Agroindustrial by-products from tomato, grape and myrtle given at low dosage to lactating dairy ewes: effects on rumen parameters and microbiota

The inclusion of by-products in composite pellet feeds could be a strategy to recycle nutritional components and a commercial opportunity for feeds industries. Aim of this study was to evaluate if the use of small amount of dried by-products containing polyphenols could alter rumen fermentation parameters and microbiota in dairy ewes. Thirty-six ewes (9 animals per group) were fed control diet (CON), and diets supplemented with 100 g/d per animal of tomato pomace (TP), 100 g/d per animal of grape marc (GM), and 75 g/d per animal of exhausted myrtle berries (EMB). Treatment showed significant effects only on pH, whereas sampling time affected almost all rumen fermentation parameters. No differences in the proportion of any phylum were detected in GM group compared to CON group. TP, compared to CON, evidenced higher abundance of Proteobacteria phylum (counts of 4.86; log fold chain of 5.61) which was dominated by Acetobacteraceae family with Acetobacter genus. The supplementation of EMB resulted in higher abundance of Succinivibrionaceae and lower abundance of Veillonellaceae family. Furthermore, in EMB group the Paraprevotellaceae and Prevotellaceae families dominated the phylum of Bacteroidetes. This phylum was significantly different between EMB and CON diet (counts of 57.06; log fold change of 1.10). The estimated production of methane and rumen fermentation parameters were not affected by the diets. The supplementation in small doses of GM, TP and EMB in the diets of sheep did not evidence a clear variation in rumen fermentation parameters nor changes in the general structure of rumen microbiota.HIGHLIGHTS The agroindustrial by-products did not affect the rumen biochemical parameters. The structure of bacteria community was influenced by EMB diet. GM and TP diets did not increase rumen ammonia.