RUMINAL BIOHYDROGENATION OF FATTY ACIDS IN RAMS COMPLEMENTED WITH Saccharomyces cerevisiae

Grain-rich diets decrease ruminal pH and affect bacterial populations related to biohydrogenation. This reduces the production of stearic acid, which is a precursor of unsaturated fatty acids in muscle and affects the nutritional quality of meat. Saccharomyces cerevisiae (Sc) stabilizes pH and allows an efficient ruminal function. This would stabilize the biohydrogenation in lambs fed with a concentrated diet. The objective of the study was to evaluate the effect of Sc in the ruminal biohydrogenation of long-chain fatty acids in rams. Four Rambouillet rams (72.35 +/- 4.6 kg PV) with ruminal and duodenal cannula were fed 3 d with 80 % of concentrates, supplemented with 3, 5, and 10 g d(-1) of Sc per ram. pH, volatile fatty adds, and ammoniacal nitrogen were evaluated in ruminal fluid. The percentage of fatty acid methyl esters in ruminal and duodenal fluid was measured, along with the percentage of ruminal biohydrogenation. The experimental design was 4 x 4 cross-over with four evaluation periods. Samples were taken every 4 h per 12 h each clay. The fixed effect of the treatments was included in the analysis and the means were separated using the PDIFF option of LSMEANS. Ruminal biohydrogenation was analyzed based on orthogonal polynomials, in order to test the linear and quadratic effect. Sc complementation did not modify the ruminal pH, volatile fatty acids, or ammoniacal N (p >= 0.05). The ruminal biohydrogenation was similar between treatments (oleic: T1: 80.04, T2: 79.89, T3: 80.89, T4: 81.03%; linoleic: T1: 90.27, T2: 89.60, T3: 90.92, T4: 90.51 %; and linolenic; T1: 88.61, T2: 87.89, T3: 88.65, T4: 88.84 %). Sc levels do not modify the ruminal dynamics or the biohydrogenation of long-chain fatty adds.