Mapping Net Feed Efficiency Genes

Summary

In beef cattle production systems, the feed requirement of the breeding herd is a large proportion (around 50%) of the total production costs. Competing meat production systems (e.g. pigs and poultry) have much lower maintenance feed requirements because of larger reproductive rates and faster growth rates of progeny. In addition to the costs of cow maintenance, steers fed for the Japanese market have very high feed costs.

​Adelaide University established a cattle gene-mapping program ten years ago. The basis of this program was a cross between two very different breeds of cattle (Limousin and Jersey). Specifically, three crossbred (F,=X) bulls with genes from both parent breeds were mated to purebred cows to produce large numbers (120-130 per sire) of Jersey (XJ) or Limousin (XL) backcross calves. The aim of this cross was to locate genes that affect many production and meat quality traits. These locations are known as Quantitative Trait Loci (QTL) and form the basis for developing genetic tests in cattle selection programs.

​The first objective was to identify gene markers for feed efficiency. Many QTL were identified for a range of traits. One QTL for feed intake was particularly large and if cattle were selected based on this QTL, the result would be a large reduction in feed intake (14%) with a small effect on cattle size (5%). This would improve net feed efficiency by 10%.

This project has gone beyond the original objectives by conducting additional analyses (e.g. principal components) and by mapping QTL in the mouse as well as cattle.

The second objective was to report synergies between production traits for selection to improve net feed efficiency. This is being conducted in collaboration with AgResearch (New Zealand) and can not be reported until a multi-party intellectual property agreement (currently under development) is signed.

A cost benefit analysis (third objective) was conducted for a system producing steers for the Japanese market with long periods of grain feeding. The analysis clearly showed that utilising a DNA test would be more profitable than current (expensive) systems of measuring feed intake in young bulls.

The next stage in developing a gene marker test is termed "fine mapping" (final objective) and involves collecting additional data on many animals but in specific regions of interest. In total, it is recommended that five of the QTL located should be pursued. Four of these were also significant in the model species (mouse) studied in a sister project. Candidate genes for these regions are being identified based on results from both species. In addition, over the last three years parallel work has been conducted with the aim of developing a single nucleotide polymorphism (SNP) platform which will aid both fine mapping and commercialisation.

It is recommended that the Trangie animals that were part of the MLA funded project (DAN.075) be utilised for fine mapping. These animals have good pedigree and performance records, DNA available, and staff that are good collaborators. As anticipated at the beginning of this project, the Beef CRC is the obvious network for development of the commercial test.