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Association Of Age At First Conception, Week Of Conception In Lactation, And Number Of Inseminations With Sex Ratio In Holstein Cows
by Michael R. Murphy, Roger D. Shanks, Naomi Harris, Patrice Collins, and Robert C. Riggs


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Heifer age at conception tended to be linearly associated with sex ratio of single calves: from 45(male):55(female) at 14 months to 60:40 at 19 months. A 14% reduction in the value of calves from heifers could occur over this range at a heifer:bull calf price ratio of 3:1.

Sex ratio of single calves born to multiparous cows tended to increase linearly from 53:47 to 57:43 as number of inseminations increased from 1 to 5. This result suggested that cows in better body condition produced a higher proportion of bull calves, and could represent a 4% reduction in the value of their calves.

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