Rumen and hindgut microbiomes of dairy Italian Holstein Friesian heifers fed with camelina sativa cake

Camelina represents a terrestrial vegetable and sustainable source of omega-3 PUFAs. These compounds can have interesting features both in rumen and hindgut environments, significantly contributing to animal health and production. The present study was aimed to understand how rumen and hindgut microbiota of dairy Italian Holstein Friesian heifers can be impacted by the inclusion of Camelina sativa cake in the diet. The trial was conducted at the tie stall dairy barn of the Experimental Farm of Animal Production Research and Teaching Centre of Lodi, University of Milan, Italy for 56 days. Sixteen Italian Holstein Friesian heifers 12 months old were randomly divided in two homogenous groups and subjected to 2 different treatments: CAME (n=8) receiving the basal diet supplemented with 800 g/ head/day of camelina cake and CTR (n=8) receiving the basal diet supplemented with an isonitrogenous and isoenergetic soybean-based premix. Basal diet consisted of a dry TMR composed by alfalfa hay, durum wheat middlings, sugar cane molasses, corn meal, soybean hulls, rice bran, sunflower meal, and minerals (15.15 PG, 42.63 NDF, 19.43 starch on DM basis). Performances were recorded weekly, feed intake daily. Rumen and fecal samples were collected at day 0, 28 and 56 of the trial and subjected to metabarcoding analysis. The V3-V4 hypervariable regions of the bacterial 16S rRNA gene were sequenced in two MiSeq (Illumina) runs with 2×250-base paired-end reads. Performance data were analyzed by PROC MIXED of SAS for repeated measures. The 16S rRNA gene analysis revealed significant differences in the alphaand beta diversity of the rumen and hindgut microbiota between timepoints (p <= 0.01). After correcting for time effects, differences between treatments were significant for richness and diversity indices (Chao1, ACE, Fisher's alpha, Shannon, Simpson) in the rumen microbiota, and for evenness indices (Simpson_E) in the rectum microbiota. As for specific taxa, the phylum Actinobacteria and the classes Coriobacteria and Deltaproteobacteria showed a significantly different between-treatment abundance (p <= 0.05) in the rectum microbiota, the order Mycoplasmatales (p <= 0.01) in the rumen microbiota.In conclusion, the cow rumen and rectum microbiotas showed a clear evolution over time, and some of their components seemed to significantly respond to the dietary supplementation with Camelina sativa.