By Roelof Bezuidenhout

At one time (actually not so long ago), stud breeders focused on breeding animals that could win prizes at shows. They have, however, come to understand that their clients – ordinary commercial livestock farmers – want animals that can bring in money through their meat, fibre or milk production. The legendary late Prof Gert Erasmus, for many years attached to the University of the Free State’s Department of Animal Science, had some really good advice for breeders on how to distinguish fact from myth.

Myth 1: An animal’s true genetic potential can only be realised through optimum feeding.

This may be true, but how useful is it in animal breeding? A more relevant term is “genetic ability”, because under poor feeding conditions it’s just as important as genetic potential, if not more so.

To breed animals with low sensitivity to environmental changes, selection must take place in conditions opposite to the desired change. For example, to increase weaning weight, body weight or fleece yield, selection should occur under poor feeding conditions. Conversely, wool growers aiming to reduce fibre diameter should select animals under optimal feeding conditions. This counterintuitive principle is known as Falconer’s paradox.

Myth 2: Two or more traits with unfavourable genetic correlation cannot be improved at the same time.

This would only be true if the correlation were perfect – which is rarely the case. In reality, an unfavourable genetic correlation makes simultaneous improvement more challenging, but not impossible. A prime example is the relationship between body weight and fibre diameter. For years, it was widely believed that fine-wool sheep had to be small. Today, there are many large fine-wool Merinos in South Africa, proving that breeders have successfully reduced fibre diameter while increasing body weight.

The most effective way to achieve this is by selecting animals based on combined BLUP (best linear unbiased prediction) breeding values for both traits. While some argue that animal breeding cannot be reduced to a single figure, this misconception is gradually being replaced by the understanding that, although challenging, it is not only possible but also essential.

Today, simultaneous selection for multiple traits is a sophisticated multidisciplinary science with strong genetic and economic foundations.

Myth 3: Breeders should stick to a specific bloodline within a breed.

Relying solely on one bloodline would be very silly, as genetic diversity provides the essential building blocks for improvement. In fact, breeders can even use material from related breeds to enhance specific traits – provided they strictly adhere to well-defined selection criteria.

That said, the Merino breed already has such genetic variation that outcrossing is generally unnecessary. In fact, Merinos possess the greatest genetic diversity of all the sheep breeds in South Africa. Genetic diversity is a valuable asset and should be carefully maintained.

Breeders should be cautious of placing too much emphasis on breed standards and purity. A breed is not a fixed entity but an evolving process, as geneticist and evolutionary biologist Theodosius Dobzhansky so aptly stated. Prof Almero de Lange, formerly of the University of the Free State’s Department of Animal Science, rightly points out that breed standards are typically a description of what has been achieved in a breed, not what to strive for.

Myth 4: Measuring and recording production (and reproduction) performance is the sole saviour of the stud breeding industry.

The opposite view – that performance recording poses a threat to the industry – is equally misleading. Whereas measurements (or scores, when traits cannot be precisely measured) are essential, they must be recorded correctly, accurately and meaningfully analysed. Otherwise they can be highly misleading.

Genetic comparisons between animals are only valid within so-called contemporary groups, where non-genetic factors – such as age, sex, and nutritional and managerial levels – are identical. It stands to reason that breeders must strive for few, large and uniform contemporary groups.

The fact that animals can only be compared within contemporary groups makes performance testing on its own rather useless. In an effort to address this challenge, the Merino industry introduced group breeding schemes, veld ram clubs, control tests, a centralised progeny test, and a show for measured production. But BLUP has rendered most of these methods obsolete, and they should eventually be phased out.

It is, however, important to know that these early initiatives were instrumental in helping breeders understand how to genetically improve livestock in practice. Breeders who have worked within these frameworks are now better positioned to apply BLUP breeding values effectively, as they already understand the underlying principles.

Making performance testing compulsory can create a false complacency of scientific rigour within breed societies, leading members to believe that they are advanced simply because they follow the procedure. True genetic improvement, however, requires a deeper understanding of selection principles and breeding values, not just routine measurement.

Myth 5: Breeders should strive for an “ideal” animal.

The term “Ideal” implies perfection – something that cannot be improved. Yet the so-called “ideal” animal is often described in vague, subjective terms, such as having a broad chest, wide mouth, straight back, strong nose and soft face. These descriptors may sound appealing, but they lack measurable, objective criteria, making them meaningless in scientific breeding.

Instead of chasing an unattainable ideal, breeders should focus on shifting the overall population’s average in the desired direction for every important trait. Selective breeding is about continuous improvement, not achieving a fixed mythical standard.

As geneticist Helen Newton Turner once observed, “The image of the ideal animal has at best been shaken but not shattered.” Unfortunately, this statement still holds true today.

Also read:

• Genetics and breeding technologies in livestock farming

• Good breeding stock at Beefpower Braford production auction

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