COMPOSITE rearing systems have enjoyed varying popularity in the Australian beef industry.
For some large pastoral companies including North Australian Pastoral Co, Australian Agricultural Co and others, as well as some southern producers, composites have been a mainstay of production since the 1990s.
However, a properly managed composite breeding program requires some careful planning and a level of commitment to ensure success.
At its most basic description, composite breeding is really a crossbreeding program that will allow producers to settle on a stabilized breed mix to best suit the breeding objective.
Genetic Dr. David Johnston An expert from AGBU in Armidale described a composite breed at the Australian Beef Improvement Association’s annual conference: “A population stabilized by at least one intragenerational mating after the initial crossing of two or more breeds. The design aims to exploit sex differences and maintained heterosis in future generations without crossing.
Producers looking to use composite cattle as part of their programs have the option of purchasing and using composite bulls within their existing programs or taking the more challenging route of developing their own composites. In most cases, producers who choose to purchase composites do so to introduce or take advantage of the traits and advantages of heterosis that exist in their selected mothers.
In most cases, producers who buy composite bulls buy stabilized bulls after using four different breeds to achieve a balance of traits. In doing so, these bulls exhibit up to 75% of the average expressed level of heterosis of the F1 animal.
In practical terms, this should help producers increase the calf weaning rate per exposed cow by approximately 17.5%.
A significant advantage in purchasing composite bulls comes from the ease of management for the producer. The greatest focus comes from spending time looking at the bulls on offer and identifying the best bull to achieve your breeding goal.
Many of the established bull breeders offering composite bulls are now able to provide genetic information through IGS, as well as provide pedigrees and performance records to assist producers in sire selection.
An often overlooked advantage in purchasing composite bulls is small herds looking to capture the increased performance from heterosis. Some small herds are considered more difficult to manage crossbreeding and a composite bull can give producers access to hybrid vigor without having to struggle to achieve effective crossbreeding.
For producers considering developing their own composite animals, some clear planning is needed before starting any program. The most important step is to be clear about your breeding goal and the traits required to achieve that goal.
In doing so, producers must consider both environmental constraints, market specifications, and actual genetic and phenotypic requirements.
If this step can be carried out effectively, it will make it easier for producers to view breed selection within the framework defined by their breeding objectives. Although there is often a desire to introduce or start testing new cattle breeds, to manage the variability of the cattle to be bred in the program, use breeds with known performance on as many traits as effective as possible.
One of the biggest challenges for manufacturers looking to develop their own composites is the need to use large numbers of mothers. Research in the industry and through programs such as the US Clay Center has proven the need to use 15-20 bulls per breed to avoid inbreeding and ensure the genetics used are adequately representative of the breed.
In addition to using a large number of mothers, each generation will need to use an equally large number of females – research suggests at least 500 cows per generation.
Once the program starts, it is important to have a clear mating program not only for sires and offspring. Part of the pairing program also includes at least two random pairings ( between pairings) after the initial transition.
This is important for stabilizing the composite sex ratio at both individual and maternal heterosis levels. If this does not happen, the contributions of the foundation animals and the levels of heterosis will vary between generations, resulting in variable performance of the generation.
Ultimately, the development of new composites is a long-term breeding commitment. Producers should objectively consider their breeding goals and determine whether a similar result can be achieved by using purchased composite dams or by using alternative crossbreeding methods that operate over a shorter time horizon.
Alastair Rayner is director of RaynerAg, a NSW-based agricultural consultancy. RaynerAg is affiliated with BJA Stock & Station Agents. He regularly lists and sells cattle for clients and also attends bull sales to support client purchases. Alastair provides pre-sale selections and classifications for seed producers in NSW, Qld and Victoria. He can be contacted here or via www.raynerag.com.au