The effect of prepartum protein feeding on post-partum lactation performance of Ayrshire heifers and cows

Thirty Ayrshire cows, 14 multiparous (MP-cows) and 16 heifers (heifers), were used to investigate the response of animal performance to prepartum rapeseed meal supplement (RSM). The basic diet was formulated from oats and barley(l:l DM basis) and wilted grass silage. Both heifers and MP-cows were paired by their expected date of calving to form two groups of each. One of each MP-cow pair (control cows; CC) and heifer pair (control heifers, CH) were offered 3 kg d(-1) the basic diet without protein supplement. Part of the grain was replaced by 1.5 kg d(-1) RSM in the diet of the other pairs (test cows, TC; and test heifers, TH). Mineral supplement was fed at 250 g d(-1) (heifers) and 300 g d(-1)(MP-cows). Following parturition, all animals were offered similar lactation concentrate containing oats and barley (64%), RSM (18%) and molassed sugar beet pulp (18%) with wilted grass silage. Pre- and postpartum blood samples were taken. Feed intake, body condition, body weight change, milk yield and composition were monitored. Prepartum RSM supplement increased total feed intake of TH through increased voluntary silage intake. CH consumed less DM and lost more body weight during early lactation but produced higher (P <0.09 and P <0.02) milk than the TH during 23-41 days (Period 2) and 42-60 days (Period 3) of lactation. The milk protein content of the same group was lower (P <0.04) during Period 3. Plasma and milk urea concentration was higher for the TH during 4 - 22 days of lactation (Period 1) and Period 2. Prepartum RSM supplement did not significantly affect feed intake, milk yield or milk composition of MP-cows.