CHROMOSOME-ANOMALIES IN CANADIAN GUERNSEY BULLS

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  • 1 January 1976
    • journal article
    • research article
    • Vol. 66  (4) , 476-489
Abstract
The performance records of a group of Guernsey bulls used for artificial insemination revealed lower 60-90 day non-return rates as compared to that for bulls of the Holstein breed, and 9 of the 19 Guernsey bulls in this group exhibited a fertility level below the average for this group. The reduced fertility of these bulls was due to chromosome anomalies, a relatively high frequency of chromatid breaks existed and achromatic gaps in 3 out of 19 bulls while 2 carried 59 chromosomes each including a translocation chromosome. The 1/29 translocation heterozygote and the bulls showing achromatic gaps and chromatid breaks were among the 5 bulls which were consistently below the breed average in fertility as evidenced by the t test (P < 0.01), whereas the bull with translocation 27/29 (G3) exhibited a non-return rate slightly higher than the breed average (P < 0.01). The chromosomally abnormal bulls may contribute to increased returns to service not only because of the defective gametes they themselves might produce but also through their influence on the performance of their daughters.