Influence of barley silage:concentrate ratio on rate and efficiency of liveweight gain, diet digestibility and carcass characteristics of beef steers

Abstract

Eighty steers were fed diets with eight ratios of 100:0, 75.1:24.9, 58.3:41.7, 34.4:65.6, 18.9:81.1, 8.0–92.0, 3.7:96.3 or 0:100 barley silage:concentrate on a dry matter (DM) basis. Diets were fed to provide about equal digestible energy (DE) per unit liveweight for 24 wk, then fed to appetite until the steers reached a market weight of about 515 kg. Steers receiving the 100% silage diet were fed for ad libitum intake from week 24 to week 52 (28 wk) and were then fed 100% concentrate diet until they reached market weight. The average daily gain (ADG) of steers fed 100% silage was lower than that of those fed forage and concentrate. Efficiency of DE utilization for liveweight gain increased at a decreasing rate as level of concentrate in the diet increased. Carcass backfat thickness increased with rate of gain. Digestibility of energy, DM, crude protein (CP), and starch exhibited a curvilinear response to increasing levels of concentrate in the diet. The proportion of concentrate in the diet for maximum economic benefit depends on the cost per unit of DE from silage versus that of barley, the efficiency of DE utilization for liveweight gain and time to reach market weight. Key words: Beef cattle, barley, barley silage, forage:concentrate ratio, digestibility