Showing papers in "Journal of Animal Science in 1990"

Physiological mechanisms controlling anestrus and infertility in postpartum beef cattle.

Abstract: Postpartum infertility is caused by four factors: general infertility, lack of uterine involution, short estrous cycles and anestrus. The general infertility component is common to any estrous cycle and reduces potential fertility by 20 to 30%. Incomplete uterine involution prevents fertilization during the first 20 d after calving but is not related to anestrus. Short estrous cycles prevent fertility during the first 40 d after calving by causing the cow to return to estrus before pregnancy recognition occurs. Anestrus is the major component of postpartum infertility and is affected by several minor factors: season, breed, parity, dystocia, presence of a bull, uterine palpation and carryover effects from the previous pregnancy as well as two major factors: suckling and nutrition. These major factors have direct effects on anestrus but also interact with one or more other factors to control postpartum anestrus. Physiological mechanisms associated with anestrus involve blockage of the GnRH "pulse generator" in the hypothalamus, but other pathways also must be involved because bypassing the pulse generator is not an effective treatment for all cows. The primary cause of anestrus probably is different for different stages of anestrus. The mediating mechanisms for anestrus are not involved with prolactin, oxytocin, the adrenal or direct neural input from the mammary gland but are at least partially involved with blood glucose and the endogenous opioid peptide system. Management options to decrease the impact of anestrus and infertility include: 1) restrict breeding season to less than or equal to 45 d; 2) manage nutrition so body condition score is 5 to 7 before calving; 3) minimize effects of dystocia and stimulate estrous activity with a sterile bull and estrous synchronization; and 4) judicious use of complete, partial or short-term weaning.

Nutrition and postpartum rebreeding in cattle

Abstract: Body weight and condition score, although perhaps imprecise or subjective, are functional indicators of energy status and rebreeding performance after calving. Inadequate precalving and(or) postcalving energy or protein nutrition lowers pregnancy rates as well as first-service conception rates and extends postpartum intervals in suckled postpartum beef females. Normal nutritional regimens for dairy cows that are fed for maximal lactation do not exhibit long postpartum intervals or reduced fertility. Yet excessive protein intake may depress postpartum rebreeding performance, especially in older dairy cows. Feeding of ionophores, with increased ruminal propionate levels in the rumen, results in an earlier return to estrus postpartum. Underfeeding of the postpartum cow extends the period of ovarian inactivity. The underfed postpartum cow's lack of ovarian activity appears to be due to a suppression of the pulsatile release of LH from the anterior pituitary gland, which in turn is controlled by release of GnRH from the hypothalamus. Some metabolic compound(s) presumably act on the hypothalamic-pituitary-ovarian axis as the nutritional state of the animal is altered.

A review of synchronization of estrus in postpartum cattle.

Abstract: Estrus has been synchronized in cattle with progestogens, prostaglandins (prostaglandin F2 alpha and its analogues), progestogen-estrogen combinations and progestogen-prostaglandin combinations. Progestogens administered for 14 to 20 d are effective in synchronizing estrus; however, fertility at the synchronized estrus is subnormal. Duration of progestogen treatment can be reduced by combining it with an estrogen. Syncro-Mate B is a progestogen-estrogen combination that results in a tightly synchronized estrous response. Prostaglandins can be used in double- or single-injection programs. Fertility of the estrus after prostaglandin treatment is similar to that of controls. Estrus also has been synchronized effectively by combining a 5- to 9-d progestogen treatment with prostaglandin at or near the end of treatment. When prostaglandin is used alone, cattle in the late stages of the luteal phase (d 11 to 15 of the estrous cycle) at the time of prostaglandin injection have a higher estrous response and may be more fertile than those injected with prostaglandin in the early part (d 6 to 9) of the luteal phase. More recently, a 14-d progestogen treatment has been combined with a prostaglandin injection given 16 to 18 d after progestogen withdrawal. This system places cattle in the late luteal phase of the estrous cycle at the time of prostaglandin injection and has resulted in an estrus with greater fertility than that immediately following progestogen treatment.

Evaluation of attributes that affect longissimus muscle tenderness in bos taurus and bos indicus cattle

