Host genetic control on rumen microbiota and its impact on dairy traits in sheep.

BACKGROUND: Milk yield and fine composition in sheep depend on the volatile and long-chain fatty acids, microbial proteins, vitamins produced through feedstuff digestion by the rumen microbiota. In cattle, the host genome has been shown to have a low to moderate genetic control on rumen microbiota abundance but a high control on dairy traits with heritabilities higher than 0.30. There is little information on the genetic correlations and quantitative trait loci (QTL) that simultaneously affect rumen microbiota abundance and dairy traits in ruminants, especially in sheep. Thus, our aim was to quantify the effect of the host genetics on rumen bacterial abundance and the genetic correlations between rumen bacterial abundance and several dairy traits, and to identify QTL that are associated with both rumen bacterial abundance and milk traits. RESULTS: Our results in Lacaune sheep show that the heritability of rumen bacterial abundance ranges from 0 to 0.29 and that the heritability of 306 operational taxonomic units (OTU) is significantly different from 0. Of these 306 OTU, 96 that belong mainly to the Prevotellaceae, Lachnospiraceae and Ruminococcaceae bacterial families show strong genetic correlations with milk fatty acids and proteins (absolute values ranging from 0.33 to 0.99). Genome-wide association studies revealed a QTL for alpha-lactalbumin concentration in milk on Ovis aries chromosome (OAR) 11, and six QTL for rumen bacterial abundances i.e., for two OTU belonging to the genera Prevotella (OAR3 and 5), Rikeneleaceae_RC9_gut_group (OAR5), Ruminococcus (OAR5), an unknown genus of order Clostridia UCG-014 (OAR10), and CAG-352 (OAR11). None of these detected regions are simultaneously associated with rumen bacterial abundance and dairy traits, but the bacterial families Prevotellaceae, Lachnospiraceae and F082 show colocalized signals on OAR3, 5, 15 and 26. CONCLUSIONS: In Lacaune dairy sheep, rumen microbiota abundance is partially controlled by the host genetics and is poorly genetically linked with milk protein and fatty acid compositions, and three main bacterial families, Prevotellaceae, Lachnospiraceae and F082, show specific associations with OAR3, 5, 15 and 26.

Thresholds for the presence of glacial megafauna in central Europe during the last 60,000 years.

Lake sediment records from Holzmaar and the infilled maar of Auel (Eifel, Germany) are used to reconstruct landscape changes and megafauna abundances. Our data document a forested landscape from 60,000 to 48,000 yr b2k and a stepwise vegetation change towards a glacial desert after 26,000 yr b2k. The Eifel landscape was continuously inhabited from 48,000 to 9000 yr b2k by large mammals, documented by the presence of spores of coprophilous fungi from Sordaria and Sporormiella fungi that grow on fecal remains of the megafauna. Megafauna reached higher numbers during cold stadial climates but was present also during the warmer interstadials. Highest abundance was at 56,500/48,500/38,500/33,000/27,000/21,000/16,200/14,000 yr b2k, i.e. under different climate regimes. Some of these dates were associated with clear human presence, which indicates that megafauna was not overkilled by humans. In contrast, human presence could quite likely have been stimulated by the abundant food supply. Megafauna presence decreased significantly when tree abundance increased during interstadials. The Megafauna disappeared finally at 11,400 yr b2k with the development of the early Holocene forest cover, which appears to be the most important threshold for megafauna presence.