Biomedical subjects

C J Wilcox

Publications and source records attributed to C J Wilcox.

At least 73 records · Page 4Linked to original sources

PubMed1988

Effect of pregnancy, milk yield, and somatic cell count on bovine milk fat hydrolysis.

During 12 mo, 1818 milk samples were collected from Holsteins and Jerseys (n = 261) to evaluate effects of advancing lactation and pregnancy on milk fat hydrolysis. Aliquots, cooled immediately and stored 48 h at 4 degrees C, were analyzed for free fatty acid content. Holsteins had higher acid degree values than Jerseys (.90 vs. .62). No difference in values was detected between alternate a.m. (.74) and p.m. (.76) sampling times. Repeatability of acid degree values from lactation to lactation was low (.22). Days in milk, days pregnant, and milk yield had curvilinear effects on acid degree values, whereas SCC effects were linear. Estimated acid degree value at 335 d in milk (average dry-off) was lowered from .80 to .63 when adjusted for days pregnant and to .48 when adjusted also for milk yield. These responses agree with the increased acid degree values associated with two late lactation events: increasing day pregnant and decreasing milk yield. Estrogen secreted by the developing fetal-placental unit could mediate changes in milk composition that promote milk fat hydrolysis.

Animals↗

PubMed1988

Lactational responses to dietary magnesium, potassium, and sodium during winter in Florida.

Forty-eight midlactation Holstein cows were used to evaluate dietary treatments arranged as a 4 x 2 x 2 factorial: .26, .38, .48, or .60% Mg, .24 or .62% Na, and 1.14 or 1.59% K. Supplemental Mg, K, and Na were supplied by feed-grade magnesium phosphate, potassium bicarbonate, or sodium chloride. All dietary treatments were equal in Ca and P. There were no effects of dietary Na or K on feed intake or milk production. Feed intakes were equal with .26, .38, and .48% Mg but declined 4.9% with .60% Mg. Milk yields responded curvilinearly to dietary Mg. Similarly, 4% FCM yields responded curvilinearly, increasing 7% with .48% Mg compared with .26% Mg then declining with .60% Mg. Milk fat percentages were unaffected by dietary Mg concentration, but milk fat yields responded curvilinearly. Milk protein percentages declined linearly as dietary Mg increased. Plasma Mg concentrations increased linearly from 2.52 to 2.68 mg/dl as dietary Mg increased. Renal fractional excretions of Ca responded curvilinearly as dietary Mg increased and decreased as dietary K increased. Results of this experiment suggested that current recommendations for dietary Mg do not maximize lactational performance. A companion laboratory experiment showed that feed-grade magnesium phosphate had less alkalizing capacity than two MgO sources.

Animals↗

PubMed1988

Effects of administration of bovine somatotropin on milk yield and composition.

Thirty-two Holstein cows were assigned to four treatment groups in a continuous lactation trial to evaluate effects of daily subcutaneous injections of 0 (A), 5.15 (B), 10.3 (C), and 20.6 mg (D) of recombinantly derived bovine somatotropin monomer. Responses were milk yield and composition, component yields, net energy intake, body weight, and somatic cell counts. Treatments began in fall, 28 to 35 d postpartum, and continued for 266 d. Base ration was corn silage and concentrate. Least squares means of milk and constituent yields and gross efficiency of milk production differed among treatments, but percentage fat and protein, energy intake, body weights, and somatic cell counts did not. Least squares means of 3.5% FCM were 21.3 (A), 25.0 (B), 26.2 (C), and 28.5 kg/d (D); fat and protein yields showed similar response to treatment. Milk yields adjusted for pretreatment yields were 21.1 (A), 25.5 (B), 26.5 (C), and 29.3 kg/d (D). Orthogonal contrasts showed lower milk and constituent yields and net energy intake for control (A) than for hormone-injected cows (B, C, D), but no differences were detected between treatments B, C, and D. Gross efficiency of production (3.5% FCM/feed net energy intake) was greater for hormone-injected cows.

