Dans quelles conditions de disponibilité en herbe est-il nécessaire de complémenter en énergie la jument en lactation au pâturage ?

Our study investigated the effects of daily herbage allowance (DHA) and energy supplementation on daily herbage intake in lactating saddle mares grazing high-quality regrowths. Three contrasting DHAs at ground level: low, medium and high, i.e. 35, 52.5 and 70 g DM.kg BW-1.d-1, were obtained by adjusting pasture strip width. For 3 successive 2-week periods, 3 groups of 3 supplemented mares (S, 2.6 kg DM barley.d-1) and 3 groups of 3 non supplemented mares (NS) grazed each DHA according to a Latin-square design. Whichever their level of supplementation, all the mares responded in the same way to DHA variations by linearly increasing their herbage intake from 18.5 to 23.4 g DM.kg BW-1.d-1 with increasing DHA. However, barley supplementation allowed to S mares to realize total digestible dry matter intake and net energy intake higher than the ones of NS mares. Contrary to S mares, NS mares no longer met their energy requirements on low and medium DHA. The linear relation between DHA and herbage intake allowed to estimate at 66 g DM.kg BW-1.d-1 (i.e. 39 kg DM.mare-1.d-1) the DHA threshold below which lactating mares need an energy supplementation to fully meet their requirements in our grazing conditions.