The nutritive value of protein in subtropical pasture species grown in south-eastern Queensland

Abstract

Examination of the data from 138 indoor pen-feeding trials with sheep showed that, for 22 grasses and 6 legumes grown in south-east Queensland, crude protein digestibility was related to percentage crude protein content (R = 0.885 ; P<0.001) and to the nitrogen balance of the sheep (R = 0.776 ; P<0.001). The equations derived from these relations can be used to estimate the nutritive value of protein from the crude protein content. Under ad lib. feeding; zero nitrogen balance was estimated to occur at a crude digestibility of 49 per cent (95 per cent fiducial limits = 47, 52) and this digestibility was attained at a crude protein content of 8 per cent (95 per cent limits = 7.0, 9.0). The implications of these estimates are illustrated with the aid of some data on changes with age in the crude protein content of sub-tropical grasses and legumes.