Animals↗

PubMed1988

Comparison of different methods of expressing dietary protein for lactating dairy cows.

Data were from Holstein cows from 20 experiments at the University of Florida (1688 cow-period observations). Objectives were to compare milk responses to increasing dietary percent or daily intake of CP, estimated undegradable CP, and estimated metabolizable protein from Burroughs and Chalupa equations and to determine if higher producing cows (26.8 kg milk/d) responded differently to increasing dietary protein percent or intake than do lower producing cows (18.9 kg milk/d). The mathematical model included experiment, cow-within-experiment, period, body weight, and source of roughage. Intake of protein (kg/d) had a greater effect (cubic polynomial) on milk yield than protein percent of DM since CP, undegraded protein, Chalupa metabolizable protein, and Burroughs metabolizable protein intakes explained 17.2, 20.9, 23.5, and 24.1% of residual variation in milk yield compared with .6, 2.1, 1.7, and 2.1%, for percents of DM. High producing cows responded more to increasing protein intake than did low producing cows. Respective protein intake variables explained 20.6, 23.7, 30.5, and 31.2% of residual variation in milk yield in high production group compared with 17.2, 23.1, 20.6, and 20.6% in low production group.

Animals↗

PubMed1987

Avulsion of the bovine prepuce from its attachment to the penile integument during semen collection with an artificial vagina.

Avulsion of the prepuce (AP) from the penile integument during intromission into an artificial vagina (AV) is the most common injury involving the penis and prepuce of bulls collected for the production of frozen semen at artificial insemination (AI) centers. We observed clinical cases at two AI centers. Because temporary loss of seminal collections from genetically superior bulls occurs and the possibility of impotency exists, the economical loss from AP is significant. Surgery, rather than a nonsurgical procedure, is the preferred method for repair of AP if the diagnosis occurs on the same day as the injury. After injury, seminal collection is avoided. The bull can then begin a conditioning program prior to returning to a normal semen collection schedule. A specific etiology for AP remains undetermined; however, many variables potentially involved in its occurrence are known. Bulls with good libido following 4 to 5 yr of sexual inactivity are particularly susceptible to AP. No genetic predisposition was observed. At present, we believe that AP is caused by many factors and that implementing preventive measures does help.

Journal Article↗

PubMed1987

Effects of neutral detergent fiber and roughage source on dry matter intake and milk yield and composition of dairy cows.

Data were from 20 experiments that utilized early to midlactation Holstein cows fed complete mixed diets or fed at constant forage:concentrate ratios. Within-cow diet comparisons (1688 cow-periods) were analyzed by least squares analysis of variance; mathematical model included experiment, cow in experiment, period, body weight, and source of roughage. Objectives were to determine relationships between neutral detergent fiber content of diet and milk yield and dry matter intake. Roughages and number of cow-periods were: sugarcane bagasse/silage (507), cottonseed hulls (504), corn silage (268), ground corrugated boxes (170), alfalfa/peanut hay (132), and others (107). Dry matter intake and estimated net energy intake had linear effects on milk yield and explained 21.6 and 24.0% of its residual variation; milk yield had curvilinear (quadratic) effect and explained 22.4% of dry matter intake residual variation. Interaction between neutral detergent fiber and source of roughage on milk yield, 4% fat-corrected milk, and dry matter intake resulted in reductions of 5.6, 5.6, and 13% in residual variations. Results suggest neutral detergent (% of dry matter) has greater effect on dry matter intake than on milk yield and its use in formulating diets for dairy cows will be within roughage source.

Animal Feed↗

PubMed1987

Mineral content of milk, colostrum, and serum as affected by physiological state and mineral supplementation.

