The effects of two dietary protein levels and pen bedding in a summer growing and finishing feedlot trial on steer performance, carcass traits, and pen surface temperatures

Abstract Text: A summer grow-finishing feedlot trial evaluated effects of dietary crude protein level and bedding pens, on animal performance, feed efficiency, carcass traits and pen surface temperatures.   One hundred thirty six Angus, fall born (n = 66) and yearling steers (n = 70) were blocked by BW and allotted to 1 of 16 pens.  Fall calves were fed a growing phase diet (GPD) for 56 d before transitioning to the finishing phase diet (FPD).  Yearling steers were marketed after 110 d and fall steers after 96 d on FPD.  Protein treatments were similar in energy (1.10 and 1.21 Mcals/kg NEg; GPD and FPD, respectively) and either 12.2 (Con) or 16.0% CP (HP).  Bedding treatments were corn-stover (BD) or no bedding (NB).  Treatments were arranged in a 2 x 2 factorial with pen as experimental unit.  Both protein and bedding treatments had 4 pens / treatment for GPD and 8 pens / treatment for FPD.  Air and pen surface temperatures were recorded three times daily (morning, noon, and evening) for 3, 28 d periods.  The GPD protein treatments had similar (P ≥ 0.17) ADG (1.89 ± 0.05 kg), DMI (10.8 ± 0.44 kg*hd^-1*d^-1), and G:F (0.15 ± 0.003).  Bedding treatments had similar (P = 0.41) DMI.  The BD treatment had lower (P ≤ 0.05) ADG and G:F compared to NB (1.80 vs. 1.98 kg/d and 0.14 vs. 0.16; ADG and G:F, respectively).  In FPD, neither bedding pens nor protein level had any effect (P ≥ 0.22) on ADG (2.03 ± 0.05 kg/d), DMI (12.9 ± 0.33 kg), G:F (0.16 ±  0.01) or final BW (647.2 ± 20.28 kg).  Carcass traits were similar (P ≥ 0.18) among protein and bedding treatments, except marbling score.  The BD and CON treatments tended (P ≤ 0.10) to have higher marbling scores than NB and HP treatments (510.8 and 513.5 vs. 484.6 and 482.0 ± 23.3, respectively).  Average air and pen surface temperature numerically increased from morning to evening and decreased (P < 0.01) from period 1 to 3, across all readings.  The morning surface temperature was similar (P = 0.41) between the NB and BD (19.8 and 20.5 °C, respectively).  The temperature spread between BD and NB was greater at noon and evening, with NB having higher readings (P < 0.01; 2.3 and 1.7 °C, respectively).  Overall, HP did not significantly impact animal performance.  Bedding pens lowered G:F and ADG in GPD.

"Keywords: " protein, bedding, feedlot