than or equal to .01) than untransported pigs. However, pigs given amperozide in connection with transport had a receptor concentration comparable to that in untransported pigs. Our study shows conclusively that transport stress had long-term effects on cortisol, CBG and glucocorticoid receptor concentrations. In addition, amperozide had long-term effects on cortisol and receptor concentrations.