Crushed flaxseed versus flaxseed oil in the diets of Nubian goats: Effect on feed intake, digestion, ruminal fermentation, blood chemistry, milk production, milk composition and milk fatty acid profile

Plant oils or oil-rich seeds that are rich in unsaturated fatty acids can be used as feedstocks to modify milk fatty acid profiles. The effect of providing lactating Nubian goats with flaxseed oil or crushed seeds on the feed intake, digestion, ruminal fermentation, lactational performance and milk fatty acid profile was assessed. Fifteen lactating does, weighing 33.2 ± 0.8 kg after parturition, were randomly assigned to three treatments in a quintuplicated 3 × 3 Latin square design. Does were stratified according to their previous milk production, parity and expected average milk yield in a 90-day experiment. Does were fed a basal diet containing 500 g of berseem clover and 500 g of concentrates (Control treatment) or the control diet supplemented with 50 g of crushed flaxseed containing 37.5% oil (Seed treatment) or 20 mL of flaxseed oil (Oil treatment). Without affecting the feed intake, crushed flaxseed and flaxseed oil increased (P<0.05) the organic matter and crude protein digestibilities. Flaxseed oil lowered (P<0.05) ruminal pH and acetate proportion. Flaxseed and oil increased (P<0.05) total volatile fatty acids and propionate concentration and proportion. Flaxseed oil had no effect on fibre digestibility, but crushed flaxseed increased (P<0.01) fibre digestibility. High concentrations of serum glucose (P<0.05) and low (P<0.001) concentrations of triglycerides (P<0.001), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and beta-hydroxybutyrate were observed with crushed flaxseed and flaxseed oil. Flaxseed oil and crushed flaxseed increased (P<0.05) milk production and milk (feed) efficiency; however, flaxseed oil decreased (P<0.05) milk fat content. Moreover, crushed flaxseed and flaxseed oil decreased (P<0.05) milk saturated fatty acids and atherogenicity index and increased the concentrations of unsaturated fatty acids and total conjugated linoleic acid. In conclusion, supplementing the diet of lactating Nubian goats with flaxseed oil or crushed flaxseed enhanced milk production and altered milk fatty acid composition. However, crushed flaxseed is preferable to flaxseed oil.