Biomedical subjects

B T McDaniel

Publications and source records attributed to B T McDaniel.

At least 19 recordsLinked to original sources

PubMed1991

Relationships among milk yield, metabolism, and reproductive performance of primiparous Holstein cows treated with somatotropin.

Thirty-two primiparous Holsteins were assigned to receive 0, 5.15, 10.3, or 16.5 mg/d recombinant bST. Treatment began between 28 and 35 d postpartum and continued until 60 d prior to next expected calving or 400 d postpartum. Metabolic hormones and metabolites were measured in blood weekly during the first 10 wk of treatment, and progesterone was measured in milk twice weekly to assess ovarian activity until conception. Milk production (305 d, actual) was 8350 +/- 562, 8348 +/- 515, 9571 +/- 515, and 9070 +/- 515 for cows given 0, 5.15, 10.3, or 16.5 mg/d and did not differ statistically. Insulin, glucose, NEFA and blood urea nitrogen were not influenced by dose of bST. However, insulin-like growth factor-I increased linearly with dose of bST. Days from parturition to first detected estrus, days open, and services per conception did not differ among groups; however, days from parturition to first service increased with dose of bST. Rate of detection of estrus decreased with dose of bST, resulting in a longer interval to first insemination. The lower rate of detection of estrus in bST-treated cows may have been associated with reduced expression of estrus. Additional statistical analyses were conducted to determine the relationship between metabolism, milk production, and reproduction over all doses of bST. There was a negative correlation between 305-d milk yield and glucose (r = -.44) and insulin (r = -.46) concentrations during 30 to 100 d postpartum. In stepwise regression analyses, insulin accounted for 21% of the variance in 305-d milk yield. Glucose and NEFA accounted for 18% of the variance in days open, and there was a negative correlation (r = -.32) between glucose and days open. Days open and milk production were not correlated.

Animals↗

PubMed1989

Genetics of reproduction in primiparous Holsteins.

Effects of genetics and relationships between yield and days from parturition to first service, first service conception rate, number of services, and a reproductive performance code based on several reproductive components were investigated in primiparous Holsteins. Recorded breedings and DHI production records were from 3393 daughters of 174 bulls in six experimental herds. Subsets included progeny of 78 sires, with greater than or equal to 5 daughters calving in April through July (n = 817) and August through March (n = 1162). Daughter-dam regressions (n = 2593 pairs) and paternal half-sibs were used to estimate heritabilities of fertility traits and associations between yield and reproduction. Results showed increased FCM was associated with lowered fertility. For paternal half-sibs, the greatest antagonism was between conception rates and FCM (rG = -.65 +/- .10). Daughter-dam regressions estimated a favorable genetic correlation of .43 +/- .32 between conception rates and yield. Heritabilities were highest for April through July calvings and ranged from .08 +/- .10 for first service conception to .24 +/- .12 for reproductive code. Correlations between sire least squares constants from warmer and cooler calving seasons were lower than heritabilities of traits would suggest.

Animals↗

PubMed1986

Growth and reproduction characteristics of purebred and crossbred dairy cattle in first lactation.

Breed additive, maternal, and heterozygotic effects on 11 monthly postpartum body weights, average size, weight gain, age at first calving, and days open were estimated by linear regression analyses from records of 680 purebred and crossbred animals. Calving year, age, and milk yield were significant environmental effects. Positive regressions of age on body weights indicated late calving cows were heaviest postpartum and had most days open. Negative regressions of milk yield on weight gain and postpartum weight showed greatest losses of weight associated with highest yields. There were breed differences in growth; purebreds highest to lowest were Brown Swiss, Holstein, Red Dane, Jersey, and Ayrshire and for weight gain, Brown Swiss, Ayrshire, and for weight gain, Brown Swiss, Ayrshire, Jersey, Holsteins, and Red Dane. Crosses were superior to purebreds in these traits. Additive effects of Holstein were greater than Ayrshire, Jersey, and Red Dane for postpartum body weights and average size. All constants for heterozygotic effect combinations were significant for postpartum weights and average size. Heterozygosity effects increased in magnitude with advancing lactation. Generally, age at first calving and postpartum interval to conception reflected little heterozygotic or maternal effects. There was some indication of breed differences in mean and additive effects for age at first calving.

