Feed efficiency of beef cows help to calculate their feeding allowances through the quantification of the non-productive expenses

Abstract

Beef cows allocate 70% of their energy intake to their maintenance and this expenditure contributes to their efficiency. The revision of the INRA feeding recommendations was intended to quantify the expenditure of energy to obtain an improved control the major variation factors. A database has been compiled, including animals from 30 experiments (101 treatments) carried out on beef cowsfrom the INRA. The energy for non productive functions (EDNP) expressed in net energy for lactation (UFL) was calculated for each treatment as the difference between the energy intake and the energy required for lactation, gestation, and variations of the body mass estimated according to its chemical composition. The average production of milk was low (8 kg/day) but remained a priority regardless of the feeding level. Estimated from chemical composition (37 and 21% of lipids respectively), the energy value of 1 kg of body mass change corresponded to 2.4 and 1.8 UFL/kg for multiparous and primiparous cows, respectively. EDNP can be expressed as a single equation with the following variables are: maintenance (Emaintenance), physical activity (Iact) , body weight changes (ΔBWc) and body condition score at calving (BCS) : EDNP = (Emaintenance x Iact) + (0,0073 x ΔBWcxBCS). The interfering term (ΔPVc x NEC) corresponded to the adaptation of constrained metabolism or plethoric nutritional situations. Saving energy associated with lower intake (or vice versa) will allow breeders to optimize feeding planes. The changes in non-productive energy expenditures and their variations should be the purpose of future research.