Prediction of liveweight gain by growing cattle fed silages of contrasting digestibility, supplemented with or without barley

Abstract

This study was conducted to determine the accuracy of average daily gain (ADG) predictions based on digestible energy (DE) estimated from acid detergent fiber (ADF) and on the nutrient requirements of beef cattle when applied to growing cattle fed silages of contrasting digestibilities with or without barley. A feeding trial was conducted with 45 Charolais × Simmental calves fed either a control silage (early cut, E) with no barley or two other silages (medium cut, M; late cut, L) fed with (M + barley and L + barley) or without 60% dry-matter (DM) basis rolled barley in the diet. Total dry-matter intake (DMI) of diet E was higher (P < 0.05) than that of diets M and L. The addition of barley in diets M + barley and L + barley led to an increase (P < 0.05) in total DMI. ADG of steers fed diet E was higher (P < 0.05) than that of steers fed diets M and L but lower (P < 0.05) than that of steers fed diets M + barley and L + barley. A digestion trial was conducted concurrently, using five steers fed at 90% ad libitum. The apparent digestibility values of the DM for the five diets tested were (E) 68.5, (M) 60.8, (L) 56.8, (M + barley) 70.8 and (L + barley) 70.1%. Gains predicted when forage DE was estimated from ADF or determined in vivo were, respectively, 57 and 92.6% of observed values. When barley–supplemented diets were studied separately, it was apparent that most of the prediction error was due to the inability to predict forage DE from ADF. Further research is needed to develop methods to accurately predict the energy content of forage silages grown in Canada. Key words: Energy, forages, silages, cattle