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

Rates of hoof growth and wear in Holstein cattle.

Rates of hoof growth and wear were recorded on 223 Holstein cows in two herds during 20 mo. Herd 1 was mainly on pasture or dirt lots, and herd 2 was completely or partially confined in a new freestall facility. Growth and wear were measured on both dorsal and lateral surfaces of front and rear outside claws. Lateral measurements were taken 1 cm in front of the junction of wall and heel. No differences were detected in rates of hoof growth for various places on the dorsal wall. Herd effects influenced rates of growth and wear. Cow differences were not significant for hoof growth but were for a few wear rates. Monthly rates of dorsal hoof growth during first lactation were 6.04 mm for front claws and 6.58 mm for rear claws. Corresponding monthly wear rates were 5.78 and 6.11 mm, respectively. Wear rates on front and rear claws decreased with advancing stage of lactation. Front hooves grew and wore less than rear hooves. Lateral walls grew faster and wore more than dorsal walls on both front and rear hooves. Cows completely confined had higher rates of hoof growth and wear than cows on pasture. Rates of growth and wear were lowest during winter and highest during spring and summer.

Animals↗

PubMed1986

Genetics statistics and relationships of teat and udder traits, somatic cell counts, and milk production.

Teat lengths and diameters, udder clearance, cleft depth, and distances between teats were measured from 1967 to 1982 on Holstein cows. Numbers of observations per trait ranged from 5934 to 11,449. Cows were from six herds owned by the North Carolina Department of Agriculture and two research herds of North Carolina State University. Repeatabilities between adjacent lactations for physical traits of udder were mostly between .60 and .80. Repeatabilities between first and second lactations for average somatic cell count and mean log somatic cell count were .11 +/- .04 and .21 +/- .04. Heritabilities in first lactation were .63 for front teat length, .44 for teat diameter, .56 for rear udder clearance, .10 for cleft depth, .32 for mature equivalent milk, and .18 for somatic cell counts. Heritabilities of distances between teats ranged from .33 to .48. Cows with udder clearance higher from the ground, deeper clefts, smaller distances between teats, and teats of smaller diameter had lower somatic cell counts. Multiple regression analysis showed that dams' somatic cell counts and rear udder clearances were not significant predictors of daughters' somatic cell counts. Lactation average somatic cell counts of daughters were predicted with greater accuracy from averages of somatic cell counts of multiple lactations of dams than from single lactations of dams. Milk production and somatic cell counts seemed positively genetically correlated, more so in first than later lactations.

Animals↗

PubMed1985

Effects of cytoplasmic inheritance on production traits of dairy cattle.

Pedigrees of 4461 cows were traced to the original female in a maternal line. Cytoplasmic origin was defined as the first female in the maternal lineage. There were 102 cytoplasmic lines. Most cows were at least 10 generations removed from the origin. After adjustment for sire, herd, calving year, calving month, and age, cytoplasmic effects accounted for 2.0, 1.8, 1.8, and 3.5% of total variation of milk yield, milk fat yield, 3.7% fat-corrected milk yield, and milk fat percentage in first lactation. Cytoplasmic effects were also in models that included adjustments for sires, maternal grand-sires, and dam's production. Correlations among independent subsets agreed with expectations. Cytoplasmic origin was a significant source of variation of production traits of dairy cattle.

Animals↗

PubMed1985

Udder and teat morphology related to mastitis resistance: a review.

Annual losses by mastitis are estimated to be in excess of two billion dollars in the United States. Udder and teat morphologies have been associated with incidences of mastitis without clear conclusion on the closeness. Streak canal diameter was correlated with udder health, but it is difficult to measure. Udder depth and teat-end shape have been associated with udder health. Selection to reduce frequencies of cows with deep udders and flat, disk, or inverted teat ends may reduce mastitis incidence. Heritabilities of udder morphology are moderate to high, and a single score during the lifetime of a cow may be adequate for selection. There is no concensus in the literature on relationships between mastitis and teat size, general teat shape, teat-end lesions, teat pigmentation, or milk flow rate. Different breeds, milking procedures, measures of mastitis, and statistical procedures may account for different conclusions. Genetic approaches to improve mastitis resistance of dairy cattle seem warranted. This paper attempts to summarize evidence dealing with possible physical bases for genetic variation associated with mastitis in dairy cattle.

