Biomedical subjects

C J Wilcox

Publications and source records attributed to C J Wilcox.

At least 55 records · Page 3Linked to original sources

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↗

PubMed1991

Measurements of genetic variation in residual metabolizable energy intake of laying hens.

An experiment was conducted to determine heritability of the residual component of feed consumption. The effect of test period length was also examined to determine the shortest test period that would result in reliable data. Three hundred and thirty-five pedigreed White Leghorn hens were used. The experiment began when the hens were 26 wk of age and lasted for 28 wk. The residual component of energy intake was determined for each hen for time periods of 2, 4, and 8 wk in length. These values were used to determine heritability. Analyses of the data for each period were performed in two steps. A reduced model, without pedigree information, was used to develop a regression model. A complete model was used for analyses of data. The procedure of starting egg mass output measurements 2 days after body weight measurements was more effective than starting records on the same days that body weights were obtained. The partial regression coefficients of ME intake decreased with age. Also the partial regression coefficients of ME on body weight change increased with the length of the test period. The partial regression coefficients of ME on egg mass increased slightly with age. Heritability of ME intake adjusted for metabolic body weight, body weight change, and egg mass output was highest (.567 +/- .186) when the test was calculated by 8-wk periods. However, the range of estimates over time was lowest when made for 4-wk periods.

Animals↗

PubMed1991

Comparison of energy utilization efficiency among six lines of White Leghorns.

Individual records were used of feed consumption, BW, BW change, and egg mass (EM) output during a 4-wk period for 180 hens from six different lines of White Leghorn chickens (30 hens per line). The diet contained 16.45% protein and 2,825 kcal ME/kg. Feed consumption was used to calculate actual ME intake (AcME) for each hen. Multiple regression of AcME was performed with metabolic BW, BW change, and EM production as independent variables. The regression coefficients and the independent variables were then used to calculate the expected ME intake (ExME). The following values were calculated for each hen and were used to compare energy efficiency among the six lines: the residual component of energy intake (RES), defined as the difference between the AcME intake and ExME intake; the relative efficiency ratio (RER), defined as (ExME divided by AcME) X 100 (calculated using the partial regression coefficients of the overall equation); and feed conversion, the ratio of feed consumed to EM. Significant differences among the lines in efficiency of EM produced were observed regardless of the efficiency measurement used. Feed consumption did not indicate differences in RES or RER. A multiple regression equation was derived for each line. Significant differences were found among the six lines in their energy requirements for maintenance and for egg production. These results suggest the possible use of the partial regression coefficients as selection criteria for separately improving maintenance efficiency and egg production efficiency.

Analysis of Variance↗

PubMed1990

Interleukin-1 receptor antagonist activity of a human interleukin-1 inhibitor.

Three interleukin-1 inhibitors have been purified to homogeneity from medium conditioned by human monocytes. Partial sequence analysis and digestion with N-glycanase indicate that these are glycosylation forms of a single protein. The protein binds to the interleukin-1 receptor but has no interleukin-1-like activity, even at very high concentrations, and is therefore a pure receptor antagonist.

Amidohydrolases↗

PubMed1990

Effects of feed intake and thermal stress on mammary blood flow and other physiological measurements in lactating dairy cows.

Six midlactation Holstein cows were exposed to treatments of thermal comfort environments with ad libitum or restricted (70% of ad libitum) DM intake and a thermal stress environment with ad libitum intake in two balanced 3 X 3 Latin squares to evaluate effects on mammary blood flow and other physiological measurements. Daily DM intake decreased from 17.8 kg in thermal comfort with ad libitum intake to 12.5 kg in thermal comfort with restricted intake and to 14.8 kg in thermal stress. Daily milk production decreased from 23.9 kg in thermal comfort ad libitum to 22.2 kg in thermal comfort restricted and 21.6 kg in thermal stress. Mammary blood flows (half udder) over the entire sampling interval (18 h) were 5.1, 4.3, and 4.5 L/min for treatments: thermal comfort, ad libitum intake; thermal comfort, restricted intake; and thermal stress, ad libitum intake. Mammary blood flows did not differ significantly among between treatments. Relationship of hald udder blood flow (L/min) to previous day's DM intake (kg/d) was described by the linear equation: L/min = .49 + (.27 kg/d); r2 = .46; and the quadratic equation: L/min = 6.04 - (.54 kg/d) + (.03 [kg/d]2); r2 = .55. Mammary blood flows 10 min before through 10 min after milking machine attachment were greater for cows at thermal comfort and ad libitum intake than for cows at thermal comfort and restricted intake or thermal stress and ad libitum intake (5.5, 4.8, and 4.8 L/min).

