Technical information - selection

New Genes and future Challenges

by Alex Ashwood,

Alinta BrahmanStud,
Lennox Head, New South Wales

Selection is the primary tool available for changing the expression and potential of Brahmans. Fortunately, a better appreciation of genetic principles and genetic variation has lead to increased breeding opportunities.

Uniformity and Prepotency

An examination of early Brahman pedigrees show an obvious recurrence of common ancestors – “necessity was often the mother of invention”. Much of the early progress of Brahmans was due to inbreeding and line breeding.

Line breeding subsequently acquired “magical” qualities and was seen as a suitable breeding management practice to develop prepotent stock. What actually occurred was the production of uniform stock which is quite difference to prepotency.

There is no doubt that with limited resources the early breeders did a tremendous job. Emphasis was placed on the selection of outstanding stock but due to the limited gene pool careful intense selection sometimes led to line breeding.

When stud breeders sought imported genetics they realised that a restricted gene pool leads to selection depression, depressed fertility and milk production and reduced breed performance-uniformity yes, prepotency no.

A major challenge is to breed prepotent traits and not simply uniform stock.

Genetic Variation

Cattle have 30 pairs of chromosomes and each chromosome has hundred of genes. Not only do chromosomes come in pairs but each gene on one chromosome has a partner in the other chromosome.

Obviously two situations might occur:

  • Both genes of the pair may be identical – homozygosity (uniformity).
  • Both genes of the pair may be different – heterozygosity (variation).

When the parents are related there is a higher probability of homozygosity and uniformity. Alternatively with unrelated parents there is a higher probability of heterozygosity and variation. This variation allows maximum selection and prepotency.

SELECTION TRAITS

Since each gene within a gene pair is functional and one gene is not able to dominate the other, many genes interact with one another to produce a particular trait.

A particular characteristic becomes obvious only when selective pressure is applied which organises the combination of genes to allow a trait to increase in frequency and eventually become dominant.

Thus, the term a “ bull with dominant genes” is not strictly correct. Instead, it is the characteristic trait which are dominant or otherwise.

The selection of suitable beef and type characteristics from a large genetic pool leads to prepotency and breed vigour. Unfortunately if it was a simple as it sounds there would be an abundance of so called “prepotent” sires.

Genetic variation in parents allows maximum selection.

New Genes

There has been a wide variation in the style and attributes of the recent imports and some characteristics have not suited all breeders.

It is undeniable that the imported genetics have benefited the Brahman breed and there is no doubt that careful breeding and selection will benefit future generations.

Certainly there has been mixed results to recent imports with both successes and disappointments. Initially, the selection pressure was not able to organise the groups of genes necessary for the dominance of desirable traits.

However, as a result of better selection, that is mating progeny with the best traits with stock with similar traits there has been increased levels of dominance and prepotency.

Genetic Improvement

Providing that selection is for an appropriate goal (not fads) and steps are taken to maintain genetic prepotency, the selection of new genetics can lead to sustainable improvements in animal performance Genetic improvement is permanent, cumulative and usually highly cost effective.

It is permanent, since it influences the performance of animals for life. Improvements made in one generation are passed on and are cumulative in subsequent generations.

Genetic Pyramid

Despite embryo transfer technology and artificial breeding which has produced a more level playing field, the structure of most breeding industries can be described as a pyramid ie. A nucleus of big breeders form the tip, then there are one or more middle layers of small breeders and a final layer of commercial herds.

In this generalised model, the big breeders introduce new genetic pools to large pools of cattle.

The middle group, the multipliers have access to these same genetic pools with a lower proportion of cattle and often they try and improve the stock from larger breeders. Finally, commercial breeders, select from a large collection of bulls.

As a result, genetic improvement flows through the pyramid, hence the selection new genetic material can have a major impact on the sustainability of seed stock.

Studs providing the large numbers of seed stock can have a major impact on the performance of the breed.

Potential Benefits

The goal of genetic improvement should be increased product value and reduced costs of production or both.

Benefits accrue if the local industry becomes more viable and competitive. Subsequently effective genetic material and improvement programs are vital to the underlying efficiency and long term sustainability of the beef industry.

Alternatively, the failure to sustain effective genetic improvement programs can cost the Brahman breed dearly compared to its competitors.

Future Challenges

The continued careful selection for the right characteristics that will maximise production efficiency with desirable confirmation and function will provide a challenge to all breeders.

With restricted resources and a limited genetic pool the efforts and initiative of the early breeders moulded Brahmans into a suitable breed for Australia and particularly sub-tropical environments.

Given the availability of new technology and the depth of genetics the challenge for influential studs is to take the breed to even greater heights to ensure Brahmans are competitive in the local and global market place.

The Brahmans of the future will be bred by cattlemen who can combine “the best of the best with the best.”