Evaluation of the effects of different diets on bacterial diversity and on fatty acid composition in goat rumen.

The equilibrium of ruminal microbiota depends on diet, which carries fermentation substrates and strongly affects the efficien- cy of ruminal microbiota. High-starch diets can lead to a reduced efficiency of fibre digestion, decreasing the number of fibrolytic bacteria and also diets supplemented with unsaturated fats improving the profile of milk fatty acids negatively affect the fibrolytic activity of ruminal microbiota. The objective of this study was to assess the effects of linseed or hemp seeds diet sup- plementation on bacterial diversity and on fatty acid profile in the rumen content of goats using the Next Generation Sequencing and gas chromatography techniques, respectively. In nine pluriparous Alpine goats fed the same pre-treatment diet for 40 days, ruminal fluid samples were collected before feeding using an aesophageal polyethylene probe. After this pre-treat- ment period, the goats were arranged to three dietary treatments consisting of control diet (C), linseed (L) and hemp (H) seeds supplementation. The chemical composition of the administered diets, in terms of neutral detergent fibre (NDF), starch, and ether extract (EE), were as follows, for C, L and H, respectively: NDF: 41.6, 42.2 and 43.3 % DM; starch: 17.2, 13.2 and 13.2 % DM; EE: 2.66, 6.3 and 5.6 % DM. Ninety days later, the same ruminal sample collection procedure was repeated. The bacterial DNA was extracted using a specific protocol and 16S rRNA gene amplicons on V3-V4 region analyzed by Miseq (Illumina). Contemporary, for the same ruminal samples, the fatty acid (FA) composition was determined by using a gas chromatograph equipped with a flame-ionization detector and a high polar fused-silica capillary column. Data of ruminal fluid samples were analysed with a mixed linear model and treatment effects were declared significant at P<0.05. In the three dietary treatment groups, bacterial community was dominated by Bacteroidetes and Firmicutes with a high abundance of Prevotellaceae, Porphyromonadaceae and Veillonellaceae and a low presence of Ruminococcaceae and Lachnospiraceae. A tendency towards a separation of the samples in the three diet groups was observed evaluating the principal components of the inter-sample variabil- ity. Linseed and hemp seeds supplementation determined a sig- nificantly increase of C18:0, C18:1 t6-10, C18:1c9 and c15. Linseed supplementation, moreover, increased C18:2 t11c15, one of the ?-linolenic acid biohydrogenation products.