Get Those Bulls In Shape Now

The bull pen can be that behind-the-barn pen that is forgotten as calving gets under way. A careful eye is scanned over the cows from sunrise to sunrise, but the bulls may just be fed. In fact, they may be watching us more than we are watching them, writes a North Dakota State University specialist.
calendar icon 4 April 2011
clock icon 4 minute read

However, next year’s calf crop is on the line and those bulls need to be ready for bull turnout. At bull turnout, the bull is expected to be physically fit and fertile. From a management aspect, managers need to understand that, without a doubt, neither of these two expectations can be met by attending a two-week short course and coming home with a quick fix.

If one is not convinced, go to the gym. Starting now, or at least two months before you expect to turn the bulls out, management needs to focus on the bulls, as well as the cows and calves. Bull fitness is a function of total body condition. Perhaps fitness is best gauged by simply monitoring the body condition on the bulls. However, even that is not easy. Increasing energy input for the bull can put on body fat, but keep in mind that these bulls are not intended for the harvest rail. Instead, the bulls are going to the breeding pasture, so they don’t need much fat.

Bull conditioning needs to follow a fine line between improving body condition and not adding fat. Some would call that getting physically fit. Maybe one does not need to hire a trainer, but keep in mind the balance between activity and nutrition is important. A good nutritional consultant would help. That is why now is the time to make sure the bulls are conditioned adequately.

Likewise, there is no quick fix to poor bull fertility. Spermatogenesis is a roughly two-month process from start to finish. Viable, aggressive sperm cells are not produced overnight. If bulls are stressed, underfed or sick, spermatogenesis can be disrupted or may cease.

In such cases, these bulls may test bad or have periods of low fertility later in the breeding season. Spermatogenesis in the male is similar to an assembly-line process. As the spermatozoa are made, they progress along a very long assembly line as various parts are assembled. As was noted earlier, from the actual initiation of spermatogenesis to the finished spermatozoa, the process takes about two months. Any time the assembly line is shut down, the result will be fewer spermatozoa available two months later.

This delay in production often is long forgotten once the bulls are turned out to pasture. Fortunately, like all living things, there are backups, such as multiple spermatozoa assembly lines in production at different times. However, maximum production can be diminished. If stress, poor nutrition or health problems are severe enough, the result is open cows in the fall. One cannot emphasize enough this time delay in fertility, so the need to start monitoring bulls is now.

Those new yearling bulls probably are getting a lot of attention, but do not forget the older bulls. Breeding soundness exams, as well as weighing and condition scoring should be planned and scheduled. Although not always available, if one has fall weight numbers for the bulls, their winter progress can be gauged better. Last fall at the Dickinson Research Extension Center, the two 3-year-old bulls that were kept averaged just less than 1,660 pounds. The yearling bulls that were coming up on being 2 years old averaged a little more than 1,340 pounds.

Essentially, all the keeper bulls had a body condition score of 6. These keeper bulls had been lounging on pasture with the other bulls, so you would expect a condition score of 6. Some would have come off the breeding pastures thinner, but they had time to gain back their flesh, so they still should have a condition score of 6.

For those who are not aware of the condition scoring system, bulls with body condition scores of 3 or less would be skinny and have skeletal features evident. Body condition scores of 4 to 6 are bulls that express normal skeletal frame and muscle without evidence of excessive fat or fat patches. Condition scores of 7 to 10 are cattle that have an obvious fat covering. It is more obvious as a bull approaches a 10 body condition score.

Given a keen eye for adequate body condition and an expectation that most bulls can add 300 pounds a year in muscle, the bulls should be on target for the breeding season.

Bulls that under or overconditioned, underweight or lack luster need to be dealt with now. Don’t wait because the penalty is low fertility and open cows. May you find all your ear tags.

March 2011

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