Effects of repeated oral inoculation of artificially fed lambs with lyophilized rumen fluid on growth performance, rumen fermentation, microbial population and organ development

Early life development and growth are critical in determining the lifelong growth performance and health of ruminants, and weaning poses the greatest challenge to young animals and has the most profound consequence. In this study, we aimed to investigate the effects of microbial intervention on the growth and development of young lambs and their rumen microbiota as they went through weaning. Forty-eight lambs were allocated to two groups, with one group being orally inoculated with lyophilized rumen fluid, and the other receiving no inoculation served as the control. Growth performance, rumen fermentation characteristics, and carcass measurements were determined weekly one week before and two weeks after weaning. We also determined the population dynamics of total bacteria, protozoa, fungi, and select genera and species of known rumen bacteria and assessed the temporal changes in the activities of glucanase (both endo- and exo-), xylanase, β-glucosidase, and amylase in the rumen content. Our results showed that the early life inoculation significantly increased the apparent digestibility of feed dry matter and crude protein before weaning, and post-weaning crude protein digestibility remained elevated in the inoculated lambs compared to the control lambs. Starch digestibility tended to be higher in the inoculated lambs than in the control lambs two weeks after weaning. Molar proportion of ruminal propionate and amylolytic enzyme activity were higher in the inoculated lambs than in the control lambs after weaning. Different temporal fluctuation patterns of Megasphaera elsdenii and Selenomonas ruminantium, and a lower abundance of Ruminococcus flavefaciens were noted in the rumen of the inoculated lambs compared to the control lambs after weaning. The development of internal organs, including the lower gut and liver, was also stimulated by the inoculation. In conclusion, some rumen bacterial populations of young lambs were clearly affected by the inoculation with rumen microbiota, which could contribute to the digestion of the nonstructural carbohydrates available in the starter feed. Improved digestion of starter feed may enhance the energy and nutrient harvest and utilization in young ruminants during the critical weaning phase.