The effect of certain dietary regimes on growth pattern and performance of young Friesian bulls fattened for beef

Abstract

SUMMARYTwenty-four Friesian bull calves purchased at 10 weeks old were reared in three groups to slaughter at 420 kg live weight. One group (BB) was fed on a barley-concentrate diet to grow rapidly at 1·41 kg/day, a second (GG) was fed on dried grass cubes to grow slowly at 0·97 kg/day and the other (BG) was fed to grow rapidly to a live weight of 250 kg and thereafter at a slow rate, overall 1–20 kg/day.Efficiency of food conversion, energetic efficiency and efficiency of dissectible muscle production were best for BB animals, followed by BG and then GG. Changes in carcass composition mainly resulted from differential fat deposition, and bone/ muscle development was allometric in relation to fat-free empty body mass. The development of certain characteristics, the head, depth of forequarter, pelvic length and tibia length followed a time scale and may have reflected the priority for nutrients of some entire male characteristics irrespective of body size.In addition to being most efficient, the fastest growing bulls yielded carcasses with sufficient fat deposition to meet grading requirements, whereas both the slower growing groups of bulls were penalized in this respect.