Management of preputial injuries in bulls
Keywords:bulls, preputial injury, reproductive management
Veterinarians are frequently asked to examine bulls for reproductive inefficiency. The goal of most beef producers is to utilize 1 herd bull per 25-35 cows for breeding and this is the goal upon which breeding soundness evaluations of beef bulls is designed. Veterinarians and livestock producers should have a firm understanding of normal fertility or reproductive efficiency in cattle. Age, parity, health, body condition, length of breeding season, number of cows per bull and fertility of cows and bulls affect reproductive performance. Average first service conception percentage in healthy herds is approximately 65%. Therefore, in a herd of a normal, healthy, fertile cows a normal healthy fertile bull would be expected to get 65 cows pregnant after one heat cycle. The remaining 35 open cows would be normal and with 65% conception rate on the next heat cycle, an additional 23 cows would be pregnant resulting in 88 pregnant cows after 2 heat cycles. Of the remaining 12 normal, healthy open cows, 8 (65%) would be expected to be pregnant after 3 heat cycles. Consequently, 96 cows should be pregnant after 3 heat cycles. A thorough understanding of the anatomy, physiology and behavior of bulls is necessary to diagnose causes of reproductive inefficiency. Inefficiency may be due to the absolute inability of a bull to reproduce, impotentia generandi. These bulls may suffer impotentia generandi, the inability to achieve erection, impotentia erigendi, the inability to complete coitus, or impotentia coeundi, the inability to produce an adequate volume of morphologically normal progressively motile sperm. More frequently reproductive inefficiency is evident as a bull failing to get a large percentage of cows pregnant during a limited breeding season. A thorough history, physical examination, semen evaluation and perhaps observation during coitus may be necessary to identify causes of reproductive inefficiency.