Abstract: Biological tenderness differences between longissimus muscles (LM) from Bos indicus and Bos taurus breeds were evaluated. Steers and heifers of Hereford x Angus (H x A, n = 10), 3/8 Sahiwal x H, A or H x A (3/8 SAH, n = 6) and 5/8 Sahiwal x H, A or H x A (5/8 SAH, n = 11) crosses were utilized. Muscle temperature and pH were monitored every 3 h for the first 12 h and at 24 h. Samples were obtained within 1 h and at 24 h postmortem from the LM for determination of calcium-dependent protease (CDP) -I and -II and CDP inhibitor (INH) activities. At 1 and 14 d postmortem, LM samples were removed for determining cathepsin B and B + L activity, soluble and total collagen, sarcomere length, muscle-fiber histochemistry, shear force and sensory-panel traits. Data were analyzed using least squares procedures with fixed effects of breed cross, sex and their interaction. No significant breed cross effects were observed for carcass traits or rates of pH and temperature decline. Steaks from H x A had lower (P less than .05) shear-force values and higher (P less than .05) sensory scores for tenderness at 1 and 14 d postmortem than steaks from 3/8 and 5/8 SAH. Correspondingly, 5/8 SAH had lower (P less than .05) myofibril fragmentation indices than H x A at 1, 3, 7 and 14 d postmortem. Breed cross effects were not significant for sarcomere length, fiber types, soluble and total collagen, cathepsin B and B + L specific activity, CDP-I and -II activity and INH activity within 1 h postmortem. However, INH total activity/100 g of muscle was greater (P less than .01) at 24 h postmortem for 5/8 SAH (208.8 +/- 14.8) and 3/8 SAH (195.6 +/- 19.3) than for H x A (136.3 +/- 14.9). For H x A, SDS-PAGE revealed that by d 1 desmin had been subjected to proteolysis, and by d 14 desmin could not be detected, but a 30,000-dalton component was clearly evident. However, in 5/8 SAH, desmin remained visible at d 14 without a 30,000-dalton component appearing. This reduced protein hydrolysis may account for less tender meat in SAH; INH apparently influences this process.

Suckling as a regulator of postpartum rebreeding in cattle: a review.

Abstract: An extended and variable period of anovulation and anestrus occurs in suckled beef cows following parturition. This imposes both biological and economic constraints on the efficiency of beef production. A large body of knowledge has linked these phenomena to an attenuation of neuroendocrine signals that subserve gonadal function. During late gestation, high concentrations of placental estrogen inhibit the synthesis of LH, and pituitary stores of LH are depleted at parturition. Maximum pituitary stores of LH, releasable pools of LH and the ability of hypothalamic centers to respond to positive feedback effects of estradiol occur within 3 to 4 wk after calving in suckled cows. However, the requisite pattern of pulsatile LH secretion, which accompanies similar changes in nonsuckled cows within 2 to 3 wk after calving, occurs in only 30 to 50% of suckled animals. The period of acyclicity that continues in the remainder is exacerbated by poor body condition and may persist in some females for periods exceeding 100 d. Utilizing data from the cow, as well as other species, a model for suckling-induced inhibition of pulsatile LH release is proposed. The biological and economic impact of current and future techniques for controlling suckling-induced anestrus also is considered, including a conceptual analysis of nonbiological limitations.

Effects of feeds on flavor of red meat: a review.

Abstract: The effects of diet ingredients on red meat flavor are dependent on the type of diet, and, to a large extent, on the species: pork, mutton or lamb and beef Sensory analysis of meat flavor has been used in most of the studies on the effects of feeds on meat flavor In general, high-energy grain diets produced a more acceptable or a more intense flavor in red meats than low-energy forage or grass diets Feeding pigs unsaturated fats increases the unsaturation in pork fat but results in only minor changes in pork flavor Sheep must be fed protected, unsaturated fats in order to increase the unsaturation in their fat to be similar to pork fat This increased unsaturation results in a greater flavor change in lamb or beef than in pork Several dietary ingredients such as fish products, raw soybeans, canola oil and meal, and pasture grasses cause undesirable flavors in red meat Analyses of lamb and beef produced on different diets have shown that type of feed affects the concentration of many flavor volatile compounds However, only a few studies have quantified the volatiles of beef and lamb produced on different diets, and no reports of studies were found in which the volatiles of pork produced on different diets had been investigated Hence, the importance of these changes in volatile concentration to meat flavor has not been determined

Transient hypersensitivity to soybean meal in the early-weaned pig.

Abstract: An experiment was conducted to determine whether baby pigs develop hypersensitivity to dietary soybean proteins. Thirty-two pigs were orally infused with either dried skim milk (5 g/d; control) or soybean meal (48% CP; 5 g/d) from d 7 to 14 after birth. Sows were fed a corn-corn gluten meal-based diet supplemented with lysine and tryptophan to avoid exposure of pigs to soybean proteins. Pigs were weaned at 21 d of age and fed diets containing either soybean meal or milk proteins until d 56. One half of the pigs were killed at 28 d of age and the rest at 56 d of age. Segments of small intestine were collected, and intraepithelial lymphocytes were isolated. At 28 d of age, pigs fed diets containing soybean meal had lower (P less than .05) villus height (221 vs 298 microns) and rate of gain (86 vs 204 g/d) than control pigs did. Pigs fed a diet containing soybean meal had higher (P less than .05) immunoglobulin G (IgG) titers to soybean protein than did pigs fed a milk protein-based diet. Blood and intestinal lymphocytes collected on d 28 and 56 did not exhibit any proliferative response when cultured with purified soy proteins (2.5 or 5 microns/ml). Phytohemagglutinin- and pokeweed mitogen-induced lymphocyte proliferations were higher (P less than .05) at d 56 than at d 28, but there were no differences attributable to protein source. There were no differences (P greater than .05) in skin-fold thickness measurements following intradermal injection with soy or milk proteins. Decreased villus height and increased serum IgG titers to soybean proteins coinciding with inferior performance of early weaned pigs fed diets containing soybean meal indicate that conventionally processed, commercial soybean meal may retain some antigens that can cause transient hypersensitivity in piglets.

