Effects of live yeast on growth performances and meat quality of beef cattle fed fast or slow fermentable diets

The aim of the trial was to evaluate the effects of the administration of Saccharomyces cerevisiae (CNCM I\u20131077) on growth performance and meat quality in beef cattle fed slow (SF) or fast (FF) fermentable diets. Eighty three male Charolaise cattle were divided in four homogenous groups: SF\u2013C=n 24, FF\u2013C=n 17, SF\u2013T=n 21 and FF\u2013T=n 21, and fed slow (SF; RUP 30.60%, NDF 31.20%, NFC 44.60, starch 34.20 on DM) or fast (FF; RUP 26.90%, NDF 30.60%, NFC 44.70, starch 32.40 on DM) fermentable diets with (T) or not (C) S. cerevisiae (8 7109 cfu/d). ADG (evaluated at day 70 and 98 of the trial), and longissimus dorsi colour characteristics, chemical composition, pH at 24h post mortem, tenderness and fatty acid composition were compared using the GLM of S.A.S. with contrasts. SEUROP classes frequencies in the groups were analyzed by a PROC FREQ of S.A.S. with a chi-square test. Improved ADG was highlighted in SF\u2013T and FF\u2013T vs. FF\u2013C (1.61 kg/d, 1.57 kg/d and 1.49 kg/d respectively; P 640.05). An increased lightness (L*) was recorded in SF\u2013T vs. other groups (41.3 vs. 39.3 SF\u2013C, 38.9 FF\u2013C and 37.4 FF\u2013T; P 640.01) and a decreased yellowness (b*) was observed in FF\u2013C (8.3 vs. 10.0 SF\u2013C, 10.3 SF\u2013T and 9.8 FF\u2013T; P 640.01). No differences were found in meat chemical composition, carcass characteristics, meat pH, cooking losses, or fatty acid composition of the meat except for a lower EPA content in FF\u2013T. Tenderness was increased independently from slow or fast fermentable diets when live yeast was fed to cattle (SF\u2013T 3.7 kgF, FF\u2013T 3.6 kgF, SF\u2013C 4.1 kgF, FF\u2013C 4.1 kgF; P 640.05). The inclusion of live yeast in both slow and fast fermentable cattle diets affected positively performance and meat tenderness, while the use of slow fermentable rations in association with S. cerevisiae (CNCM I\u20131077) determined increased lightness and yellowness of the mea