Showing papers in "Journal of Animal Science in 1981"

Heat stress as it affects animal production.

Abstract: It is well documented that the stress of hot environments lowers productive and reproductive efficiency, in farm animals. Likewise, research information is available to aid in the management of livestock in such adverse conditions. However, practical methods to achieve the desired levels of productive and reproductive performance are lacking. Summer forages that will support a high level of productivity in subtropic and tropic regions are needed for ruminants. More critical information is needed on the total dietary needs of all farm animals in hot environments. Dietary emphasis should be to increase intake or to alter levels of proteins, amino acids or other nutrients to improve the conversion of feed units into production units. Increasing nutrient intake to support a higher level of production will render animals more sensitive, in terms of productive efficiency, to environmental modifications that improve comfort. This should be especially pertinent in the humid Southeast and other regions where production responses to environmental modifications have been variable. There is limited information on the effect of the night cooling cycle on productive efficiency and on the effect of severe heat stress on reproductive phenomena not related to conception.

The relationships between energy balance, milk production and ovulation in postpartum Holstein cows

Abstract: Energy balance and serum progesterone concentrations were monitored during early lactation in a group of high producing Holstein cows. The postpartum interval to normal ovulation averaged 36 +/- 6 days (range 6 to 83 days). Average energy balance during the first 20 days of lactation (cumulative daily calculated energy balance divided by days in milk) was inversely related to days to normal ovulation (r = -.60) and to milk production (r = -.80). Milk yield during this period was not closely related to days to ovulation (r = .30). Milk yield was also not significantly related to serum prolactin concentrations over the first 12 weeks of lactation (r = .27). During early lactation, energy balance was maximally negative until peak milk yield and then began returning toward zero, with the magnitude and duration of negative energy balance being quite variable. On the average, ovulation and the initiation of the first normal luteal phase occurred approximately 10 days after energy balance began returning toward zero. During this 10-day interval, a transient elevation in serum progesterone concentrations occurred in eight of 13 cows. These results suggest that energy balance during the first 20 days of lactation is important in determining the onset of ovarian activity following parturition.

Aspects of in vitro fertilization and embryo culture in domestic animals.

Abstract: Summary Various aspects of the major components of in vitro fertilization and embryo culture in domestic farm animals are discussed. An examination of the spermatozoa and oocyte incubation media showed no media or protein supplement to be superior in promoting in vitro fertilization in cattle, sheep or swine. Generally, ovulated oocytes or activated follicular oocytes were penetrated by sperm more frequently than were immature oocytes. Spermatozoa that were incubated in vivo or in the oviducts of a different species generally achieved higher oocyte penetration than did spermatozoa incubated in vitro. In most in vitro fertilization studies, an in vivo component was introduced, generally oocyte or sperm maturation, which served to confound analysis of the in vitro results. Furthermore, the relatively low level of success and high incidence of chromosomal abnormalities with in vitro fertilization in other species require that careful and complete studies analyzing the components of in vitro fertilization in domestic farm animals be conducted. The culture of embryos from domestic farm animals is detailed, with emphasis on in vitro conditions and rate of success. As with laboratory animals, bovine, ovine, porcine and caprine embyos of fewer than eight cells are more difficult to culture to the blastocyst

Testicular Development and Establishment of Spermatogenesis in Holstein Bulls

Abstract: Fifty-two Holstein bulls were castrated at 12, 16, 20, 24, 28 or 32 weeks to (1) determine whether testicular development is influenced by season of birth (April or October) and (2) examine quantitatively the establishment of spermatogenesis Season of birth (spring or fall) did not influence (P less than 05) either testis weight at castration or the establishment of spermatogenesis With age held constant, scrotal circumference and testis weight were correlated (79; p less than 05) Testis weight increased from 9 +/- 1 g at 12 weeks to 117 +/- 10 g at 32 weeks of age Seminiferous tubules occupied 44% of the testicular parenchyma at 12 weeks and 81% at 32 weeks Differentiation of basal indifferent supporting cells to Sertoli cells started at 20 weeks, and formation of Sertoli cells was completed near 28 weeks Gonocytes predominated at 12 weeks, but by 20 weeks most had been replaced by prespermatogonia and A-spermatogonia Thus, transformation from a prepubertal testis to a pubertal testis containing Sertoli cells and A-spermatogonia occurred between 16 and 24 weeks (testis weight = 18 to 42 g) Preleptotene to diplotene spermatocytes appeared sequentially between 16 and 28 weeks and their numbers increased through 32 weeks Significant numbers of pachytene spermatocytes and spermatids were not present before 28 and 32 weeks, respectively Establishment of spermatogenesis was completed by 32 weeks (testis weight less than 80 g) Testes weighing less than 80 g were producing few if any sperm Thus, the establishment of spermatogenesis was progressive, associated with more than a fourfold increase in testis weight, and occurred over a period of about 16 weeks

Cold stress as it affects animal production.