Effects of microbial supplements containing yeast and lactobacilli on roughage-fed ruminal microbial activities

Abstract: Effects of two microbial feed supplements on microbial activities in rumen-stimulating cultures and the rumens of steers fed a fescue hay-based roughage diet were evaluated. The yeast culture supplement contained Saccharomyces cerevisiae (1.4 to 4.2 x 10(9) colony-forming units [cfu]/g), whereas the mixed microbial supplement contained yeast, lactobacilli and enterococci (1.4 to 2.7 x 10(9) cfu/g, 1.2 to 2.3 x 10(9) cfu/g, and 1.5 to 2.6 x 10(10) cfu/g, respectively). Concentrations of viable yeast cells were increased consistently in continuous cultures and rumens of steers receiving either supplement (1 g/kg of feed). However, neither supplement consistently altered the relative concentrations of volatile fatty acids or ammonia in continuous cultures and rumens of steers. The pH tended to be greater (P = .13) in continuous cultures receiving yeast culture supplement than in cultures receiving the unsupplemented diet (6.50 vs 6.36), but pH in the rumens of steers was not affected by the supplements. Concentrations of cellulolytic microorganisms in cultures and the rumens of steers receiving supplements containing only yeast were from 5 to 40 times greater than those observed in cultures or steers receiving the unsupplemented diet. Supplements that had been treated with heat (121 degrees C for 15 min) to inactive yeast cells did not alter the concentrations of cellulolytic bacteria in rumen-stimulating cultures. These results suggest that live yeast culture supplements stimulate growth of cellulolytic microorganisms in the rumen.

Effects of body composition, pre- and postpartum energy level and early weaning on reproductive performance of beef cows and preweaning calf gain.

Abstract: Mature Charolais x Angus rotational cross cows were adjusted to moderate body condition by d 190 of gestation then randomly blocked to a maintenance (ME) or low-energy (LE) diet At parturition, the 128 cows were randomly allotted within prepartum (PRP) diet to a high-energy (HE) or LE diet At d 30 postpartum (PP), cows were randomly blocked to two treatments in which calves were weaned early (EW) or normally (NW) at 7 mo of age Cows receiving a LE PRP diet had lighter calves at birth (347 vs 390 kg) and 105 d (1279 vs 1446 kg) Prepartum and PP energy interacted to affect postpartum anestrous interval (PPI, d) and cycling activity (%), respectively (LE-LE = 726, 333; LE-HE = 543, 563; ME-LE = 657, 529; ME-HE = 684, 543) High PP energy averaged over PRP diet increased (P less than 10) pregnancy rate by 227% and 105-d calf weight by 151 kg Early weaning reduced PPI by 243 d (P less than 01) and first service conception rate by 217% (P less than 10) Cycling activity within 60 d PP was affected (P less than 01) by PRP diet and suckling status (LE-EW = 625, LE-NW = 267, ME-EW = 889, ME-NW = 133%) Thin cows had a longer PPI but had a higher first service conception rate than moderate and fleshy cows Higher pregnancy rates were observed in cows approaching or maintaining average body condition from parturition to conception than for cows moving away from moderate body condition Results suggest that fleshy and thin cows at parturition should be managed to approach moderate body condition before the breeding season to optimize reproductive performance and preweaning calf gain

Energy utilization in pregnant and lactating sows: modeling of energy requirements'

Abstract: Data on energy metabolism and body composition changes of the pregnant and lactating sow have been considered in order to propose methods for determination of energy requirements according to a factorial approach. Daily requirements for maintenance at thermoneutrality amounts to about 105 and 110 kcal ME& BW7’ in pregnant and lactating sows, respectively. During pregnancy, maintenance represents 75 to 85% of the total requirements and is affected greatly by environmental temperature and activity of the animals. Requirements for total uterine gain are low, but they increase with advancement of pregnancy. In addition, the daily ME requirements during pregnancy depend on the amount and composition of maternal weight gain and on the previous lactation body weight loss. The factorial approach indicates clearly that daily ME recommendation in pregnant sows varies from 6 to more than 10 Mcal and must be adapted to each sow within a herd. A method for prediction of ME requirements in lactating sows that considers a relatively precise estimate of energy output in milk is proposed. Results indicate that daily ME requirements are particularly high (15 to more than 20 Mcal) and generally are not met by voluntary feed intake. Emphasis also has been given to prediction of body composition changes that occur over the reproductive life of the sow. Data from the factorial approach allow for optimization of sow energy nutrition to ensure a normal evolution of body weight changes and to avoid major changes in body weight and composition. However, no available data demonstrate whether such a strategy is concomitant with optimal lifetime

Severity of liver abscesses and efficiency of feed utilization of feedlot cattle.

