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Trends in average days open and services per conception from 1976 to 1999 were examined in 532 Holstein and 29 Jersey herds from 10 Southeastern states. Three-year averages for eight intervals (time) were calculated (first: 1976 to 1978; eighth: 1997 to 1999). Milk, fat, fat-corrected milk, and number of cows increased across time. Herds of both breeds had(More)
Heritabilities, genetic and phenotypic correlations among growth, forage consumption, and BW changes of heifers and feed consumption, BW changes, and yields of first lactation cows were estimated. Data were from 1266 Holstein progeny of 74 sires born from 1972 to 1985 at three Agriculture Canada research herds. Heavier heifers at 26 wk consumed more feed(More)
Holstein and Jersey cows were mated to 4 Holstein (H) bulls and 4 Jersey (J) bulls to create HH, HJ, JH, and JJ genetic groups (sire breed listed first) in a diallele crossbreeding scheme. Calvings (n = 756) occurred in research herds in Virginia, Kentucky, and North Carolina with 243, 166, 194, and 153 calvings in the HH, HJ, JH, and JJ groups,(More)
A total of 253 heifers bred at first estrus after 350 d of age (350-d breeding age group) and 249 contemporary heifers bred at first estrus after 462 d of age (462-d breeding age group) were used to study the effects of age at first breeding on productive and reproductive performances of first lactation heifers. Heifers of both breeding age groups were(More)
Additive and nonadditive genetic effects on lifetime yields of milk and milk components and lifetime profitability were estimated from 5070 cattle in a Holstein pureline, an Ayrshire-based pureline, and 10 crossbred groups of these purelines. Lifetime yields of milk, fat, protein, and lactose and lifetime milk value and annualized discounted net returns(More)
A total of 920 cows of Holstein-based H line, Ayrshire-based A line, and cross-bred C line between H and A lines was used to determine the genotypic and gene frequencies of milk protein types and to study the relationships of milk protein loci to first lactation yields. Effects of milk protein loci on first lactation performance were examined using(More)
A total of 890 heifers was used to study the effects of four milk protein loci (alpha S1-casein, beta-casein, kappa-casein, and beta-lactoglobulin) on heifer growth and reproduction. The additive effects of gene substitutions at the four milk protein loci were significant only in 4 of 56 cases for all traits studied. Dominance effects at alpha S1-casein,(More)
The proportional hazards model with censoring was used to assess the effects of breeding value, disease, calving, size, and udder and lactation traits on length of herdlife of 3881 heifers in five herds. Data were recorded over 10 yr from three lines: a Holstein line, an Ayrshire-based line, and a crossbred line. Influences on survival were assessed from(More)
Incidence of retained placenta in dairy cows was evaluated in 627 parturitions. The herd was divided prepartum into three groups: 1) control, no treatment (n = 217 cows); 2) cows injected intramuscularly (n = 190) 21 to 10 d prior parturition with 45 mg Se and 2040 IU of vitamin E; and 3) cows intraruminally administered (n = 220) with two 30-g pellets(More)