Fatty acid composition of beef cattle finished on tropical pasture and supplemented with crude glycerin

The aim of this study was to evaluate the effect of crude glycerin supplementation on the chemical composition and fatty acid profile of the muscle of cattle grazing on Urochloa decumbens. Thirty-five crossbreed bulls, with an average initial body weight of 428.0 +/- 32.11 kg, were supplemented with dry matter corresponding to 1% body weight for 74 days on pasture and distributed to five treatments (0, 3, 6, 9 and 12% low purity glycerin in the total dry matter of the supplement) in a completely randomised design. After 74 days, the animals were slaughtered, and the longissimus dorsi muscle was sampled and frozen for meat composition analysis. The addition of glycerin did not affect the mean moisture (73.6 +/- 0.3%), protein (22.8 +/- 0.4%), total lipid (1.1 +/- 0.1%) and ash (1.0 +/- 0.04%) contents of the animal muscle. However, there was an increasing linear effect (P < 0.05) on the contents of trans-vaccenic acid (increase of 175% in relation to the control) and conjugated linoleic acid (CLA) (25% increase in relation to the control). We observed an increasing linear pattern in monounsaturated fatty acid levels (39.8 to 44.5%) and a decreasing linear pattern in polyunsaturated fatty acid content (13.5 to 9.5%). The inclusion of crude glycerin promoted a linear decreasing pattern for omega-3 fatty acids. Thus, the inclusion of crude glycerin in the supplement of beef cattle affects the fatty acid composition of the meat. The use of this byproduct promotes desirable changes in the chemical composition of fatty acids, increasing the levels of conjugated linoleic fatty acids (18: 2 c9 t11) and monounsaturated fatty acids.