USE OF SEMEN FROM A BULL HETEROZYGOUS FOR THE 1 29 TRANSLOCATION IN AN IVF PROGRAM/

In cattle, a translocation of the Robertsonian type between the larges t and smallest chromosome leads to a reduction in fertility. This is s ubstantiated by reduced nonreturn rates in daughter groups of bulls ca rrying the 1/29 translocation and in the heterozygous bulls themselves . This reduction in fertility is thought to be due to the early death of embryos with unbalanced karyotypes. The influence of semen from a b ull known to be heterozygous for the 1/29 translocation on the outcome of a bovine IVF program was investigated. There was a significant dif ference (P<0.005) in terms of cleavage rate (59.8 vs 71.1%) and blasto cyst rate (12.0 vs 20.0%) between the carrier and control bull, respec tively. There was no difference in blastocyst quality as measured by c ell number. The results observed in vitro are consistent with the fiel d fertility records of the 2 bulls in terms of nonreturn rates (59.2 v s 70.6%, for the carrier and control bull, respectively).