A 22-mo experiment was conducted to determine effects of mineral supplementation of cows on mineral elements in milk, colostrum, and blood serum. Purebred Brahman beef cows grazing pastures grown on sandy and well-drained soils were allotted to three treatments of 12 cows each as follows: control, a complete commercial mineral mixture, control plus dietary and injected Se, and control plus fortified mineral mixture. Milk and serum were analyzed for minerals 2 consecutive yr at parturition and 3 mo postpartum. Mean cow serum, Ca, Mg, P, and packed cell volume values were higher at parturition than 3 mo later, whereas serum Cu was highest at 3 mo. Mean serum concentrations were affected by year with higher Ca and hemoglobin and lower Cu concentrations in 1982 than in 1981. Increasing dietary Se resulted in higher serum Se. Colostrum was higher in Mg, P, Cu, Fe, Se, and Zn than milk, whereas milk was higher than colostrum in Mn. Means for treatment X time showed cows fed dietary and dietary plus injected Se and vitamin E had more Se in milk than milk from cows fed no supplemental Se.

Animals↗

PubMed1987

Occurrence and reoccurrence of clinical mastitis.

Clinical mastitis records for 6.5 yr (July 1977 through November 1983) from a large north Florida dairy were analyzed. Observed frequencies of clinical mastitis were calculated in 7240 Holstein and Jersey lactations. Least squares analyses used Holstein and Jersey lactations greater than 200 d and limited maximum parity to 5 (6732 lactations, 5738 episodes). Solutions for number of occurrences of clinical mastitis adjusted for month of parturition and breed effects were .47, .59, .94, 1.27, and 1.50 for parities 1 through 5. Solutions for number of occurrences across lactation in Holsteins was greater than for Jerseys (1.28 vs. .63). Solutions for occurrence of first episode in Holsteins increased from .35 in parity 1 to .71 in parity 5. Occurrence of episodes two through five increased as parity increased. Similar trends were found in Jerseys with the exception of parity 2. Correlation of residuals between specific episodes increased as episode increased. From episode 2 through 5 probability of another occurrence of clinical mastitis was greater than .75. Solutions for proportion of occurrences of clinical mastitis occurring during the first 35 d postcalving were .60, .36, .31, .30, and .28 for parities 1 through 5. Clinical mastitis in first parity cows occurred primarily during the first 35 d postcalving.

Animals↗

PubMed1986

Relationship between estrone sulfate in plasma and litter size at farrowing for sows and gilts.

A positive association (P < 0.01) was detected between estrone sulfate (ES) concentrations in maternal plasma at Day 30 of pregnancy and litter size at parturition in swine. This relationship was best described by a fifth order regression equation (R(2) = 0.5) which indicated that as ES increased from 1 to 7.5 ng/ml on Day 30, litter size increased from 0 (nonpregnant) to 18 piglets farrowed. Day of sampling (P < 0.02), month (P < 0.04) and parity (P < 0.08) were major sources of variation in the model. This indicated that effects of environmental factors such as heat stress, which influence conception rate and embryonic survival, are reflected in changes in maternal ES. Also, larger litter size associated with parous sows is reflected in increased ES in maternal plasma. We conclude that measurement of ES early in gestation may be useful in reproductive management to identify nonpregnant gilts and sows as well as those with small litters.

Journal Article↗

PubMed1986

Prostaglandin F2 alpha as the luteolysin in swine: VI. Hormonal regulation of the movement of exogenous PGF2 alpha from the uterine lumen into the vasculature.