Animals↗

PubMed1990

Lactational responses to and in vitro ruminal solubility of magnesium oxide or magnesium chelate.

Thirty-six midlactation Holstein cows were used in a randomized incomplete block design to evaluate lactational responses to varying dietary concentrations of Mg supplemented by MgO or Mg chelate. Basal diet was 41:4:55 corn silage:cottonseed hulls:concentrate (.21% total Mg). Magnesium oxide was added to the basal diet to give .32, .37, and .43% total dietary Mg, and Mg chelate was added to provide .23, .25, and .27% Mg, DM basis. Dietary treatments were formulated to supply equal concentrations of bioavailable Mg from either Mg source. Dry matter intake and milk yield were greater by cows fed MgO-supplemented than Mg chelate-supplemented treatments. Milk fat percentages were not affected. Milk protein percentages increased with Mg chelate compared with protein percentages with MgO. Treatments did not affect gross efficiency (4% FCM/DM intake) or body weight change. Lack of response to Mg chelate suggested that either the bioavailability was not as high as assumed or that sufficient total bioavailable Mg was not provided in those treatments. A companion in vitro experiment showed that MgO-supplemented concentrates, with more total supplemental Mg, supplied two to three times more soluble Mg than Mg chelate-supplemented concentrates.

Animal Feed↗

PubMed1990

Effects of stage of lactation and pregnancy and their interactions on milk yield and constituents.

Effects of stage of lactation and pregnancy and their interactions on 17 milk yield and constituent traits of Holsteins and Jerseys were studied. Data were 11,120 Jersey and 11,092 Holstein daily milk samples. After adjustment for all other known and systematic genetic and environmental effects, stage of lactation influenced all traits and accounted for 11.8 to 26.3% of variation in yields and .2 to 9.9% in percentages. In general, yields declined and percentages increased after about 3 mo of lactation. Chloride percentage showed an initial decline and then a rise after 2 mo. Stage of pregnancy accounted for small but significant variation in most traits; variation was .2 to .4% and less than .1 to 3.0% in yields and percentages for Holsteins, and less than .1 to .2% and .1 to 1.1% for Jerseys. Interactions between stage of lactation and pregnancy were investigated by response surface methodology and found to be very small.

Animals↗

PubMed1989

Effects of thermal stress and level of feed intake on portal plasma flow and net fluxes of metabolites in lactating Holstein cows.

Six Holstein cows (averaging 475 kg body weight, 2.3 parities and 96 d in lactation) fitted with catheters in the hepatic portal vein, mesenteric vein and intercostalis posterior artery were exposed to treatments of thermal comfort environments with 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 to evaluate effects of thermal stress on portal plasma flow and net fluxes of metabolites. Portal plasma flow was measured by administering a primed, continuous infusion of para-aminohippurate into a mesenteric vein and determining its concentration and dilution in portal vein plasma. Thermal stress treatment increased rectal temperatures and respiration rates. Dry matter intake decreased from thermal comfort ad libitum level (15.1 kg/d) to lower levels in thermal comfort restricted (11.5 kg/d) and thermal stress (11.1 kg/d) treatments. Portal plasma flow was related directly to level of DM intake, declining about 14% with thermal comfort restricted intake and thermal stress environment treatments compared with the thermal comfort restricted intake and thermal stress environment treatments compared with the thermal comfort ad libitum intake treatment. Net flux of alpha-amino N was reduced 20 and 35% by thermal comfort restricted intake and thermal stress treatments compared with the thermal comfort ad libitum intake treatment. Net fluxes of urea N, ammonia N and glucose were not affected by experimental treatments. A portion of the negative effects of thermal stress on milk production can be explained by decreased nutrient intake and decreased nutrient uptake by the portal-drained viscera of the cow.

Amino Acids↗

PubMed1989

Genetic effects on dairy calf growth.

