Simplified rotational grazing management of dairy cows : Effects of rates of stocking and concentrate

Abstract

An experiment was carried out in Normandy between 1986 and 1988 over c. 6 months in each year, using a simplified rotational grazing technique (two paddocks in spring, four in autumn) with a total of 162 high-yielding cows (mean milk yield of 30.0 kg/day at turn-out). Three stocking rates, designated control (T : 2.3 cows/ha over the total area of the system), moderate (F : 2.6 cows/ha = 115 % of T) and high (TF : 3.0 cows/ha = 130 % of T), were compared at two rates of concentrate supplement, 3.7 kg/cow per day (H) and 0.5 kg/cow per day (B) . Individual milk yield differed by only a non significant 5 % between the extreme stocking rates (21.3 vs 20.3 kg fat-corrected milk (FCM) for treatments T and TF, respectively). Milk production/ha was 23 % greater in the TF treatment (9816 vs 7970 kg FCM for TF and T, respectively). Concentrate supplementation led, on average, to a 9 % milk yield improvement (21.8 vs 20.0 kg FCM for H and B rates, respectively), i.e. a mean efficiency of 0.6 kg FCM/kg supplement. This response tended to be greater in the higheryielding cows and for the high stocking rate. The sward measurements contributed to a better understanding of herbage utilization by the cows.