The Effect of Exposure to High Ambient Temperature on Spermatogenesis in the Dairy Bull

The effects of seasonal influences on reproductive activity in domestic animals have been reviewed in detail by Anderson (4), and seasonal variations in reproductive activity in the dairy bull have been reported by several investigators Recently, Weeth and Herman ( Mercier and Salisbury (8) reported a low level of sperm production during June and July in five Holstein and five Guernsey bulls, accompanied by lower than average levels of fertility for these 2 months. Subsequent studies by Mercier and Salisbury (9, 10) indicate that hours of daylight are a predominant factor in seasonal variations in fertility. Erb and Waldo (6) observed a relationship between season and non-return rates in bulls used for artificial breeding. The rates were lowest in January, February, March and April and gradually increased to the highest level in September, October and November.