The Cow-Calf Manager
Livestock Update, May 2004
John B. Hall, Extension Animal Scientist, Beef, VA Tech
Bull Management Essential for a Successful Breeding Season
Good healthy bulls are essential to the success of a cow/calf operation. However, bulls are often the most ignored animals on the farm. Breeding season, especially for spring calvers, coincides with the very busy part of the year. Hay making (or winter feeding in fall programs), harvest or planting of other crops often makes us just turn the bull out and "let him go to it". But failure to manage bulls before and during the breeding season is crucial.
On the average, performance tested bulls with good EPDs cost $1400-$2500 in Virginia. Bulls with excellent EPDs often cost $4000 and up. After making that kind of investment, it makes sense to spend a little time and effort on bull's upkeep. A few simple steps can make the difference between a good breeding season and a bad one. Mismanaged bulls result in decreased calf crop and lower income. If cows are thin, the problem is just compounded.
Breeding Soundness Exams. All bulls should have a breeding soundness exam about 30 days before the start of the breeding season. Even bulls that were successful breeders last year need to be checked. Injuries and infection are the most common cause of sterility in previously fertile bulls. Studies in Ohio and Indiana indicate that between 11 and 15% of all bulls are infertile or subfertile. However, in a recent Virginia survey less than 10% of the farms indicated that they gave breeding soundness exams to "proven" bulls. Because bulls can become subfertile or sterile between breeding seasons using an untested bull is like playing the lottery, you don't know which one is a winner and which is a dud.
Table 1. Relationship Between Scrotal Circumference and Pregnancy Rate
|Scrotal Circumference||Pregnancy Rate*|
|Less Than 28 cm||55|
|28 to 32 cm||64|
|Over 32 cm||82|
* Exposed to 15 to 20 heifers for 45 days
Adapted from: Lunstra, 1986. Proceedings of the Beef Improvement Federation.
In young bulls, scrotal circumference can have a significant impact on fertility and pregnancy rates (Table 1). Older bulls also should have a scrotal circumference of at least 36-38 cm. Measurements of scrotal circumference is one part of a breeding soundness exam.
A veterinarian must do a breeding soundness exam. It consists of a general physical examination of the bull, an internal and external examination of the bulls' reproductive tract and a semen examination. Poor mobility or bad eyesight can hamper a bull's ability to find and service cows. Infections in the seminal vesicles or infection or damage of the testis are not uncommon. Injuries or deformities of the penis can make breeding impossible. Abnormal sperm morphology (shape) results in failure of sperm to penetrate and fertilize the ovum (egg). Few of these problems can be identified in the field. Breeding soundness exams cost about $30 to $50 per bull.
Vaccinations. Bulls generally should receive the same pre-breeding vaccinations as the cow herd. Lepto and Vibrio vaccines are probably the most important, but IBR, PI3, BVD and BRSV are usually included as well.
Conditioning. Bulls will have to travel great distances over various terrain during the breeding season. Bulls that are out of shape may stop servicing cows or have lower fertility. Bulls should be conditioned before the breeding season. The easiest way to condition bulls is to put them in a large pasture with feed or salt on one end and water on the other. This will make bulls walk. Bulls should be in body condition score 5 or low 6 - neither fat nor too thin - at the start of the breeding season.
During the Breeding Season
The first few days. Management and observation of bulls is critical during the first few days of the breeding season. This is especially important for young bulls. Mainly, you are looking for indicators of libido and performance. Bulls should be observed several times a day until you are sure of the following:
Keeping bulls healthy. Bulls should be seen at least weekly although daily is much better. Producers should spend enough time to thoroughly exam the bull. Make sure he is not getting to thin. Is he injured? Is he still interested in cows?
Bulls that are injured should be removed and replaced immediately. A limping bull is not going to get better or get many cows bred without a rest. Several years ago I was in a herd where a young injured bull had been left with the herd because the producer did not have a replacement bull. We suggested that he replace the bull right away. A neighbor let him borrow a replacement bull for the last 30 days of the breeding season. The percentage of cows bred by the injured bull and the replacement bull are indicated in Figure 1. By replacing the bull, he saved himself from a disaster.
In addition to feet and leg injuries, reproductive injuries can also result. Hematoma of the penis or broken penis is not an uncommon injury. It is most common in multi-sire mating situations or in young small framed bulls among large framed, aggressive cows. Injuries or cuts to the sheath are often caused by bulls trying to jump or break through fences to get to other cows or bulls. Sometimes these cuts cause adhesions so breeding is impossible or too painful for bulls.
Keeping bulls in condition. All bulls should be checked for body condition during the breeding season. Extremely thin bulls should be replaced. Young bulls are still growing and often need more energy than the grass can provide. Yearling to 2-year-old bulls should be supplemented during the breeding season. Four to eight pounds of cracked corn daily should be enough. This often means training the bull to come into a special pen or stanchion to be fed. A small portable pen works well. If he is trained to this feed regime before the breeding season, it will make it much easier.
Keeping bulls interested. For some reason, certain bulls seem to lose their desire to seek out cows in heat and do a good job breeding during the breeding season. If you see bulls ignoring cows in heat, this could be the problem. In a commercial herd, the solution is usually to switch bulls between breeding groups or replace the bull. Exposure to the "new girls" usually gets them back in the mood. In purebred operations, the solution is more complicated because of positive identification of sires. Switching bulls is an option, but calves should be blood typed if producers cannot be absolutely sure of the calf's sire.
Figure 1. Effect of Injury to Bull during the Breeding Season on Percentage of Cows Pregnant.
Manage your bulls properly during breeding season and you will be rewarded with a better calf crop next year. Remember when in doubt switch him out!