Abstract/Summary

An accurate prediction of maintenance energy requirement is essential for rationing growing cattle and suckler cows for improved production efficiency and reduced environmental footprint. There is evidence that the current UK energy feeding system (Agricultural and Food Research Council,1993) underpredicts maintenance energy requirement for growth of modern cattle. The objective of the present study was to develop updated maintenance energy requirements for growing cattle. Data used were collated from calorimeter chamber studies (each with digestibility measurements) undertaken at the Agri-Food Biosciences Institute (n = 249) and the University of Reading (n = 48) between 1993 and 2015. The dataset comprises data from 176 growing dairy and beef steers, 88 growing Holstein-Friesian heifers and 34 dry mature suckler cows. Cattle were offered diets containing either forage only (n = 81) or a mixture of forage and concentrates (n = 211) at various feeding levels. Energy intake and outputs were measured using indirect open-circuit respiration calorimeter chambers and digestibility trials. Linear and multiple linear regressions between retained energy (RE) and ME intake (MEI) were used to determine the net energy (NEm) and metabolisable energy (MEm) requirements for maintenance of body tissue energy without loss or gain. Data were analysed using a linear mixed model (restricted maximum likelihood estimation method), with animal gender, live weight, forage type and dietary forage proportion fitted as additional fixed effects while research centre, experiment and chamber number as random effects. The NEm derived from the linear relationship between RE and MEI was 0.42 MJ/kg0.75 of live weight (equivalent to 0.40 MJ/kg0.75 of calculated empty body weight). The MEm values were determined to be 0.53 and 0.55 MJ/kg0.75 of live weight (equivalent to 0.50 and 0.52 MJ/kg0.75 of calculated empty body weight) using multiple linear regressions of MEI against metabolic live weight and positive and negative RE. The present NEm or MEm values are 24% or 13% and 17% higher than those recommended by AFRC (1993). The present result indicates that use of AFRC (1993) to ration modern growing cattle underestimates their maintenance energy requirements.