Influence of different ratios of corn and corn silage, housing systems and seasons on the performance of feedlot steers.

Observations on the effects of season, housing and diet were made on 916 steers in three winter and two summer trials. Diets consisted of corn grain and corn silage, in balanced rations, fed ad libitum with energy ratios of 25:75 (Diet 1), 55:45 (Diet 2) and 85:15 (Diet 3). There were three types of housing systems: outside lots without access to overhead shelter (NS), outside lots with access to overhead shelter (OS) and an open-front confinement building (C). Average ambient temperatures and precipitation for winter and summer trials were -1.0 and 15.3 C and 4.67 and 10.81 cm/mo, respectively. Steers gained more (P less than .05) in summer than in winter. Within housing system, OS and NS steers gained faster and consumed more dry matter (DM) and energy (P less than .05) than C steers; C-fed steers were less (P less than .05) efficient (kg feed DM/kg gain) than OS steers. Steers fed Diet 1 had lower (P less than .05) average daily gain (ADG) than those fed Diets 2 and 3. Steers on Diet 3 consumed less DM (P less than .05) than those on Diets 1 and 2. Estimated metabolizable energy intake (MEI) was significantly less for cattle fed Diet 1 than those fed Diets 2 or 3. Diet 3 was more (P less than .05) efficient than Diet 1. Season x diet (P less than .10) and season x housing (P less than .10) interactions were found for daily DM intake and MEI. This resulted in greater cattle growth rate responses to higher grain diets in summer than in winter and more pronounced adverse effects of confinement rearing in summer than in winter. No evidence was found of other two-way or three-way interactions for any of the performance characteristics studied. These results indicate that in addition to important singular effects of season, housing and diet, important interactions of these factors also exist.