Effects of daily herbage allowance and stage of lactation on the intake and performance of dairy cows in early summer

Abstract

The aim of this study was to investigate the relationship between daily herbage allowance (DHA) and the performance of dairy cows at two stages of lactation. Spring-calving (n=42, mean calving date 17 February) and autumn-calving (n=42, mean calving date 22 September) Friesian cows were divided into three equal groups and assigned to three levels of DHA (above a cutting height of 35 mm), 17 (L), 20 (M) and 23 (H) kg of dry matter (DM) per head, from late April to late June, 1996. The spring-calving cows grazed to sward heights (mm) of 47, 56 and 65 (s.e. 0.6) and residual herbage organic matter (OM) masses (above 35 mm) of 294, 408 and 528 (s.e. 12.1) kg/ha for L, M and H, respectively. The autumn-calving cows grazed to corresponding sward heights of 51, 60 and 69 (s.e. 1.1) mm and leftresidual herbage OM masses of 364, 445 and 555 (s.e. 12.9) kg/ha for L, M and H, respectively. Pastures were mechanically topped post grazing. Spring-calving cows consumed 13.3, 14.7 and 15.5 kg OM (s.e. 0.47) per day, and autumn-calving cows consumed 13.3, 13.8 and 14.9 kg OM (s.e. 0.43) per day for L, M and H, respectively. Mean daily solids-corrected milk yield was 23.1, 23.8 and 24.8 (s.e. 0.34) kg for the spring-calving cows, and 17.5, 18.4 and 18.7 (s.e. 0.35) kg for the autumncalving cows, for L, M and H, respectively. Milk yield could be predicted from preexperimental yield (PMY) and daily herbage organic matter allowance (DOMA, kg) according to the following equation: y = −1.13 + 0.76 (s.e. 0.030) PMY + 0.22 (s.e. 0.057) DOMA (r.s.d. 1.32, R2 0.89). The results indicate that high individual cow and herd production levels can be achieved from high quality herbage alone during early summer at a DHA of 23 kg DM for spring-calving cows and 20 kg DM for autumn-calving cows.