Factors affecting maintenance requirements of beef cows

Abstract

ABSTRACTThe maintenance energy requirements of 29 Hereford × Friesian and 27 Blue Grey (White Shorthorn × Galloway) cows each offered one of six levels of feeding supplying between 0·5 and 1·2 likely maintenance requirements for 56 days were estimated, from regressions of daily live-weight change on energy intake, as the energy intake corresponding to zero live-weight change.There were no effects of level of intake on diet digestibility or of genotype on maintenance requirements.Maintenance requirements (M, MJ metabolizable energy per day) were shown to be determined by both live weight (LW, kg) and body condition score (C) according to the relationship: M = 0·147LW – 0·016C.LW.The estimates derived are compared with other published values and the hypothesis is advanced that maintenance requirements are likely to be more closely related to body protein mass than to body weight.The dietary energy equivalent of 1 kg loss of live weight is calculated to be 26·7 MJ and it is estimated that in non-lactating cows body tissue is used for maintenance with an efficiency of 0·77.