Biomedical subjects

C J Wilcox

Publications and source records attributed to C J Wilcox.

At least 19 recordsLinked to original sources

PubMed1995

Technical note: subjective enumeration of episodic events (spikes) in animal physiology experiments.

Blood samples of nine sheep were taken over time and analyzed for estrone, estradiol, and progesterone. Results were plotted for each sheep, and graphs were evaluated by 26 evaluators with various previous experience. Sheep were sampled for different time periods. Repeatabilities for the number of spikes of estrone, estradiol, and progesterone recorded for sheep were variable, ranging from .019 to .547. Repeatabilities for evaluators ranged from .033 to .427, but these values decreased to < .001 to .030 when adjusted by covariance for the number of spikes possible. Results indicated that either an objective procedure for counting spikes should be used in comparable research or that evaluators should be trained in visual counting procedures to improve their repeatability.

Animals↗

PubMed1995

Effects of variable sources of distillers dried grains plus solubles on milk yield and composition.

This study compared diets supplemented with distillers dried grains plus solubles originating from whiskey distilling with those from fuel alcohol production or soybean meal. Forty-eight cows in mid and early lactation were offered a different dietary treatment in each of three 28-d periods. Dietary design included three supplements at 14 or 18% CP of dietary DM, with or without blood meal. Additionally, a third, darker, fuel ethanol source was added at 14 and 18% CP without blood meal during period 3 to incorporate greater variation in quality of distillers grains. No detectable differences occurred in DMI or in any variables because of blood meal. Milk yield was higher when cows were fed diets at 18% rather than at 14% CP. Cows fed the two lighter distillers grains diets yielded .8 kg/d more milk than cows fed soybean meal diets, and cows fed whiskey distillers grains yielded 1.3 kg/d more SCM than cows fed diets with darkest distillers grains. Milk protein percentage was depressed when the darkest distillers grains were fed. Distillers dried grains plus solubles can provide an excellent substitute for soybean meal and corn in dairy cow diets.

Analysis of Variance↗

PubMed1995

Effects of varying forage types on milk production responses to whole cottonseed, tallow, and yeast.

Four forage treatments (45% corn silage, 33.75% corn silage plus 11.25% alfalfa hay, 11.25% bermudagrass hay, or 11.25% cottonseed hulls on a DM basis) were arranged factorially with no added fat, 12.5% whole cottonseed, or 2.5% tallow. Different diets were fed during three 28-d periods to 20 control Holstein cows and to 20 cows receiving yeast continuously in a split-plot design. Milk yield of cows fed cottonseed hulls with corn silage was 2.4 kg/d higher than with corn silage plus bermudagrass hay and .7 kg/d higher than with corn silage only or corn silage plus alfalfa hay. Whole cottonseed depressed milk yield by 1 kg/d. Cows fed yeast had increased DMI, and yeast interacted with forage so that more milk was produced by cows fed alfalfa diets. Yeast depressed milk protein percentage. Holstein cows in a commercial Florida dairy were fed no yeast or 10 g/d continuously for 60 d; milk fat percentage was greater (3.51 vs. 3.37%) with yeast. In summary, effects on milk and SCM were positive when cottonseed hulls were utilized with corn silage, negative with whole cottonseed, and neutral with supplemental tallow. Yeast effects on SCM, although not significant for either experiment, tended to be positive for both (mean +1.2 kg/d per cow).

Animal Feed↗

PubMed1995

Effects of interrelationships of production and reproduction on net returns in Florida.

Economic aspects of reductions in reproductive efficiency associated with increased production of milk and fat were evaluated for Holsteins and Jerseys in Florida during warm and cool seasons. Net returns from sire selection for increased production were examined with and without incorporation of such negative effects. The economic framework is the application of risk analysis in portfolio selection to selection of dairy sires. Estimates of effects of production on reproduction were from an earlier study of 4293 Holstein and 2143 Jersey cows in first lactation on 14 Florida dairy farms in warm and cool seasons. The scenario represented the typically low reproductive efficiency of cows, especially Holsteins, during summer in Florida, although some statistics used represented US values. Least squares estimates of net returns after adjustment for reproductive losses showed major reductions in net returns for both breeds for both seasons, for example, $28 to $30/yr per lactation, representing 47 to 53% of predicted net returns for Holsteins and 27 to 31% for Jerseys. The results also suggested that increased use of young sires, which results generally in higher conception rates and lower semen costs, might be justified in tropical and subtropical areas, particularly during hot seasons.

