In sheep, temperament is known to affect animal welfare and the quality of animal products. While the composition of the gut microbiota is different between depressed patients and healthy human patients, in sheep, the influence of temperament on ruminal microbial species and abundance remains unknown. This study investigated the effects of temperament on parameters of rumen fermentation and microbial composition of rumen contents of Hu ram lambs. Using the pen score test, 6 lambs that scored 2 points or below (calm) and 6 lambs that scored 4 points or more (nervous) were selected from 100 ram lambs. The sheep were fed a standard diet for 60 days and rumen samples were collected at slaughter. The concentrations of propionic acid, isovaleric acid, valeric acid, and the ammonia nitrogen concentration were different between the calm and the nervous groups (p < 0.05). At the phylum level, there were significant differences in Bacteroidetes, Tenericutes, and Spirochetes (p < 0.05); and at the genus level, there were significant differences in the Christensenellaceae R-7 group, Treponema 2, Fibrobacter, and Ruminococcaceae UCG-003 (p < 0.05). The present study suggests that differences in the rumen microbiota between the calm group and the nervous group could have an impact on the metabolism of carbohydrates and polysaccharides and explain why Calm Hu sheep have a higher energy utilization efficiency than nervous Hu sheep. More studies are needed to further understand the effect of temperament on specific pathways of the rumen microbiota.

The objective of this study was to evaluate the effect of tyrosine on behavior and ruminal meta-taxonomic profile of Altay sheep. Twelve rams with the lowest behavioral responses to humans and twelve rams with the highest behavioral responses were sorted into calm and nervous groups, respectively. Following the 2 × 2 factorial design, the rams from each group were equally assigned two treatments of a basal diet and a diet with an extra 4 g of tyrosine for 30 d. The temperament trait, growth performance, rumen fermentation parameters, ruminal epithelium antioxidant capacity, and rumen microbial composition were measured at the end of the feeding experiment. The results showed that tyrosine treatment led to a decreased number of crosses in the arena test in nervous sheep (p < 0.05). The tyrosine treatment led to increased antioxidant markers in the rumen epithelium, such as catalase, total antioxidant capacity, and GSH content in rumen epithelial tissues (p < 0.05) in calm and nervous sheep. The total volatile fatty acids and propionic acid content in the rumen were increased by tyrosine treatment in nervous and calm sheep (p < 0.05). The rumen microbial study revealed that the dominant microbial genera were Cryptobacteroides, Prevotella, Limivicinus, Quinella, UBA1711, RUG740, Sachharofermentans, Limomorpha, Soladiphilus, Flexinia, and others in both the tyrosine treatment and temperament groups. A combined effect of treatment and temperament was seen on the abundance of two microbial genera, UBA1711 and RUG740 (p < 0.05). These findings suggest that tyrosine-treated Altay sheep would experience less stress during production, resulting in reduced oxidative stress in the rumen epithelium and improved propionic acid production in the rumen compared with that of basal-diet-treated Altay sheep. Meanwhile, the effect of the dietary tyrosine treatment on ruminal microbial diversity was lower, suggesting lesser degradation of tyrosine by ruminal microbes in Altay sheep.