The effect of herbage mass and allowance on herbage intake, diet composition and ingestive behaviour of dairy cows

摘要

An experiment was conducted to examine the effects of herbage mass [HM, based onregrowth intervals of 35 (T) and 21 (S) days] and herbage allowance [HA, 20.2 (H) and12.7 (L) kg organic matter (OM)/cow] on herbage OM intake (OMI), dietary compositionand ingestive behaviour of dairy cows. Four groups of three cows each were usedin a 4 × 4 greco-latin square design along with four oesophageal-fistulated cows. Thetreatment periods were 7 days and the squares (SQ) were repeated three times in a balanced way. The experiment was conducted from 11 April to 3 July 1986. The HM(organic matter) above 3 cm was 3064, 3472 and 3515 kg/ha for T and 2395, 1113 and2396 kg/ha (s.e. 94) for S, for SQ 1 to 3, respectively. Organic matter digestibility(OMD) was 842, 799 and 778 g/kg for T, and 851, 842 and 804 g/kg for S (s.e. 0.9), forSQ 1 to 3, respectively. Sward height (cm) after grazing was 8.5 and 7.6 for T and S,and 9.6 and 6.5 for H and L (s.e. 0.18), respectively. OMI was 15.2, 14.8 and 15.2 kg for TH, 12.3, 11.9 and 10.7 kg for TL, 15.8, 14.8 and 14.5 kg for SH and 11.9, 11.1 and 11.2kg for SL (s.e. 0.24), for SQ 1 to 3, respectively. The OMD of the diet was closely related to proportion of live leaf in the diet and sward OMD. Average biting rate increased with decreasing HM (R2 0.65). Grazing time was 8.93, 9.11 and 9.06 h for TH, 8.13, 7.96 and 7.91 h for TL, 8.96, 9.59 and 9.29 h for SH and 8.56, 9.36 and 8.52 h for SL (s.e. 0.155), for SQ 1 to 3, respectively. Multiple regression analysis showed that OMI was significantly related to HM (+0.48 kg/t), OMD of the sward (+0.18 kg per 10 g/kg) and pre-experimental milk yield (+0.37 kg/kg) (R2 0.89). The increase in OMI with potential milk yield, as indicated by pre-experimental yield, accounted for 0.80 of the supplementary energy requirements.