Effects of altering the ratio of n-6 to n-3 fatty acids and concentrations of polyunsaturated fatty acids in diets on milk production and energy balance of Holstein cows

Objective: Our objective was to examine the effects of different ratios of n-6 to n-3 (n-6/n-3) fatty acids (FA) and amounts of PUFA on milk production and nutrient utilization in mid-lactating Holstein cows. Materials and Methods: Twenty-four lactating cows (550 +/- 50 kg of BW and 100 +/- 5 DIM) were randomly assigned to receive 1 of the 4 diets: (1) high n-6/n-3 (8.45) FA and low PUFA (19.0 g/kg of DM) concentration (n6-SFA), (2) high n-6/n-3 (8.78) FA and high PUFA (26.7 g/kg of DM) concentration (n-6-UFA), (3) low n-6/n-3 (5.74) FA and low PUFA (21.2 g/kg of DM) concentration (n-3-SFA), and (4) low n-6/n-3 (6.22) FA and high PUFA (26.7 g/kg of DM) concentration (n-3-UFA). Results and Discussion: The n-3-SFA diet improved milk production, fat- and energy-corrected milk, milk fat and protein yields, and digestibility of NDF compared with other diets. Dry matter intake, milk fat and protein content, BW, and BCS were not affected, although estimated energy balance was lower in n-3-SFA compared with the other diets. The n-3-SFA diet had the greatest feed efficiency value. Partial replacement of SFA with n-3 FA (n-3-SFA) could be considered for improving production and feed efficiency in dairy cows. Implications and Applications: Decreasing the ratio of n-6/n-3 and the amount of dietary PUFA increased milk, milk-fat, and milk-protein yields, whereas DMI was similar; thus, feed conversion to milk improved. Therefore, diets containing similar concentrations of fat but greater n-3 FA and less content of PUFA may be beneficial for improving production in mid-lactating Holstein cows.