Showing papers in "Journal of Animal Science in 1980"

Manipulating Metabolic Parameters to Improve Growth Rate and Milk Secretion

Abstract: Several opportunities for improving animal efficiency through manipulation of metabolism are discussed. The first opportunity is through identification and selection of animals achieving close to theoretical efficiencies. Based upon differences between highly efficient and average animals, the estimated opportunity for improvement is 20%. A second opportunity for improvement is through manipulation of apparent maintenance requirements. Several contributors to differences in efficiencies are considered. One is the contribution of differences in relative organ weights to differences in apparent maintenance requirements. A potential benefit in the order of 10 to 20% through selection or manipulation seems possible. Manipulations of ion transport and protein turnover could yield maximum benefits of 30 and 15%, respectively. However, complete elimination of these processes is not feasible. Without ion transport, membrane potentials would not be maintained and, without turnover, many important regulatory processes would be affected. the limit to manipulation of these characteristics is unknown. A third opportunity for improvement of animal efficiency is through improvement of apparent biosynthetic efficiency by manipulation of patterns of nutrient utilization. If we could produce, through hormonal or other types of manipulations, an optimum pattern of nutrient use, decreases in heat increments of production in growing animals in the order of 50% might be achieved.

Crossbreeding in Beef Cattle: Evaluation of Systems

Abstract: Summary The basic objective of beef cattle crossbreeding systems is to optimize simultaneously the use of both nonadditive (heterosis) and additive (breed differences) effects of genes. Experimental results evaluating rotational crossbreeding systems indicate that high levels of heterosis are sustained in successive generations and that the relationship between loss of heterosis and loss of heterozygosity approaches linearity. Major differences among breeds have been demonstrated for most characters that contribute to production efficiency. Results based on both experimentation and computer simulation indicate that differences in additive genetic merit of breeds for specific characters can be used in specific crossbreeding systems to synchronize genetic resources with other production resources and to provide for complementarity through terminal sire breeds. Rotational crossbreeding systems have the advantage of using heterosis in all females and progeny in a self-contained commercial herd; however, fluctuation between generations in additive genetic composition relll~es use of breeds that are generally compatible. This requirement restricts the use that can be made of breed differences to synchronize germ plasm resources with other production resources and eliminates the use of complementarity other than in a combined breed-rotation, terminal-sire system. A static terminal-sire crossbreeding system provides opportunity to synchronize germ plasm resources with other production resources in about 50% of the cow herd, to use maximum (FI) heterosis in about 67% of the calves marketed and to use complementarity in

Effect of Embryo Removal and Intrauterine Infusion of Embryonic Homogenates on the Lifespan of the Bovine Corpus Luteum

Abstract: Three experiments were conducted to determine the day at which the bovine embryo first affects luteal lifespan and if intrauterine infusion of homogenates of bovine embryos would extend luteal lifespan in nonpregnant heifers. Exp. I was a 2 x 2 factorial design and utilized 23 pregnant or nonbred Holstein heifers that were subjected to embryo removal procedures on day 15 or day 18 postestrus (estrus = day 0). Exp. II was a 4 x 2 factorial design and utilized 39 pregnant or nonbred Holstein or beef x Holstein heifers that were subjected to embryo removal procedures on day 13, 15, 17 or 19 postestrus. Removal of embryos at day 18 (Exp. I) and day 17 or 19 (Exp. II) prolonged (P<.01) luteal lffespan as compared to nonbred controls or when embryos were removed on days 13 or 15 of pregnancy. In Exp. III, seven heifers received twice daily intrauterine infusions of a homogenate of 17and 18-day-old embryos and seven received control infusions. As compared to the control group, intrauterine infusions of homogenized 17and 18-day-old embryos lengthened (P<.01) the interestrous interval by delaying regression of the CL. The results of these experiments indicate that between days 15 and 17 of pregnancy the bovine embryo produces a substance that prolongs the functional lifespan of the CL. (

Nutrition and the postpartum interval of the ewe, sow and cow.

