Fate of Young Sires Used for Artificial Insemination

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Abstract
Vital records of 3,774 dairy sires which entered artificial in-semination (AI) service at less than 3 yr of age were analyzed to deter-mine the proportion entering which survived until proof for milk pro-duction became available. Data were grouped by breed, age of entry, and time period. All main effects and most interactions were statis-tically significant. For 1,068 sires entering service at less than 2 yr of age during the period of 1939-50, survival (55 percent) was lower (P<0.01) than for 1,866 sires entering from 1951-61 (64 percent). Corresponding survival rates for 530 and 310 2-yr-olds were 44 and 52 percent, respectively (P<0.05). Major causes of loss for the 2 age groups were reproductive failure (15 and 21 percent), disease (7 and 8 percent). accidents and injury (2 and 3 percent), and other reasons (15 and 21 percent). Increased survival during 1951-61 has resulted from decreased losses due to reproductive failure. Losses due to disease and injury have not decreased. Real differences among breeds in survival rates of bulls entering during 1951-61 were found and ranged from 41 percent for Milking Shorthorns to 70 percent for Brown Swiss.
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