Effect of duration of restricted-feeding on nutrient excretion, animal performance, and carcass characteristics of Holstein × Zebu finishing steers

Restricted-feeding may be a useful management tool available to reduce environmental impact in feedlots. Therefore, the objectives of the present study were to determine the effects of the duration of restricted-feeding on nitrogen (N) and phosphorus (P) excretion, growth performance and carcass characteristics of finishing steers. Twenty-five Holstein × Zebu steers (average initial bodyweight (BW) = 319 ± 16.2 kg; age = 19 ± 1 months) were used. Five steers were slaughtered to provide baseline empty BW (EBW) and empty body composition at Day 0. The remaining steers were randomly allotted to four groups of five steers, which were restricted to 85% ad libitum feed intake for either 0 (R0), 28 (R28), 42 (R42) or 84 (R84) days of an 84-day finishing period. All steers were fed a diet of 40% corn silage and 60% concentrate (DM basis) for 84 days. Total excretion of faeces and urine were collected during two periods: Days 25 to 27 (period 1) and Days 73 to 75 (period 2). The DM intake, average daily gain (ADG) and gain-to-feed ratio (G : F) were evaluated in three blocks, Days 0 to 28, Days 28 to 42 and Days 42 to 84. As expected, DM, N and P intakes were greater (P 0.05) DM, N and P intakes compared with R0 steers. Faecal N and urinary P excretions did not differ (P ≥ 0.40) among restricted and ad libitum-fed steers in either period evaluated. However, greater (P 0.05). Final BW, overall ADG, G : F and carcass characteristics were not affected (P ≥ 0.11) by treatments. Restricted-feeding Holstein × Zebu steers to 85% of ad libitum intake for 84 days in the feedlot reduced DM intake and P excretion, without impairing steer growth performance or carcass characteristics. Nevertheless, it is important to highlight that the small sample size was one limitation of this present experiment.