The influence of slaughter weight and level of feeding on growth rate, feed conversion and carcass composition of bulls

Andersen, H.R.

Livestock Production Science 2(4): 341-355

1975


ISSN/ISBN: 0301-6226
DOI: 10.1016/0301-6226(75)90118-9
Accession: 000579942

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Abstract
Male Red Danish calves, average age 73 days and weight 95 kg, in 28 groups of 6, were tested with 7 slaughter weights, 180, 240, 300, 360, 420, 480 and 540 kg, and 4 feeding intensities: freely (A) or with 85% (B), 70% (C) or 55% (D) of the average intake to appetite in Scandinavian feed units. The calves were given the same weight of hay and varying amounts of skimmed milk concentrates and molassed beet pulp, according to feeding intensity. Protein amount was the same in each diet. Maximum daily gain occurred at 275 kg at all feeding intensities. Dressing percentage increased with increasing slaughter weight at the 3 higher feeding intensities, but there was no increase at the lowest; it also increased with increasing amounts of feed. With feeding to appetite the maximum daily gain in bone occurred before 200 kg, in lean at 275 kg and in fat at 480 kg. Lean:bone ratio increased with increasing slaughter weight. As feeding intensity was reduced, the decrease in daily gain of fat was greater than that of lean and bone, and the differences increased with increasing slaughter weight. Maximum daily gains of fat at the 4 feeding intensities were at 480, 450, 375 and 300 kg liveweight, respectively. At low slaughter weights, lean:bone ratio was higher on free than on restricted feeding, but the differences between feeding intensities decreased with increasing slaughter weight, so that the lean:bone ratio depended on both slaughter weight and feeding intensity. The best feed conversion rate was at 85% of feeding to appetite. At lower slaughter weights carcass composition was little affected by feeding intensity, but at heavier weights, as feeding intensities decreased, relative weights of lean and bone increased and of fat decreased. Relative weight of forerib + shoulder + neck and of flank + brisket + flat ribs + foreshank increased with increasing slaughter weight, and the relative weight of the pistol cut decreased. Relative weight of flank + brisket + flat ribs + foreshank rose with increased feeding intensity. The muscles in the distal part of the limbs developed earliest and those in the neck and dorsal part of the shoulder latest. At higher feeding intensities muscles in flank and brisket showed a relative increase, whilst the relative muscle weight of neck decreased.