293 Effects of restricted feeding on enteric methane production and energy and nitrogen balance in growing steers.

Abstract Dry matter intake (DMI) is a strong predictor of enteric methane production in beef cattle. Limit feeding is a management strategy that can increase gain efficiency in growing and finishing beef cattle. We evaluated the effects of restricted feed intake on energy balance using 7 beef × dairy steers (initial BW = 306 ± 18.5 kg) in a repeated Latin square design with 4 periods. Treatments included feed offered to slick bunk management to target no residual feed at 0730 h (100R) and 4, 8, and 12 % restriction of slick bunk management (96R, 92R, and 88R, respectively). Each experimental period consisted of a 14-d diet adaptation, 7 d of total fecal and urine collections, and a 24-h gas exchange collection using indirect respiration calorimeter headboxes. Dry matter (DM) intake, gross energy (GE) intake, and apparent DM digestibility did not differ among treatments (P ≥ 0.71). Lack of differences in intakes of DM and GE resulted from restrictions being applied within periods of the Latin square and occasional feed refusals on a given day within periods. Fecal energy loss, digestible energy (DE), and urinary energy loss did not differ among treatments (P ≥ 0.55). Methane energy loss and methane as a proportion of GE intake did not differ among treatments (P ≥ 0.81). Metabolizable energy (ME), ME as a proportion of GE intake, and ME as a proportion of DE did not differ among treatments (P ≥ 0.60). Heat production (HP) and HP as a proportion of GE intake did not differ among treatments (P ≥ 0.87). Recovered energy (RE) and RE as a proportion of GE intake was not different among treatments (P ≥ 0.95). Nitrogen intake and apparent nitrogen digestibility did not differ among treatments (P ≥ 0.67). Fecal and urinary N excretion and fecal and urinary N excretion as a proportion of total N intake did not differ among treatments (P ≥ 0.30). Therefore, retained N and retained N as a proportion of N intake did not differ among treatments (P ≥ 0.47). Overall, no differences in energy or N balance were detected, likely because of the lack of differences in DMI.