SHLOMIT DACHIR, ROBERT W. BLAKE, and PAUL G. HARMS. Department of Animal Science. Texas A&M University. College Station 77843. ABSTRACT.
Ovarian Activity of Holstein and Jersey Cows of Diverse Transmitting Abilities for Milk 1 S H L O M I T D A C H I R , ROBERT W. B L A K E , and P A U L G. H A R M S Department of Animal Science Texas A&M University College Station 77843 ABSTRACT
The relationship between ovarian activity and milk yield was studied in 35 daughters of 24 Holstein sires and 17 daughters of 14 Jersey sires in the same herd. Ovulations and length of estrous cycles were determined by progesterone concentration in postmilking strippings three times per week, by weekly palpation per rectum, and by twice daily estrus detection. Transmitting abilities were for 4% fat-corrected milk of cows and their sires. Yields of 4% fat-corrected milk were estimated for 60, 90, 120, and 305 days in lactation. Postpartum intervals to first ovulation averaged 22 and 20 days for Holsteins and Jerseys, but the interval to first standing estrus was shorter for Jersey than for Holstein. Postpartum intervals to each of the first three ovulations and length of estrous cycles were unrelated to actual yield or transmitting ability for yield of 4% fat-corrected milk in either breed. The percentage of cows observed in standing estrus at each of the first three ovulations increased from 23 to 43%. INTRODUCTION
Dairy producers are concerned that selection for milk impairs fertility of dairy cows. In a field study of New York dairy herds (21), cows yielding more than 907 kg milk above herd average (6305 kg/305 days) had conception rates to first service 20.5% less than herdmates
Received August 29, 1983. 1Technical Article 18944 of the Texas Agricultural Experiment Station, College Station 77843. Project 2491, a contributing project to Southern Regional Project, $49, Genetic Methods of Improving Dairy Cattle for the South. 1984 J Dairy Sci 67:1776--1782
yielding more than 908 kg below herd average. Further, intervals to first service and to conception were 12.6 and 36.8 days longer for highest than for lowest yielding cows. Berger et al. (1) and Hansen et al. (10) estimated antagonistic genetic correlations between yield of fat-corrected milk (FCM) and measures of reproductive performance of Holstein cows. Genetic correlations with 305-day FCM yield of pluriparous cows in these studies were .49 + .10 and 0 -+ .18 for postpartum interval to first breeding, .18 -+ .09 and .17 + .18 for days open, .10 + .09 and .16 + .28 for services/conception, and .16 -+ .09 and .66 + .86 for service period (i.e., interval from first to successful service). In both studies genetic correlations were similar within primiparous and pluriparous age classes with a tendency to larger correlations in primiparous cows for days open (.62 -+ .14, .34 -+ .11), services per conception (.62 -+ .22, .40 + .13), and service period (.56 + .12 and 1.01 + 1.36). Similarly, Otds et al. (15) reported small phenotypic correlations between 305-day milk yield and reproductive performance of .13 for days to first service, .21 for days open, .17 for services per conception, and .16 for service period (all P
Journal of Dairy Science Vol. 67, No. 8, 1984
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FCM yield of Jerseys, the interval to first estrus increased (P.I) and increased to 40% (P
