Degradation of two protein sources at three solids retention times in continuous culture.

Effects of solids retention times (SRT) of 10, 20, and 30 h on protein degradation and microbial metabolism were studied in continuous cultures of ruminal contents. Liquid dilution rate was constant across all retention times at .12 h(-1) (8.3 h mean retention time). Two semipurified diets that contained either soybean meal (SBM) or alfalfa hay (ALFH) as the sole nitrogen source were provided in amounts that decreased as SRT was increased. Digestion coefficients for DM, NDF, and ADF increased with increasing SRT. Digestion coefficients for nonstructural carbohydrates were higher in the SBM diet than in the ALFH diet but were not affected by SRT. Protein degradation in the ALFH diet averaged 51% and was unaffected by retention time. In the SBM diet, digestion of protein was 77, 78, and 96% at 10-, 20-, and 30-h retention times, respectively. Microbial efficiency decreased with increasing SRT and was greater for the SBM than for the ALFH diet. Efficiencies ranged from 30.6 to 35.7 and 20.8 to 29.2 g of N/kg of digested DM for the SBM and ALFH diets, respectively, as SRT decreased from 30 to 10 h. The diaminopimelic acid content of the microbes increased as SRT increased, indicating that changes in microbial species occurred owing to passage rates. From these results, we concluded that the digestibility decreases associated with increased ruminal turnover rates may be less for nonstructural carbohydrates and protein than for the fiber fractions.

Effect of form of nitrogen on growth of ruminal microbes in continuous culture.

A study was conducted to determine the effect of various forms of N on the growth of ruminal microbes in a continuous culture system with solids and liquid dilution rates comparable to those of a high-producing dairy cow. Nitrogen forms were isolated soy protein, soy peptides, individual amino acids (AA) blended to profile soy protein, and urea, which were fed alone and in combinations so that the total N provided was 1.6% of the diet DM. The 100% soy protein treatment resulted in reduced digestion of N and nonstructural carbohydrate compared with other N forms, and outflow of bacterial N/24 h was less than when peptides were fed. This suggested that proteolysis rather than peptide uptake was the rate-limiting step in N utilization in this study. Non-urea N forms increased ADF digestion, total VFA production and the molar percentages of isobutyrate, isovalerate, and valerate compared to urea, which reflected the contribution of carbon skeletons of AA. When combinations of N forms were used, each form contributed an equal quantity of N, 50% of the total treatment, which was .8% of the diet DM. Combinations of N forms did not enhance, and in most cases reduced, ADF and NDF digestion when compared with individual N forms, and no combinations increased microbial growth over that of the individual forms. These results confirm that N forms other than ammonia are needed not only for maximum microbial growth, and they further demonstrate a need for non-protein N for the fiber digestion. In addition, results of this study suggest a requirement for a minimum level of peptide or AA N, which was met only when individual N forms were fed.

Age-related alterations in follicular development and hormonal profiles in rats with 4-day estrous cycles.

Two experiments were conducted to examine the hypothesis that an alteration in follicular development is associated with advancing maternal age in the absence of prolonged estrous cycles. In Experiment 1, serum and four follicles (from one ovary per rat) were collected from young and middle-aged, 4-day cycling rats on estrus or metestrus. Number and diameter of nonatretic antral follicles greater than 200 microns in diameter were determined from serial sections of the other ovary from each rat. In Experiment 2, serum and follicles (12 +/- 2) from both ovaries were collected from young and middle-aged rats on each day of a 4-day estrous cycle. All microdissected follicles were assayed for estradiol-17 beta (E2) and all sera were assayed for E2, follicle-stimulating hormone, and luteinizing hormone by radioimmunoassay. Numbers of follicles greater than 400 microns in diameter did not differ, while numbers of follicles 200-400 microns in diameter were reduced in middle-aged rats compared to young rats (Experiment 1). The mean diameter of follicles greater than 400 microns in diameter and the follicular content of E2 was greater in middle-aged than in young rats. In Experiment 2, a greater proportion of large follicles were observed in middle-aged rats than in young rats on all days, and a greater proportion of follicles with high concentrations of E2 were observed on diestrus. We interpreted these data as indicative of an early age-related change in the control of follicular recruitment, growth, and maturation.

Effects of fish meals on rumen bacterial fermentation in continuous culture.

