Effects of yeast and exogenous fibrolytic enzyme additives on lamb performance and feed efficiency.

Yeast and fibrolytic enzymes serve as additives incorporated into the nutrition of ruminants to regulate rumen fermentation and increase the digestibility of fiber, thereby enhancing the efficiency of rumen fermentation. Two experiments were conducted to assess the impact of five diets: a control diet without additives, diets with yeast (Saccharomyces cerevisiae) or exogenous fibrolytic enzymes (EFE), and diets with a blend of 0.7yeast + 0.3EFE or 0.7EFE + 0.3Yeast (based on recommended levels in g/kg of total DM). In the first experiment, 40 five-month-old Santa Ines lambs (mean weight 25.0 ± 1.3 kg) were distributed in a completely randomized design (5 treatments and 8 lambs) for 81 days to evaluate performance, ingestive behaviour, and serum metabolites. In the second experiment, 25 Santa Ines male lambs weighing 25.7 ± 4.1 kg were housed in metabolic cages, in a randomized design with 5 treatments and 5 lambs, evaluating digestibility, nitrogen balance, and rumen pH. EFE supplementation increased intakes of dry matter (DM), total digestible nutrients (TDN), and apNDF (mean of 38.1, 5.26, and 27%, respectively) compared to yeast or the 0.7yeast-0.3EFE blend. Feed conversion was most efficient (mean of 27.1%) in lambs fed Yeast, 0.7EFE + 0.3yeast, and the control diet. Lambs fed 0.7yeast + 0.3EFE spent less time eating (mean of 16.5%) and more time idling (mean of 10.75%), whereas EFE-fed lambs spent more time eating (mean of 19.73%), and 0.7EFE + 0.3yeast-fed lambs spent more time ruminating (mean of 20.14%). Control group lambs chewed and ruminated less (means of 24.64 and 17.21%, respectively) compared to other treatments. Lambs on the 0.7yeast + 0.3EFE blend had higher eating and rumination efficiency rates for DM and apNDF (mean of 19.11 and 17.95%, respectively) compared to other additive treatments or individual additives. They also exhibited lower (means 7.59 g/d) urinary N excretion, with improved N retention (mean 3185 g/d) compared to the control group. There were significant effects on serum albumin and cholesterol concentrations, with the 0.7yeast + 0.3EFE blend showing higher albumin (mean 4.08 g/dL) levels, while diets without additives and yeast-EFE blends had higher cholesterol (mean of 62.51 g/dL) concentrations. Including Saccharomyces cerevisiae yeast along with 0.7 yeast + 0.3 EFE blend is recommended when feeding similar lamb diets to those used herein because it improves the efficiency of intake, rumination of DM and NDF, and nitrogen utilization without affecting the lamb performance.

Fatty acid profile, physicochemical composition and carcass traits of young Nellore bulls fed Acacia mearnsii extract.

Fatty acid profile, physicochemical composition, and carcass traits of 32 young Nellore bulls were assessed following the supplementation of Acacia mearnsii extract at levels of 0, 10, 30, and 50 g/kg of total dry matter (DM) in a completely randomized experiment with four treatments and eight replicates. Adding 50 g/kg DM of condensed tannins (CT) from Acacia mearnsii in the bulls' diet reduced DM intake, average daily gain, and meat lipid oxidation (P ≤ 0.05). The pH, centesimal composition, collagen, and meat color indexes of the longissimus muscle were not altered by the addition of Acacia mearnsii (P > 0.05). Cooling loss increased (P = 0.049) linearly. Including Acacia mearnsii in diet reduced the Warner-Bratzler shear force (WBSF, P = 0.018) of longissimus muscle of the bulls. The concentration of C16:0, C17:0, C24:0, t9,10,11,16-18:1, c9t11-18:2, C18:2n-6, C20:4n-6, 20:5n-3, 22:5n-3, and 22:6n-3 in the muscle increased due to the addition of Acacia in the diet (P ≤ 0.05), with the highest muscle concentrations caused by the addition of 10 to 30 g Acacia. c9-18:1 and t16-18:1 reduced linearly. Æ©SFA, Æ©BI, Æ©cis- and Æ©MUFA, Æ©n-3, Æ©n-6, and Æ©PUFA (P ≤ 0.05) quadratically increased at higher concentrations of addition of Acacia, above 30 g/kg DM. It is recommended to include Acacia mearnsii extract up to 30 g/kg total DM in diets for young bulls as it improves CLA, PUFA and TI and reduces lipid oxidation. Acacia mearnsii extract as source of CT at 50 g/kg DM negatively impacted the young bulls performance.