Effect of a Bacillus probiotic strain on Nellore cattle finished on pasture during the dry season

• Published in: Livestock science 2022-10, Vol.264, p.105068, Article 105068
• Main Authors: Calaca, A.M.M., Figueiredo, C.B., Silva, M.B., Fernandes, J.J.R., Fernandes, M.H.M.R., Silva, L.F., Couto, V.R.M.
• Format: Article
• Language: English
• Subjects: Additives; Bacillus, Probiotic; Beef cattle; Grazing; Supplementation
• ISSN: 1871-1413; 1878-0490
• DOI: 10.1016/j.livsci.2022.105068

•We evaluated Nellore bulls fed high-concentrate diet in tropical grass pasture.•Bacillus probiotic strain didn't affect performance and carcass traits.•Animals fed probiotic had lower amounts of subcutaneous fat.•Bacillus probiotic strain might influence fat metabolism.•Isovalerate was higher in animals fed Bacillus toyonensis. The objective of this study was to evaluate the productive performance of Nellore bulls raised under grazing conditions during the dry season and fed a diet supplemented with a Bacillus probiotic strain, and its influence on ruminal and intestinal mucosa development. In addition, the probiotic effects on digestibility and ruminal fermentation were determined. The experiment was conducted between July and November 2017, corresponding to the dry period in the state of Goias, Brazil. Eighty-four animals (approximately 24 months old) were included in the study. Four animals were randomly slaughtered at the beginning of the experiment to assess carcass yield. The remaining animals (80 Nellore bulls, initial body weight (BW) of 354 ± 3.4 kg) were blocked based on their initial BW and assigned to one of two treatments: concentrate with probiotics and concentrate without probiotics (control). Bulls were divided into 16 paddocks of palisade grass (Urochloa brizantha spp.) pasture, supplemented with concentrate at 2% BW. After 133 days, the animals were slaughtered, and carcass traits were measured. Tissues from the ruminal ventral sac and jejunum were collected to evaluate the morphology of the rumen papillae and intestinal villi. No differences were detected in performance data; a tendency was found in improving the dressing percentage, carcass average daily gain (ADG), and gain to feed ratio based on carcass ADG. The 12th rib fat thickness was significantly lower in animals fed probiotic than in control group (4.06 vs. 2.97 mm, p < 0.05). No significant effect on the development of the ruminal and intestinal epithelia was observed with the use of probiotics. Later, an in vivo digestibility trial was carried out to investigate the influence of the Bacillus probiotic strain on rumen fermentation, with the same treatments, using eight rumen-cannulated steers in a cross-over design. Fecal output and forage intake were estimated using titanium dioxide and indigestible neutral detergent fiber (iNDF), respectively. Administration of the probiotics did not improve dry matter (DM) intake or nutrient digestibility. Isovalerate levels were higher in