Abstract: Almost two-thirds of all livestock in North America are raised in regions where the mean January temperature is below 0 C The effects of cold conditions on productivity and efficiency of feed conversion by swine, dairy and beef cattle are reviewed Swine are rather cold-susceptible and are therefore usually kept in heated housing when raised in colder regions Lactating or fattening cattle are extremely cold-hardy and rarely experience climatic conditions below their lower critical temperature Despite the absence of a challenge to homothermy in cattle, there are marked seasonal fluctuations in the cattle's level and efficiency of production which probably arise from hormonal and adaptive changes occurring as a consequence of mild cold stress Primary among these changes are an increase resting metabolic rate, and hence an increased energy requirement for maintenance, and an increased rate of passage of digesta, which results in reduced digestive efficiency With cold there is stimulation of appetite, which may partially counteract the reduced level of production but not the reduced efficiency of utilization of dietary energy

Effects of lasalocid or monensin on lactate-producing or -using rumen bacteria.

Abstract: Lasalocid or monensin inhibited most of the lactate-producing rumen bacteria (Butyrivibrio fibrisolvens, Eubacterium cellulosolvens, E. ruminantium, Lachnospira multiparus, Lactobacillus ruminis, L. vitulinus, Ruminococcus albus, R. flavefaciens, Streptococcus bovis). Minimum inhibitory concentrations ranged from .38 to 3.0 micrograms/ml. Among the lactate producers, those that produce succinate as a major end product (Bacteroides, Selenomonas, Succinimonas, Succinivibrio) were not inhibited by lasalocid or monensin. Also, none of the major lactate fermenters (Anaerovibrio, Megasphaera, Selenomonas) was inhibited by lasalocid or monensin. Veillonella alcalescens was inhibited by 24 micrograms/ml of lasalocid but was resistant to monensin. Hence, the reported increase in propionate in lasalocid- or monensin-fed cattle may result from selection for succinate producers and lactate fermenters. Lasalocid and monensin appeared to inhibit selectively the production of L(+), but not D(-) lactic acid. The inhibition of major lactate-producing bacteria (Streptococcus and Lactobacillus) suggests that lasalocid or monensin may be used to prevent lactic acidosis in ruminants.

Supplemental dietary fat for peripartal sows: a review'

Abstract: Summary Insufficient energy may contribute to the high mortality rate among piglets. Supplemental fat in the sow's diet during late gestation does not affect the piglets' body stores of carbohydrates at birth but increases slightly carcass fat stores. Supplemental dietary fat during late gestation and(or) lactation increases milk production and the fat concentration of colostrum and milk. This increase in colostral and milk fat increases the survival rate among the piglets if the herd survival rate is relatively low (less than 80%) and the sow consumes at least 1,000 g of fat before farrowing. The importance of continuing the fat supplementation after farrowing has not been established. The increased survival rate does not cause a decrease in the mean piglet weaning weight. Rather, the mean piglet weaning weight appears to increase if the dietary fat concentration is at least 8%. There are practical problems associated with the

Assessing Minimum Amounts and Form of Roughages in Ruminant Diets: Roughage Value Index System

Abstract: Summary Ruminants require adequate amounts of coarse-textured feeds to avoid metabolic disorders and, in the case of dairy cows, reduced milk fat production. Coarse-textured feeds help to maintain both proper muscle tone in the digestive system and proper rumen pH, both of which contribute to productivity and health. Texture of feeds is quantitatively reflected in the chewing activity of ruminants, and chewing stimulates saliva secretion. Saliva contains bicarbonates and other buffers that alter tureen environment and help avert disorders. Because chewing time reflects feed texture, a series of experiments were conducted in which feed intake, chewing time and milk and fat produc- tion were measured. Roughage value indexes (RVI) were partitioned for feed ingredients from regression equations. In addition, an equation was developed that predicts RVI from sieving and chemical data: RVI = 10.86 + PS (21.59) - DMI (1.91) + NDF (.541), where RVI is minutes/kilogram, PS is particle size in mean diameter, DMI is dry matter intake in kilograms and NDF is neutral detergent fiber percentage. The minimum RVI for the produc- tion of 3.5% fat milk was determined. By coupling an RVI requirement of 31 min/kg with feed RVI, one can formulate, by computer, diets for lactating cows that not only are nutritionally adequate, but also are adequate in a Presented at the Symposium on "Potential Com- plications Associated with Feeding Ruminants

