Effects of proportion and digestibility of grass-clover silage on milk protein, mineral and fatty acid compositions in Danish Holstein cows

Abstract

ABSTRACT The objective of this study was to investigate the effects of proportion and organic matter digestibility (OMD) of grass-clover silage on milk composition. Grass-clover silages with low (LD) or high (HD) OMD were mixed at low (30:70, LP) or high (70:30, HP) proportion (DM basis) with maize silage to arrange 4 total mixed rations (TMR) with a forage-to-concentrate ratio of 60:40. The TMR were fed ad libitum to 36 cows in a 4 × 4 Complete Latin Square design. The proportion × OMD interaction showed that feeding a high proportion of low-digestible grass-clover silage resulted in a higher content of milk urea nitrogen (P < .001). The diets had a minor impact on milk protein and mineral compositions. Decreasing the grass-clover to maize silage ratio from 70:30 to 30:70 improved the nutritional value of milk fat by decreasing the share of saturated and increased the share of unsaturated fatty acids (P < .001).