The Cow-Calf Manager
Livestock Update, May 2003
John B. Hall, Extension Animal Scientist, Beef, VA Tech
Assessing Bull Fertility is Essential
Over the past several months, The Cow Calf Manager has focused on the challenges of ensuring cows are ready for the breeding season after a tough winter with limited feed supplies. While management of the breeding female is essential, concentrating management solely on the cows and not worrying about the bulls could be a disaster.
This winter, bulls faced many of the weather and nutritional challenges as the cows. Many bulls came through the winter in fair shape nutritionally, but physically and reproductively they may not be as sound. The cold, wet, windy winter created conditions for scrotal frostbite for bulls. Frostbite to the scrotum and testes can result in a temporary to permanent decrease in fertility. In addition, the frozen ground with snow and ice resulted in poor footing and increased possibilities for injury for bulls. The bottom-line - all bulls need a breeding soundness exam performed by a qualified veterinarian or trained professional.
How important is the nutritional management of the cow and a breeding soundness exam for the bull?
A trial was conducted in the 1980's which compared a reproductive management of two herds. In Herd 1, cows were body condition scored and fed supplements, if necessary, to maintain good body condition (BCS 5 or better) and the bulls were given a breeding soundness exam. Cows in Herd 1 were also limited to a 60 day breeding season and 48 hour calf removal was used at the beginning of the breeding season. In Herd 2, cows were fed hay and bulls were not tested. Cows in Herd 2 were allowed a 120 day breeding season and received no additional management. Each herd had almost 90 cows.
Cows in Herd 1 bred back sooner and calved earlier the next year (Table 1). The reproductive management system cost for Herd 1 cows was $2,120 more than Herd 2 because of feed purchases and reproductive evaluation of the bulls, but it produced over $4,000 more profit after accounting for the increased costs. This figure is based on 1980's feed prices and $70 calves. Considering today's feed costs and calf value the additional profit may be well over $5,000.
Remember calves will weigh about 35 lbs. less for every 21 days later they are born in the calving season. Putting money into reproductive management in the form of feed and reproductive examinations will reap large benefits. A greater percentage of cows will become pregnant early in the breeding season which ensures more calves will be born earlier in the next calving season.
Table 1. Comparison of reproductive performance between a reproductively managed herd (O'Conner) and an unmanaged herd.
|Repro. Management (O'Conner) System Herd 1||Control System Herd 2||Difference|
|Cows in heat after 25 d of breeding (%)||95||59||36|
|Cows in heat after 45 d of breeding (%)||98||72||26|
|Pregnant after 1st service||80||50||30|
|Calving distribution by day of next calving season|
|After 20 days||80||28||52|
|After 40 days||91||52||39|
|After 60 days||99||72||27|
|After 120 days||99||93||8|
Breeding soundness exams
A breeding soundness exam for bulls consists of four parts.
Most experienced producers can perform the physical soundness and libido portions of the exam to eliminate testing bulls that would fail these portions. Any bull that has obvious mobility problems, severe hoof defects or is blind/partially blind can be eliminated. Other obvious problems such as a swollen testicle or broken penis would eliminate bulls as well.
Libido (desire) testing can be performed by exposing the bull to a limited number of cycling cows. Often producers perform a libido test simply by watching the bull during the first 5 to 7 days of the breeding season. If he shows interest, seeks out cows in heat, and mounts them he passes the libido test. If he fails to attempt to mount cows in heat or is disinterested then his ability as a breeder is questionable. Although not part of the libido test, bulls should also be observed to see if they successfully penetrate and service cows.
Examination of the reproductive tract will include measuring scrotal circumference, palpation of the testes, and palpation of the seminal vesicles. Then bulls are collected and semen evaluated. The Beef Improvement Federation adopted the breeding soundness exam guidelines recommended by the Society for Theriogenology. The minimum criteria for passing the scrotal circumference and spermiogram (reproductive tract exam and semen evaluation) are:
Cost of breeding soundness exams varies depending on a variety of factors including location of test (on-farm vs. in clinic), number of bulls, and facilities available. In general, the actual exam is $30 to $50 per bull. A cheap price compared to open cows or calves born late in next year's calving season.