Volume 42, 54-59

Tropical Grasslands (2008) Volume 42, 54–59

Diet quality, intake and growth performance of South African Mutton Merino sheep on Triticum × Secale and Lolium multiflorum pastures at different grazing pressures

W.A. VAN NIEKERK, ABUBEKER HASSEN AND R.J. COERTZE

Department of Animal and Wildlife Sciences, University of Pretoria, Pretoria, South Africa

Abstract

This study was undertaken to determine the influence of 3 grazing pressures [20 (HGP), 33 (MGP) and 50(LGP) g DM/kg LW/d] using South African Mutton Merino wether lambs, on qualitative and quantitative intake of Triticum × Secale cv. Pan266 (triticale) and Lolium multiflorum cv. Midmar (ryegrass) pastures as well as animal performance. Oesophageal samples at the start and end of the grazing period were analysed to determine diet quality in terms of nitrogen (N), ash, neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) and in vitro digestibility of organic matter (IVDOM) concentrations. Intake and average daily liveweight gain were determined for each group. In both pastures, the ADF concentration was higher, while IVDOM concentration was lower at the end compared with the start of the grazing period. For triticale, HGP resulted in lower dietary N, and higher ash and NDF concentrations than MGP or LGP. The DOMI and ADG of lambs at HGP were lower than those on LGP. For ryegrass, dietary N was lower at HGP than LGP, while the NDF concentration was higher (P<0.05) at HGP or MGP than at LGP. However, ADG at HGP was lower than at LGP or MGP for each species. Intake of both pastures declined during the study. The overall diet quality on ryegrass pasture seems better than on triticale, as reflected in higher (P<0.05) N and lower NDF concentrations. Performance of lambs on ryegrass pasture was higher than on triticale pasture, through higher (P<0.05) DOMI and subsequently higher ADG. Maximum gains/head in lambs seem to be achievable at an allocation of 33 g DM/kg LW/d. Further studies are warranted to examine the benefits of grazing triticale earlier in the season.