Comparison of ruminal fermentation parameters, fatty acid composition and flavour of beef in finishing bulls fed active dry yeast (Saccharomyces cerevisiae) and yeast culture

This study was conducted to compare the effect of active dry yeasts (ADY) and yeast cultures (YC), two typical products of yeast preparations, on ruminal fermentation parameters, and on the fatty acid composition and flavour of beef from finishing bulls fed a high-concentrate diet. Forty-five finishing bulls (mean bodyweight +/- s.d.: 505.4 +/- 29.1 kg body weight) were allocated to three groups of 15 bulls and assigned randomly to one of three diets, which were CON diet (basal diet), ADY diet (basal diet + Levucell SC) and YC diet (basal diet + Diamond V XP). After 112 days trial, all bulls (mean bodyweight +/- s.d.: 591.6 +/- 64.2 kg body weight) were slaughtered. The rumen fluid of each animal was collected at slaughter and cross-sectional samples of longissimus lumborum were collected from three treatments at carcass segmentation after a 24-h chill. The result indicated that both ADY and YC supplementation had no significant effect (P > 0.05) on rumen pH, concentration of ammonia-N and total volatile fatty acid compared with CON. ADY had no significant effect (P > 0.05) on percentage of rumen individual fatty acid whereas YC significantly decreased valerate molar percentage (P = 0.008) and increased acetate molar percentage (P = 0.029) and the ratio of acetate to propionate (P = 0.035). In addition, compared with CON, ADY significantly (P = 0.003) increased the concentration of C16: 1n7 and significantly (P = 0.012) decreased the concentration of C18: 3n6c compared with CON. YC significantly decreased the concentration of C18: 3n6c (P = 0.014) compared with CON. However, both ADY and YC had no significant effect (P > 0.05) on other individual fatty acid concentrations, the proportions of saturated fatty acids and monounsaturated fatty acids and nutritionally important values including the ratio of n-6/n-3, polyunsaturated fatty acids/saturated fatty acid and C18: 2n6/C: 18: 3n3. Both ADY and YC significantly improved beef tenderness for cooking method of chaffy dish (P< 0.05) and beef tenderness also tended improve for ADY(P = 0.075) andYC(P= 0.097) when samples were fried. Both ADY and YC did not show improvements in flavour or juiciness compared with CON for either cooking method.