Abstract: Relationships of gain, intake, feed efficiency and severity of liver abscesses were evaluated in 12 experiments involving 566 head of individually fed cattle. Concentrate level in the diets ranged from 64 to 95%. In all experiments, livers were scored as unabscessed (0), one or two small abscesses (A-), two to four small active abscesses (A) or one or more large, active abscesses (A+). Based on homogeneity of variances, nine of the experiments were divided into two groups. In one group (four experiments) the incidence of liver abscesses was 32.1% and no significant (P greater than .25) effects of liver abscess severity score on feedlot performance variables were found. In the second group (five experiments), the incidence of liver abscesses was 77.7%. In the second group, liver abscess severity score affected final live weight (P less than .10), hot carcass weight (P less than .0001), dry matter intake (P less than .10), daily gain based on live weight recorded 24 h prior to slaughter (P less than .10), daily gain based on live weight estimated from hot carcass weight with a 62% dressing percentage (P less than .0001), feed efficiency using final live weight estimated from hot carcass weight (P less than .0001) and dressing percentage (P less than .01). In all cases, performance means for cattle with A+ liver scores were the only ones that differed significantly from those of non-abscessed cattle.

Energy cost of absorption and metabolism in the ruminant gastrointestinal tract and liver : a review

Abstract: Contributions of various biochemical processes to overall energy expenditure in the gastrointestinal tract (GIT) and liver have been assessed in this review. The GIT and liver are responsible for a disproportionately high fraction of whole-body energy utilization. The energetic cost of Na+, K(+)-ATPase, protein synthesis and degradation, substrate cycling and urea synthesis contribute substantially to energy expenditure in the ruminant. In the splanchnic bed, these biochemical processes account for approximately 22.8% of whole-body O2 and, consequently, ATP utilization; they are influenced by several factors, including dietary composition, level of intake, age, endocrine status and physiological state. In the GIT and liver, the energetic cost of Na+, K(+)-ATPase is by far the most energetically demanding process; it is related to the active transport of substrates and the maintenance of ionic homeostasis. The high rate of protein synthesis in the GIT is associated with cellular turnover and sloughing, secretion and enzymatic action. In the liver, protein synthesis is important in the mediation of hormonal induction, which influences regulation of body systems, synthesis of plasma proteins, enzymatic and cellular turnover and detoxification of blood. Regulation of these processes and the signals involved in the differential contribution of each biochemical event are not well understood. The large contribution of these biochemical events in the GIT and liver to whole-animal energy utilization suggests that their manipulation may alter the energetic efficiency of meat, milk or wool production.

The effect of various levels of ractopamine hydrochloride on the performance and carcass characteristics of finishing swine

Abstract: Six trials involving 888 pigs (Study 1) and three trials involving 360 pigs (Study 2) were conducted at various geographical locations in the US and Canada to evaluate the effect of ractopamine hydrochloride on the performance and carcass characteristics of finishing swine All trials were conducted using a randomized complete block design Trial data were pooled within study for statistical analysis Pigs averaged approximately 645 kg (Study 1) and 659 kg (Study 2) initially and had ad libitum access to a 16% crude protein corn-soybean meal or barley-soybean meal diet Ractopamine was included in the diet at 0, 25, 5, 10, 20 or 30 ppm (Study 1), or at 0, 5, 10, 15 or 20 ppm (Study 2); diets were fed for an average of 45 d (Study 1) and 50 d (Study 2) to a final weight of about 1043 kg (Study 1) and 1066 kg (Study 2) Carcass dissection data were collected in three of the six trials in Study 1 (0, 5 and 20 ppm ractopamine) and in all three trials in Study 2 (0, 5, 10, 15 and 20 ppm ractopamine) All ractopamine levels improved (P less than 05) ADG and feed: gain (Studies 1 and 2) above those of control pigs Ractopamine levels of 10 to 30 ppm (Studies 1 and 2) improved (P less than 05) dressing percentage over controls Pigs fed ractopamine at 5 and 20 ppm (Study 1) and 10, 15 and 20 ppm (Study 2) had increased (P less than 05) dissected leanness compared with controls(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of Ca2(+)-dependent protease activities by hydrophobic and ion-exchange chromatography.

Abstract: Hydrophobic and ion-exchange chromatography were compared for yield of Ca2(+)-dependent proteases and their inhibitor in studies designed to quantify Ca2(+)-dependent proteases activity for comparative purposes. Ion-exchange (DEAE-Sephacel) proved superior to hydrophobic chromatography (Phenyl-Sepharose). Under the proper conditions, DEAE-Sephacel effectively separated low-calcium-requiring form of Ca2(+)-dependent protease (CDP-I) and CDP inhibitor. Characterization of the assay system for components of the Ca2(+)-dependent proteolytic system separated by ion-exchange chromatography indicated that proteolytic degradation of casein by Ca2(+)-dependent proteases was linear with time for up to 60 min at 25 degrees C and that it was linear up to .4 to .45 units of activity. Therefore, we recommend that, after identification of fractions containing Ca2(+)-dependent protease (CDP-I or CDP-II), these fractions be pooled, and reassayed at a volume that yields values of less than .45 units of activity. Unlike CDP-I and CDP-II, CDP inhibitor lost its activity rapidly with frozen storage (frozen in liquid nitrogen, then stored at -70 degrees C); therefore, inhibitor should be assayed in fresh (unfrozen) samples only.

Intestinal absorption of protein hydrolysis products: a review.

