Ovarian Activity of Holstein and Jersey Cows of Diverse Transmitting Abilities for Milk

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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 3 times per wk, 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 1st ovulation averaged 22 and 20 days for Holsteins and Jerseys, but the interval to 1st standing estrus was shorter for Jersey than for Holstein. Postpartum intervals to each of the first 3 ovulations and length of estrous cycles were unrelated to actual yield of 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 3 ovulations increased from 23 to 43%.