To test the endocrine-exocrine theory of maternal recognition of pregnancy in the pig 16 gilts were assigned randomly to a 2 X 2 factorial involving pretreatment with sesame oil (SO) or estradiol valerate (5 mg; EV) injected on Days 11 through 14 of the estrous cycle and an intrauterine injection of saline (5 ml; SA) or prostaglandin F2 alpha (50 micrograms; PGF) on Day 14. Peripheral blood samples were collected for 120 min postinjection and analyzed for 15-keto-13,14-dihydro-PGF2 alpha (PGFM). PGFM concentrations were lower in EV than SO gilts (438 vs. 844 pg/ml; p less than 0.05). There was heterogeneity of regression between EV and SO gilts (p less than 0.01), with EV gilts having a slower release of PGF from the uterine lumen into the vasculature. Prostaglandin F2 alpha did not increase mean PGFM concentrations (p greater than 0.10), but resulted in an altered temporal pattern of PGFM (p less than 0.05) compared to SA gilts. There was an interaction between the two treatments over time, with EV-PGF gilts demonstrating a slower, more gradual release of PGFM than SO-PGF gilts. To test whether prostaglandins of the E series were involved in this mechanism, gilts were assigned to two 4 X 4 latin squares balanced for residual effects and treated with saline or flunixen meglumine (Banamine). Each gilt was treated with four PGE:PGF infusion sequences (SEQ) in each uterine horn: phosphate-buffered saline (PBS; PBS-SEQ), PGE1 (50 micrograms), PGE2 (50 micrograms), and PGE1 (25 micrograms) + PGE2 (25 micrograms) (PGE-SEQ), with each infusion followed 15 min later by PGF (25 micrograms).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Responses of lactating cows to dietary sodium source and quantity and potassium quantity during heat stress.

Effects of heat stress and added dietary sodium bicarbonate (0 or 1.0% of dry matter), sodium chloride (0 or .73% of dry matter), and total dietary potassium (1.3 or 1.8% of dry matter) on acid-base status, production, and mineral metabolism of lactating Holstein cows were evaluated. Design was split-plot with 24 cows in shade or no shade environments; dietary treatments were arranged as a 2 X 2 X 2 factorial within each environment. Basal diet (38% corn silage:62% concentrate) contained .18% sodium; sodium bicarbonate and sodium chloride treatments were in addition. All dietary treatments were equal in chloride content. Cows in no shade exhibited signs of respiratory alkalosis during the hot part of the day. Daily feed intake was lower in no shade than shade but milk yield and percent milk fat were not affected by environment. Sodium bicarbonate addition increased actual and 4% fat-corrected milk yields and percent milk fat. Sodium chloride addition increased actual and 4% fat-corrected milk yield when adjusted for amount of feed intake, and 1.8% dietary potassium increased feed intake and actual milk yield. Increasing total dietary sodium from .18 to .55%, from either supplemental source, enhanced 4% fat-corrected milk production, but combination of sources (.88% total sodium) showed no additional benefit over .55%.

Acid-Base Equilibrium↗

PubMed1986

Factors influencing passive transfer in dairy calves.

Records from 2105 calves born over 2 yr on a large dairy in a subtropical climate were examined to delineate factors that influence passive transfer of colostral immunoglobulins and the effect of passive transfer of immunoglobulin on calf mortality. Seasonal effects on immunoglobulin absorption were detected with highest serum total protein occurring in February and March. Lower total protein concentrations were associated with elevated environmental temperatures in the summer months. Maternal antibody was highest in calves from second parity cows; and dystocia appeared to decrease the amount of immunoglobulin absorbed by the neonatal calf. Calves that died of infectious disease during the first 14 wk of life had significantly lower serum total protein concentrations than those that lived. Heritability of serum protein concentration in calves was .02 +/- .03.

Animals↗

PubMed1986

Genetic and environmental effects upon reproductive performance of Holstein crossbreds in the Sudan.

Data from a herd near Khartoum for 1955 to 1977 were evaluated. Climate was semidesert with most rainfall (151 of 165 mm) in July through September. Mean maximum daily temperatures ranged from 30.7 (January) to 41.1 degrees C (May); mean minima were 14.6 degrees C (January) and 26.9 degrees C (June). Original base population (1907) was Butana with additions of Butana, Dairy Shorthorn, Ayrshire, Guernsey, and Holstein. Breed groups and % Holstein were 1, 0 to 25%; 2, 26 to 49%; 3, 50%; 4, 51 to 71%. Numbers and mean performance were gestation length, 2474, 279 d; services per conception, 2403, 2.07; calving interval, 4004, 441 d; days open, 3204, 165 d. Calving intervals (1689) were shorter for Group 3 -25 to -31 d as were postpartum days open (-27 to -31 d), and number of services per conception was lower (.21 to .37). These animals were Holstein by Butana crossbreds, so their superior performance could reflect effects of heterosis. Gestation lengths were affected by month of parturition (January greater than June, 5.6 d), which also affected services per conception (March greater than August, .75 services). Over time, not gestation length but services per conception, calving interval, and days open increased. Repeatabilities and heritabilities for these measures were .14 and .07; .07 and 0; .10 and 0; .07 and 0. Phenotypic correlation between days open and calving interval was .99 and with gestation length was -.12. Other phenotypic correlations ranged from -.01 to -.04. Heritability of age at first parturition (888) was .31. Estimates were similar to those from temperate dairy areas.