Animals↗

PubMed1984

Associations of subjective udder edema scores and descriptive trait codes for udder types.

Edema severity was scored by herd personnel in six North Carolina Holstein herds from 1 (none) to 5 (extremely severe). Cows (2612) were scored at calving and 1 and 2 wk postpartum. Total score was calculated as the sum of these three scores. Official Holstein-Friesian classification descriptive udder trait codes were available on a subset of the cows. All statistical analyses were within lactation and included adjustments for herd-year and age as well as classifier and stage of lactation where appropriate. Correlations between corresponding edema scores for first and second lactations were .18, .18, .19, and .20 for scores at calving, 1 wk, 2 wk, and for total score. Stepwise regression procedures showed that udder support codes were associated with a larger amount of variation of edema scores than for any other single mammary trait code. Fore and rear udder codes also were associated with significant variation of edema scores in some analyses. Prediction models showed edema was a significant predictor of subsequent udder support codes, although udder trait codes were not significant predictors of subsequent edema severity. It appeared that severe edema may be one of the causes of pendulous udders.

Animals↗

PubMed1984

Genetic and environmental variation of hoof characteristics of Holstein cattle.

Genetic and environmental components of variation of hoof measurements were ascertained from 257 Holstein heifers and 1051 cows in eight herds in North Carolina. Angles and lengths of both claws, heel depth, and base area of the hoof were measured on both right feet for four herds. Angles, lengths, and heel depths were measured only on the right rear foot for four other herds. Heritabilities combined across all lactations were .30 or above but for individual lactations were as low as .12. Number of sires ranged from 16 to 40 for individual lactations. Average repeatabilities among measurements in same lactation were mostly above .40. Age affected all hoof measurements in heifers. Herd effects had a large impact on hoof measurements. Averages for hoof angles by ages ranged from 42 degrees to 45 degrees and from 60 to 70 mm for hoof length. Ratio of length to angle ranged from 1.36 to 1.68, heel depth from 34 to 44 mm, and base areas of hoof from 93 to 103 cm2. Lengths of medial and lateral claws for front and rear feet increased with advancing age. Medial front and lateral rear claws were longer than respective opposing claws.

Age Factors↗

PubMed1983

Relationships of predicted differences of dairy bulls and the performance of their crossbred progeny.

Actual milk and milk fat yields of 328 crossbred cows in first lactation in four experimental herds and Predicted Differences for the same traits on their 165 sires were the basic data used. Predicted Differences (PD) for milk and fat on a 1974 base were the measures of transmitting value. They were computed from all straightbred progeny of these bulls in milk recorded herds in the United States. Standard deviations of PD for the 95 Holstein and 70 Brown Swiss bulls were similar to those of all bulls of their breeds in use in artificial insemination at the same time. Regressions of milk yields of crossbred progeny on PD for milk were .77 +/- .44 for Holstein-sired crosses and 1.42 +/- .58 for crosses sired by Brown Swiss bulls. Corresponding values for milk fat were .55 +/- .41 and 1.25 +/- .60. The four regression coefficients averaged 1.00. Correlations corresponding to the four regressions were .22, .35, .17 and .31, respectively. These averaged .26, slightly higher than their expected value based on heritabilities of .25 for milk and fat yields. Regressions based on 405 straightbred Holstein and Brown Swiss progeny in the same four experimental herds averaged .99, while respective correlations averaged .21. These results suggest that selection of dairy bulls based on their progeny tests from straightbred progeny would be effective in improving lactation yields of crossbred progeny.

Animals↗

PubMed1983

Use of later records in dairy sire evaluation: a review.