Abstract: Many experimental techniques have allowed researchers to probe the fate of hydrolysis products from proteins in the small intestine. An overview of amino acid and peptide absorption from the small intestine is presented with attention given to historical perspectives that have led to current concepts. Speculation about nutritional significance of these processes is offered. Species differences exist in site of amino acid absorption. Numerous mechanisms are available for the transport of amino acids, including Na(+)-dependent carriers (energy-requiring), Na(+)-independent carriers and diffusion. The relative contribution each transport system makes to absorption is dependent on substrate concentration. Individual amino acids are not absorbed with equal efficiency; methionine usually is absorbed in the greatest proportion. There are interactions among amino acids for transports by specific transport systems. Small peptides (mostly di- and tripeptides) are absorbed from the small intestine more rapidly than are free amino acids; peptides are transported by systems independent of those responsible for transporting free amino acids. Evidence exists that the active transport of these peptides is via a proton gradient. Although the concept that peptides are absorbed intact into the circulation is not universally accepted, evidence supporting the possibility of tissue utilization of these small peptides is accumulating.

Mechanisms associated with the variation in tenderness of meat from brahman and hereford cattle

Abstract: To study possible mechanisms for differences in meat tenderness, 10 purebred Hereford and 10 American Grey Brahman steers were fed a typical feedlot diet and slaughtered when ultrasound measurements indicated that they had approximately 1 cm of fat thickness at the 12th rib. Longissimus muscle from Brahman cattle was less (P < .05) tender after 7, 14,21, 28 and 35 d postmortem than muscle from Hereford cattle, but muscle from Hereford cattle showed greater improvement in tenderness from 7 to 14 d postmortem than muscle from Brahman cattle (interaction P < .05). Cathepsin B or cathepsin B+L activities and the myofibrillar response to elevated ionic strength were not different between breeds, but both could be related to the postmortem increase in tenderness of both breeds. Calciumdependent protease activity, as modulated by calcium-dependent protease inhibitor, seems to play a major role in the inherent tenderness differences between breeds. (Key Words: Beef, Brahman, Ion Strength Effects. Proteases, Tenderness.) J. Anim. Sci. 1990. 68:42W220

Determination of the alteration in fatty acid profiles, sensory characteristics and carcass traits of swine fed elevated levels of monounsaturated fats in the diet.

Abstract: The present study was designed to determine the effects of supplemental fat or oil rich in oleic acid on the fatty acid profiles (FAP) and physical and sensory traits of pork carcasses. Sixty barrows and gilts were equally distributed among five dietary treatments consisting of a control diet of corn and soybean meal and four similar test diets that contained 10% animal fat (45.3 oleic), safflower oil (72.1 oleic), sunflower oil (80.9 oleic) or canola oil (57.7 oleic). The pigs were slaughtered after being fed these diets for 90 d at about 100 kg live weight. Carcass traits, FAP and sensory properties were evaluated for each treatment. First-rib fat thickness, ham muscling score and longissimus muscle areas were not different (P less than .05), but last-rib fat thickness was increased (P less than .05) with the supplemental dietary fat or oils. No differences existed for marbling scores, lean color, firmness or texture scores between the controls and pigs supplemented with either animal fat or safflower oil. However, pigs supplemented with sunflower or canola oil had lower marbling scores, lean color, firmness and texture scores. Fat became softer and more oily (P less than .05) with the supplemental dietary safflower, sunflower and canola oils. Sensory evaluation (loin chops) showed no differences (P less than .05) in sustained juiciness, tenderness or flavor intensity evaluations among treatments. However, the pigs fed canola oil had lower (P less than .05) flavor quality scores or overall palatability evaluations. Chops from the pigs fed canola oil also had 46% more off-flavors than all other treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Acceleration of postmortem tenderization in lamb and Brahman-cross beef carcasses through infusion of calcium chloride.

Abstract: A study involving 24 lamb carcasses was conducted to determine the effects of electrical stimulation and CaCl 2 infusion on meat shear forces. Infusion of lamb carcasses with CaCl 2 accelerated postmortem tenderization such that postmortem storage beyond 24 h to ensure meat tenderness was not necessary. Low-frequency electrical stimulation of lamb carcasses had no effect on shear force and was not a necessary step prior to CaCl 2 infusion

A review of the physiological significance of hypertonic body fluids on feed intake and ruminal function: salivation, motility and microbes.

Abstract: Mechanisms exist in the ruminant to detect changes in osmolality and volume of plasma during feeding to maintain fluid and electrolyte homeostasis. Feed intake during a meal can be limited by the rise in osmolality of ruminal fluid, which is sensed in the wall of the rumino-reticulum. Ruminal microbes appear to be resilient to the short-term changes in ruminal fluid tonicity, but in vitro growth rates are inhibited when the tonicity of the culture medium is increased beyond physiological levels. Although mixing contractions of the rumen are not inhibited by the normal increases in tonicity of ruminal fluid, time to first rumination is increased. This aspect of motility requires further research. The tonicity of plasma increases toward the end of a large meal as a consequence primarily of absorption of VFA and Na+ from the rumen and fluid shifts into the gut. This hypertonicity is sensed centrally to inhibit parotid secretion by a reduction in the parasympathetic stimulation to the gland. Increases in animal production may result from future research directed toward developing ways of counteracting these negative effects of hypertonicity in body fluids on feed intake and ruminal function.