Abstract: The effects of nutrition on the length of the postpartum interval (PPI, the interval from parturition to the first postpartum estrus that is accompanied by ovulation) were reviewed for the ewe, sow and cow. Unfortunately, information on the effects of nutrition on the PPI of the mare is nonexistent. Absence of estrus following weaning is a problem in postpartum sows, especially during the summer. High feed intake (more than 3 kg daily) immediately after weaning decreases the incidence of anestrus in sows of some breeds, but not in others. The incidence of prolonged intervals between weaning and estrus and the incidence of anestrus is more frequent in primiparous than in multiparous sows. The effect of nutrition on the PPI of the ewe is more controversial than that for the sow. In mature Merino ewes, neither lactation nor undernutrition during lactation affects the duration of the PPI while both factors increase the length of the PPI in coarse-wool breeds. Undernutrition during lactation increases the incidence of anestrus in primiparous fall-lambing Merino ewes. A cow must conceive by 80 days postpartum to have a 365-day calving interval. Excessive length of the PPI in dairy cows does not appear to be one of the major detriments to fertility since most dairy cows have a PPI of considerably less than 80 days. While feeding high protein diets to high-producing dairy cows shortens the PPI; this practice also increases the interval from parturition to conception. Weight changes, both before and after calving, and body condition at calving interact to affect the PPI of suckled beef cows. The length of the PPI in cows that are in good body condition at calving is not affected by either pre- or postpartum weight changes. More cows in moderate and thin body condition showed estrus by 60 days postpartum if the cows had gained weight prior to calving compared with those that lost weight prior to calving. A high percentage of thin cows that lose weight prior to calving does not show estrus following calving unless they gain weight after calving. The length of the PPI is affected by many factors, for example: parity, breed, lactation, environment and endocrine status. Designs of future experiments must be cognizant of these factors and the possible interactions of these factors with the nutritional status of the animal.

Genetic and Biological Aspects of Zebu Adaptability

Abstract: The utility and documentation of traits and characteristics of Zebu, Bos indicus, cattle in beef production in the United States are discussed with reference to adaptation. Zebu cattle are uniquely suited to hot climates due to coat, hide, skin and hematological attributes. Form, growth and physiological aspects are unique genetic attributes which are different from those of Bos taurus cattle. Compared with Bos taurus cattle, Zebu cattle are lower in reproduction, later maturing, slower growing and lower in beef quality. Zebu cattle are valuable in crossbreeding, with adaptive aspects transmitted and large amounts of heterosis in growth, maternal effects and reproductive traits.

Degradation of soluble and insoluble proteins by Bacteroides amylophilus protease and by rumen microorganisms.

Abstract: Various soluble and insoluble proteins (6.25 mg) were incubated at 37 C with partially purified protease from Bacteroides amylophilus (156 micrograms) in 2.0 ml of .1 M potassium phosphate buffer, pH 7.6, for 2, 4, 6 and 18 hr, and the liberated amino acids were determined by the ninhydrin method. Results showed that (1) although soluble, serum albumin and ribonuclease A were resistant to hydrolysis; (2) soluble and insoluble proteins of soybean meal were hydrolyzed at almost identical rates; (3) soluble proteins from soybean meal, rapeseed meal and casein were hydrolyzed at different rates, and (4) treatment of resistant proteins (serum albumin, ribonuclease A and insoluble fish meal and rapeseed meal proteins) with mercaptoethanol in 8 M urea or oxidation with performic acid rendered these proteins susceptible to hydrolysis. It is concluded that (1) solubility or insolubility of a protein is not by itself an indication of the protein's resistance or susceptibility to hydrolysis by rumen bacterial protease; (2) structural characteristics of the properties which renders feed protein resistant to degradation is the presence of crosslinking disulfide bonds.