Performance in first lactation has been the standard of evaluation for most genetic studies with dairy cattle. First records are available sooner on more cows and are less susceptible to error from selection, injury, previous days dry, and mastitis than are later records. However, first records have been considerably less than perfect in predicting traits of lifetime performance, which should be the primary selection objective in dairy cattle. Later records provide additional information for more accurate sire evaluations and should be a better index of health and resistance to mastitis than first lactations. The economic importance of later records relative to first is that there are more and actual yields are higher. Herds with more older cows can reduce commitment of resources to heifer rearing, and heifers can be selected more intensely prior to first calving than herds with more cows of younger ages. Some sire evaluation systems ignore later records because of computational expense, potential selection bias, and difficulty of age adjustment. Later records may contain useful information relative to lifetime profitability of sire progeny groups. Development of proper methodology for utilizing information available in later records appears fruitful for research.

Animals↗

PubMed1983

Modified contemporary comparison sire evaluations from first, all, and later lactations.

Modified Contemporary Comparisons are calculated by the United States Department of Agriculture from first and later lactations, results of which form the published progeny evaluations for all lactations. Characteristics of such evaluations on 200 Holstein sires, each with more than 500 daughters in each data set in the Summer 1981 run, were studied. Predicted Differences for milk averaged 245, 286, and 292 kg for first, all, and later lactation evaluations, with standard deviations of 271, 253, and 254 kg. The average difference (later minus first) was 47 kg (standard deviation, 149 kg). Average absolute difference was 123 kg (standard deviation, 97 kg). Correlations were .95 between first and all, .84 between first and later, and .97 between all and later. The correlation between progeny test for first lactation and difference was -.38 (-.28 for absolute difference). Percent of first lactations culled was correlated -.49, -.47, and -.37 for first, all, and later evaluations. Important variables in prediction of later lactations were first, percent of firsts culled, and sire's age, with first alone producing a coefficient of determination of .71. Sire's age was correlated -.11, -.19, and -.23 with first, all, and later evaluations indicating possible differences in genetic trend for first and later progeny tests for these sires. Fat yield behaved similarly to milk except that correlations between progeny tests and sire's age or culling were less than for milk. Ranking of bulls for daughter milk yield in later lactation changed from first lactation.

Age Factors↗

PubMed1983

Modified contemporary comparisons for first and second lactations in the same and different herds.

Separate sire evaluations by Modified Contemporary Comparison for first and second lactations were calculated for 200 widely used Holstein bulls from a file containing only first or second records of all daughters and from two independent subsets of the same data. Sire evaluations based on both first and second lactations also were computed. Correlations between first lactation evaluations in one independent data set and second lactation evaluations in the other were .87 and .84. First lactation evaluations accounted for only about 75% of the variation in second record evaluations, suggesting a need for some form of later record sire evaluation, at least for the selection of sires of sons. Within sire, daughter variation for first records was not useful in predicting difference between first and second record sire evaluations. Second lactation evaluations increased relative to firsts as culling increased, suggesting culling bias in Modified Contemporary Comparisons for later records. An adjustment based on an empirical regression of later records on firsts produced second evaluations with means and standard deviations nearly identical to those of first records. Correlations between first and adjusted second evaluations were .87 for both independent data sets. Difference between adjusted second and first evaluations were correlated .15 with culling, compared to .25 for unadjusted seconds. Important sire differences in first and second lactation evaluations were detected in all data sets. Such differences were unaltered by adjustment for selection.

Animals↗

PubMed1983

Influence of herd relocation upon production and endocrine traits of dairy cows.

Effects of potential stress encountered by two Holstein herds relocated into a new double-six herringbone parlor and free-stall facility were studied by evaluating alterations of milk yield and fat percentage, mastitis status, corticosteroids, and heat detection. One-half of one herd (18 cows) was moved 100 m to new facilities (Merged), and the remaining 18 cows were maintained in their original tie-stall barn (Control). The same day, the second herd of 50 cows (Moved) was transported via stock trailer 7 km to new facilities. Milk yield by Merged and Moved cows was decreased at first milking, but subsequent milk yields were similar to yields prerelocation. Milk fat percentage was decreased for only 3 days for Moved cows but was unchanged for Merged cows. Across groups, older cows and cows in late lactation tended to have greatest decreases in milk yield. Corticosteroids in serum were increased in Merged cows for only 2 days after relocation. No changes in milk somatic cell count or percentage heats detected were associated with relocation. Detrimental effects of herd relocation were slight and indicate that dairy herds can be moved without adversely affecting production traits.

