Effects of partial substitution of rosemary distillation residues to oat hay on digestive aspects, milk production, and metabolic statute of Tunisian local goats.

In the Mediterranean area, the by-products of medicinal and aromatic plant distillation became very attractive as additive and/or alternative feedstuff. Subsequently, the aim of the present study was to evaluate the effect of distilled rosemary (Rosmarinus officinalis L.) leaves (RDL) on digestion and ruminal aspects, metabolic statutes, and milk yield of the Tunisian native goat breed. Thirty-six adult goats were divided into three homogeneous groups (C, RDL20, and RDL40) receiving daily (per head) 0.5 kg of concentrate and 1 kg of roughage composed of 100% of oat hay for C group, 20% of RDL and 80% of oat hay for RDL20 group, and 40% of RDL and 60% of oat hay for RDL40 group. Milk yield and composition, and goats' and kids' BW were measured weekly; also measurement of the diet digestibility, nitrogen balance, rumen fermentation, and blood metabolites was carried out. Dry matter intake was significantly (P < 0.001) higher for the RDL40 group while the dry matter and crude protein digestibility was similar among groups. The goats' milk yield, milk composition, and blood metabolites were not affected by the dietary treatments. The results of this study indicate that RDL can partially substitute oat hay without negative effects on animal productivity.