A two-step feeding of calcium salts of fish oil improves reproductive performance in Holstein cows

Aim of study: To examine the effects of a biphasic schedule of feeding n-3 fatty acids on dairy cows.Area of the study: Isfahan, Iran.Materials and methods: 140 lactating Holstein cows were allotted at calving into two groups of 70 animals and received one of two dietary treatments: 1) saturated fatty acids (SFA, containing 80% palmitic acid) or 2) calcium salt of fish oil (CSFO, containing 16% eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA)), with an n-6/n-3 FA ratio of approximately 7 for SFA and 5 for CSFO treatments. The dietary supplements were fed to the respective groups at 240 g/head.day from 0 to 21 days in milk, and 120 g/head.day from 22 to 150 days in milk. Milk yield was recorded biweekly and milk composition was evaluated monthly. The concentration of FA in the milk and blood was determined on d-90 of the experiment in 10 cows randomly selected from each group. Reproductive indices were recorded until d-150.Main results: The CSFO supplementation did not affect average milk yield, milk composition or milk somatic cell count (SCC); however, in some weeks it decreased milk SCC (p<0.05). Plasma concentrations of palmitic acid and n-3 FA as well as milk fat concentration of EPA and DHA increased in the CSFO-fed cows (p<0.05). Feeding the CSFO decreased open days (100 vs 119 days, p<0.05), service per conception and all service conception rates (p