By Glen L. Jensen, DVM – Carbon and Emery Animal Health
One of the common things I hear from many cattle producers when I mention veterinary bull breeding soundness evaluations is; “I know he is good, I have calves out of him.” There are very few truly infertile bulls, they are all different levels of infertile, after all, have you ever seen a bull with 100% pregnancy rate and only one breeding per cow? When a bull sale advertises “guaranteed fertile,” and these bulls have been “fertility checked,” what does that really mean? It is very unfortunate, but we have created this idea that the bull is good or not as if it is black and white, fertile or not fertile, when in reality there is nothing farther from the truth.
Herd fertility is vital to its survival and profitability. In fact, it is considered to be five times more important than growth or improving the genetics for weaning weight. The interesting thing is that fertility has everything to do with the pounds of product available at the time of weaning. This doesn’t only come from a few more calves, the gains come from having calves early in the breeding season. Every cycle of the cow that is lost is about 42lbs of lost beef for sale at weaning. This really adds up.
Consider comparing two bulls. The better bull is 80% effective; he gets 80% of the cows he breeds pregnant each cycle. This allows him to have 99.2% pregnant cows in three cycles or 63 days. Bull number two is only 60% effective, getting 60% pregnant each time he breeds. At the end of three cycles, he gets 93.6% pregnant. As all producers know, he most likely only breed about 30 cows, or at least let’s assume that. 29.8 cows were pregnant with the first bull and 28.1 cows were pregnant with the second bull. If this is your herd will you sit back and say; “you know, I’ll bet I have a bull that isn’t doing as good of a job as I would like.” Yet, over the course of five years with this 20% less effective bull, you will loose about $13,000 from the loss of a few calves but mostly the loss of pounds raised do to later calving cows not having the time to put the same weight on their calves as the earlier calving cows did.
Even when keeping very good records, it is difficult to recognize the losses that can occur from a slightly subfertile bull. The best way to protect yourself is to ensure every bull is tested every year prior to the breeding season. This includes bulls you may have just purchased, even if the sale advertised that they were “semen checked.” Understand that the bull producer will do everything they can to get a certificate saying he “passed.” They want to sell every bull they can; some may be subfertile and you will pay the price if it is, for years to come. The best time to test your bulls is as close to the breeding season as you can. This helps to ensure the results are truly reflective of what you should expect during the breeding season.
Many things can affect the bull’s fertility/subfertility including genetics, the season or time of year, the weather – both hot and extreme cold – disease, stress, toxins and many more. Most of these insults are temporary; we see the damage by examining the sperm morphology (cell structure). The damage is seen usually one to four weeks after the insult. If we see a high number of abnormal sperm cells, it is best to recheck in about 3-4 weeks. Some damage can be permanent. The higher the number of abnormal cells present, the lower the expected pregnancy rates.