Inbreeding in cattle: What are the pros and cons associated with mating a bull to its mother and sisters?

By Nan Smith | 9 January 2017

Dr Danie Odendaal, veterinarian, says living organisms survive and produce offspring because they carry many different genes. These genes make it possible for them to adapt to the conditions in which they must survive and reproduce.

Genes determine and direct the function of every cell in an animal’s body. The problem is that there are also some genetic ‘faults’ in the animal’s chain of genetic material. Mostly these faults only affect the animal’s functioning when the fault occurs simultaneously in both chains – that is, the mother’s chain and the father’s chain. More correctly for cattle, in the dam and in the sire.

When you mate two unrelated animals, with a significant difference in genetic material, the chance of the fault occurring in the calf offspring is extremely small. Each parent contributes 50% of the genetic make-up.

But, if you mate a bull to its mother, 75% of the genetic make-up will be the same and the chance of the fault occurring simultaneously in both chains is very high. This is called in-breeding and must be avoided wherever and whenever possible.

In-breeding can cause major problems such as weak skin, a short lower jaw or stunted growth. Sometimes the defect may not be visible, but can affect function needed for survival, such as the immune system, or cause heart problems.

A stockman will always get the best results for growth and longevity when he (or she) uses an unrelated bull on the cows. This is called out-breeding. In commercial cattle production, the effect of out-breeding is called heterosis, which is the positive effect you get by combining two unrelated genetic chains.

The results of these out-breeding crosses are improved fertility, survival and growth – the three factors most important for production.

What to do with inbreeding problems?

If you have in-breeding problems, start fixing them now. Most cattle farmers in Africa run their animals in communal grazing areas and there are inevitably problems with in-breeding. But, equally clearly, there are solutions.

A stockman or woman, must be serious about herd productivity; without a serious, profit and production based approach, there is simply no way to improve herds, upgrade animals and start becoming a commercial farmer.

You can keep the bulls in for two seasons; after that they must be replaced. It’s that simple. If you don’t do this, there will be in-breeding. If you are running animals in a group with other cattle farmers, get together to talk about breeding.

Work out a deal so that you can sell off the bulls you have and get new stock in from outside your area. Remember to test, test and test again before you move animals into your herd.

Either you want to upgrade your cattle, in which case you start doing something about it, or you keep them as they are at scrap cattle status. If you choose the latter option, other farmers, or agri-businesses, will jump in and take the place that could so easily have been yours.

Whether it’s five, 50 or 100 animals you need to keep pushing for quality. In-breeding will not give you quality, so don’t do it.