Real ileal protein and amino acid digestibilities in feedstuffs for growing pigs as determined with the 15N-isotope dilution technique.

Abstract: Twelve gilts, with an average initial BW of 38 kg, were fitted with a simple T-cannula at the distal ileum and two catheters in the external jugular veins. The animals were fed 700 g of one of the experimental diets, twice daily at 0800 and 2000. Diets 1 and 2 were cornstarch-based diets formulated to contain 16% CP from soybean meal and canola meal, respectively. Diets 3 and 4 contained 93.9% wheat and barley, respectively. Chromic oxide was included to determine nutrient digestibilities. Following recovery from surgery, 15N-leucine was infused continuously via a jugular catheter for 9 d at a rate of 40 mg.kg BW-1.d-1. Blood samples were taken at every feeding. Ileal digesta were collected for 24 h on d 7 and 9 of the infusion period. Assuming that the 15N-enrichment excess in the trichloroacetic acid-soluble fraction of the blood was similar to that in endogenous N, the contribution of endogenous to total N in ileal digesta was calculated. The amount of endogenous protein (N x 6.25) recovered in digesta collected from the distal ileum were 25.5, 30.5, 27.4 and 27.7 g/kg DM intake for the pigs fed diets 1, 2, 3 and 4, respectively. In the same order for the diets, the real ileal protein digestibilities were 97.5, 84.1, 99.0 and 94.2%, respectively. In addition, the real ileal amino acid digestibilities were calculated. The recoveries of endogenous protein in ileal digesta and the real ileal protein and amino acid digestibilities were higher than those determined by feeding protein-free diets for determining the recovery of endogenous protein and amino acids in ileal digesta.

Energy requirements for maintenance of crossbred beef cattle with different genetic potential for milk.

Abstract: Maintenance energy requirements were estimated in two gestation and one lactation feeding trials for three groups of cows All cows in the second gestation trial completed the first gestation and lactation trials The three groups were chosen to represent cattle similar in growth rate and mature size but different in amount of milk provided to their calves The low (L) group included Hereford x Angus, the medium (M) group included Red Poll x Angus and the high (H) group included Milking Shorthorn x Angus cows Cows were individually fed to maintain net body weight (minus gravid uterus for gestation) constant Allowances were made in energy intake for gestation and lactation Cow weights were adjusted to an average condition score in each trial Daily maintenance requirements during gestation were 18% lower than those during lactation The H and M cows required 12% more energy per unit metabolic weight than L cows to maintain body weight during both gestation and lactation Differences in milk production explained 23% of the variation in maintenance requirements, suggesting that important differences exist beyond those associated with milk production potential Repeatabilities of maintenance requirement measurements ranged from 44 to 64 Maintenance requirements for calves under feedlot conditions in the postweaning phase were estimated from data collected from 494 calves, half-sibs and offspring of the cows described previously Energy requirements were 11% higher for the H and M groups than for the L group

Influence of flake density on the comparative feeding value of steam-flaked corn for feedlot cattle.

Abstract: Two trials were conducted to examine the influence of flake density (FD) on the feeding value of steam-flaked corn. Treatments consisted of corn that had been steam-flaked to mean densities of .42, .36 and .30 kg/liter (28, 24 and 20 lb/bu). In Trial 1, treatment effects on characteristics of digestion were evaluated using three crossbred steers with cannulas in the rumen and proximal duodenum. In Trial 2, treatment effects on feedlot performance were evaluated in a 112-d finishing trial involving 72 crossbred steers with an average initial weight of 312 kg. Flake density was directly related to flake thickness (P less than .01) and inversely related (P less than .01) to in vitro enzymatic digestibility of starch. Decreasing the FD resulted in a linear decrease (P less than .01) in ruminal pH and linear increases (P less than .05) in postruminal and total tract digestibility of starch. Postruminal digestibility of N and total tract digestibility of OM, N and energy also increased linearly (P less than .05) with decreasing FD. Flake density did not influence (P greater than .10) feedlot performance or carcass merit. There was a tendency (P greater than .10) for depressed rate and efficiency of gain for steers fed the 30 kg/liter FD corn. Improvements in digestibility and N utilization of SF corn-based diets as a result of decreasing FD from .42 to .30 kg/liter did not enhance feedlot performance. This may be due to digestive dysfunction, perhaps related to processing effects on ruminal pH.

Effects of grain type, roughage level and monensin level on finishing cattle performance.

