The effect of amount of protein in the concentrates on hay intake and rate of passage, diet digestibility and milk production in British Saanen goats

Abstract

ABSTRACTDuring the first 2 weeks after kidding, 27 multiparous British Saanen goats were offered 1·5 kg hay (98 g crude protein (CP) per kg dry matter (DM)) and from 0·45 increasing to 0·70 kg concentrates (152 g CP per kg DM) daily. Week 2 was used as a covariance period. At week 3 of lactation all the goats were allocated to one of three groups and were offered hay ad libitum and 1 kg concentrates containing 117 (LP), 152 (MP) or 185 (HP) g CP per kg DM daily to week 15. During weeks 4 to 15, hay intake and milk yield were highest in the HP group. With increasing protein in the concentrates, hay DM intake was 1·20, 1·19 and 1·37 (s.e. 0·060) kg/day respectively and milk yield was 3·04, 3·21 and 3·36 (s.e. 0·080) kg/day respectively (linear response P < 001). There was no significant effect on the concentration of solids-not-fat, fat, total nitrogen or casein in milk. The digestibility of dietary organic matter, acid-detergent fibre and total nitrogen measured after week 15 was significantly greater with HP than with LP (P < 0·05), with MP values being intermediate (linear response P < 005). The rate of passage of ytterbium-labelled hay was unaffected by the treatments. The results indicate that, with lactating goats given hay and concentrates, beneficial responses may be expected to increasing concentrate CP to at least 185 g CP per kg DM.