An evaluation of the effects of grazing management systems involving preferential treatment of high‐yielding dairy cows on animal performance and sward utilization

Abstract

AbstractTwo systems of grazing management involving preferential treatment of high‐ yielding dairy cows were compared with a grazing system in which both high‐ and low‐yielders received uniform treatment. Cows were rotationally grazed across I‐day paddocks without concentrate supplementation from 23 April to 8 October 1985, with a mean stocking rate over the season of 5‐4 cows ha−1. Preferential treatment of high‐yielding cows was achieved either by using a leader/follower approach (LF) with high‐yielding cows in the leader group, or by preferential forage feeding (PFF) where high‐yielding cows were allowed access to grass silage for 1 ‐5 h daily and grazed alongside low‐yielders. Control (C) cows grazed together as a single group. The high grazing stocking rates used on all three treatments resulted in good grass utilization with residual sward heights, assessed by a rising‐plate sward stick, of 45, 50 and 48 mm for the LF, PFF and C treatments respectively. Animal performance data for the LF, PFF and C treatments respectively were: milk yield (kg d−1) 15middot;1, 15middot;6 and 14middot;7 (s.e. 0middot;78); milk fat yield (g d−1) 598, 606 and 567 (s.e. 34); milk protein yield (g d−1) 500, 519 and 480 (s.e. 31); and live weight gain (kg d−1) 0middot;12, 0middot;23 and 0middot;25 (s.e. 0·05). These results indicate that leader/follower grazing had little overall effect on animal performance when high grazing severity was imposed, with the improvement in animal performance of high‐yielding cows in the leader group being offset by the reduced performance of the follower group. Buffer‐feeding of high‐yielding, rotationally‐grazed cows with high‐quality grass silage had little effect on animal performance and resulted in a decrease in the efficiency of grassland utilization. Silage appeared to substitute for herbage, with a reduction in herbage DM intake of 0middot;55 kg per kg silage DM consumed.