Objectives were to establish growth patterns for weight and height in dairy calves from birth to 90 d and to estimate appropriate genetic parameters. Measurements were 7943 body weights and 7005 wither heights of 752 calves. Represented over 12 yr were three breeds, 348 dams, and 115 sires; data resulted from designed calf nutrition experiments. Sources of variation considered in various least squares analyses of variance were breed, sire in breed, calf in sire in breed, sex of calf, treatment-year category, and several interactions. Repeatabilities of weights and heights between birth and 90 d were .64 and .88; heritabilities were .22 and .30; genetic and phenotypic correlations were .53 and .73. A regression equation was estimated for each calf. From these 752 equations, heritabilities of initial weight, initial height, and rates of growth in weight and height were .53, .50, .44, and .19. Genetic correlations were .81; -.07; -.05; .26; .14; .84. Selection schemes for these traits in dairy cattle should consider that although weights and heights at birth and thereafter are highly and positively correlated genetically, as are gains, birth measurements and gains to 90 d may be uncorrelated.

Animals↗

PubMed1989

Effects of bovine somatotropin on milk yield and composition, dry matter intake, and some physiological functions of Holstein cows during heat stress.

Thirteen Holstein cows (46 to 106 d postpartum) were assigned to a partially balanced incomplete block experiment to evaluate effects of bovine somatotropin (20.6 mg monomer/d) and environment (shade and no shade) on milk yield and composition, feed intake, rectal temperature, respiration rate, and concentrations of hormones in plasma. Two treatment periods were 29 d each, preceded by 10-d preliminary periods. Water and cotton-seed hull-based diet were available ad libitum. Mathematical model for statistical analyses included cow, period, treatment, environment, day, and estimable interactions. Black globe temperature and respiration rate and rectal temperature of cows were higher in no shade. Milk and 3.5% FCM yields and feed intake of cows in no shade were approximately 9.5 and 16% less than for cows in shade. Much of the effect of heat stress was associated with reduced DM intake. The 3.5% FCM, but not milk yield, was increased by injections of bovine somatotropin. Dry matter intake was unaffected, but milk, 3.5% FCM, and component yields were increased by bovine somatotropin when adjusted for DM intake. Response of cows to bovine somatotropin was not different in the two environments, except cows injected with bovine somatotropin had slightly higher body temperature and respiration rate. Increased production responses of heat-stressed cows due to bovine somatotropin were less than in cows injected under more temperate conditions.

Animal Feed↗

PubMed1989

Effects of sire of fetus upon subsequent milk production and reproduction of Jersey cows.

Estimates of variation associated with sire of fetus effects were obtained from 14,147 Jersey records that originated in four southeastern states. After adjustment for age of cow and length of record, the complete model included sire of fetus, sire of cow, herd-year-season effects, and effects of all possible interactions. Deletion of some or all interactions was necessary for mixed model analyses. Completely random models yielded unrealistically high estimates for sire of fetus variances for milk and fat yields and for fat percent, as had previous research. Mixed model analyses suggested that sire of fetus effects were small, albeit real and measurable. As a portion of total variability they accounted for: in milk and fat yields, 1 to 2%; fat percentage, 1 to 4%; days open, 0 to 1%. Gestation lengths were affected by fetal sire, regardless of whether the model was random or mixed; variances were 9.3 to 13.6% of the total. Preliminary estimates of interactions involving sire of fetus, sire of cow, and herd-year-season suggested that they are not zero and warrant further study.

Animals↗

PubMed1988

Restricted conceptus mobility results in failure of pregnancy maintenance in mares.