Aging↗

PubMed1994

Transformation of measurements percentage of white coat color for Holsteins and estimation of heritability.

Percentage of white coat color was measured on registration certificates of 4293 Holstein heifers on eight dairy farms in Florida. Measurements of white percentage were by visual evaluation on one side of the upper body (head, neck, and trunk) only and obtained in increments of 5%. Mean, median, mode, standard deviation, and skewness of white percentage were 25.6, 15, 0, 26.9, and 1.03. Distribution of white percentages showed lack of normality. Original data were transformed using an extension of the Box-Cox transformation to approach normality and to provide maximum likelihood estimators of the transformed parameters. Heritability estimates for percentages of white coat color were computed using derivative-free REML with an animal model. Estimates of heritability were .715 from untransformed data and .779 for transformed. Standard errors of estimates were slightly lower (.032 vs. .035) following transformation. Additional study to find an improved transformation procedure still seems warranted.

Animals↗

PubMed1992

Use of oral tolerance tests to investigate disaccharide digestion in neonatal foals.

Oral tolerance tests were performed on 13 neonatal foals to determine their ability to digest disaccharides on d 1, 3 and 5 postpartum. Foals were assigned randomly to treatments consisting of 20% (wt/vol) solutions of either maltose, lactose, or sucrose, dosed at 1 g/kg of BW, or glucose, dosed at .5 g/kg of BW. After a 2-h fast, an initial blood sample was collected via jugular catheter. Foals were administered the appropriate solution orally, and blood was collected every 15 min for 1 h and then every 30 min for 3 h. Plasma glucose increased after dosing with lactose or glucose but not with sucrose. Plasma glucose concentrations increased slightly on d 3 and 5 in foals dosed with maltose. These findings suggest that although lactose is well digested by neonatal foals, maltose is digested only slightly, and sucrose is not digested by d 5. Results of this experiment indicate that maltose and sucrose would not be suitable for inclusion in artificial diets for foals less than 1 wk old. Oral tolerance tests could be useful for determining the ability of premature or sick foals with lactose intolerance to digest alternate carbohydrate sources.

Animal Feed↗

PubMed1992

Factors affecting days open, gestation length, and calving interval in Florida dairy cattle.

Effects of several factors on reproductive performance were evaluated. Mean performance and number of observations were for days from parturition to first service, 93 and 7730; days from first to successful service, 35 and 11,751; days open, 123 and 8571; gestation length, 280 and 13,612; and calving interval, 400 and 8524. Data covered 52 yr during which no detectable trends in calving interval occurred; other variables changed slightly. Jerseys had 8 fewer d from parturition to first service, 16 fewer d from first service to conception, 8 fewer d open, and 8-d shorter calving intervals than did Guernseys and Holsteins, which did not differ. Cows freshening in warm rather than cool weather suffered by 7, 7, 12, and 13 d for these variables. Repeatabilities ranged from .05 to .12; heritabilities were .05 and .06. Nonmaternal estimate of heritability of gestation length was .22. Phenotypic and genetic correlations between days from parturition to first service and calving interval were .48 and .87; for days open and calving interval, they were .97 and .96. Although days from first to successful service were essentially uncorrelated with days open and calving interval phenotypically (.05), genetic correlations were greater than 1.0 and estimated as unity. Results show no discrepancy between estimates for measures of reproductive performance in a subtropical environment and numerous studies in temperate areas. Large studies from subtropical areas are sparse; essentially none concerns long-term trends.

Animals↗

PubMed1992

Postpartum performance of dairy heifers freshening at young ages.

