Optimal level of physically effective neutral detergent fibre in corn stover cracked-corn-based finishing diets on the growth performance, dietary energetics, carcase characteristics, and nutrient digestion in fattening lambs

Two trials were conducted to determine the optimal physically effective neutral detergent fibre (peNDF) level in corn stover-cracked-corn-based finishing diets for feedlot lambs. Concentrations of peNDF (10.0, 12.5, 15.0, and 17.5%) were controlled by replacing cracked corn grain with corn stover. In Trial 1, 32 Rambouillet × Katahdin intact male lambs (body weight [BW], 28.47 ± 2.70 kg) were used in a 63-d feeding trial. Dry matter intake (DMI), average daily gain (ADG), and feed efficiency (GF) were greater at the 12.5% peNDF level (quadratic component, P <.05). The dressing percentage increased linearly (p <.01) as peNDF decreased, but hot carcase weight (HCW) was greater for lambs fed 12.5% peNDF (quadratic effect, p <.01) than those fed different concentrations. In Trial 2, eight ruminally cannulated Pelibuey lambs (29.3 ± 4.2 kg BW) were used in a replicated 4 × 4 Latin square design to evaluate the effects of the treatment on total tract digestion. Ruminal pH, registered at 4-h post-feeding, linearly decreased (p <.01) from 6.70 to 5.77 as the level of peNDF decreased. The digestibility of dry matter (DM), organic matter (OM), and NDF increased linearly (p <.01) as the peNDF level decreased, but the apparent digestible energy (Mcal/kg) showed a quadratic effect (p <.01) with a peNDF of 12.5%. The findings show that the estimated optimal peNDF level in cracked-corn-based finishing diets for lambs in the finishing phase of fattening is approximately 11.5%.HIGHLIGHTS Physically effective NDF levels in finishing rations for lambs were tested; the study provides better understanding of peNDF level on finishing lambs Levels lower than 12.5% and greater than 15.0% peNDF decrease performance and carcase yield Total tract digestion and energy efficiency were maximal at 11.5% peND