GROWTH AND CARCASS CHARACTERISTICS OF LATE-FATTENING STEERS ON DIFFERENT FEEDING SYSTEMS

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Abstract
One hundred Charolais-cross feeder steers (average weight = 280 kg) were allotted to one of five feeding systems: HG, a diet comprising 75% concentrates fed throughout the trial; MG, a diet comprising equal amounts of concentrates and corn silage provided throughout the trial; CS, corn silage fed throughout the trial; CS-HG, corn silage fed to 400 kg liveweight followed by feeding the 75% concentrate diet; and AS-HG, alfalfa silage provided to 400 kg liveweight followed by feeding the 75% concentrate diet. The steers were slaughtered at a constant estimated finish (8 mm fat thickness 11th/12th ribs), in order to grade Canada A1. Grade and carcass characteristics data were collected for all carcasses and a sample of eight carcasses per treatment was selected at random to determine muscle content, fat partitioning and distribution. Average daily rates of gain for steers on HG, MG, CS, CS-HG, and AS-HG were 1.27, 1.25, 0.79, 1.15, and 1.03 kg/day, respectively. The rates of gain for steers on feeding systems HG, MG, and CS declined with time contrary to steers on feeding systems CS-HG and AS-HG, which showed accelerated rates of growth following the backgrounding period. Steers having the highest overall rates of gain had the best feed to gain conversions. Increased rates of gain were related to less time on feed and lighter slaughter weights. Carcass dissection showed no major differences with respect to muscle:bone ratio, wholesale cut distribution, fat partitioning and distribution due to the feeding system employed. Net energy retention for gain, estimated from carcass specific gravity, was much lower than values obtained from NRC. Forage feeding late-fattening steers under 400 kg and subsequent concentrate feeding did not affect major carcass traits. However, late-fattening cattle provided with diets based on large amounts of forages or corn silage may not attain desirable finish at acceptable slaughter weights. Key words: Late-fattening cattle, slaughter weight, carcass, feeding systems, backgrounding