Inclusion of dried citrus pulp in the barley-based supplementary concentrate to beef cattle offered grass silage: Intake, digestibility, feed efficiency, and carcass and meat quality traits

Abstract

Interest in the use of human-inedible by-product feed ingredients as alternatives to cereals in concentrate feedstuffs for beef cattle is increasing. Three experiments were carried out to determine the effects of replacing rolled barley with dried citrus pulp (DCP) in the supplementary concentrate on intake, apparent total-tract digestibility, feed efficiency, carcass characteristics, and meat quality and sensory traits of steers offered perennial ryegrass dominant grass silage. The control concentrates were based on rolled barley (865–910 g/kg fresh weight) and in the treatment concentrates, barley was replaced with DCP. Inclusion levels of DCP (g/kg fresh weight) were; 0, 400 and 800 (Experiment 1); 0, 265, 556 and 803 (Experiment 2), and 0 and 768 (Experiment 3). Concentrates were formulated to have similar concentrations of metabolisable protein and, additionally, to be isoenergetic in Experiments 2 and 3. Concentrate supplementation levels were 4.0, 3.0 and 2.9 kg dry matter (DM) daily, offered over 124, 103 and 91 days, respectively, for Experiments 1, 2 and 3. In Experiment 1, inclusion of DCP in the concentrate supplement had no effect on grass silage DM intake but daily live weight gain was lower and feed conversion ratio was poorer for DCP-800 compared to DCP-0 and DCP-400, which did not differ. Inclusion of DCP had no effect on carcass weight and carcass traits, and no effect on ultimate pH, temperature, drip loss, colour or sensory characteristics of the M. Longissimus muscle. In Experiment 2, there was no effect of DCP inclusion on live weight gain or feed conversion ratio. In Experiment 3, concentrate type had no effect on intake, live weight gain, feed efficiency, carcass weight or carcass traits, but estimated carcass gain was greater for DCP-768 compared to DCP-0. In rumen fluid, pH and the concentrations of lactic acid and total volatile fatty acids did not differ, but the concentration of ammonia, molar proportions of butyrate and valerate were lower, and the molar proportion of acetate was higher, for DCP-768 than DCP-0. Apparent total-tract digestibility of dietary and concentrate DM, crude protein and organic matter was greater for DCP-0 than DCP-768. In conclusion, DCP can be used to partially replace rolled barley in the supplementary concentrate to beef cattle offered grass silage without impairing carcass weight, carcass traits or selected meat quality and sensory attributes, thereby enhancing human-edible food-feed efficiency of beef production.