Records from Florida Agricultural Experiment Station dairy herd for 1144 heifers freshening from 1959 to 1979 were studied to evaluate effects of age and problems at parturition on subsequent yield and reproduction. Statistical analysis was by method of ordinary least squares analysis of variance; five measures of reproduction, survival to second lactation, and 15 measures of yield were studied. Mean first parturition age was 25.8 mo with 40% of individuals less than or equal to 23 mo; survival to second parturition was 67%. No effects of age at first parturition were detected on survival, postpartum reproductive performance, or milk composition other than lactose-mineral, chloride, and acidity percentages; effects on yield were similar to previous reports. Stillbirth did not affect subsequent reproductive performance but was associated with decreased milk yield: 181 kg or 5.2% of overall mean. Milk yield was depressed by 239 kg for retained fetal membrane, 173 kg for dystocia, and 98 kg for metritis; milk composition essentially was unaltered. Heritability of postpartum days to first estrus was .14; estimates were 0 for days to first service, days open, and calving interval. Additional research is needed on interrelationships of gestation length with subsequent yield and reproduction and in alleviating detrimental effects of problems at parturition.

Age Factors↗

PubMed1992

Milk yields and hormone concentrations of Holstein cows in response to sometribove (somatotropin) treatment during the dry period.

Holstein cows (n = 135) under commercial management were used to determine whether sometribove (recombinant methionyl bST, 25 mg/d) administered during the dry period affected milk yield during the ensuing lactation. Cows scheduled to begin lactations (greater than or equal to 2) during January to March were assigned randomly to treatments of sodium bicarbonate excipient (n = 67) or bST (25 mg/d, n = 68). Subcutaneous injections were given for 14 d, corresponding to d -21 to -7 relative to expected calving date. Days dry prior to first injection (64.0, 60.2) and number of injections received (13.9, 13.8) were similar for control and treatment groups, but days from last injection to calving (8.8, 7.1) differed. No differences in incidence of dystocia or udder edema were detected. Previous lactation yields were 8251 and 7952 kg, and yields for lactations following treatment were 8328 and 7852 kg, based on complete lactation data. Mean test date 3.5% FCM yields for control and treated groups during experimental lactation differed before (30.3 vs. 28.1 kg) but not after (29.5 vs. 28.4 kg) covariance adjustment for previous total lactation milk yield. Test of heterogeneity of regression provided no evidence that respective curves for FCM yield during lactation were not parallel or of different magnitude. Elevation of serum bST during 2 wk of the dry period resulted in no apparent increase in extent of mammogenesis or lactogenesis that was translated into an increase in milk yield.

Animals↗

PubMed1992

Disappearance of phosphorus in phytate from concentrates in vitro and from rations fed to lactating dairy cows.

Objectives were to determine concentrations of P in phytate in selected concentrates, disappearance of P in phytate from these concentrates in vitro, and extent of hydrolysis of phytate in vivo. Total P and P in phytate were determined for eight concentrates; 32 to 81% of total P was in phytate. Six concentrates were incubated in vitro to determine the extent of phytate disappearance from solids and its appearance and disappearance from solution. Greater than 90% of P in phytate disappeared from solids between 6 and 8 h of incubation in vitro (wheat middlings, rice bran, hominy, soybean meal, and dried distillers grains) or between 12 and 24 h (cottonseed meal). Phosphorus in phytate in solution was hydrolyzed by 12 h except for cottonseed meal (by 24 h). Hydrolysis of the inositol ring to release P in vivo was greater than 99%, based on total fecal collection from 11 cows and the use of Cr as an indigestible marker in excreta, and between 94 to 98% for the same samples when acid detergent lignin was used as an indigestible marker to calculate phytate disappearance. These results further indicate that P in phytate should be considered available to lactating dairy cows when rations to meet their P requirements are being formulated.

Animal Feed↗

PubMed1992

Effects of concentration of dietary phosphorus on amount and route of excretion.