Animals↗

PubMed1986

Genetic methods of improving dairy cattle for the south: a review and prospects from Regional Project S-49.

Objectives of Southern Regional Research Project S-49, comprising eight contributing experiment stations, are to determine direct response to selection in milk and the resultant correlated responses in nonyield traits, to define and evaluate selection criteria for total economic merit or profit, to quantify genetic and environmental components of underlying physiological characters responsible for genetic gains in economically important traits, to determine interactions of genotype by environment, and to estimate genetic values for males and females. More than 150 scientific articles from S-49 have been published in journals from 1975 to 1985. These results have contributed in a major way in identifying issues and understanding the genetic control of cow performance and economics of genetic improvement programs.

Animals↗

PubMed1986

Effects of retained fetal membranes on milk yield and reproductive performance.

Effects of retained fetal membranes on subsequent productive and reproductive performance were measured in a single Florida Holstein dairy herd (n = 216 retained fetal membranes and 208 normal cases). Mean performance was peak daily milk yield, 31.9 kg; 305-d milk yield, 6317 kg; days to first service, 60; days open, 115; and services per conception, 2.3. Yield was unaffected by retained fetal membranes; however, retention resulted in an increase of 4 d to first service, 19 d open, and .2 services per conception. Detrimental effects of parturitions in hot weather (July through September) compared with cool (December through February) were peak daily milk yield, 5.5 kg; 305-d milk yield, 512 kg; days to first service, 3; days open 39; and services per conception, .9. Interactions could not be detected between diagnosis (retained or normal) and season for any response. Sex of calf effects could not be detected for any response. Continued research to reduce occurrence of retained fetal membranes or to obviate its effects should lead to improved reproductive performance.

Animals↗

PubMed1986

Induction of lactation: histological and biochemical development of mammary tissue and milk yields of cows injected with estradiol-17 beta and progesterone for 21 days.

Lactations were induced in nonpregnant, nonlactating dairy cows by subcutaneous injections of estradiol-17 beta and progesterone for 21 d (.10 and .25 mg/kg body weight/d) and dexamethasone (.028 mg/kg body weight/d) on d 31 to 34. Milking was initiated on d 35. Each cow was biopsied two or three times during the experiment with five to eight mammary tissue biopsies on d 0, 7, 14, 21, 28, 35, 49, and 130. Mammary tissue preinjection had abundant connective and adipose tissues with limited lobuloalveolar structures. Beginning on d 7, there was decreased stroma, increased epithelial cell area, increased lobuloalveolar architecture, plus the accumulation of intracellular and intraluminal secretions which were high in lipid droplets. From d 7 through 35, these changes were progressive although variable among cows. Changes in activities of enzymes and concentrations of ribonucleic acid and deoxyribonucleic acid were gradual during this time but essentially paralleled histological development. Tissue samples during lactation (d 49 and 130) showed increased histological and biochemical development; development was maximal for d 130 samples. Fourteen of 15 cows that lactated had mean daily yields of milk more than 5 kg and yields of milk of 12 cows with projected or actual 305-d lactations were 63.0% of that during their previous natural lactations. Reasons for less yields of milk and for varied patterns of tissue development were not identified nor explained by concentrations of several selected hormones in plasma.

Animals↗

PubMed1985

Periparturient endocrine changes of conceptus and maternal units in Holstein heifers bearing genetically different conceptuses.