Cycling pony mares were bred and used to test the effect of restricted conceptus mobility on luteal maintenance (i.e. maternal recognition of pregnancy). In Experiment 1, uterine horns were ligated to restrict conceptus mobility to one uterine horn, Group 1; one horn plus the uterine body, Group 2; or one horn, the body and approximately 80% of the second horn, Group 3. Pregnancies were monitored with real-time ultrasonography. Four of five mares in Group 1 and two of four mares in Group 2 returned to estrus (Day 16.0 +/- 1.9 and 14.5 +/- 0.7, respectively) and subsequently lost the embryonic vesicles (Day 17.2 +/- 1.2 and 15.7 +/- 0.7, respectively). None of the four mares in Group 3 lost the vesicles. There was a significant effect of the interaction of treatment (amount of uterus available to the conceptus) and day on plasma progesterone (P) concentration (p less than 0.005). In Experiment 2, conceptus mobility was restricted to one uterine horn in two groups of mares, of which the second was treated with the synthetic progestin, Regu-Mate (allyl trenbolone). In the first group, each of three mares lost the vesicle (Day 17.3 +/- 4.3). In the second group, four of five mares maintained the pregnancies, indicating that pregnancy failure was due to the effects of declining P. These data indicate that restricted conceptus mobility results in luteolysis in the mare, and that the subsequent decline in P leads to embryonic death.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Nycterohemeral patterns of acid-base status, mineral concentrations and digestive function of lactating cows in natural or chamber heat stress environments.

Effects of heat stress on multiparous lactating Holstein cows were evaluated in a continuous design in natural environments (a shade management system vs no shade, n = 6/treatment, early- to mid-lactation cows) and in a single-reversal design in climatic chambers (thermoneutral vs thermal stress, n = 4/treatment, mid- to late-lactation cows). Objectives were to compare effects of nycterohemeral heat stress vs nonheat stress environments on acid-base status, mineral concentrations and rates of ruminal liquid dilution and solid phase digesta turnover. In the shade vs no shade experiment, the complete mixed diet consisted of 38% corn silage and 62% corn-based concentrate mix. In the chamber experiment, the diet consisted of 40% alfalfa haylage and 60% corn-based concentrate mix. In both experiments, respiration rates, rectal temperatures, blood and urine were sampled hourly for 26 h. Measurements of rectal temperature, respiration rate and blood gas composition indicated that chamber heat stress simulated natural heat stress. In both experiments, cows exhibited signs of respiratory alkalosis only during hours of heat stress. Ruminal turnover rates of liquid were measured with chromium-ethylenediaminetetraacetate and solid turnover rates with ytterbium-marked fecal fiber, both dosed through the ruminal cannula. Turnover rates of liquid and solid digesta and total volatile fatty acids were lower in the heat stress vs the thermoneutral environment. The results illustrate the necessity of frequent sampling to characterize nycterohemeral patterns of physiological measurements during heat stress.

Acid-Base Imbalance↗

PubMed1988

Effects of supplemental potassium and sodium chloride salts on ruminal turnover rates, acid-base and mineral status of lactating dairy cows during heat stress.

Effects of added dietary sodium and potassium chloride salts on ruminal turnover rates, acid-base balance and mineral status of lactating dairy cows experiencing a nycterohemeral cycle of heat stress were examined. Black globe-humidity index in the chambers averaged 94 during the daytime and 68 during the nighttime. Four ruminally cannulated multiparous Holstein cows in mid-lactation were confined in climatic chambers for a single-reversal experiment consisting of two 17-d periods. To the basal diet (50% corn silage: 50% concentrate, which contained .97% potassium, .19% sodium and .20% chloride), 1.25% sodium chloride plus 1.85% potassium chloride were added, making the high mineral treatment (1.93% potassium, 68% sodium and 1.85% chloride). Liquid dilution rates from the rumen were measured by chromium-ethylenediaminetetraacetate disappearance. Turnover rates of solids were determined by appearance of ytterbium in feces. Ruminal contents, arterial blood and urine were collected hourly for 26 h. Grab samples of feces were sampled over 6 d. Dry matter intakes and milk yields were not affected by the diets (averaging 17.8 and 21.1 kg/d, respectively). Cows fed the high mineral diet drank 17% more water (P less than .01). Tests for homogeneity of regression were utilized to compare chromium disappearance and ytterbium appearance data, which were best described by second-order polynomial functions. Increased ruminal chromium disappearance (P less than .01) and decreased total volatile fatty acid concentrations (P less than .01) suggested faster liquid dilution rates with high mineral diet, but turnover rates of solids were not affected. Urinary potassium secretion compensated for the high potassium content of the high mineral diet without an alkalogenic effect on acid-base status. Lower urine pH and higher urine ammonium concentrations during cool hours suggested that the high chloride content of the high mineral diet had an acidogenic effect. The results are interpreted to indicate that high level inclusion of sodium and potassium chloride salts altered digestive, acid-base and mineral status of heat-stressed lactating cows.

