Effect of Feeding Mixed Forage Diets on Milk Production

Abstract

For dairy farmers involved in winter milk production a high intake of forage is required by autumn calved dairy cows to produce a high milk yield with a moderate level of concentrate supplementation. Since intake of grass silage is often limiting, alternative forages or feeds may be needed to maximise forage intake. In areas not suitable for growing maize alternative forages need to be considered. These could include limited amounts of very high quality grass silage (DMD 750-800 g /kg), grazed autumn pasture or bulky by-product feeds, e.g. superpressed sugar beet pulp. An experiment was conducted involving 5 treatments in which a standard good quality grass silage (S) was partially replaced with either very high quality grass silage, which was either unwilted (U) or wilted (W), ensiled pressed sugar beet pulp (P) or with autumn pasture (G). These additional feeds were fed at a level of 5 kg DM/day to autumn calved cows in early lactation over a period of 8 weeks from late October to late December. The pressed pulp diet (P) included 0.5 kg DM soyabean meal to increase its protein level. The autumn grass was cut daily and fed indoors. The additional feeds were fed on top of the standard silage in individual feeding boxes and the standard silage was fed ad libitum to cows on all treatments. The cows were fed concentrates at 6 kg/day in two feeds on all treatments. The digestibility of the standard grass silage (754 g DMD/kg) was higher than planned and was only slightly less than that of the high quality supplementary silages (783 g DMD/kg). Feeding the U and W silages did not increase total forage intake but did increase milk yield by 1.7 - 1.9 kg/day compared with silage S alone. Milk fat and protein concentration tended to be reduced on the diets containing U and W silages, consequently yield of fat and protein were not significantly increased compared with silage S. Forage intake was increased by 8% (0.8 kg DM/day) when silage S was supplemented with autumn grass and milk yield was increased by 1.5 kg/day without affecting milk composition. Intake of silage was reduced by 37% by feeding grass. Feeding the pressed pulp supplement (P) increased intake of forage (+1.1 kg DM/day), increased milk yield by 2.7 kg/day and also improved milk protein concentration and yield (+121 g/day). Cows gained in liveweight to a similar extent on all diets. It was concluded that feeding pressed pulp with a good quality grass silage had the greatest effect on forage intake and milk production whereas feeding high quality grass silages or autumn grass had a smaller effect. Larger increases in intake and milk production would be expected from these feeds if the standard grass silage was of lower digestibility (~700 g DMD/kg), similar to average quality first cut silage.