Interaction of environmental temperature and anti-quality factors on the severity of summer fescue toxicosis.

Abstract: Two experimental strains of tall fescue grass (Festuca arundinacea Schreb) that had previously been shown to produce differences in animal performance during the summer period were fed to Holstein calves in temperature controlled rooms. In the first year, GI-306 (less toxic) and GI-307 (more toxic) tall fescues were fed during July in rooms maintained at 10 to 13, 21 to 23 and 34 to 35 C. In the second year, the same tall fescues and orchardgrass were fed at a high temperature during May (32 to 33 C), July (34 to 35 C) and October (31 to 32 C). A comparison at a lower temperature (16 to 18 C) was also included in the July and October trials, On both years, calves consuming GI-307 tall fescue consistently had lower dry matter intakes, higher rectal temperatures, higher respiration rates and lower weight gains than those fed GI-306 tall fescue or orchardgrass at temperatures above 31 C. At lower ambient temperatures, differences in dry matter intake, rectal temperature and respiration rates between animals on the two strains of forage were not statistically different. The results demonstrate the poor performance of cattle grazing fescue is related to environmental temperature and that the toxic substance(s) is present throughout the growing season.

Nutrient digestibility and performance of pigs fed sorghums varying in tannin concentration.

Abstract: Four sorghums, ranging widely in tannin content, and yellow corn were evaluated in two 5 x 5 Latin square digestion trials and a growth trial. All grains were grown in the same field under similar conditions. The sorgums and their tannin contents (milligrams of catechin/100 mg of dry matter, as determined by a modified vanillin-HCl method) were: Ga615, 3.40; NK300, 3.17; TAM680, .83, and G766-W, .88. Diets were supplemented with casein to provide .70 and .60% lysine in digestion trials 1 and 2, respectively. In trial 1, conducted with noncannulated, 25-kg pigs, digestibilities of dry matter, gross energy and N averaged for the low tannin sorghums (TAM680 and G766-W) were higher (P greater than .01) than the corresponding digestibilities averaged for the high tannin sorghums (Ga615 and NK300). N balance data indicated that utilization of absorbed N was not reduced in pigs fed the high tannin sorghums. Corn and the low tannin sorghums had similar digestibilities. In trial 2, conducted with 50-kg pigs fitted with T-cannulas at the terminal ileum, digestibilities of dry matter, gross energy, N and all amino acids again averaged higher (P greater than .01) for the low tannin sorghums than for the high tannin sorghums, whether measured at the end of the small intestine or over the total digestive tract. The one exception was methionine digestibilities at the terminal ileum, which did not differ between the high and low tannin sorghums. Among the amino acids, digestibilities of glycine, proline and histidine appeared to be the most depressed in the high tannin sorghums, as compared to the low tannin sorghums. Digestibilities of most nutrients were higher for NK300 than Ga615, suggesting a difference in type of tannin, or other compound, between grains. Corn and the low tannin sorghums, averaged together, had similar digestibilities for most nutrients. In the growth trial, 10 pigs, individually fed form 20 to 94 kg, received grain-soybean meal diets based on each grain except NK300. Gains were not affected by diet, but feed consumption was 9% higher (P greater than.05) and feed efficiency 10% (P greater than .01) poorer for pigs fed Ga615 than for those fed low tannin sorghums. Performance was similar (P greater than .10) for animals fed the low tannin sorghums and those fed corn.

