Breed and diet influence the ruminal bacterial community of sheep

Abstract

Context Ruminal microbial communities are important in production ruminants, as they can affect health and production efficiency. Differences between meat- and wool-producing sheep breeds have not yet been fully explored. Aims In this study, we aimed to determine the impact of diet on ruminal microbial populations of sheep selected for different production traits, namely, meat production (White Suffolk) and wool production, and quality (Poll Merino). Methods The study utilised 24 White Suffolk and 24 Poll Merino ewes, assigned to either a roughage (20% pellet and 80% chaff) or high-grain diet (80% pellet and 20% chaff). Following acclimatisation for 21 days, they each had a ruminal sample taken and analysed for bacterial communities, using 16S rRNA sequencing. Entry and exit weight of the ewes and their feed intake were measured. Key results There was a preference for the high-grain diet (P < 0.0001), with greater amounts consumed, although there was no significant difference in ewe weights between the two dietary treatments. However, White Suffolk ewes lost weight on the roughage diet, whereas all other groups gained weight (White Suffolk roughage −5.9 ± 2.6 kg, White Suffolk high-grain 7.8 ± 1.7 kg, Poll Merino roughage 9.2 ± 2.7 kg, Poll Merino high-grain 5.0 ± 1.8 kg). There were significant ruminal bacterial differences associated with both diet and breed. The average dissimilarity in ruminal bacterial phyla associated with diet was 14.13%, with the top 50% of phyla contributing to the dissimilarity being Verrucomicrobia, Lentisphaerae, Elusimicrobia, SR1 and Fibrobacteres, which were significantly more abundant in the roughage dietary group, and Proteobacteria, which were significantly more abundant in the high-grain dietary group. Conclusions We have demonstrated that although diet strongly influences the ruminal microbiota, there is a significant interaction between diet and breed in effects on ruminal microbiota and also animal performance. Implications The differences in microbial composition between breeds were related to some of the animal productivity differences of the two breeds, indicating that at least some of the genetic differences in animal productivity are generated by differences in the responsiveness of the ruminal microbiota to diet.