Suckling and Four-Times Daily Milking: Influence on Ovulation, Estrus and Serum Luteinizing Hormone, Glucocorticoids and Prolactin in Postpartum Holsteins

Abstract: Holstein cows were assigned at calving to be (1) milked at 12-hr (n = 5) or (2) 6-hr (n =5) intervals or (3) suckled ad libitum by one calf and milked at 12-hr intervals (n = 6). Suckling resulted in an increase in the postpartum (PP) interval to first ovulation (39.7 vs 21.2 days), but increased milking frequency did not. Delayed resumption of episodic luteinizing hormone (LH) secretion was associated with the increased PP interval to ovulation in suckled cows. Both frequency and amplitude of episodic LH peaks were reduced (P less than .05) on days 7 and 14 PP in suckled cows compared to nonsuckled cows (1.2 vs 2.5 peaks/4.5 hr and 1.8 vs 2.8 ng/ml, respectively). Suckling did not significantly modify basal of milking-induced concentrations of prolactin or total glucocorticoids. Nor did serum concentrations of progesterone or estradiol-17 beta differ between suckled and nonsuckled cows, or between day 7 and day 14 PP. Milking-induced secretion of both prolactin and total glucocorticoids were greater (P less than .05) on day 14 PP than on day 7 PP in both suckled and nonsuckled cows. These results suggest that suckling may delay the first PP ovulation by suppressing episodic LH secretion. Alternations in prolactin, total glucocorticoids, progesterone or estradiol-17 beta do not apper to mediate directly the effects of suckling on PP episodic LH secretion and (or) ovulation.

Utilization of Dietary Fiber from Alfalfa by Growing Swine. II. Volatile Fatty Acid Concentrations in and Disappearance from the Gastrointestinal Tract

Abstract: Production of volatile fatty acids (VFA) in the cecum and colon and their utilization as an energy source were studied in growing and finishing swine fed diets containing 0, 20, 40 or 60% alfalfa meal. The pH in the cecum and colon had an average value of 5.9, which supports fermentation of lumen contents. Increasing dietary fiber increased the concentration (raM/liter) of VFA in the large intestine; VFA ratio was changed in the cecum (increased acetic: propionic-butyric acids) but not in the colon. VFA disappearing from the lower gastrointestinal tract were equivalent to 79, 147, 227 and 155 kcal per day for pigs fed 0, 20, 40 and 60% alfalfa meal, respectively, at 48 kg body weight and 47 ,231 ,285 and 245 kcal per day, respectively, at 89 kg body weight. VFA produced in the large intestine can therefore provide up to 6.9, 11.3, 12.5 and 12.0% of the energy required for maintenance in the 48 kg pig and 4.8, 11.4, 14.0 and 12.0% in the 89 kg pig fed O, 20, 40 and 60% alfalfa meal, respectively. (

Bovine prolactin, TSH, T and T concentrations as affected by tall fescue summer toxicosis and temperature.

Abstract: Serum concentrations of prolactin (PRL), thyrotropin (TSH), thyroxine (T4) and triiodothyronine (T3) were compared between Holstein calves fed a toxic fescue (G1-307) and Holstein calves fed a less toxic fescue (G1-306) at one of three environmental temperatures (low, 10 to 13 C; medium, 21 to 23 C; high, 34 to 35 C). Three calves were assigned to each treatment combination, and hormone concentrations were determined before (basal) and after thyrotropin-releasing hormone (TRH) was injected at 15 microgram/100 kg body weight via jugular cannula. Calves fed the toxic G1-307 had lower basal PRL concentrations than those fed G1-306 (1.8 +/- .1 vs 6.0 +/- 1.2 ng/ml). Increasing ambient temperature increased basal PRL levels in calves fed G1-306 (i.e., low [2.3 +/- .3] < medium [3.6 +/- .9] < high [12.1 +/- 1.3 ng/ml]) but not in calves fed G1-307 (i.e. low [1.8 +/- .1] = medium [2.0 +/- .1] = high [1.6 +/- .1]). Similarly, after TRH injection, PRL release was greater in calves fed the less toxic G1-306 (35.7 +/- 5.2 ng/ml) than in those fed G1-307 (5.6 +/- .6 ng/ml) and was positively affected by temperature (i.e., low [6.9 +/- 1.2] < medium [18.8 +/- 5.6] < high [36.3 +/- 5.9 ng/ml]). In contrast, basal and TRH-induced TSH concentrations were unaffected by temperature or fescue. However, T3 (time 0) was inversely related to temperature (1.06 +/- .1, 1.40 +/- .1 and 1.87 +/- .2 ng/ml for high, medium and low temperature, respectively). After TRH injections, T3 increased linearly and at the same rate (.007 ng/ml/min) at all temperatures, but T4 concentrations increased only in low temperature groups. Neither T4 nor T3 concentrations were affected by forage fed. We conclude that some factor(s) in toxic fescue inhibits PRL secretion, especially at high temperature, an environmental condition closely associated with fescue summer toxicosis in cattle. Increased body temperature and respiration rates associated with fescue summer toxicosis apparently are not mediated by TSH or thyroid hormone secretion.

