Effects of dietary pomegranate pulp silage supplementation on milk yield and composition, milk fatty acid profile and blood plasma antioxidant status of lactating dairy cows

The objective of this study was to determine effects of inclusion of pomegranate pulp silage (PS) in lactating dairy cows' rations, in replacement of mainly corn silage, on milk yield, chemical composition, somatic cells count, colony forming units, and fatty acid (FA) concentrations of milk, as well as on blood antioxidant status. Fifteen lactating Holstein dairy cows, with a milk yield of 26.6 ± 3.86 kg/day and lactation number of 2.9 ± 1.17, were assigned to one of three dietary treatments in a 3 × 3 Latin square design, with three 25 days periods. The PS was added to the total mixed ration (TMR) at levels of 0, 75 and 150 g/kg TMR on a dry matter (DM) basis to create dietary treatments PS0, PS75 and PS150, respectively. Experimental rations were iso-net energetic (6.20 MJ NEL/kg DM) and iso-nitrogenous (150 g CP/kg DM), and the TMR were offered to cows individually twice a day with feed residues recorded. In the last 5 days of each experimental period, milk yield was recorded and milk samples collected for chemical composition and FA analysis. Inclusion of 75 or 150 g PS/kg of TMR (on a DM basis) did not affect milk yield, milk composition or milk bacterial and somatic cell counts. Milk FA analysis showed a linear decrease (P < 0.05) in concentrations of C8:0, C10:0, C12:0, C14:0, C15:0 and C16:0 saturated FA (SFA), and linear increase (P < 0.05) in concentrations of trans-11C18:1, cis-9C18:1, C18:2n-6c, C18:3n-3 and cis-9, trans-11C18:2 unsaturated FA (UFA). As dietary PS inclusion levels increased, medium chain FA, SFA, the SFA/UFA ratio and atherogenicity index linearly decreased (P < 0.05), whereas, long chain FA, monounsaturated FA and polyunsaturated FA linearly increased (P < 0.05). Linear and quadratic effects (P < 0.05) occurred in the n-6 FA concentration. Blood plasma glutathione reductase activity linearly decreased (P < 0.05), whereas glutathione S- transferase and superoxide dismutase activity linearly increased (P < 0.05), with increasing dietary PS feeding level. Inclusion of PS up to 150 g/kg DM in dairy cows' TMR did not affect milk yield and chemical composition, but improved the milk FA profile and blood plasma antioxidant status.