Objectives were to determine the effect of dietary concentration of P in DM on routes of excretion of P and to evaluate direct and indirect measures of calculating DM digestibility and P excretion. Twelve lactating Holstein cows were fed 20 kg of DM containing .41% P daily for 4 wk and then were assigned randomly to one of three diets: low (.30%), medium (.41%), or high (.56%) in P for 9 wk. Total collections of excreta (feces and urine) and milk were made during wk 4, 7, 10, and 13. At wk 4, cows excreted 88.2% of P consumed daily: 68.6% of excreted P in feces, 1.0% in urine, and 30.3% secreted in milk. Cows assigned to the low P diet decreased intake by 26.8% and excretion of P in feces by 22.7% in wk 13 compared with wk 4, whereas cows fed the high P diet increased intake by 36.5% and excretion of P in feces by 48.6%. Digestibility of DM was 62.6% when calculated from total collection of feces but only 55.7 or 56.5% when estimated indirectly using Cr or acid detergent lignin as indigestible markers. Apparent excretion of P was less than that estimated using either of the marker techniques (49.7 vs. 59.1 and 58.1 +/- .7 g/d of P) because digestibility of DM was underestimated. A prediction equation was developed for P excretion based on P intake and milk production.

Animals↗

PubMed1992

Milk composition of Majaheim camels.

To determine composition, milk samples were obtained at random from camels at two camel rearing areas near Riyadh, Saudi Arabia. Proximate analyses indicated 3.15% fat, 2.81% protein, 4.16% lactose, 10.95% total solids, .15% acidity, .83% ash, and 88.33% water. Mineral composition was (milligrams per gram) 30.03, Ca; 72.48, K; 43.10, Na; .28, Fe; .18, Pb; and 4.50, Mg. Results should contribute to the overall knowledge of camels as a food source, but much still needs to be learned if efficient improvement programs are to be initiated.

Animals↗

PubMed1991

Effects of steroid administration on pituitary luteinizing hormone and follicle-stimulating hormone in ovariectomized pony mares in the early spring: pituitary responsiveness to gonadotropin-releasing hormone and pituitary gonadotropin content.

These experiments tested the hypothesis that administration of steroid hormones to ovariectomized (OVX) mares during the vernal transition to the breeding season would influence LH and FSH secretion. Circulating gonadotropin concentrations, response to exogenous GnRH, and pituitary gonadotropin content were monitored. Experiments 1 and 2 were conducted, beginning 10 March, and 3 February, respectively, utilizing a total of 30 long-term OVX pony mares. In experiment 1, mares were administered vehicle (n = 5) or estradiol-17 beta (E2, n = 5, 5 mg/3 ml sesame oil), twice daily for 16 days. Blood samples were collected daily for assessment of circulating LH and FSH concentrations. On Day 10 of treatment, 400 micrograms GnRH were administered to all mares. LH increased significantly over days of treatment in the estradiol-treated group, but pituitary response to GnRH tended to be less than in control mares. Circulating FSH tended to decline over days of treatment in estradiol-treated mares, and the pituitary response to GnRH was significantly reduced. Pituitary LH, but not FSH, was increased on Day 16 of treatment with estradiol. In experiment 2, 20 OVX mares received, twice daily, vehicle (n = 5), E2, n = 5; 5 mg), progesterone (P4, n = 5; 100 mg), or progesterone plus estradiol (P4/E2, n = 5; 100 + 5 mg). Treatment continued for 14 days. GnRH (100 micrograms) challenges were administered on Days 6 and 13 of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Anestrus↗

PubMed1991

Effects of a microbial inoculant and(or) sugarcane molasses on the fermentation, aerobic stability, and digestibility of bermudagrass ensiled at two moisture contents.