What is animal stress and how is it measured

Abstract: The meaning of the term "stress" as it applies to animal husbandry is discussed. Because "stress" is used with various meanings, its application is often misinterpreted. Stress in general is looked upon as a symptom resulting from exposure of an animal to a hostile environment. To some it is a nonspecific response to all environmental forces; others feel there are specific stress symptoms caused by specific environmental forces. The term stress is sometimes used to describe the hostile environment. The correct usage depends upon the school of thought espoused. A common working definition of physiologists is that "stress" consists of external body forces that tend to displace homeostasis and "strain" is the internal displacement brought about by stress. There are environmental forces continuously acting upon animals that disrupt homeostasis, resulting in new adaptations that can be either detrimental or advantageous to man's interest. Measuring the magnitude of stress often means measuring the degree of adaptation. The important function of livestock management is to avoid the detrimental adaptations and capitalize on the advantageous ones.

Prevention of lactic acidosis in cattle by lasalocid or monensin.

Abstract: Intraruminal administration of lasalocid or monensin (1.3 mg/kg body weight) effectively prevented in glucose- or corn-induced lactic acidosis in cattle. Administering the antibiotics for 7 days before experimentally inducing acidosis with corn (27.5 g/kg body weight), effectively prevented acidosis, while 2 days' were sufficient to prevent glucose-induced acidosis (12.5 g/kg body weight). The different responses observed in the two trials probably stemmed from the difference in amounts of carbohydrate used to induce acidosis. Antibiotic-treated cattle had higher rumen pH values and lower L(+) and D(-) lactate concentrations that control cattle that received no antibiotics. Ruminal VFA in control cattle decreased, while total VFA and the molar proportion of propionate increased in antibiotic-treated cattle after grain engorgement. Control cattle exhibited classic signs of acidosis, such as lowered blood pH; increased blood lactate, particularly D(-) isomer; hemoconcentration, and depleted alkali reserve with a pronounced based deficit. Antibiotic-treated cattle exhibited no signs of systemic acidosis.

Monensin supplementation and in vivo methane production by steers

Abstract: The effect of monensin on methanogenesis was examined. Growing steers were fed 4.1 kg daily of a low roughage diet (12.6% crude protein, 12% acid detergent fiber) or 5.4 kg daily of either a medium roughage (12.3% crude protein, 27% acid detergent fiber) or a high roughage diet (14.4% crude protein, 40% acid detergent fiber) with or without 200 mg of supplemental monensin. At the low and high roughage levels, monensin increased (P less than .05) the molar proportion of ruminal propionate and decreased acetate. Methane production and inhibition by monensin declined with time postprandially. Monensin decreased methane production by 16% (P less than .05) at the two lower roughage levels and 24% (P less than .01) at the high roughage level. Total heat production and respiratory quotient remained unaltered by monensin. Averaged across roughage levels, metabolizable energy was increased (P less than .01) 5.2% by monensin. Although dry matter digestibility and N retention were not statistically altered, both tended to increase with monensin. Reduced ruminal methane production with monensin feeding can explain a portion of the increased feed efficiency.

Influence of fasting and transit on ruminal and blood metabolites in beef steers.

Abstract: Nine ruminally cannulated steers (average weight 477 kg) were randomly assigned to serve as controls (C) or to be fasted (F) or fasted and transported (FT). C steers were allowed free access to alfalfa hay, water and plain salt during the experiment; F steers were deprived of feed and water for 32 hr, and FT steers were deprived of feed and water and transported for 32 hr in a gooseneck trailer. After 32 hr, F and FT steers were allowed access to alfalfa hay, salt and water. Rumen samples were withdrawn via cannula at 0, 18, 32, 36, 46, 56, 80 and 104 hr after the start of the experiment. Jugular blood was sampled at the same times, except for 36 and 46 hours. Rumen pH of F and FT steers increased (P less than .05) during the 32 hr fasting/transit period over that of C steers and then decreased (P less than .05) on refeeding. Total VFA concentrations were lower in F steers (39.5 mmoles/liter) at 32 hr than in FT steers (202.2 mmoles/liter). Total counts of rumen bacteria and protozoa were lower (P less than .05) in F and FT steers than in C steers at all times except 0 and 104 hr, and recovery of microbial numbers was slower in FT and in F steers. VFA data suggest rumen motility may be impaired in FT steers compared with that in F steers. Blood glucose was higher (P less than .05) at 18 an 32 hr in FT than in F steers. Serum glutamic oxaloacetic transaminase was higher (P less than .05) at 18 hr (104.7 IU/liter) in FT steers than in steers in the other two groups (average 84.3 IU/liter). Serum Fe tended to be lower at 18 and 32 hr in FT steers than in F and C steers, and serum triglycerides were lower (P less than .05) in FT steers at 32 and 56 hr than in C. Most other blood constituents were not greatly affected by treatment. These data suggest that the physiological response of fasting alone differs considerably from that of fasting and transit stress, because transit appears to impose influences on rumen fermentation and blood chemistry beyond those imposed by fasting.