Holstein heifers (n = 21) were balanced across sires and assigned to three service-sire-breed groups in which heifers were inseminated artificially to either purebred Angus (n = 7), Holstein (n = 7) or Brahman (n = 7) bulls. Semen from four bulls was used for each service sire-breed group. Blood samples were collected from a jugular vein thrice weekly from d 160 to 265 of pregnancy, daily thereafter until 15 d postpartum, and then thrice weekly until d 60 postpartum. Concentrations of progesterone, estrone, estradiol, and estrone sulfate from 23 d prepartum to parturition, and of 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) from 2 d prepartum to d 15 postpartum were measured by radioimmunoassay. Heifers within the Brahman-service-sire group had longer gestations (P less than .05) than those of Holstein- or Angus-service-sire groups (285.0 vs 278.7), 279.0 d). Calf birth weight was lower (P less than .05) in Angus- than Holstein- and Brahman-service-sire groups (30.6 vs 36.1, 43.4 kg). Daily trends of prepartum maternal progesterone concentrations were approximately 1 ng/ml lower (P less than .01) in Angus- than Holstein- or Brahman-service-sire groups until luteolysis occurred. Heifers bearing crossbred Angus conceptuses had lower daily trends of prepartum estrogens concentrations (P less than .01), whereas heifers of the Holstein- and, even more dramatically, of the Brahman-service-sire groups had a higher magnitude and greater rise of plasma estrogens concentrations between d -10 and -1 prepartum (less than .01). Postpartum mean concentrations (P less than .05) and response curves of PGFM were lower (P less than .01) in the Angus- than in the Holstein- or Brahman-service-sire groups. Calf birth weights were correlated with least-squares means for maternal concentrations of prepartum estrone (r = .57), estradiol (r = .59) and estrone sulfate (r = .64) and postpartum maternal concentrations of PGFM (r = .56). Functional responses of the conceptus (e.g., estrogens) and maternal units (e.g., progesterone and PGFM) were influenced by conceptus genotype during the periparturient period.

Animals↗

PubMed1985

Carry-over effects of periparturient endocrine changes on postpartum reproductive function of Holstein heifers bred to genetically different service sires.

Effects of fetal sire on postpartum reproductive changes of the dam were studied in 21 Holstein heifers whose pregnancy had been initiated by either Angus (n = 7), Holstein (n = 7) or Brahman (n = 7) bulls. After parturition, all heifers were managed uniformly. Heifers in each service-sire-breed group were bled via jugular venipuncture thrice weekly from d 160 to 265 of pregnancy, daily thereafter until 15 d postpartum, and three times per week until d 60 postpartum. Ability of heifers to release prolactin (PRL) and luteinizing hormone (LH) was evaluated on d 10 postpartum after a simultaneous injection of thyrotropin releasing hormone (TRH; 100 micrograms) and gonadotropin releasing hormone (GnRH; 100 micrograms). Between d 5 and 60 postpartum, the reproductive tract of each heifer was examined rectally thrice weekly after collection of blood samples. Basal concentrations of LH from d 1 to 10 postpartum, as well as ability of the pituitary gland to release LH and PRL after the GnRH-TRH challenge, did not differ between service-sire-breed groups (P greater than .1). Means and profiles of progesterone concentrations during the first 60 d postpartum did not differ between service-sire-breed groups (P greater than .1). However, increases in progesterone concentrations following the GnRH-TRH challenge were synchronized more precisely in Angus (P less than .02) than in Holstein- and Brahman-service-sire groups. Daily rates of reduction in cervical and uterine horn diameters were higher (P less than .01) in Holstein- and Brahman- than in Angus-service-sire groups and were associated with higher profiles of postpartum 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) concentrations. Within-cow PGFM concentrations were correlated positively with cervical (r = .36) and uterine horn (r = .32) diameters. Postpartum ovarian responsiveness and uterine involution in Holstein heifers may be affected by genotypes of the conceptus they bore during pregnancy.

Animals↗