Question:

I have a small cattle farm of about 20 heifers. I started two years ago and bought a Hereford bull from another farmer. I had 10 heifers at that stage. My calves that I got from the bull were 70 percent purebred and are now starting to be ready for slaughter. I just want to know if I can use the bull to breed his own calves for the first season or will I have to get a new bull to breed the calves. I heard from my neighbours that you can do it. I just want to get an expert’s advice.

Answer:

Using a bull on his own daughters is not a good idea at all and should be avoided as far as possible. Basically, there are two main dangers.

1. A great many scientific studies show that animals with high levels of inbreeding (i.e. offspring of closely related parents) are seriously affected by so-called fitness traits. These are traits that are related to survival, namely reproduction (fertility) and the ability to survive, especially until puberty (the age at which the animal can be mated). Each calf that is born receives half of its genetic makeup from each of its parents. A calf is therefore at least 50% related to its father (more, if they are also further related in the rest of the family tree). The offspring from such a mating are therefore a minimum of 25% inbred. The recommended maximum level of inbreeding is only 6.5%.

2. The second major danger is that, should the bull be a carrier of an undesirable, and even lethal (deadly) gene, there is a chance that he will pass it on to his daughters, who will also not show its effects, because they are also simply carriers. The mating of two carriers has resulted in as many as 25% of the calves resulting from such mating being affected by the effects of the genes. Examples of these are several genes that lead to early death of embryos (and resorption), double muscling and a number of other abnormalities. This risk is of course small if the bull is not a carrier of one of the genes responsible for the conditions, but without genomic testing the risk is unknown.

My recommendation is therefore to avoid father-daughter crosses. The same applies to the mating of all closely related family members, even half-siblings (half brothers and sisters, son-mother, etc.)

Answered by Dr Japie van der Westhuizen, general manager at SA Studbook.

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