Milk Production Milk Quality and Behaviour of Dairy Cows Grazing on Swards with Low and High Water-Soluble Carbohydrates Content in Autumn: A Pilot Trial

摘要

Improving the performance of grazing systems and reducing their environmental impact are crucial in the current and future world contexts. In temperate grazing dairy systems, perennial ryegrass is widely used. Its nutritional composition can by modified via cultivar selection and management. We tested two swards: (1) a high-sugar cultivar submitted to fertilisation and defoliation regimes aimed at increasing sugar content and sugar-to-protein ratio and (2) a standard cultivar submitted to fertilisation and defoliation regimes aimed at decreasing sugar content and sugar-to-protein ratio. We tested these two swards with mid-lactation dairy cows grazing in daily strips for nine days in autumn and measured the amount of forage offered and consumed, the milk production and composition, and the grazing behaviour between morning and afternoon milkings. We found that the amount of residual herbage was greater in the standard cultivar sward, but the herbage consumed per cow was similar. Cows spent less time grazing in the high-sugar sward, but no difference was observed in the rumination time. Milk production and composition were similar between the two groups. This could imply that good-quality pastures would require a greater difference in nutritional composition to have an impact on animal performance.