December 30, 2003

Sunflower Oil and Other Feed Additives Can Enhance Beef Quality

Researchers have discovered that sunflower oil and other feed additives can significantly increase performance and enhance carcass quality in beef cattle. They may also potentially improve health benefits of meat for consumers.

"We have identified a number of additives that can improve average daily gain, feed conversion efficiency and carcass grade in feedlot steers," says Dr. Tim McAllister, a ruminant nutritionist at Agriculture and Agri-Food Canada's Lethbridge Research Center, who led a three-year study of feed additives, which was supported in part by the Canada Alberta Beef Industry Development Fund (CABIDF).

"The results are likely to benefit producers who are willing to try a new approach to enhance the productivity of their operations," says McAllister. "Feed efficiency in ruminant animals is generally low because of the indigestible nature of many of the feeds they consume. It is the complexity of the rumen environment that enables ruminants to derive energy from feeds that many other livestock species cannot utilize. Unfortunately, the balance between various rumen microbes is not always the most beneficial for feed nutrient utilization. In our study, we used feed additives to alter the rumen microbial populations, with the aim of enabling higher feed efficiency."

While some microbes contribute to fiber digestion, others are predators of beneficial rumen bacteria. Because rumen bacteria represent the main source of protein for the animal, protozoa that prey on bacteria inhibit protein availability and therefore decrease feed metabolism efficiency.

Past research has demonstrated that the protozoa, Entodinium spp., is the species predominantly responsible for consuming rumen bacteria in cattle fed barley-based diets. McAllister worked alongside Dr. John Baah, also of AAFC Lethbridge, Dr. Alexander Hristov, University of Idaho, and Dr. Mike Ivan, AAFC Lethbridge. The research team focused their work on finding additives that reduce the population of this group, while preserving other beneficial protozoa species.

Throughout the three-year study, various feed additives were evaluated for their potential to reduce protozoan or bacteria populations in the rumen. Compounds evaluated included plant extracts, bentonite, free fatty acids (vegetable oils) and bioactive agents. The effects of the additives on other metabolic processes were also recorded, to ensure any negative effects did not outweigh positive effects.

"We found that long-chain unsaturated fatty acids, in particular linoleic acid, had a distinct inhibitory effect on protozoa without negatively affecting ruminal fermentation or bacterial activities," says McAllister. "When applied at proper rates, some of the bioactive agents--such quillaja extract, tannic acid, ionophore antibiotics and lecithin - also showed potential."

Sunflower oil, which is high in linoleic acid, was selected as an additive for final evaluation in a growth study with feedlot cattle. Replacing 6% dry matter of a barley-based feedlot finishing diet with sunflower oil improved average daily gain in steers by about 13% and feed efficiency by 7%, in addition to improving overall carcass grade.

"Carcass grade improved because the linoleic acid inhibited buildup of excessive body fat and increased the lean mass in the cattle," says McAllister. The results indicate that producers can improve the overall cattle performance by supplementing their feed with oil that contains linoleic acid whenever it is economical to do so.

Linoleic acid has also shown potential human health benefits, he adds. In its conjugated form, linoleic acid has demonstrated properties associated with reducing cholesterol and lowering the risk of cancer. Ultimately, beef with an increased conjugated linoleic acid content could provide a health advantage to consumers.