Ruminants are able to digest the dietary fibres present in their feed thanks to the micro-organisms - particularly bacteria - present in their fore-stomach (rumen). The relationship between the composition of this ruminal microbiota and various traits of interest, such as feed efficiency, milk composition and animal health, has been established in cattle. Researchers from the GesPR and NED teams of GenPhySE laboratory have studied these relationships in dairy sheep.
Using samples from 700 Lacaune ewes at the La Fage experimental unit (12), they analysed the bacterial population present in their rumen. These ewes had been selected on the basis of their milk production abilities in different lines. A first line of ewes was selected on the somatic cell count in the milk, these cells indicating inflammation of the udder; a second line of ewes was selected on their milk persistence, i.e. on the maintenance of the quantity of milk produced throughout the lactation.
High-throughput sequencing technologies were used to analyse the diversity of the microbiota and to determine the different bacteria present in the rumen. Among them, 11 families and 112 genera of bacteria were counted. The researchers showed that selection could influence the composition of the rumen microbiota. Bacterial abundances showed slight differences between ewes with low and high somatic cell score. However, there was no difference in the persistence of milk production in the selected lines: whether the ewes had good or poor milk persistence, their microbiota were similar. These results suggest that genetic selection for zootechnical traits, such as udder health and milk production curves, has little or no effect on rumen bacterial abundance, and thus on the ability of animals to extract energy from their diet. Furthermore, relationships between particular bacteria and the fine composition of milk have also been shown. For example, the presence of large numbers of Prevotella bacteria has a beneficial effect on milk production. These bacteria produce propionate, which is essential for the synthesis of lactose that is excreted in milk. Work is on progress on estimating the heritability of the ruminal microbiota, its genetic correlations with the fine composition of milk and the detection of particular loci (QTL) in the ewe's genome influencing its microbiota.
Reference: Martinez Boggio G., Meynadier A., Daunis-i-Estadella P., Marie-Etancelin C. (2021) Compositional analysis of ruminal bacteria from ewes selected for somatic cell score and milk persistency. PLoS ONE 16(7): e0254874. Article