Vet’s Voice: Observing breeding bulls | TSLN.com

Vet’s Voice: Observing breeding bulls

Dave Barz, DVM

I think June will go down as the wettest June in our area, and we didn’t receive the heavy rains some of you did. As a result, the grass is green, the nights are cool, and every day on my way to work I see bulls covering cows in the pastures. Our last article, June 18, dealt with reproductive efficiency in the cow, but it is important to watch bulls closely during the first thirty days of the breeding season.

Before turnout, I’m sure all of the bulls were semen evaluated. This breeding soundness exam (BSE) evaluates five factors on the day the exam was conducted:

1. Physical soundness;

2. reproductive tract soundness;

3. scrotal circumference;

4. minimum percentage of normal sperm cells; and

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5. sperm motility.

Not all bulls are created equal. It’s easy to measure the components of the BSE, but it is much more difficult to measure breeding ability and libido, or the desire to breed cows. Remember, a bull’s breeding status is dynamic in that it changes daily. Sometimes a bull is great one day and unable to breed and settle cows the next.

By watching bulls closely during the first thirty days of the breeding season, producers can assess the bull’s libido as well as bull dominance. In the herd setting where a battery of bulls are used, the dominant bull may breed a very high percentage of the herd, as much as 75 percent. This leaves the outliers to be bred by the young or less dominant bulls. Many cows may be double mated by several bulls while she is in heat. If your dominant bull appears to be lame or is reluctant to mount cows as a result of decreased libido, he should be removed immediately allowing other bulls to pick up the slack.

Some old timers recommend never using two bulls in a pasture, as they prefer three or more. That way, if two bulls are fighting, the other bull sneaks in to get the job done. Pastures with single bulls need to be watched very closely to make sure females are properly bred.

Yearlings pose an interesting problem as they tend to “fall in love.” They may repeatedly breed a single female while several other fertile females are passed over and missed. This will greatly extend the breeding/calving season.

It is important not to trust yearling bulls early in the breeding season because they need to hone their breeding skills. Turning yearling bulls into groups of synchronized females may result in a disaster. Yearlings raised in a bull test setting where the emphasis is on growth and gain, usually have a high percentage of abnormal sperm cells at early turnout. If possible, hold yearling bulls back until the end of the breeding season and use them for cleanup – think of it as training for next year. I realize time is money, but over-confidence in a yearling bull can also be very expensive.

Temperature extremes, both climatic and body, can result in infertility. High temperatures may cause the cow to absorb her embryo and return to heat months later. The bull tries to maintain optimum sperm production and quality by keeping his testicles a few degrees cooler than his 102° F. body temperature.

Bulls which do well in warm conditions have pendulous testicles. Some bulls with short, fat-filled scrotums are unable to keep their testicles cool enough for good quality sperm production. Old frost damage scars to the tip of the scrotum may also inhibit movement. If the bull develops a temperature as a result of disease, we generally consider him lower in fertility for 60 days.

Always watch closely for lameness and breeding injuries. There is a correlation between being polled and having a looser sheath, as horned bulls tend to have less injuries. There is a connection between polledness and the strength and development of the retractor-prepucial muscles. As polled bulls relax, they prolapse their prepuce. The prepuce is easily cut by brush, grass or barbed wire. These injuries will not allow the bull to mate properly. The fractured penis is characterized by a hematoma (blood clot) under the skin on the penis below the scrotum. Either of these injuries requires medical and possibly surgical care, usually with only a 50-50 chance of recovery. At best, these bulls are out for the rest of the season once injured.

Lameness and pinkeye are always problems. Bulls with these problems could be used in small pastures with a few cows, but will not do well in a large pasture where extensive travel is needed. Some lameness to the front foot can be treated and the bull returned to pasture, but hind foot lameness requires more careful observation. Be sure the treated hind leg lameness allows the bull to mount.

In most of our operations we utilize bulls 45-60 days a year. Careful planning and astute observation will help make those days as productive as possible. The higher the reproductive efficiency of your herd, the more profitable it can be.