Acid-Base Equilibrium↗

PubMed1988

Effects of thyroxine and growth hormone treatment of dairy cows on mammary uptake of glucose, oxygen and other milk fat precursors.

Four cows received thyroxine injections (T4; 20 mg/d) and three cows received growth hormone injections (GH, 44 mg/d) for 4 d during successive 16-d experimental periods. Milk fat, lactose output, mammary uptake of glucose, oxygen and milk fat precursors were determined with each treatment. Injection of T4 increased lactose yield by 25% and fat yield 42%. The injection of GH increased fat and lactose yields by 24%. Both GH and T4 increased mammary glucose uptake by 35% and 45%, respectively, while T4 administration was associated with an increase in plasma glucose concentration from 67 to 84%. Thyroxine, but not GH, increased the ratio of mammary glucose uptake to lactose output from 1.24 to 1.58. Blood plasma acetate concentration declined following GH and T4 treatment by 17%. Mammary acetate uptake increased in response to GH injection in two of three cows but did not change with T4 injection. The injection of GH had no effect on plasma propionate concentration or mammary uptake. Thyroxine reduced plasma propionate content and mammary uptake. Neither T4 nor GH changed plasma free fatty acid concentration or mammary uptake. Thyroxine had no effect on plasma triglyceride concentration or mammary uptake, whereas GH increased mammary triglyceride uptake to the end of the experimental period. Mammary oxygen uptake was increased by GH as milk production increased. Increased mammary oxygen uptake following T4 treatment was transient. Change in mammary metabolism with T4 treatment permitted increased milk output without change in mammary oxygen consumption. Such a change may involve increased mammary utilization of pre-formed long-chain fatty acid and increased metabolism of glucose via glycolysis.

Animals↗

PubMed1988

Interactions of climatic factors affecting milk yield and composition.

Objectives were to evaluate effects of interactions of maximum temperature, minimum relative humidity, and solar radiation on milk yield and constituent traits. Effects of climate variables and their interactions were significant but small in most cases. Second order regression models were developed for several variables. Six were examined in detail: Holstein and Jersey milk yields, Holstein fat and Feulgen-DNA reflectance percent, and Jersey protein percent and yield. Maximum temperature had greatest influence on each response, followed by minimum relative humidity and solar radiation. Optimum conditions for milk production were at maximum temperatures below 19.4 degrees C, increasing solar radiation, and minimum relative humidity between 33.4 and 78.2% (cool sunny days, moderate humidity). Maximum Holstein fat percent of 3.5% was predicted for maximum temperatures below 30.8 degrees C, minimum relative humidity below 89%, and solar radiation below 109 Langleys; actual mean Holstein fat percent was 3.35%. Optimum climatic conditions for Jersey protein percent were at maximum temperature of 10.6 degrees C with solar radiation at 300 Langleys and relative humidity at 16% (cool sunny days, low humidity). Because noteworthy interactions existed between climate effects, response surface methodology was suitable for determining optimum climatic conditions for milk production.

Animals↗

PubMed1988

Climatic effects on occurrence of clinical mastitis.

Clinical mastitis records for 6.5 yr from a large north Florida dairy and corresponding daily weather data were analyzed. Monthly incidence of clinical mastitis was expressed as percent of cow-days in milk and graphed against monthly average daily maximum temperature humidity index values and monthly total rainfall. No trends were evident with rainfall. In 3 of 6 yr, monthly incidence of clinical mastitis increased more than 50% above annual incidence, and this followed high monthly temperature-humidity values. Least squares was used to estimate regression coefficients of temperature-humidity index categories based on 999,969 Holstein records. A temperature humidity index category represented the number of days used to calculate average daily maximum temperature-humidity index value. Sources of variation in observed occurrence of clinical mastitis were cow, parity, month, year, interaction of parity by month, and continuous effects of temperature-humidity index categories 2, 6, 15, 30, 60, each to third order and 60 by parity interaction. In all temperature-humidity index categories as the temperature-humidity index value increased, occurrence of clinical mastitis increased. When values rose from 55 to 80, twice as many for 2 d cows showed signs of clinical mastitis.

Animals↗