Effects of various forms of fish meal on microbial metabolism were investigated in continuous cultures of rumen contents. Five diets were formulated to contain 12% ruminally degradable protein and 47 to 48% nonstructural carbohydrate. Soybean meal was the major protein source in the control diet, whereas in the other four diets, various fish meals were substituted for 6% of total diet DM. Fish meals were: fish meal containing 34.4% FFA, fish meal containing 34.4% FFA with CaCl2 added, fish meal containing 65.6% FFA, and fish meal defatted using 1:1 ethanol:ether extraction. The five treatments were fermented with pH either held constant at 6.2 or not controlled. When pH was maintained at 6.2, the inclusion of any fish meal except defatted fish meal reduced the acetate:propionate ratio, decreased protein digestion, and reduced microbial N produced/per kilogram DM digested when compared with the soybean control. When not controlled, pH decreased after feeding to 6.0 or lower. Under these conditions, the soybean control had a lower acetate:propionate ratio and lower NDF digestion than all diets containing fish meal. In this study, oil-containing fish meal affected microbial metabolism more negatively when the fermentation pH was held at 6.2 than when the pH was 6.0 or lower.

Phenotypic relationships of scrotal circumference to frame size and body weight in performance-tested bulls.

The objective of this study was to determine if frame size (height) is related to scrotal circumference. A total of 695 bulls (425 Angus, 65 Hereford, 70 Charolais, 135 Simmentals) were tested for postweaning gain in five stations over a period of 1 to 3 years. Variables examined included hip height, weight and scrotal circumference at beginning and completion of a 140-d feeding period. Correlations among these traits, adjusted for age (7 to 10 months at entry), year, station and management were estimated for each breed. Both height and weight were correlated positively with scrotal circumference at the start and the end of the test period in all four breeds. When height and scrotal circumference were adjusted for weight, correlations were negligible, with the exception of end-of-test values for Charolais bulls (-0.26). Negative correlations were obtained between the scrotal circumference at the start of the test and the change in height during the test after adjustment for weight in Angus bulls (-0.18) and in Charolais bulls (-0.15). These small negative phenotypic relationships indicate that a bull's fertility is not seriously reduced by large frame size at the completion of a feedlot performance test. For maximum fertility in bulls, scrotal circumference needs to be evaluated independently of frame size.

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

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

Digestibility, intake and mineral utilization of combinations of grasses and legumes by lambs.

Defined mixtures of two grass (orchardgrass, perennial ryegrass) and two legume (alfalfa, red clover) hays, harvested in two cuttings in 2 yr, were fed in digestibility, intake and mineral balance trials to wether lambs. Each mixture was fed in ad libitum amounts to six crossbred wether lambs weighing 35 to 45 kg. The effect of increasing proportion of legume in mixtures on dry matter digestibility (DMD), neutral detergent fiber digestibility (DNDF) and digestible dry matter intake (DDMI) differed with species combination. For all combinations, a quadratic regression (P less than .05) for DMD and DNDF indicated a small, negative associative effect for mixtures of grasses and legumes compared with pure species. Dry matter intake (DMI) showed a quadratic increase with level of legume inclusion, indicating a positive associative effect. The observed increase of DMI was approximately 6 to 7% over predicted values with 25 or 50% legume in the mixture. Intake of NDF also showed a quadratic response to level of legume, but lambs tended to eat to a fairly constant intake of 42 to 43 g NDF/kg wt.75. Mineral utilization (apparent absorption, retention) differed (P less than .05) with cutting but not species combination, and generally improved with increasing legume content in the mixture. With the exception of calcium retention (negative quadratic effect), there was little evidence for significant associative effects between grasses and legumes in mineral utilization.

Age, dose of FSH and other factors affecting superovulation in Holstein cows.

Effects of age of donor and other factors on superovulation and production of transferable embryos were investigated. Data were obtained on 987 recoveries of embryos performed between November 1980 and June 1984 by Select Embryos, Inc. The 339 Holstein donors ranged in age from 1.8 to 17.8 yr. The effects of age of donor and dose of follicle stimulating hormone (FSH) were examined using regression analysis. For on-farm recoveries, numbers of embryos, rates of fertilization, quality scores of all embryos and numbers of transferable embryos decreased (P less than .01, P less than .001, P less than .05, P less than .01, respectively) with increasing age of donor. For in-clinic recoveries, numbers of embryos plus ova recovered were affected by age of donor, dose of FSH and the interaction of the two (P less than .05). Among older donors, increasing doses of FSH were associated with an increase in the number of ova plus embryos recovered. However, among younger donors, increasing doses of FSH had a negative effect. Numbers of embryos, rates of fertilization and numbers of transferable embryos decreased (P less than .05) with advancing age and increased (P less than .05) with increasing doses of FSH. Greater numbers of ova plus embryos were recovered when treatment with FSH was begun on d 10 or 11 as compared with d 7, 8, 9, 12, 13 or 14 (P less than .001). It was concluded that an increase in age of donor had a negative influence on the success of superovulation and the production of transferable embryos, and that the response to FSH was affected by age of donor.