Abstract: Interactions among grain type (grain sorghum, corn or wheat), roughage level and monensin level were studied in four feedlot trials using pen-fed crossbred yearling cattle. In Trial 1, cattle fed high-moisture corn (HMC) were more efficient (.1537 vs .1406 for gain/feed; P less than .01) than cattle fed dry-rolled grain sorghum (DRGS). As level (0, 3, 6, 9%) of dietary roughage was increased, feed efficiency (gain/feed) decreased (.1566, .1461, .1479, .1382; linear, P less than .01). In Trial 2, a grain type (DRGS; dry-rolled corn, DRC; dry-rolled wheat, DRW) x roughage level interaction was observed for daily gain and feed efficiency. Feed efficiency (gain/feed) was decreased when roughage was added to diets containing DRC (.1608 vs .1750) or DRGS (.1674 vs .1465), but not to the diet containing DRW (.1664 vs .1607). In trial 3, a grain type x roughage level x monensin level interaction (P less than .08) was observed for feed efficiency. The addition of 27.5 mg of monensin per kilogram of the 0% roughage-DRC diet tended to improve feed efficiency (.1633 vs .1531), but the addition of monensin to the 7.5% roughage-DRC diet tended to depress feed efficiency (.1476 vs .1575). The addition of either roughage (.1493 vs .1420) or monensin (.1500 vs .1413) to the DRW diet improved feed efficiency. In Trial 4, cattle fed a combination of 75% DRW and 25% DRC were more efficient (.1618 vs .1591; P less than .06) than cattle fed DRC. As level of roughage (0, 3.75, 7.5%) increased, feed efficiency decreased linearly (.1645, .1599, .1569; P less than .0001). Monensin had no effect on feed efficiency. The value of feeding roughage and monensin was variable both across grain types and within similar grain types.

Supplementation of dormant tallgrass-prairie forage: I. Influence of varying supplemental protein and(or) energy levels on forage utilization characteristics of beef steers in confinement.

Abstract: Three experiments were conducted to evaluate effects of supplemental protein vs energy level on dormant forage intake and utilization In Exp 1, 16 ruminally cannulated steers were blocked by weight (avg wt = 242 kg) and assigned randomly to a negative control or to one of three isocaloric supplement treatments fed at 4% BW: 1) control, no supplement (NS); 2) 12% CP, low protein (LP); 3) 28% CP, moderate protein (MP); 4) 41% CP, high protein (HP) In Exp 2 and 3, 16 ruminally cannulated steers were blocked by weight (avg wt = 332 kg, Exp 2; 401 kg, Exp 3) and assigned randomly to a 2 x 2 factorial arrangement of treatments The treatments contrasted low (LP) and high (HP) levels of supplemental protein (66 g CP/kg BW vs 132 g CP/kg BW) with low (LE) and high (HE) levels of supplemental ME (92 kcal/kg BW vs 184 kcal/kg BW) In Exp 1, forage DMI as well as ruminal DM and indigestible ADF fill at 4 h postfeeding were greater (P less than 10) with the MP and HP steers than with control and LP steers Total DM digestibility increased (P less than 10) for supplemented steers (355% for control vs 473 for supplemented steers); however, LP depressed (P less than 10) NDF digestibility In Exp 2, forage DMI, indigestible ADF flow and liquid flow were depressed (P less than 10) in LP-HE supplemented steers In Exp 3, HP steers had greater (P less than 10) forage DMI, indigestible ADF fill values (4 h postfeeding), liquid volume and tended (P = 11) to have greater ruminal DM fill (4 h postfeeding) In summary, increased levels of supplemental protein increased intake and utilization of dormant tallgrass-prairie forage (less than 3% CP) Increasing supplemental energy without adequate protein availability was associated with depressed intake and digestibility

Predicting beef-longissimus tenderness from various biochemical and histological muscle traits.

Abstract: Our objective was to determine the predictive value of various biochemical and histological traits for tenderness of the longissimus muscle. Data collected from 27 crossbred cattle included longissimus pH, temperature, sarcomere length, total and percentage of soluble collagen, muscle-fiber type and area, cathepsin B and B + L activities, calcium-dependent protease (CDP)-I, -II and inhibitor activities, myofibril fragmentation indices (MFI), Warner-Bratzler shear (WBS) force, sensory-panel tenderness (SPT) ratings and carcass traits. Stepwise regression analyses were performed among breeds or pooled within breeds with WBS and SPT as dependent variables. When MFI were included in the analysis, MFI at d 7 explained 50% of the variation in WBS and SPT at d 14. An additional 19% of SPT was accounted for by the addition of CDP inhibitor d 1 activity and percentage-area of alpha R fibers to the model. However, because variation in MFI was not significant within breed subclasses and MFI could be classified more as a dependent variable, it was removed from the model. This resulted in CDP inhibitor d 1 activity explaining 44% of the variation in WBS and SPT at d 14. Also, percentage-area of beta R fibers, 6 h pH and cathepsin B + L d 14 activity appeared in the model. In addition, CDP inhibitor activity was the only variable to be significant within breed groups. These data suggest that d 7 MFI could be used as a single predictor of d 14 longissimus muscle tenderness; however, CDP inhibitor d 1 activity (a biological event) also may be useful in predicting tenderness.

Zinc bioavailability in feed-grade sources of zinc.