Influence of age, sex and calcium and phosphorus levels on the mechanical properties of various bones in swine.

Abstract: Seventy-two 4-week-old pigs were randomly assigned by sex (gilts, barrows, boars) to two dietary treatments and four age periods for determinations of the effects of age, sex and Ca and P levels on the mechanical properties of various bones in swine. Pigs were individually fed diets containing either. months after the initiation of the trial. The femur (Fem), humerus (Hum), third and fourth metacarpal (3Me, 4Me), third and fourth metatarsal (3MT, 4MT), third rib (Rib) and thoracic vertibrae were collected at each age period for mechanical tests and determination of percentage of ash. Bending moment, ultimate stress, yield stress and modulus of elasticity were determined by a flexure test in which the bone was treated as a simply supported , centrally-loaded beam (three-point loading). Bending moment of bones from boars was similar to that of bones from gilts or barrows. When expressed as force per unit area, the ultimate stress of bones from boars was less than that of bones from gilts or barrows. Percentage of ash did not differ significantly between sexes, but tended to be lower in bones from boars than in bones from gilts or barrows. Bones from pigs fed T2 had a higher bending moment than bones from pigs fed T1, regardless of age. At A1, the Fem, Hum and Rib of pigs 1Published as Paper No. 6094-, Journal Ser., Ne-braska Agr. Exp. Sta. a Dept. of Anita. Sci. Acknowledgment is made to Chuck Clanton for assistance with engineering equations and to Cecilia Stodd and Mary Barnes for laboratory assistance. fed T2 were able to withstand a greater stress than the same bones of pigs fed T1. At A3 and AS, the ultimate stress of all bones increased with increasing levels of dietary Ca,P. At A7, the Fem, 4MT and Rib failed to show a response to increased levels of Ca, P.

Housing and management to reduce climatic impacts on livestock.

Abstract: Weather is a constraint on efficient livestock production systems. Evaluation of the degree of constraint is a difficult, but necessary task before selection of appropriate modifications in management or environments can be made. The basis for rational selection from available alternatives for the limitation of climatic stress in livestock has continued to improve, particularly with the development of rudimentary functional relationships between animal performance and weather parameters. Such relationships, when combined with probabilistic knowledge of the weather parameters, permit prediction of the reduction in animal performance under natural conditions, or of the benefits to be derived from proposed housing or management practices. Even with the imprecision still present in current models, such information provides livestock managers with improved bases for rational decisions on the housing or management of their animals compared with the broad generalizations now serving as guides. Refinement of present livestock response relationships and the development of new models will further improve their decision making and should be pursued as rapidly as resources permit.

Effect of sorghum particle size on digestibility of nutrients at the terminal ileum and over the total digestive tract of growing-finishing pigs.

Abstract: The effect of sorghum particle size on nutrient digestibilities at the terminal ileum and over the total digestive tract of growing-finishing pigs were investigated in a replicated 3 X 3 Latin square trial. Sorghum-casein diets were used. Sorghum was dry rolled (C) or ground in a hammer mill through 6.4 mm (M) or 3.2 mm (F) screens, producing particles with a modulus of fineness of 3.57, 2.85 or 2.36, respectively. Each successive reduction in particle size improved (P less than .05) the apparent ileal digestibility of dry matter, starch, gross energy and N. Measured over the total digestive tract, digestibilities of these components were highest (P less than .05) for the F diet but they did not differ (P greater than .10) between diets M and C because of increased (P less than .05) disappearance in the large intestine of dry matter, starch and gross energy from the C diet. N loss in the large intestine was also higher for pigs fed diet C than for those fed diet M, but the difference was not significant. The digestibilities of most amino acids at the terminal ileum were improved (P less than .05) as particle size decreased. Lysine digestibilities were not affected (P greater tha .10). Amino acid digestibilities measured over the total digestive tract were consistently higher (P less than .05) for diet F than diets M and C, which did not differ (P greater than .10) from one another. A comparison of ileal and total tract digestibilities indicated a net disappearance of all measured amino acids except lysine during large intestine transit. These data indicate that increasing fineness of grind will improve digestibility of nutrients in sorghum by growing-finishing pigs.