Abstract
There were no significant differences in fertility between semen diluted in Caprogen and stored at ambient temperatures with egg yolk levels of 20, 5,2, and 1%. There was, however, a highly significant interaction between sires and egg yolk concentrations in a trial comparing 5, 2, and 1 % egg yolk. This effect resulted from reducing egg yolk level with semen of one sire. Reducing egg yolk level for this sire from 5 to 2% and 5 to 1 % lowered the 49-day nonreturn rate by 5.8 and 17.1 %, respectively. Possible reasons for sire differences are discussed.