Effect of organic grain supplementation on production, body weight, body condition score, and fatty acid profiles of organic dairy cows

Abstract Text: Organic cows (n = 153) were used to evaluate the effect of grain supplementation levels during 2 grazing seasons (May to September 2012 and May to September 2013) on production, body weight, body condition score (BCS), and fatty acid profiles of organic dairy cows.  Cows were assigned to 1 of 3 replicate supplementation groups: 1) no grain supplementation (100% pasture, GRS, n = 51), 2) low grain (2.72 kg/head/day, LOW, n = 51), and 3) high grain (5.44 kg/head/day, HI, n = 51), and calved at the University of Minnesota West Central Research and Outreach Center, Morris, Minnesota.  Supplement (organic corn and minerals) was fed with a partial mixed ration (PMR) of corn silage and alfalfa haylage, and at least 30% of diet dry matter intake for LOW and HI cows consisted of organic pasture.  Milk production, from daily milk weights, was averaged weekly for cows, and body weight and BCS were recorded bi-weekly.  Milk for fatty acid analysis was collected monthly and analyzed at R-Tech Analytical Laboratory (Arden Hills, MN).  The PROC MIXED of SAS was used for statistical analysis, and independent variables were fixed effects of year (2012 or 2013), season of calving (fall or spring) nested within year, parity (1, 2, 3+) nested within year, supplementation group, breed group; week nested with supplementation group, with replicate nested within year and cow nested within supplementation group and breed group as a random effect with repeated measures.  The GRS (14.4 kg/d) cows had lower (P < 0.05) energy-corrected milk than LOW (16.2 kg/d) and HI (17.0 kg/d) cows; however, the LOW and HI cows were not different from each other.  The GRS, LOW, and HI cows were not different for body weight across the grazing season (491, 498, 498 kg, respectively); however, GRS (3.05) cows had lower (P < 0.05) BCS than LOW (3.14) and HI (3.15) cows.  Milk urea nitrogen was higher (P < 0.05) for GRS (19.5 mg/dl) than LOW (12.0 mg/dl) and HI (9.9 mg/dl) cows.  Furthermore, omega-3 fatty acid was higher (P< 0.05) for the GRS (0.05%) cows compared to the LOW (0.04%) and HI (0.03%) cows.  Organic dairy cows that consume 100% pasture had lower production, but milk from cows that consume 100% pasture compared to pasture and PMR had fatty acid composition of potential benefit to human health.

Keywords:

organic, fatty acid profile, pasture