Factors affecting reproductive performance of dairy cows.

We conducted two studies to determine how herd management practices and traits of individual cows affect performance of the herd and of the cow within a herd. Management practices, reproductive performance of the herd, and relationships between management and reproductive performance were characterized on 83 dairy farms with 7596 cows. Data included 21 management variables (e.g., facilities, herd health program, estrous detection program) and 8 performance variables obtained from Dairy Herd Improvement or unofficial records (e.g., size of herd, production, days open). Although varying among herds, annual average herd incidences of reproductive disorders and reproductive performance were similar to those reported. Managerial practices influenced incidences of retained placenta and uterine infection, days open of cows not bred and of all cows, services per conception, and percentages of herd open more than 100 days and culled for low production. Veterinarian was the most consistent variable influencing herd reproductive performance. Data also were collected from production and lifetime records of 2532 cows in 19 herds. Reproductive performance was affected by season of calving, production, maturity, and reproductive disorders. Several cows with extremely poor reproductive records were maintained.

Selenium, cadmium, zinc, and copper in human kidney cortices and post mortem indices of hypertension.

Kidneys from 32 autopsied Caucasian human subjects aged 16-60 were frozen then lyophilized while the flasks were kept in insulating containers. (Subjects with evidence of extensive weight loss, chronic renal failure, or carcinoma were not included). Replicate samples of cortex were removed, weighed, and wet-ashed in HNO3-HClO4. Zn, Cd, and Cu were estimated by atomic absorption spectrophotometry with the 2261 Å line used for Cd background correction. Se was estimated by fluorescence with DAN in a Turner fluorimeter, but a #74 Kodak Wratten filter was added to minimize the 500 nm interference noted by E. Pickett (personal communication, 1980).Means and variability for the three elements in kidney cortex were similar to those in a North Carolina study as was Cd/(Cd+Zn)×100. Cortical Cd (P<0.05), Zn (P<0.10), and Cd/(Se·Zn) (P<0.05) increased with age, whereas Se showed no significant relationship with age. Age(2), nonlinear effects of age, had a slight influence upon Cu (P<0.05) only if data were not adjusted for gender. There was no influence of ageper se upon Cu with or without adjustment for gender. The scatter diagrams of element concentrations plotted vs age contained several provocative "outlier" values.A positive association of kidney cortex Cd concentration, or Cd/(Se ·Zn), with postmortem indices of hypertension existed only if age, gender, and age(2) were omitted from the multiple regression equation. This adjustment was not included in a similar study of North Carolina cases and appears to be the source of the major difference in their respective inferences drawn about the positive relationship of kidney cortex Cd with evidence of hypertension. This difference in statistical models does not however account for the failure of the West Virginia sample to indicate a protective role of kidney cortex Se suggested for the North Carolina subjects. Larger samples, drawn from regions differing in Se abundance, will be necessary to test the latter question adequately.

Distribution of visible follicles on the ovarian surface in ewes.

Two studies were conducted to determine the distribution of follicles on the ovarian surface in ewes. In Exp. 1, the effect of the corpus luteum on the distribution of follicles was investigated on d 9, 12 and 14 postestrus in unilaterally ovulating ewes. Follicles (greater than or equal to 2 mm diameter) were inventoried by size and distance from the center of the corpus luteum or corpus albicans. There were more small follicles (less than or equal to 4 mm diameter) on d 9 than on d 12 and 14, Although the ovary bearing the corpus luteum had a greater number of large follicles, no positive relationship of the corpus luteum to the diameter of the closest follicle or the distance of the largest follicle was found. In Exp. 2, follicles were inventoried on ovaries from ewes during the estrous cycle, postpartum anestrus, seasonal anestrus and the peripuberal period. During the estrous cycle, two apparent waves of follicular growth were noted. In addition, during the luteal phase the luteal ovary consistently had a larger follicle than the nonluteal ovary. When estimates were made of the effects of size of follicle on distance of the follicle from the reference structure and of distance on size of follicle, presence of luteal tissue, and day of estrous cycle were found to influence the variances. In addition the interaction of these characteristics affected the variation of size or distance. Weighting the distribution of ovarian structures for relative ovarian mass allowed an examination of localization of structures to standardized ovarian areas. More follicles and corpora lutea were found in the middle of the ovary than on the ends. Although the numbers of follicles in a standardized area were correlated with ovarian mass, occurrence of corpora lutea in a standardized area was not significantly correlated with ovarian mass. Collectively, these results are indicative of a local effect by the corpus luteum on the diameter of the largest follicle and a systemic effect on the number of follicles. In addition, because specific regions appear to be more favorable for follicular activity and ovulation, a precise local effect of the corpus luteum is difficult to determine.