Tifton 81 bermudagrass was harvested and ensiled either directly (D; 32.4% DM) or wilted (W; 44.1% DM). Four treatments applied to each harvesting method were 1) control (C), or no additive; 2) dried cane molasses (M) at 5% of DM; 3) microbial inoculant (I; Pioneer 1174); and 4) a combination of Treatments 2 and 3 (MI). Wilting reduced the rate of decline of silage pH (P = .001) and produced silages with greater lactic acid concentrations (P = .069), lower acetic acid (P = .001) and ammonia contents (P = .001), and greater in vitro OM (IVOMD; P = .001) and ADF digestibilities (IVADFD; P = .001). These high-quality silages were less stable under aerobic conditions, as evidenced by greater average temperatures (P = .001) and greater yeast and mold counts (P = .001). Adding M to D forage resulted in silage with lower pH (P = .001), greater concentration of lactic acid (P = .001), greater IVOMD (P = .092), and lower acetic acid (P = .009) and ammonia concentrations (P = .002) than inoculated D silage. Wilted silage treated with MI averaged lower pH (P = .025), greater lactic acid content (P = .001) and IVOMD (P = .001), and lower acetic acid (P = .001) and ammonia concentrations than silages treated with M or I alone. These results indicate that wilting improved bermudagrass silage the most, and that the addition of molasses and inoculant to wilted bermudagrass further enhanced silage quality.

Aerobiosis↗

PubMed1991

Extent and site of mineral release from six forage species incubated in mobile dacron bags.

A study was conducted to measure the extent of DM disappearance and mineral release from six forage species within the rumen, abomasum and intestines of the adult bovine using the mobile bag technique. Three nonlactating Holstein cows, fitted with ruminal and duodenal cannulas, were given ad libitum access to alfalfa hay. One gram (DM) of alfalfa, rhizoma peanut, dwarf elephantgrass, bahiagrass, bermudagrass, and limpograss was individually weighed into 8-cm x 3-cm dacron bags. After ruminal incubation for 24 h, bags were incubated in an acid-pepsin solution (a simulated abomasal environment) for 1 h, inserted into the duodenum via cannula, and collected in the feces upon excretion. Ruminal incubation accounted for 86% to 100% of total DM disappearance. Release of Ca from all forages was at least 65%, with the majority having extents of release of over 70%. Most Ca was released in the rumen, but acid-pepsin incubation and washing increased Ca release an additional 17 to 272%. Forages with the highest NDF concentration (bermuda, bahia, and limpograss) sequestered Ca in the intestines. Total tract P release ranged from 84 to 98%, with an average of 7.5 percentage units occurring postabomasally. Grasses released more P in the intestines than legumes. Eighty-eight to 98% of total Mg was released in the rumen. Acid-pepsin incubation increased Mg release only slightly, with some Mg being sequestered in the intestines. Potassium release was complete in the rumen. Ranking of minerals based on maximal extent of release was K greater than Mg greater than P greater than Ca. With the exception of K, legumes released more of their minerals than grasses.

Abomasum↗

PubMed1991

Ontogeny of hepatic bovine growth hormone receptors in cattle.

A series of studies examined the binding characteristics and ontogeny of hepatic growth hormone binding sites in dairy bulls on d 2, 30, 180, and 365 of age. Binding of iodinated recombinant bovine growth hormone ([125I]rbGH) to liver membrane receptors was membrane protein-dependent. Receptors were considered growth hormone-specific, because physiological concentrations of bovine prolactin (bPRL) failed to displace [125I]rbGH from bovine hepatocyte membranes. Only 50% of [125I]rbGH was bound reversibly to hepatic microsomes. Addition of dithiothreitol (DTT) to the receptor-assay buffer increased the binding of [125I]rbGH to hepatic membranes in a time-dependent manner. Moderate concentrations of Ca++ and Mg++ in the receptor-assay buffer had no detectable effects on binding of [125I]rbGH to hepatic microsomes. In growing dairy bulls, specific binding of [125I]rbGH per milligram of membrane protein increased from 1.9 +/- 1.8% at d 2 to 14.1 +/- 1.8% at d 180 and then declined to 5.2 +/- 1.6% at d 365. Likewise, concentration of insulin-like growth factor (IGF)-I in serum was low during the 1st mo of age (d 2, 13.3 +/- 8.8 ng/ml; d 30, 9.7 +/- 8.8 ng/ml), but it became maximal at d 180 (151.0 +/- 8.8 ng/ml). Circulating concentrations of IGF-II increased linearly during the 1st yr of growth. Serum concentrations of GH, triiodothyronine, and thyroxine declined from 39.9 +/- 6.5, 2.7 +/- .2, and 75.4 +/- 4.6 ng/ml at d 2 to 16.5 +/- 6.5, 1.3 +/- .2, and 53.4 +/- 4.6 ng/ml at d 30, respectively, and remained low through 1 yr of age. Insulin concentration in serum did not change significantly with development. Results indicated that increasing concentrations of specific bGH receptors in the bovine liver may play a key role in regulating postnatal growth in cattle.

