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Fate of Young Sires Used for Artificial Insemination^{1, 2,}

Department of Dairy Science, University of Florida Institute of Food and Agricultural Sciences, Gainesville

ABSTRACT

Vital records of 3,774 dairy sires which entered artificial insemination (AI) service at less than 3 yr of age were analyzed to determine the proportion entering which survived until proof for milk production became available. Data were grouped by breed, age of entry, and time period. All main effects and most interactions were statistically significant. For 1,068 sires entering service at less than 2 yr of age during the period of 1939–50, survival (55%) was lower (P < 0.01) than for 1,866 sires entering from 1951–61 (64%). Corresponding survival rates for 530 and 310 2-yr-olds were 44 and 52%, respectively (P < 0.05). Major causes of loss for the two age groups were reproductive failure (15 and 21%), disease (7 and 8%), accidents and injury (2 and 3%), and other reasons (15 and 21%). 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% for Milking Shorthorns to 70% for Brown Swiss.

¹ Florida Agricultural Experiment Station, Journal Series, no. 2613.

² The financial support of the National Association of Animal Breeders is gratefully acknowledged.

³ Present address: Instituto Nacional de Investigaciones Agropecuarias, Quito, Ecuador, South America.