Breed for efficiency, not size

Dr Roger Hunsley, former animal science professor at Purdue University in the US, told cattlemen how they can breed for feed efficiency without producing over-sized animals that burn through expensive feed. Annelie Coleman reports.

Internationally renowned animal scientist Dr Roger Hunsley is concerned about the overall efficiency of beef production.

Beef cattle breeders have long selected for growth, assuming that faster-growing animals are the most efficient. But in practice, any growth gain is offset by higher feed cost.

However, breeders can now select for feed efficiency independent of growth traits, he told participants at the 2011 Aldam Stockman’s School near Ventersburg.

“In the past we’ve made little or no progress toward improving feed efficiency in beef cattle,” explained Dr Hunsley. “Today cattlemen are feeling the effects of the highest maize price in many years. This is reason enough to become more efficient and pursue lower input costs.

“For the beef industry to survive and prosper, we must genetically identify the efficient animals that can produce 1lb (0,45kg) of meat from 3lb to 6lb (1,4kg to 2,7kg) of feed, and not 7lb to 12lb (3,2kg to 5,4kg) as is currently the case.”

Turn to NFI
“Nett feed intake (NFI) and DNA markers for feed efficiency are tools to be used in future to select and breed cost-effective beef cattle.” NFI refers to the variation in feed intake remaining after maintenance and growth requirements have been calculated, he explained.

“Dr Gordon Carstens, a beef cattle nutritionist in Texas, is working on the NFI biological trait in cattle. This is different from feed conversion or feed-to-gain ratio traditionally used to express feed efficiency.”

Genetic selection for better feed conversion leads to larger framed animals with higher maintenance requirements, while NFI measures feed efficiency independent of growth characteristics and size. “NFI offers the breeder the flexibility to move growth rate and size in any direction while improving feed efficiency,” said Dr Hunsley.

“It isn’t uncommon to find bulls with similar body weight with daily feed consumption that differs by 20% or more. “A bull with a lower NFI often shows a similar or even higher daily gain than a bull with a higher NFI. A bull with a lower NFI will obviously have a great impact on cost savings in light of today’s expensive maize.”

The right tests
To conduct individual tests on each animal requires a feed station, preferably on-farm because in Dr Hunsley’s opinion the entire management group of young bulls needs to go through the same test for the results to be of any value. “The next step is to combine DNA technology and NFI to determine the needed improvement in feed efficiency. Four genetic markers for feed efficiency in beef cattle have already been validated and released.

“GeneSTAR marbling is a DNA-based diagnostic test that measures two of the major genes – QG1 and QG2, the new feedlot marbling marker – associated with marbling in beef cattle. GeneSTAR tenderness is a DNA-based test for meat tenderness. It’s the first multi-gene single trait DNA test to include the T1, T2 and T3 genetic markers for tenderness.

A new test to predict bull fertility was recently developed. “It is an in vitro diagnostic test that detects the presence of a protein, labelled a fertility-associated antigen (FAA), that is present in highly fertile bulls,” Dr Hunsley explained. “An on-site fertility test can now be carried out with the development of an FAA-specific test kit called a lateral flow cassette, which is completed in minutes.”

He also stressed the role of the leptin protein, which influences how a beef animal consumes, stores and metabolises energy. “This is a key determinant of performance, quality and profitability,” he said. “The gene carrying the code for leptin production has been called the ‘obese’ gene because of leptin’s association with appetite and fat deposition. Ingenity-L is a DNA test to identify variations in leptin genotypes.”

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Caption:
The new FAA test has been developed to determine bull fertility, and can be conducted on-farm in minutes.
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