4 - Cattle Genetics

Key actions

  • Set the breeding objectives for your enterprise.
  • Assess merits within breed selection, of changing breeds or crossbreeding.
  • Refer to breed societies’ market-based indexes or use BreedObject™ or similar procedure, to develop an index.
  • Select bulls (or semen) based on an appropriate $Index.
  • Bring genetically unrelated bulls into the herd to avoid inbreeding.
  • Review your breeding program and tailor it to your requirements, considering traits that are of individual importance to your program (for example breeding polled cattle).
  • Ensure your breeding program matches your production system and market being supplied.

Why is genetic improvement important?

Genetics sets the potential for upper or lower production limits that animals can achieve. This can impact on the goals you set for the beef enterprise, including your market options. Important beef enterprise profit drivers related to animal performance are influenced by the genetic make-up of the herd. These include
  • weaning rate
  • cow survival rate
  • cow weight
  • calving ease
  • sale weight
  • retail beef yield
  • P8 fat depth
  • marbling score.
Using the best cattle genetics allows you to improve the animals’ contribution to enterprise profit.Although animal genetics cannot directly improve non-animal production factors such as pasture and grazing management, it can complement aspects of enterprise management. For example, superior genetics may facilitate a greater capacity for more efficient feed utilisation and growth rates. Genetics can also determine whether you are able to achieve a particular production target, like a high level of marbling or a particular muscle score.In other situations, genetics can change the way you manage the herd (such as increasing the distance cattle range or graze from water), as well as reducing operational costs (for example, improved ease of mustering and handling because of selection for better temperament).Simply put, it is about producing the best genotypes of cattle to suit specific beef enterprises and keep in mind that genetic gain is cumulative, permanent and relatively cheap.

Principles of cattle genetics

  • Most traits for cattle production are under some genetic control (heritable) and can be exploited to improve profit of the herd. Traits that are economically important and are heritable should be included in the breeding objective of beef herds.
  • Variation for economically important traits occurs within breeds, between breeds and some can be created by crossing breeds. All sources of genetic variation should be considered when planning a breeding program.
  • Bulls have the major influence on commercial breeding programs because of the number of calves they sire. Selection of sires is therefore a critical control point in the operation of an effective breeding program and genetic improvement.
  • Genetic improvement should be considered in conjunction with non-genetic means of improving performance. Non-genetic means, such as current herd selection, improved nutrition or changes to marketing procedures, may be more cost effective.

Heritability explained

Only part of the variation between animals in a contemporary group is due to genetic differences. The majority of the variation is generally due to non-genetic factors such as differences in environmental factors, such as nutrition or exposure to disease. The degree to which genetic differences influence performance varies from trait to trait. This is explained by differences in the 'heritability' of traits. Growth and carcase traits tend to have moderate to high heritabilities - 20% - 60%, whilst maternal traits tend to have low heritability -10% or lower.

What is genetic improvement?

Genetic improvement is the use of genetically superior animals as parents of the next generation. The definition of genetic superiority will be a function of many variables including the production environment and the market being supplied. Most measures of genetic superiority will be based on potential profitability of the genotype for the given production environment and market being supplied. Not all genetic superiority needs to be based on profit but in commercial cattle enterprises profitability is likely to be most important. Genetic improvement can improve your profit by not only increasing productivity and market compliance, but also by decreasing costs.Genetic improvement should be continuous and the most important variable that will limit continuous improvement is inbreeding which can be managed by implementing a sustainable genetic improvement program.

Other important considerations

A genetic improvement program must be designed in conjunction with culling decisions that influence the current herd, with the management program under which the herd is run and with considerations of markets supplied.

How does this module assist you?

This module assumes that you have made the decision to run a commercial breeding herd. Therefore you need to select a bull to breed calves. Given that decision, this module will help you buy a bull that is value for money because it improves the genetics that are related to profit in your herd. If you are still undecided about running a commercial breeding herd, consider reviewing Module 1: Setting directions.This module will assist commercial breeders whose main avenue for ongoing genetic improvement is through buying-in bulls or semen. It is not specifically designed for seedstock or stud breeders but the principles of setting a breeding objective are still the same. It takes you through the steps of establishing the breeding program to achieve animal production targets that contribute to enterprise profit. It also considers the implications of changing breeds or crossbreeding and provides a guide to selecting the best bulls for your enterprise and setting up a mating program.

Linkages to other modules

The target markets and proposed herd structure for the beef enterprise are identified in Module 1: Setting directions, in relation to the pattern of pasture growth, long-term market prices, availability of finance and owner/manager goals and constraints. Module 1 also provides guidelines for determining the current performance of the herd. There is a clear linkage to Module 7: Meeting market specifications, as well as to Module 5: Weaner throughput.

Procedures for using best cattle genetics