Growth and hormonal response of heifers to various photoperiods.

Abstract: Body growth and dry matter intake were measured in three groups of 16 Holstein heifers exposed to (1) natural, (2) 16 hr light: 8 hr dark (16L:8D) or (3) 24L:0D photoperiods for November 11 to March 10. Average daily gain (ADG) of heifers subjected to 16L:8D was 11 (P less than .05) and 17% (P less than .02) greater than ADG of animals receiving 24L:0D or natural photoperiod, respectively. Heifers subjected to 16L:8D consumed 6.9 and 8.3% more (P less than .01) dry matter per day than did animals exposed to 24L:0D or natural photoperiod, respectively. Yet feed to gain ratio of heifers exposed to 16L:8D was lower than that of heifers exposed to 24L:0D or natural photoperiod. Serum prolactin (PRL) and growth hormone (GH) were measured in six heifers in each treatment group at 30-min intervals, and serum total glucocorticoids were measured at 2-hr intervals over a 6-hr period on December 26, February 6 and March 7. Concentrations of serum PRl remained low (less than 3 ng/ml) regardless of photoperiod treatment; this would be expected, however, because mean ambient temperatures were below 0 C on all sampling days. Serum GH and total glucocorticoids were likewise unaffected by photoperiod treatment. This study demonstrates that an 8-hr period of darkness is necessary to achieve increases in weight gain when Holstein heifers are supplemented with light during the autumn-winter season in Michigan, but the mechanisms whereby photoperiod affects body growth remain unknown.

Uterine involution: its role in regulating postpartum intervals.

Abstract: An involuting uterus is a temporary barrier to fertility in cows, ewes and sows. Parturition is followed by a period when conception is not possible: about 1 week in sows and about 3 weeks in cows and ewes. Estrus and ovulation seldom occur together during this period and, if fertilization occurred and the embryo reached the uterus, placentation would be virtually impossible. The period of no fertility is followed by 2 to 3 weeks when fertility is possible, but not optimal. The extent to which the involuting uterus contributes to infertility during the second period is difficult to determine. Embryonic mortality in sows bred during this latter period appears to be a major cause of reduced litter size, so changes in uterine environment associated with involution may be essential for optimum fertility. Conception rate is lower up to 40 days after parturition than later in cows and ewes. Uterine involution appears not to be a barrier to fertility after 3 to 4 weeks postpartum in sows or 5 to 6 weeks postpartum in cows and ewes unless delayed by inflammation or infection.

A histochemical study of myofiber types in muscle of the growing pig.

