Effect of concentrate supplementation of grazing dairy cows in early lactation on milk production and milk processing quality

In both 1993 and 1994, 33 cows in early lactation were blocked into groups of three on the basis of lactation number, calving date and milk yield, and within each block were randomly assigned to either 0, 2, or 4 kg of concentrate daily. Cows were offered concentrate individually and grazed in one group. The treatments were applied from mid-April to mid-June at a stocking rate of 4.98 cows/ha. Grass allowance (> 3.5 cm above ground level) per cow per day ranged from 17 to 22 kg dry matter (DM). Grass growth rate was below normal and grazing conditions were difficult in both years. Individual animal intakes were measured using n-alkanes. Mean calving dates were 13 March and 9 March for 1993 and 1994, respectively. Supplementation with concentrate had no significant effect on herbage intake but significantly (P < 0.01) increased total DM intake. There was a significant (P < 0.01) linear increase in milk yield as the concentrate feeding level increased in both years. Grass alone supported the production of 24 kg of milk per day. The average response was 0.80 and 0.45 kg milk and 0.50 and 0.65 kg of milk per kg of concentrate for the 2 and 4 kg feeding level in 1993 and 1994, respectively. Fat and protein content of milk were unaffected by treatment, but milk protein yield increased with the level of concentrate. Supplementation with concentrate significantly (P < 0.05) reduced body-weight loss in 1993 and increased body-weight gain in 1994. Concentrate supplementation significantly (P < 0.05) reduced the number of services per conception. In 1993 concentrate supplementation significantly reduced free fatty acid (FFA) level in the milks over the 9 weeks of the experiment. The results of this study suggest that with spring-calving dairy cows in very early lactation, in situations of inadequate grass supply and/or in difficult grazing conditions, supplementation with 2 to 4 kg of concentrates daily would be advantageous.