Effects of Feed Restriction Duration on Growth Performance, Organ Weight, and Carcass Traits of Finishing Lambs Fed a Concentrate-Based Diet

This study evaluated the effect of limiting feed intake to 92% of ad libitum for 28 or 56 d of a 56 d finishing period on growth performance, carcass characteristics, and visceral organ mass in wethers. Thirty Polypay wethers (initial SBW = 25.6 ± 5.27 kg; 15 pens, 2 lambs/pen) were blocked by body weight and assigned to three treatments: ad libitum intake for 56 d (CON), 92% of ad libitum intake for 28 d and then ad libitum intake for 28 d (28L), or 92% of ad libitum intake for 56 d (56L). Cumulatively, DMI decreased as restriction length increased (p < 0.001), but the final SBW, ADG, and G:F did not differ between treatments (p ≥ 0.11). Hot and cold carcass weights along with carcass muscle and bone masses were lesser in 28L than CON, but 56L did not differ (p ≤ 0.04). Carcass fat mass was greatest in CON and least in 28L (p ≤ 0.04). Relative to EBW, liver mass was greatest in 28L and least in 56L (p = 0.03). Limit feeding for 56 d maintained carcass weight while increasing leanness compared to CON, whereas a 28 d restriction period reduced carcass and muscle mass, possibly due to visceral organ recovery.