Abstract: The conversion of myofiber types was studied in the masseter, trapezius, longissimus, rectus femoris and vastus intermedius muscles of pigs at birth and 2, 4, 8 and 16 weeks of age. The histochemical reaction for ATPase was used to classify myofibers as type I (acid-stable, alkali-labile) or type II (alkali-stable, acid labile). Type II myofibers were divided further into categories IIA and IIB. Subtypes SM, SS and MS were intermediate to types I and II and were classified on the basis of pH sensitivity of the ATPase reaction. In the longissimus, rectus femoris and masseter muscles, the proportion of type II myofibers decreased and the proportion of type I myofibers increased from birth to 8 weeks of age, and little change occurred thereafter. These three muscles had more type II than type I myofibers, regardless of age. At birth the trapezius and vastus intermedius muscles both and more type II than type I myofibers, but during development, the proportion of type I myofibers increased greatly while that of type II decreased markedly. At 16 weeks, the trapezius had about equal proportions of type II and type l myofibers, but the vastus intermedius had a much higher proportion of type I than type II myofibers. A flow diagram was developed to illustrate the proposed conversion of type II to type I myofibers via the intermediate stages identified as subtypes MS, SS and SM. Development of the type I grouped pattern and the association of myofiber proportions with functions in the masseter muscle are discussed.

Effects of the Dietary Inclusion of Copper and(or) Antibiotics on the Performance of Weanling Pigs

Abstract: Five trials involving 518 pigs were conducted to determine the effects of the dietary addition of copper (0 or 250 ppm as copper sulfate) with and without antibiotics (55 ppm chlortetracycline, CTC, or 27.5 ppm virginiamycin VIR) on the rate and efficiency of gain and survival of early-weaned pigs. The experimental animals consisted of all pigs weaned from each of 67 litters at 28 +/- 2 days of age, regardless of weight or condition. In trials 1 through 4, single additions of copper, CTC or VIR to the corn-soybean meal-based diet improved (P less than .05) daily gains by 22, 22 and 17%, respectively, and feed to gain ratios by 5.1, 8.9 and 8.2% compared with those of pigs fed the unsupplemented diet during the 28-day trials. However, only the addition of copper to the diet increased (P less than .05) postweaning pig survival. Dietary inclusion of both copper and an antibiotic (CTC or VIR) further improved daily gains (P less than .05) by 10 to 11% and feed to gain ratios by 2 to 5% compared with the single addition of each antimicrobial agent. In trial 5, 125 ppm of copper were found to optimize daily gain and feed intake, whereas 250 ppm were required to maximize pig survival. These data demonstrate that high levels (125 to 250 ppm) of dietary copper increase the growth rate and reduce the incidence of mortality among weanling pigs. The data also indicate that the growth-promoting effects of copper and CTC, a broad spectrum antibiotic, or VIR, a gram-positive antibiotic, are additive in nature.

The hypothalamo-pituitary gonadotrophic axis of suckled and nonsuckled dairy cows postpartum.

Abstract: The objective was to determine whether the suckling-induced delay in return to estrus postpartum could be explained by changes in hypothalamic LHRH content or ability of the pituitary to release LH and FSH in response to LHRH or 59 mM K+ in vitro. In addition, serum concentrations of several other hormones were measured. Nine Holstein cows were suckled ad libitum by two calves and milked by machine twice daily and eight were milked by machine only from calving until slaughter on day 14 postpartum. On day 13 postpartum, blood was collected at 15-min intervals from 0815 to 1200 hr and from 2015 to 2400 hours. Suckled cows had lower (P less than .05) mean serum LH concentrations on day 13 postpartum than did nonsuckled controls. This decrease resulted from a 60% reduction in frequency and a 40% reduction in amplitude of episodic LH peaks. Suckling did not affect body weight change postpartum or serum concentrations of progesterone, estradiol-17 beta, total glucocorticoids, prolactin or FSH during the first 14 days postpartum. The suckling-induced decrease in serum LH was not reflected by a reduction in hypothalamic LHRH or pituitary LH on day 14 postpartum. However, pituitary explants from suckled cows on day 14 postpartum secreted 50% less (P less than .01) LH in response to LHRH (25 ng/ml for 30 min) or K+ (59 mM for 30 min) in vitro than did those from nonsuckled cows. Secretion of FSH was increased 20-fold by LHRH and K+ in vitro, but differences due to suckling treatment were not significant. Decreased frequency and amplitude of episodic LH secretion in vivo and reduced capacity of pituitaries to respond to LHRH may be the cause of suckling-induced inhibition of postpartum ovulation in cattle.