Spring on our farm is busy. We are finishing lambing and kidding and all of a sudden it is time to breed the beef cows.
While researching how to prepare our bulls for breeding I discovered that the production of sperm cells requires at least 48 days. This means that you must begin to get the bull into breeding condition at least two to three months ahead of the breeding season.
The first step is to ensure that the bulls are being fed to sustain a moderate body condition and are exercising enough to develop some physical endurance. Although the bulls are in a small pen, we provided exercise by letting them out to walk for water instead of bringing the water to them. It is also important to address any health concerns quickly because a high fever for just a day or so can damage all the stored sperm cells. It will take at least 1-1/2 months for them to be replaced.
In researching methods of increasing cowherd fertility we discovered the importance of the scrotal circumference of our bulls. Experts agree that scrotal circumference is a medium to high heritability trait, which directly affects the fertility of the male offspring — increasing scrotal size will increase fertility of future generations.
Also, the scrotal circumference of a bull is positively related to the fertility of his daughters. Heifers from sires with larger than average scrotal circumference tend to reach puberty earlier than those from bulls with smaller scrotal circumferences. Increased scrotal circumference in sires is also favorably correlated to their daughter’s age at first breeding, pregnancy rate and days to rebreeding after calving. Due to low heritability, direct selection for female fertility traits has not been successful. The strong genetic relationship between scrotal circumference and female reproductive traits provides an alternative selection method.
Ideally, a qualified veterinarian should perform a breeding soundness examination on all bulls, every year shortly before the beginning of breeding. If that is not feasible, then at least the young, the old and the questionable (those that have been ill previously or are in poor condition) should be selected and checked. Few bulls are sterile; most produce some viable sperm and could settle a few cows. The purpose of the semen evaluation is to identify bulls with reduced semen quality. If one sample tests poorly, it is best to collect and examine a second sample. Even if the second sample also tests poorly, the bull should be re-evaluated three to six weeks later. By that time he should have recovered, if the problem was temporary. This is why it is very important to start early.
A complete breeding soundness examination consists of the following:
1. Observation for physical problems.
2. Testicle palpation
3. Measure of scrotal circumference.
4. Palpation of seminal vesicles (per rectum).
5. Observation of penis while extended.
6. Classification of semen (sperm motility and morphology).
The sperm motility must be evaluated on-site; maintaining the normal temperature of the semen during examination is critical. To evaluate the sperm morphology, the sperm cells are stained on a slide. An important part of a breeding soundness evaluation is looking for soundness problems. This includes feet and legs, body condition, eye and mouth problems as well as lesions of the penis, prepuce or testicles.
It is important to understand that a breeding soundness examination is neither a libido test nor a test of mating ability. The breeder best determines these at home by spending time observing the bulls’ performance.
Once the bull is taken care of it is time to remember the cows. When the cows calve in the spring there is a period of time when her reproductive abilities are put on hold until her body can build up enough energy reserves to allow her to become receptive to rebreeding. This is called anoestrus. Cows that don’t have their nutritional needs met experience more problems with reproduction than cows in good condition. Cows in good condition, with a body condition score of three to five, are considered in optimum breeding condition. These cows can re-breed 30 to 40 days after calving, while the effects of anoestrus can inhibit a poor-condition cow from rebreeding for up to 100 days.
The cheapest way to make sure our cows are on a gaining nutritional plane is to wait until the grass is here and breed them on pasture, but that could make calving a bit later in the spring than what works for our farm. Since we do not feed grain to our beef cattle, our best option is to retain a portion of the best quality hay we purchased to feed post-calving when the cows have the highest nutritional draw.
The other consideration is to supply the cowherd with a high quality mineral supplement. When the cows are healing from calving and nursing new calves their stores are at risk of being low. If their body perceives that they are not able to sustain another pregnancy due to malnutrition of any kind their anoestrus period will extend much longer.
If the feed is sufficient and the supplements in place and the cows still seem a bit slow, it could be lice. We often have a problem with lice in the spring. A quick lice powder treatment does amazing things to a cow’s general condition. It also guarantees that the calves won’t have to deal with lice. †