Feeding pellets inoculated with Bacillus amyloliquefaciens strain H57 improves production parameters in young Merino wethers

Abstract

The objective of the study was to determine if feeding the probiotic Bacillus amyloliquefaciens strain H57 (‘H57′) to young Merino wethers can improve their feed intake, productivity, energy metabolism and rumen fermentation parameters. Thirty-six Merino wethers were housed in individual pens and fed ad libitum a high-fibre pelleted diet (Control group, n = 18), or the same pelleted diet inoculated with H57 (H57 group, n = 18) for a four-week Treatment period. This was followed by a two-week Carry-over period when all wethers were fed the pelleted diet without H57. Intake of pellets was measured daily (dry matter intake, DMI), live weight (LW) and body condition score (BCS) were measured weekly, and the LW gain (LWG) and feed conversion ratio (FCR) were calculated from the DMI and LWG. During the six-week experimental period, samples of blood and rumen fluid were collected four times and analysed for blood enzymes, metabolites, hormones and rumen fermentation parameters. In the Treatment period, the H57 group had 25% larger final LW than the Control group (6.0 vs 4.8 kg, P = 0.045) and had a greater BCS (2.94 vs 2.44, P = 0.014) and DMI of pellets (1429 vs 1337 g/day, P = 0.033), resulting in a better FCR (6.8:1.0 vs 8.4:1.0, P = 0.049). The increases in final LW and BCS were most marked in the initial two weeks of the Treatment period, but persisted over the remaining two weeks and continued, albeit to a smaller extent, during the Carry-over period. Blood metabolites, enzymes and hormones did not differ between the two groups and were within the expected reference ranges for sheep. Rumen NH3 concentrations were elevated (P = 0.033) in the H57 group throughout the experiment, but overall the volatile fatty acid (VFA) concentrations were not different. B. amyloliquefaciens was present in H57 pellets throughout the Treatment period, and consequently was detected in the rumen fluid and faeces of the H57 group. In conclusion, young Merino wethers fed high-fibre pellets inoculated with H57 for four weeks grew faster, converted the pellets into final LW more efficiently and had a higher BCS than peers fed the same pellets without H57. This can be important when feeding high-fibre pellets to transition young Merino wethers onto a finishing diet. The mechanisms behind these responses remain to be elucidated.