The effect of forage type and level of concentrate supplementation on the performance of spring-calving dairy cows in early lactation

In 1993 and 1994, 40 cows in early lactation in early spring were assigned randomly to four feeding treatments. One group of cows was kept indoors with access to grass silage ad libitum, plus 6 kg of concentrate daily. The other three groups had access to grass pasture (5-6 h per day in 1993 and 11-12 h per day in 1994) plus grass silage similar to that fed to the previous group while indoors plus 6, 4 or 2 kg of concentrate daily. The average daily allocations of herbage (> 3.5 cm) were 8.5 and 14.0 kg DM cow(-1) day(-1) in 1993 and 1994 respectively. The treatments were applied for 8 weeks (26 February to 23 April) in 1993, and 7 weeks (11 March to 29 April) in 1994. Cows with access to pasture had lower (P < 0.001) silage dry-matter (DM) intakes and higher (P < 0.001) total forage DM intakes in both years than those kept indoors. This resulted in significantly higher yields of milk, fat, protein and lactose. Similarly, milk protein concentration was higher (P < 0.05 in 1993; P < 0.001 in 1994). There was a significant linear increase in total DM intake in both years with increased concentrate supplementation. In 1993, there was a linear increase in milk (P < 0.01), fat (P < 0.01), protein (P < 0.001) and lactose (P < 0.01) yields with increased concentrate supplementation. In 1994, only milk protein yield (P < 0.05) was increased. Concentrate supplementation had no effect on milk composition or liveweight change. Cows with access to grazed grass had higher liveweight gains (P < 0.05) than those kept indoors in both years. In 1993, increasing the energy intake increased the processing qualities of the milk produced. The results showed that access to grass pasture resulted in higher milk production, in reduced silage requirement and in reduced level of concentrate supplementation required for a given level of milk production with spring-calving cows in early lactation compared with those kept indoors.