The Optimum Grazing Time Based on Milk Fatty Acids and Yield for Holstein Lactating Cows through Eco-Pastoral System in Alpine Grassland

The Optimum Grazing Time Based on Milk Fatty Acids and Yield for Holstein Lactating Cows through Eco-Pastoral System in Alpine Grassland

This study aimed to detect the optimum grazing time based on milk fatty acids and yield for the Holstein cow (Bos taurus) through eco-pastoral system in Korean alpine grassland. The treatment of grazing time was 3 levels: Non-grazing, Half-day grazing, Full-day grazing. First, the difference of milk fatty acids (saturated fatty acid, unsaturated fatty acid, Total ω-3, etc.) and milk yield was checked by grazing time via ANOVA. Second, various measurements of milk fatty acids were reduced to principal components for effective and obvious detecting the variation as a grazing time. Final, the variations of milk fatty acid and yield were estimated to calculate the optimum grazing time by regression modeling based on multinomial function. For detecting the optimum grazing time, checking the crossing point between increases of milk fatty acid and decreases of milk yield, and response surface methodology were carried out. As a result, the optimum grazing time was 11.05 h by response surface methodology, respectively. For the optimum grazing time, unsaturated fatty acid, mono-unsaturated fatty acid, eicosatrienoic acid, total ω-3 and milk yield were 17.82 g/100g, 9.14 g/100g, 0.61 g/100g, 2.06 g/100g and 27.16 kg/d, respectively. The 11-hour grazing time was statistically optimal considering milk fatty acid and yield, but it would be minimal level if the loss due to milk yield reduction was covered by a premium grade and potential and long-term benefits were taken into account.