Low crude protein diets and phase feeding for double-muscled crossbred young bulls and heifers

This study aimed to evaluate the effect of underfeeding dietary crude protein(CP) during the whole or part of the fattening period on growth performance, dry matter intake (DMI), carcass and meat quality traits of crossbred bulls and heifer calves obtained from double- muscled (DBM) BelgianBlue(BB)sires and dairy or dual purpose cows.Twenty-four crossbred BB sired Young bulls and 30 BB sired heifer calves(236 + 27.0 kg BW) were housed in 12 pens with males separated from heifers. They received a control diet (CP14) with 140 g CP/kg DM for the Whole experiment (CPHH) or a low-protein diet (CP10) with 102 g/kg CP/kg DM for the Whole experiments (CPLL) or CP14 for the first 90 days and CP10 for the remaining days (94 days on average) of finishing period till slaughtering (CPHL), which occurred when heifers and bulls reached 485 and 535 kgBW, respectively. Compared to CPHH and CPLL calves,CPHL animals evidenced faster ADG (P<0.05), albeit the magnitude of this effect was limited (on average + 6.3%). During the whole trial no differences among groups were observed for DM intake(8.9 kg/d), gain:feed ratio (0.144), carcass weight (301 kg), carcass yield(589 g/kg BW), SEUROP carcass muscularity (U+) and for most of the meat quality traits. Only meat shear force was increased (P=0.04) by CPLL treatment compared to CPHH and CPHL (+17%). Bulls and heifers differed for growth performance and for many carcass and meat traits, but gender did not interact with dietary treatment for any trait. It was concluded that little benefits would be achieved using CP14 for the entire or part of the fattening period on these crossbreds. Beside, this paper covers a lack of information about quality traits of crossbred heifers and Young bulls obtained from DBM BB sires and dairy and dual purpose dams showing that carcass and meat quality traits of these subjects are comparable or better than those achievable from non-DBM beef breeds cattle.