I think June will go down as the wettest June in our area, and we didn’t receive the heavy rains some of you did. As a result, the grass is green, the nights are cool, and every day on my way to work I see bulls covering cows in the pastures. Our last article, June 18, dealt with reproductive efficiency in the cow, but it is important to watch bulls closely during the first thirty days of the breeding season.

Before turnout, I’m sure all of the bulls were semen evaluated. This breeding soundness exam (BSE) evaluates five factors on the day the exam was conducted:

1. Physical soundness;

2. reproductive tract soundness;

3. scrotal circumference;

4. minimum percentage of normal sperm cells; and

5. sperm motility.

Not all bulls are created equal. It’s easy to measure the components of the BSE, but it is much more difficult to measure breeding ability and libido, or the desire to breed cows. Remember, a bull’s breeding status is dynamic in that it changes daily. Sometimes a bull is great one day and unable to breed and settle cows the next.

By watching bulls closely during the first thirty days of the breeding season, producers can assess the bull’s libido as well as bull dominance. In the herd setting where a battery of bulls are used, the dominant bull may breed a very high percentage of the herd, as much as 75 percent. This leaves the outliers to be bred by the young or less dominant bulls. Many cows may be double mated by several bulls while she is in heat. If your dominant bull appears to be lame or is reluctant to mount cows as a result of decreased libido, he should be removed immediately allowing other bulls to pick up the slack.

Some old timers recommend never using two bulls in a pasture, as they prefer three or more. That way, if two bulls are fighting, the other bull sneaks in to get the job done. Pastures with single bulls need to be watched very closely to make sure females are properly bred.

Yearlings pose an interesting problem as they tend to “fall in love.” They may repeatedly breed a single female while several other fertile females are passed over and missed. This will greatly extend the breeding/calving season.

It is important not to trust yearling bulls early in the breeding season because they need to hone their breeding skills. Turning yearling bulls into groups of synchronized females may result in a disaster. Yearlings raised in a bull test setting where the emphasis is on growth and gain, usually have a high percentage of abnormal sperm cells at early turnout. If possible, hold yearling bulls back until the end of the breeding season and use them for cleanup – think of it as training for next year. I realize time is money, but over-confidence in a yearling bull can also be very expensive.

Temperature extremes, both climatic and body, can result in infertility. High temperatures may cause the cow to absorb her embryo and return to heat months later. The bull tries to maintain optimum sperm production and quality by keeping his testicles a few degrees cooler than his 102° F. body temperature.

Bulls which do well in warm conditions have pendulous testicles. Some bulls with short, fat-filled scrotums are unable to keep their testicles cool enough for good quality sperm production. Old frost damage scars to the tip of the scrotum may also inhibit movement. If the bull develops a temperature as a result of disease, we generally consider him lower in fertility for 60 days.

Always watch closely for lameness and breeding injuries. There is a correlation between being polled and having a looser sheath, as horned bulls tend to have less injuries. There is a connection between polledness and the strength and development of the retractor-prepucial muscles. As polled bulls relax, they prolapse their prepuce. The prepuce is easily cut by brush, grass or barbed wire. These injuries will not allow the bull to mate properly. The fractured penis is characterized by a hematoma (blood clot) under the skin on the penis below the scrotum. Either of these injuries requires medical and possibly surgical care, usually with only a 50-50 chance of recovery. At best, these bulls are out for the rest of the season once injured.

Lameness and pinkeye are always problems. Bulls with these problems could be used in small pastures with a few cows, but will not do well in a large pasture where extensive travel is needed. Some lameness to the front foot can be treated and the bull returned to pasture, but hind foot lameness requires more careful observation. Be sure the treated hind leg lameness allows the bull to mount.

In most of our operations we utilize bulls 45-60 days a year. Careful planning and astute observation will help make those days as productive as possible. The higher the reproductive efficiency of your herd, the more profitable it can be.

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