Aging↗

PubMed1991

Effects of acute thermal stress and amount of feed intake on concentrations of somatotropin, insulin-like growth factor (IGF)-I and IGF-II, and thyroid hormones in plasma of lactating Holstein cows.

Our objective was to evaluate effects of acute thermal stress, independent of reduced feed intake caused by elevated temperatures, and of reduced feed intake in thermal comfort on plasma concentrations of somatotropin, insulin-like growth factors I and II, thyroxine, and triiodothyronine. Six Holstein cows (averaging 475 +/- 18 kg BW, 2.3 +/- .3 parities, and 96 +/- 12 d in lactation) surgically fitted with catheters in the hepatic portal vein, mesenteric vein, and intercostalis posterior artery were exposed to treatments of thermal comfort environments with ad libitum or restricted (75% of ad libitum) DM intake and a thermal stress environment with ad libitum intake in two balanced 3 x 3 Latin squares. Thermal stress increased rectal temperatures and respiration rates. Dry matter intake of the thermal-stressed cows offered feed ad libitum (11.1 +/- .7 kg/d) was similar to the experimentally imposed reduction in DM intake of the thermal comfort restricted group (11.5 +/- .7 kg/d). Dry matter intake of cows in thermal comfort was 15.1 +/- .7 kg/d. Plasma somatotropin concentrations tended (P less than .08) to decrease during thermal stress but were unchanged by amount of feed intake in thermal comfort environments. Concentrations of IGF-I were not affected by treatments. Concentrations of IGF-II tended (P less than .14) to increase with thermal stress compared with thermal comfort treatments. Thyroxine concentrations tended (P less than .15) to increase in the thermal stress treatment compared with the thermal comfort restricted intake treatment. Triiodothyronine tended (P less than .11) to decrease with restriction in feed intake in the thermal comfort environment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Prepartum and peripartum reproductive performance of dairy heifers freshening at young ages.

Reproductive performance of five breeds (81% Holstein or Jersey) in the Florida Agricultural Experiment Station herd was evaluated from data collected over 20 yr. Data represented 1144 parturitions after gestations greater than 250 d with all twin births excluded. Number of services per conception was not affected by age at first insemination. Mean age of exposure to first service was 414 d; mean age at first parturition was 25.8 mo. Overall, 39.7% of heifers calved at 23 mo or less. Intermediate ages, 24 to 27 mo, comprised 33.9% of heifers, whereas 26.4% of heifers calved at greater than or equal to 28 mo. Overall incidences of problems at parturition were retained fetal membranes, 3.6%; dystocia, 3.8%; metritis, 10.5%; and stillbirth, 11.5%. Frequencies of stillbirth and retained fetal membranes apparently were not affected by age, but metritis increased linearly with age at first parturition. Holsteins experience higher incidences of all problems than did Jerseys. Heritability (from paternal half-sib correlation) of birth weights and gestation lengths were .31 and .24; genetic correlation was .14. Heritabilities of occurrence of stillbirth, retained fetal membranes, metritis, and dystocia were negative and considered to be 0. Heritabilities of age at first service, days from first service to conception, number of services, and age at first parturition were .22, .11, .05, and .43. Dairy producers can consider reducing age at first parturition to at least 22 mo, under environmental and management conditions of this study, without increased frequencies of problems at parturition.

Age Factors↗