Effects of varying dietary proportions of palm kernel meal on growth performance, ruminal fermentation, and microbiota in Tibetan sheep

This study aimed to observe the effects of varying dietary proportions of palm kernel meal (PKM) on fermentation parameters and the rumen microbiota in Tibetan sheep. At farrowing, lambs were identified as having low birth weights (LBWs, < 4.0 ± 0.35 kg) or normal birth weights (NBWs, > 5.50 ± 0.50 kg). NBW lambs were selected for further experiments. On day 60, lambs were weaned onto a common diet. A total of 120 NBW Tibetan male lambs (18.39 ± 1.25 kg) were randomly assigned to four groups. The control group (PKM control, PC) was fed a basal diet, while the three experimental groups were fed diets supplemented with 15% (low-PKM, LP), 18% (moderate-PKM, MP), and 21% (high-PKM, HP) PKM for 120 d, respectively. On days 1 and 120, body weight was recorded per pen to calculate average daily gain (ADG). At the end of the experiment, twenty Tibetan sheep (n = 5 per treatment) were selected randomly for slaughter at a commercial slaughterhouse. The rumen fluid was collected for fermentation parameter and microbiome analysis. The results indicated that both the final weight and ADG of the lambs were significantly lower in the HP group than in the PC, LP, and MP groups (P < 0.05). Furthermore, the NH₃-N content and pH of the rumen fluid samples were significantly lower in the HP group than in relative to the PC group (P < 0.05). In addition, the relative abundances of Actinobacteria and Patescibacteria were greater in the MP group than in the PC group (P < 0.05). The abundances of F082_unclassified, Succiniclasticum, and Prevotella_1 (P < 0.05) were greatest in the PC group, whereas the abundances of Ruminococcaceae_NK4A214_group and Christensenellaceae_R-7_group were significantly lower (P < 0.05). In summary, the dietary 18% PKM never negatively affected growth, rumen pH and NH₃-N content of the rumen in Tibetan sheep, potentially related to alterations in the ruminal fibrinolysis-associated microbiota. Our findings provide practical evidence for the supplementation of PKM in Tibetan sheep feeds.