Steam-Flaked Corn in Feedlot Lambs: Growth Performance, Dietary Energetics, Visceral Fat Deposition, and Carcass Characteristics

Limited empirical evidence is available validating the energy value assigned to steam-flaked corn (SFC) for small ruminants in current NRC feeding standards. Therefore, the objective of this study was to evaluate the effects of corn processing, including steam-flaking, on growth performance, dietary energetics, visceral fat deposition, and carcass characteristics of finishing lambs. Forty-eight Dorper × Katahdin ram lambs (42.0 ± 0.27 kg initial body weight) were assigned to one of four treatments (n = 12 per treatment) and fed high-concentrate diets for 45 d containing 50% yellow corn grain. Treatments differed only in the form of corn presentation: whole corn (WC), cracked corn (CC), ground corn (GC), or SFC. Cracked corn was produced using a roller mill without a sieve (mean particle size 4 to 6 mm), whereas ground corn was processed through a 3 mm sieve (mean particle size 1 to 2 mm). For SFC, WC was steamed for 20 min at approximately 102 °C before rolling, and flake density was adjusted to 0.36 kg/L by roller tension. Dry matter intake was 10.1% greater in SFC than in WC (p = 0.020), whereas CC and GC showed intermediate responses. Final body weight (+4.7%), average daily gain (+30.8%), and observed dietary net energy for maintenance (NEm; +10.4%) were greater in SFC than in GC (p < 0.05), whereas WC and CC showed intermediate responses. Gain-to-feed ratio was greater in SFC than in GC and CC (p = 0.028), representing increases of 24.6% and 18.2%, respectively. Empty body weight and visceral fat deposition were also affected by treatment (p < 0.05), with greater visceral fat deposition in SFC and CC than in GC, whereas WC showed intermediate responses. Steam-flaked corn increased longissimus lumborum muscle area by 17.7% relative to GC (p = 0.048) and increased perirenal fat deposition relative to WC, CC, and GC (p = 0.048). However, most carcass characteristics and meat quality variables were not affected during the 45 d experimental period (p > 0.05). Using a replacement technique, estimated NEm values (Mcal/kg) for CC, GC, and SFC were 2.00, 1.88, and 2.24, respectively. The NEm value for SFC was in close agreement (2.24 vs. 2.30 Mcal/kg) with current feeding standards, whereas dry-processed corn showed lower estimated NEm values (p = 0.025), representing reductions of 9% and 17% for CC and GC, respectively. In conclusion, SFC improved growth performance and dietary energy utilization relative to GC, while producing limited effects on carcass-related responses under the conditions of this 45 d study.