Effect of concentrate level and live yeast (Saccharomyces cerevisiae) supplementation on Texel lamb performance and carcass characteristics

An alternative additive that improves the nutrient use by ruminants and reduces the use of antibiotics is desirable in order to promote a sustainable and ecological animal production. The objective of the study was to evaluate the supplementation of live yeast (Saccharomyces cerevisiae) in diets of finishing lambs fed with different concentrate levels on their performance, carcass traits, metabolic profile and eating pattern. The trial was carried out at Institute of Animal Science and Pastures, in Nova Odessa city, Brazil, with 24 Texel lambs, 18.0 Kg +/- 1.14 Kg of initial live weight, and averaging 70 days-old, kept in individual pens. The animals were fed with diets comprising hay and concentrate rations in two different proportions (80 or 60%, on DM basis), supplemented or not with live yeast. A completely randomized blocks design, on a 2 x 2 factorial arrangement (2 concentrate levels with presence or absence of live yeast), was used to compare the means. Supplementation with live yeast did not affect (P > 0.05) DM intake, feed conversion, daily live weight gain, total live weight gain and final live weight, although it increased cold carcass weight (P=0.0135) and external carcass length (P=0.0104) regardless of the concentrate feed proportion in the diet. On carcass traits, supplementation with live yeasts did not modify (P > 0.05) cold carcass dressing percentage, compactness index, leg length, external chest depth, buttock circumference, carcass fat cover score, and conformation score. Lambs fed diets with greater concentrate level (80%) significantly increased (P < 0.05) DM intake, feed conversion, daily live weight gain, total and final live weight gains, cold carcass weight, compactness index, external carcass length, external chest depth, and buttocks circumference and did not modify (P > 0.05) the cold dressing percentage, degree of carcass fat cover score and conformation. The live yeast decreased plasmatic lactate (P < 0.05), did not affect (P > 0.05) plasmatic glucose, and reduced (P < 0.05) serum urea, only on the higher concentrate diets. The proportion of concentrate did not affect (P > 0.05) the plasmatic glucose and lactate. Supplementation of live yeasts did not improve (P > 0.05) the rib eye dimensions and the carcass subcutaneous fat thickness measured by ultrasound. Lambs on diet with greater concentrate level had smaller (P < 0.05) ingestion and rumination time. The supplementation with live yeast increased the rumination time and did not modify the ingestion time. It can be concluded that live yeast supplementation increases the weight and the carcass length, regardless of the amount of concentrate added to the diet. (C) 2013 Elsevier B.V. All rights reserved.