Effect of duration of limit feeding on nitrogen and phosphorus metabolism, growth performance, and carcass characteristics of Holstein × Zebu finishing steers

Objectives were to determine effects of the duration of limit feeding on nitrogen (N) and phosphorus (P) metabolism, growth performance, and carcass characteristics of finishing steers. Twenty-five Holstein ... Zebu steers (average initial BW = 319 ± 16.2 kg; age = 19 ± 1.0 mo) were used. Five steers were slaughtered to provide baseline empty BW (EBW) and empty body composition (EBC) at d 0. Remaining steers were randomly allotted to 1 of 4 treatments: ad libitum-fed for 84 d (AL84); limit-fed (LF) for first 28 d (R28); LF for first 42 d (R42); and LF for 84 d (R84). During LF periods, steers fed R28, R42, and R84 were limit-fed to 85% of ad libitum based on AL84 steer DMI. All steers were fed 40% corn silage and 60% concentrate (DM basis) for 84 d. Total excretion of feces and urine were collected during 2 periods: d 25 to 27 (period 1), and d 73 to 75 (period 2). Nitrogen and P intake, urine and fecal excretions, and absorption and retention were quantified. Steers were weighed on d 1, 28, 42, and 84. The DMI, ADG, and G:F were evaluated during: d 1 to 28, d 29 to 42, and d 43 to 84. Individual EBW, EBC, and carcass characteristics were recorded. The DM, N, and P intakes were greater (P0.05) DM, N, and P intakes compared to AL84 steers. Fecal N and urinary P excretions did not differ (P≥0.40) among limit-fed and ad libitum-fed steers in either period. However, greater (P=0.02) fecal P excretions were observed in steers fed for ad libitum intake in period 2. The EBW, EBW gain (EBWG), whole body N retention, and P retention in period 1 and 2 were similar (P>0.05) in steers fed R28 and R42, in relation to AL84 steers. Steers fed R84 had the least (P