Fish-meal supplement for severely undernourished ewes: effects on apparent digestibility and utilization of the diet

Abstract

AbstractEight non-pregnant, non-lactating adult ewes weighing 56 kg were fed for 26 days on a meadow hay (organic matter 937 g, crude protein 107 g, metabolizable energy (ME) 8·3 MJ per kg dry matter) to satisfy half of their daily energy and protein maintenance requirements i.e. 200 kj ME and 1·3 g truly digestible protein per kg M0·75. They were then allotted to two groups of four each. Control ewes continued to receive the initial diet for another 74 days while the others were supplemented with 60 g/day fish meal to receive 200 kj ME and 2·7 g truly digestible protein per kg initial M0·75 per day.In spite of its high nitrogen content, the digestibility of the hay was increased by the protein supplementation, e.g. from 0·56 to 0·60 for neutral-detergent fibre and from 0·54 to 0·59 for energy.The supplemented ewes lost significantly less body weight than the controls (96 v. 134 g/day) essentially because of their higher ME intake (272 v. 252 kj/kg average M0·75 during the experimental period). The measurements of blood metabolites suggest that the daily amounts of mobilized body protein increased with duration of underfeeding. The additional amino acids provided by fish meal were principally used as a source of energy and for wool growth.