Lactational performance of cows fed extruded flaxseed in commercial dairy herds

The objective of the current on-farm trial was to assess the impact of feeding extruded flaxseed on milk yield and composition. Thirty commercial dairy herds located in the province of Québec, Canada were recruited. The experiment began with a baseline period of 2 months during which each cow received their regular diets. Data collected during this period were used as covariate. Farms were then randomly allocated into a control group (n = 15; 767 cows) which continued to receive their regular diets, or a treatment group (n = 15; 863 cows) which received diets supplemented with extruded flaxseed (0.7 kg/d per cow) during an experimental period of 7 months. Significance was declared at P ≤ 0.05 and tendencies at 0.05 < P ≤ 0.10. Feeding extruded flaxseed did not affect feed intake but increased milk yield by 1.1 kg/d per cow, and feed efficiency by 6.5%. Dietary addition of extruded flaxseed increased milk fat (tendency) and lactose yield, whereas milk protein yield was similar between treatments. Estimated CH₄ intensity were reduced by 1.3 g/L of milk (−9.2%) in herds receiving extruded flaxseed. Feeding extruded flaxseed increased milk fat concentration of cis-9, cis-12, cis-15 18:3 and total n-3 fatty acids. Results of the current on-farm trial confirm observations made under experimental conditions that feeding moderate levels of extruded flaxseed improves production performance in dairy cows.