A comparison of digestible and net energy models to predict rates of gain of hereford steers

Abstract

Equations to predict rates of gain and efficiency of feed utilization are widely used by feedlot operators to make decisions on what and how much to feed to maximize rates of gain and/or feed utilization. Two widely used systems to predict these parameters are the net energy (NE) and the digestible energy (DE) systems. A comparison of the two systems over a wide range of diets would be useful to select the system that is the more useful to the feedlot operator. The objective of this study was to compare the observed and predicted rates of gain of steers fed eight diets ranging from 100% silage to 100% concentrate. Data from an experiment in which 80 Hereford steers were fed diets containing barley-silage and concentrate in ratios of 100:0, 75·1:24·9, 58·3:41·7, 34·4:65·6, 18·9:81·1, 8·0:92·0, 3·7:96·3 and 0:100 on a dry matter (DM) basis were used to compare the accuracy of prediction of average daily gain (ADG) from equations using the NE and DE systems. For steers fed 100 or 75% silage, the NE system more closely predicted the observed rate of gain, but when the concentrate was greater than 40% of the diet, ADG was more closely predicted using the DE than the NE system. For steers fed the all-silage diet for one year then fed an all-concentrate diet, predictions from the NE system over-estimated ADG but were closer than those from the DE system.