Performance and carcass characteristics of beef cattle fed diets containing silage from intercropped barley and annual ryegrass

A feeding trial was conducted to compare intercropped barley/annual ryegrass silage (B/RS) and barley silage (BS) on average daily gain (ADG), dry matter intake (DMI) and carcass characteristics of beef steers in a randomized complete block design experiment. Both B/RS and BS were prepared in plastic tube silos, ensiled for 168 days and then used in a feeding trial. Steers (n=120) were housed in individual pens and fed a backgrounding diet containing 350 g steam-rolled barley grain (SBG) and 600 g kg−1 B/RS or 600 g kg−1 BS and 50 g kg−1 supplement until they weighed 445 kg, after which they were adapted to a finishing diet consisting of 860 g SBG and 100 g kg−1 B/RS or 100 g kg−1 BS and 40 g kg−1 supplement. Steer weight and back-fat depth (determined by ultra-sonography) were measured every 3 weeks. Steers were slaughtered when back-fat depth was greater than 7 mm and carcass data were obtained. Content of ADF in B/RS was lower (P<0.05) than in BS, while protein content of the silages was similar. During backgrounding, ADG and DMI of steers fed B/RS (1.43, 8.5 kg per day) were higher (P<0.05) than those fed BS (1.31, 8.0 kg per day) and feed conversion efficiency were similar between two groups of steers. Acetic:propionic ratio of rumen fluid from steers fed either B/RS or BS-based diets in the backgrounding trial were similar. Steers fed B/RS and BS diets had similar ADG, DMI and feed conversion efficiency in the finishing trial. Carcass weights of steers fed B/RS diet were higher (P<0.05) than steers fed BS diet (321.5 kg versus 316.5 kg), but other variables were similar. The total dry matter yield of the intercropped barley/ryegrass was higher (57.6%) than the yield of barley.