Production System and Fatty Acid Composition of Steers

Background and Methodology
The consumption of saturated fatty acids is associated with coronary heart disease. Ruminant fat has a higher saturated fatty acids and lower polyunsaturated fatty acids: saturated fatty acids ratio. There is evidence that grass consumption by cows increases the ratio of n-3 to n-6 PUFA, but many studies are confounded by differences in carcass weight or fatness. This study determined the impact of grazed grass, grass silage and concentrates in diets of steers on intramuscular fatty acid composition.
Fifty steers were divided into 10 blocks based on body weight and assigned at random to one of five dietary treatments of grass silage for ad libitum intake with 4 kg concentrate, 8kg concentrate with 1 kg hay, 6 kg grazed grass with 5 kg concentrate, 12 kg grazed grass with 2.5 kg concentrate and 22kg grazed grass.

The concentration of PUFA in intramuscular fat was higher (P<.05) for steers offered 22 kg grazed grass than for those offered any other ration. Decreasing the proportion of concentrate in the diet increased grass intake and caused a linear decrease in the concentration of intramuscular saturated fatty acids (P<.01) and in n-6: n-3 PUFA ratio (P<.001) and a linear increase in the PUFA: SFA ratio (P<.01) and the conjugated linoleic acid concentration (P<.001).

French, P., Stanton, C., Lawless, F., O’Riordan, E. G., Monahan, F. J., Caffery, P. J., & Moloney, A. P. (2000). Fatty acid composition, including conjugated linoleic acid, of intramuscular fat from steers offered grazed grass, grass silage, or concentrate-based diets. J. Anim. Sci. 78:2849-2855.