450 Late-Breaking: Effects of bedding on feedlot receiving phase growth performance in beef steers during the winter in eastern South Dakota

Two-hundred and forty English × Continental beef steers (initial BW=365 kg [SD 22.5]) were used in a randomized complete block design to evaluate the effects of bedding application during a 36 d feedlot receiving phase on growth performance and efficiency during winter. Steers were allotted to 30 pens (n = 8 steers/pen) at the Ruminant Nutrition Center in Brookings, SD and pens were assigned to 1 of 2 treatments: 1) No bedding applied (NO) or 2) 1.8 kg (as-is basis) of wheat straw bedding/steer/d (BED). Due to the logistics of acquiring, weighing, and timely feeding of steers, the first 9 pen replicates began on test 14 d prior (begin: January 15, 2019 and end: February 20, 2019) to the last 6 pen replicates (begin: January 29, 2019 and end: March 6, 2019). Pen was the experimental unit; an α of 0.05 determined significance. Daily ambient temperature (n = 50) averaged -14.7°C [SD 5.63] and wind-chill (n = 50) averaged -17.7°C [SD 6.40]. Initial BW (365 vs. 365 ± 0.5 kg) and dry matter intake (8.19 vs. 8.22 ± 0.047 kg) did not differ (P ≥ 0.57) between NO and BED. End BW was greater for BED (P = 0.01; 419 vs. 402 ± 1.09 kg) compared to NO. Steers from BED had increased average daily gain (P = 0.01) by 48.0% and gain:feed (P = 0.01) by 49.2% over NO. Using tabular ingredient energy values and observed steer performance shrunk 4%, relative adjustments to metabolic rate were calculated. Estimated metabolic rate was elevated (P = 0.01) for NO (0.146 vs. 0.104 ± 0.0032 Mcal/BW0.75, kg). Bedding improves feedlot receiving phase growth and efficiency in eastern South Dakota during the winter. Under the environmental conditions of this experiment, steers have a 40.4% increased metabolic rate when bedding is not used and steers in bedded pens had a 35.1% increase in metabolic rate compared to (0.077 Mcal/BW0.75, kg).