Abstract: Chick bioassays were used to assess bioavailability of zinc (Zn) from inorganic Zn sources. A soy isolate-dextrose diet containing 13 mg Zn/kg diet was supplemented with feed-grade sources of ZnSO4.H2O (ZnSO4) or ZnO and fed for 2 wk after a 7-d Zn-depletion protest period. Bioavailability of Zn in ZnO relative to ZnSO4 (set at 100%) was determined by multiple regression slope-ratio methodology, using both growth and tibia Zn accumulation in chicks fed graded levels of ZnO and ZnSO4. Linear responses for gain and tibia Zn occurred at dietary Zn levels (ZnSO4.7H2O) between 13 mg/kg (basal) and 33 mg/kg (gain) or 53 mg/kg (total tibia Zn). Therefore, two bioavailability assays were conducted using supplemental Zn levels of 0, 7.5 and 15 mg/kg from each Zn source. When weight gain was regressed on supplemental Zn intake, bioavailability of Zn in ZnO was only 61.2% (P less than .01) that of ZnSO4. When total tibia Zn was regressed on supplemental Zn intake, bioavailability of Zn compared with ZnSO4 (set at 100.0%) was 44.1% (P less than .001) for ZnO. With chicks fed soy-based diets, bioavailability of Zn from ZnO was less than that of ZnSO4.

Natural plant toxicants in milk: a review.

Abstract: Elimination of plant toxicants via milk by lactating animals is considered a minor route of excretion; however, it may be important when the health of the neonate or food safety in humans is considered. Among plant toxicants excreted in milk is tremetol or tremetone, the toxin in white snakeroot (Eupatorium rugosum) and rayless goldenrod (Haplopappus heterophyllus). These plants have been responsible for intoxication of cows and their suckling calves and for many human poisonings. Other plant toxins excreted through the milk that pose a toxicity hazard include pyrrolizidine alkaloids in Senecio, Crotalaria, Heliotropium, Echium, Amsinckia, Symphytum (comfrey), Cynoglossum (hounds tongue) and Festuca (tall fescue); piperidine alkaloids in Conium, tobacco and others; quinolizidine alkaloids in Lupinus; sesquiterpene lactones of bitterweed and rubber weed; and glucosinolates in Amoracia (horseradish), Brassica (cabbage, broccoli, etc.), Limnanthes (meadowfoam), Nasturtium (watercress), Raphanus (radish) and Thlaspi (stinkweed). Many plants such as Astragalus, Oonopsis, Stanleya, Xylorrhiza, Aster, Atriplex, Sideranthus and Machaeranthera accumulate selenium and may cause intoxication when grazed. Selenium is found in the milk at concentrations relative to the amounts ingested by the lactating animal. Excretion of selenium via the milk is important in the deficiency state, but when in excess it may cause toxicity to offspring.

A species comparison of liver slice synthesis and secretion of triacylglycerol from nonesterified fatty acids in media.

Abstract: The ability of liver slices from eight species to synthesize and secrete triacylglycerol from nonesterified fatty acids contained in media was investigated. Species were grouped according to the relative proportion of lipogenesis occurring in the liver. The rate of liver triacylglycerol synthesis from nonesterified fatty acids in media was similar among species studied. Liver slices from species in which the liver contribution to lipogenesis is minor (sheep, cattle, pig and guinea pig) secreted less triacylglycerol synthesized from nonesterified fatty acids than did liver slices from species in which lipogenesis occurs predominantly in the liver (chicken and fish) or in liver and adipose tissue (rat and rabbit). The results suggest that the ability of liver to secrete triacylglycerol in very low density lipoproteins is proportional to the liver's lipogenic capacity.

Prediction of postpartum beef cow body composition using weight to height ratio and visual body condition score.

Abstract: Sixty-four mature Charolais×Angus cows, products of rotational crossbreeding, were used to compare methods of predicting postpartum (PP) body composition. Body condition score (BCS), weight and weight: height ratio (WHR) were used to predict body composition as determined by slaughter

Dietary fiber for dogs: I. Effects of graded levels of dietary beet pulp on nutrient intake, digestibility, metabolizable energy and digesta mean retention time.

Abstract: The optimal level of beet pulp (BP) inclusion in a meat-based dog diet and the effects of graded levels of dietary BP on fecal excretion responses and mean retention time of marked fiber in the gastrointestinal tract of the dog were evaluated using 30 female English Pointers assigned to isonitrogenous diets containing 0, 2.5, 5.0, 7.5, 10.0 or 12.5% BP (DM basis). Beet pulp replaced portions of dietary cornstarch. Digestibilities of DM and OM decreased by an average of 6% when comparing diets containing BP to the control diet, and quadratic and cubic responses were noted in digestibilities of fiber constituents (lower values at the 7.5 and 10.0% levels, higher values at the 2.5, 5.0 and 12.5% levels). Digestible energy (DE) and ME intakes (kcal/d) were not affected by treatment, but when expressed as a percentage of GE, values decreased (4.8% for DE; 6.2% for ME) linearly with increasing BP levels. Wet weight of feces increased (from 117 to 374 g/d) linearly as percentage of dietary BP increased. Frequency of defecation was higher (P less than .05) for dogs fed the diet containing 12.5% BP than for dogs fed the other diets (5.2 vs mean value of 2.8/24 h). Mean retention time of marked fiber decreased linearly (high value of 23.4 h for the 2.5% BP treatment, low value of 13.0 h for the 10.0% BP treatment) with increased level of BP. Beet pulp levels up to 7.5% of diet DM appear acceptable as a dietary fiber source in a meat-based canine diet.