Effect of supplementation of oilseeds co-products on production performance and fatty acids composition of Beetal goats

This study evaluated the effect of different oilseed co-product supplementations on feed intake, nutrient digestibility, N retention, yields of milk and milk constituents, and milk fatty acid (FA) profile of Beetal goats. In the lactation trial, thirty-six lactating multiparous Beetal goats (45 +/- 2.04 kg; 15 +/- 2.3 days in milk) were assigned to four experimental rations according to randomized complete block design. The blocks were balanced for daily milk yield, parity, and body weight. The goats were either fed a maize silage and wheat straw-based basal ration ad libitum (control) or the control ration was supplemented with cotton seed cake, mustard seed cake, or maize oil cake on an iso-N basis. At the end of lactation trial, four goats (44 +/- 0.8 kg BW; producing 1250 +/- 110 g milk/day) were selected and moved to individual metabolism crates for a digestibility and N balance experiment, using a Latin square design (4 x 4). Supplementation of the co-products increased intakes of forage mixture (P = 0.002), total dry matter (DM; P < 0.001), neutral detergent fibre (NDF; P = 0.003), and crude protein (CP; P < 0.001). The additional N supplied by the co-products increased (P < 0.001) N retention, yields of milk, fat, protein, and lactose. Further comparison of the rations supplemented with the co-products revealed that the greatest (P < 0.05) increase in yields of milk (240 g/day), milk protein (11.6 g/day), fats (16.3 g/day), and lactose (11.2 g/day) was recorded for maize oil cake, as compared to the control. Except C8:0, supplementation of the co-products decreased (P < 0.01) the contents of all de novo-synthesized saturated FAs (SFAs) and increased (P < 0.001) the contents of health beneficial C18:1n-9, C18:1 tans-11, C18:2n-6, C18:3n-3, C20:2n-6, C20:5n3, and total unsaturated FAs in milk fat. Our findings demonstrated that the oilseed co-product inclusion in dairy goat rations significantly improves forage biomass utilization, yields of milk and milk constituents, and milk FAs' profile, with the largest impact being observed for maize oil cake.