Adrenal Cortex Hormones↗

PubMed1983

Effects of adjustment for mate's yield, mate's sire's merit, and days open in sire evaluation.

First lactations were from the North Carolina Institutional Breeding project sine 1955 for cows and their dams where Modified Contemporary Comparisons were available for sires of both females. Each sire of cows was required to have a minimum of 20 progeny in the data. A total of 1771 cow-dam pairs by 33 sires in 7 herds and 217 herd-year-seasons passed all edits. Models including combinations of Predicted Difference milk for sire and maternal grandsire, dam's milk yield deviated from herd-year-season mean, and dam's age at cow's birth were used to predict cow's milk yield deviated from herd-year-season mean. Adjustment of yields of cow and dam for days open also was examined. Predicted Difference milk of her sire was the most important variable for predicting cow's yield; next was dam's yield. Predicted Difference of maternal grandsire and dam's age at cow's birth were not significant. Adjustment for days open reduced the percent of variation of cow's yield explained by sire's Predicted Difference. Sire's contributions to yield also were obtained by least squares and mixed model procedures in the various models with Predicted Difference milk of sire omitted. Maximum change in ranks among the 33 sires was four places, and maximum change of differences among sires was 129 kg when mate's yield and mate's sire's Predicted Difference were included in the model. Dam's yield was more useful than maternal grandsire's merit in predicting cow's yield. Differences among sires changed as much as 185 kg when cow's yield was adjusted for days open.

Animals↗

PubMed1983

Reproductive traits of Holsteins and Jerseys. Effects of age, milk yield, and clinical abnormalities on involution of cervix and uterus, ovulation, estrous cycles, detection of estrus, conception rate, and days open.

Two hundred and twelve Holstein and Jersey cows were in a study to determine factors that affected reproductive traits. First ovulation occurred about 3 wk postpartum, and interval to first ovulation was greater in cows that had clinical abnormalities postpartum than in normal cows. Jerseys producing more milk ovulated sooner postpartum than lower producing herdmates. Involution of cervix and uterus occurred later postpartum in cows that had clinical problems postpartum. Involution of genital tract occurred later postpartum in older cows and sooner postpartum in cows that had higher milk yields. Duration of first postpartum estrous cycle was 4 days less than for second postpartum cycle. Percentages of estrous cycles detected by standing estrus were 43 and 73% for Holsteins and Jerseys. Estrous detection rates were highest for cows that produced slightly above the mean milk yield and did not differ between cows in highest and lowest milk production quartiles. First detected estrus and days to first insemination occurred later postpartum in Holsteins as milk yield deviation from herdmates increased, regardless of sign. In Jerseys, days to first insemination and days open increased linearly as milk yield increased. Days to first insemination and conception were greater in cows with postpartum clinical problems. Conception rate at first insemination postpartum increased in proportion to concentration of progesterone in blood samples collected during 12 days before first insemination. Overall, clinical problems at parturition and postpartum lowered reproductive performance in both breeds. There was a slight antagonism between milk yield and reproductive performance (days open) in Jerseys but not in Holsteins.

Age Factors↗

PubMed1983

Heritabilities and correlations of lactation yields and fertility for Holsteins.

First lactations from a total of 5802 cows in the North Carolina Institutional Breeding project from 1950 to 1980 were used. Heritabilities from paternal half-sisters were .05 for days open, .05 for age at first calving, .27 for lactation milk yield, and .29 for fat yield. Corresponding estimates from regressions of cow on dam were .13 for days open, .06 for age at first calving, .35 for milk yield, and .33 for fat yield. Genetic correlations between yields and days open from various methods of estimation and editings of the data were all antagonistic and ranged from .35 to .60. Genetic correlations of yield and age at first calving were favorable, ranging from -.10 to -.36. Heritabilities for days open and genetic antagonism between days open and yield were greater for cows calving prior to the hot summer months than for cows calving in the fall. Heritabilities and variance of sires increased for days open and yield traits from the 1950's to 1980. For records from 1970 to 1980, heritability from paternal half-sisters of days open was .12. Genetic increase of 1000 kg milk would result in 5 to 10 additional days open.

Animals↗