EFFET DE DIFFERENTS TRAITEMENTS ALIMENTAIRES SUR LA CROISSANCE ET L'EFFICACITE ALIMENTAIRE DES TAURILLONS DE RACE HOLSTEIN

Abstract

This study was conducted to evaluate different feeding systems for young Holstein bulls grown from 140 to 525 kg liveweight. In phase I, which lasted 134 d, 184 bulls were assigned to five treatments involving either pasture or silage with different levels of concentrate. In phase II, which lasted until the animals weighed 400 kg, 48 bulls from one pasture treatment and all 96 bulls fed silage in phase I were reassigned, within previous treatments, to subtreatments in which corn silage was supplemented with 0, 250 and 500 g head−1 d−1 of soybean meal. In phase III, which concluded the study, bulls were maintained on corn silage but reassigned, as in phase II, to treatments involving a restricted (5 kg) or ad libitum supplement of barley. In phase I, increasing the level of concentrates up to 3 kg head−1 d−1 for bulls on pasture increased their growth rate but was not associated with improved dry matter intake or feed efficiency. Bulls gained weight faster and were more efficient on pasture than on silage, when their diet was supplemented with 1 kg concentrate. In phase II, gain and feed efficiency were improved by 50 and 28% respectively, by supplementing corn silage with 500 g of soybean meal per head and per day. In phase III, an improvement of 17% in feed efficiency was recorded for bulls fed barley ad libitum rather than at a restricted level. Generally, superior performance in phases II and III was made by bulls whose performance had been restricted in the previous phase. Bulls started on pasture, supplemented with 1 kg concentrate daily, then fed corn silage, supplemented with 500 g soybean meal head−1day−1 in phase II, gained between 920 and 960 g daily over the entire study and this performance was comparable to bulls started on grass-legume silage provided with a concentrate supplemented ad libitum in phase I, regardless of treatment applied with corn silage in phases II or III. Key words: Young bulls, pasture, grass-legume silage, corn silage, soybean meal, barley