Researchers study heifer feeding techniques and meat quality


WASHINGTON — To help satisfy consumers’ growing appetite for beef, Agricultural Research Service scientists are looking at innovative ways to make cattle production more efficient and to provide better beef products. New strategies to reduce the cost of production include more efficient nutrient use by the animals and improvements in their lifetime production efficiency.

More efficient

Instead of feeding more to pregnant and lactating cows that need additional nutrients during this period, scientists are trying to make the cows more efficient so they’ll need less feed.

Beef producers spend a large portion of their budget on feed, which represents 50 to 55 percent of the total costs of developing replacement heifers. A major part of a heifer’s diet is often cereal grains, which are becoming more expensive due to increasing human consumption and ethanol production.

Animal scientist Andrew Roberts, geneticist Michael MacNeil and their colleagues at the ARS Fort Keogh Livestock and Range Research Laboratory in Miles City, Mont., have found that reducing the amount of feed given to heifers can result in more efficient use of nutrients for growth and reproduction.

A study

Researchers studied two lifetime treatment groups composed of hybrid heifers that were 50 percent Red Angus, 25 percent Charolais and 25 percent Tarentaise. A control group was fed according to traditional industry recommendations, and a restricted group was fed 80 percent of feed consumed by their counterparts (calculated on a common body weight basis) for 140 days.

Heifers receiving less feed also gained weight more efficiently throughout the postweaning period and the following grazing season. The actual amount of feed provided to restricted heifers over the entire feeding period, which ended when animals were 1 year old, was about 73 percent of that given to the control group.

Less feeds

Using this strategy to provide less feed might reduce costs of producing each pregnant replacement heifer by more than $31, Roberts says. The practice could also extend the animal’s life, with important implications for lifetime efficiency and profitability.

In the experiment, restricted heifers had a final pregnancy rate of 87 percent and the control heifers had a 91 percent pregnancy rate, MacNeil says.

“Our results indicate that restricting feed is a matter of economics for farmers,” he says.

Second test

Another test was conducted to see if heifer efficiency could be increased through feed-restricted diets. Heifers were managed as one group from breeding through late fall, and pregnant animals were again separated into two groups — restricted feed and control — each winter. During winter months, restricted cows were fed 20 percent less supplemental feed than the control group.

Eventually, less-efficient heifers failed to reproduce and were culled if they were on a restricted diet. Increasing their feed would keep the cows in production but cost more for the producer, Roberts says. Inefficient breeders could be eliminated early to be harvested for high-quality meat.

Could improve

Researchers found that restricting feed of heifers might improve their efficiency throughout their lives. They also noticed interesting traits in second and third generations produced from cows in the restricted feed study, which began in 2001.

“The feed restriction seems to have made the second generation of calves able to withstand restriction with greater efficiency,” Roberts says.

Better survivability

While third-generation feed-restricted calves were lighter at birth and at weaning than calves from cows fed at the industry standard, feed-restricted animals themselves were slightly fatter and heavier at the calves’ weaning, he adds. “Physiologically, the second-generation restricted cow is conserving some of the nutrients taken in for body reserves, which may result in more efficient reproduction and better survivability in the herd,” Roberts says.

‘This is important because it potentially positions the heifers to withstand subsequent periods of nutrient deprivation due to naturally occurring phenomena such as drought,” MacNeil says.

Marbling study

To improve the quality of beef, Livestock and Range Research Laboratory scientists are taking a closer look at the streaks of fat in lean meat, known as marbling — a longtime indicator of palatability and basis for determining the price of beef.

Marbling, which is measured either at slaughter or by ultrasound of live animals, is an inherited trait and thus amenable to genetic improvement, MacNeil says.

“Cattle breeders would benefit greatly from having genetic indicators of superb marbling and other sought-after traits,” he says.

Geneticist Lee Alexander and his colleagues are studying these genetic traits. They used a panel of molecular genetic markers to locate specific locations in the genome of a Wagyu-Limousin cross population that contain genes that influence traits such as marbling and fatty acid composition.

Those breeds were specifically chosen because Wagyu is a heavily marbled beef, and insure is leaner.

“Genetic markers successfully identified a region of the genome associated with the amount of marbling and relative quantities of saturated and monounsaturated fats,” Alexander says. Scientists believe these findings may lead to healthier and better-tasting products for consumers through breeding methods that result in an improved fat profile in beef.

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