Impacts of bunk management on steer performance and ruminal hydrogen sulfide concentrations in steers fed modified distillers grains with solubles

Abstract

Two experiments were conducted to evaluate the impacts of bunk management on dry matter intake (DMI), growth performance, carcass characteristic, and hydrogen sulfide (H₂S) concentrations in beef steers fed modified distillers grains with solubles (MDGS; DM basis). In Experiment 1, 139 steers (440.4 ± 31.0 kg) were randomly assigned to one of 16 pens with pen randomly assigned to one of two treatments: 1) Control (CON, bunks managed to be devoid of feed prior to feeding), or 2) Over-fed (OVF, bunks managed to have minimum of 2.54 cm of feed remaining each morning) during adaptation. Following adaptation all steers in Experiment 1 were transitioned to CON bunks and followed to finishing. In Experiment 2, 126 steers (445.4 ± 40.63 kg) were randomly assigned to one of 16 pens. Treatments in Experiment 2 were arranged in a 2 × 2 factorial and include the two bunk management strategies utilized in Experiment 1 (OVF or CON) and either 25% MDGS or 50% MDGS (DM basis). Ruminal H₂S was measured via rumenocentesis during dietary adaptation. There were no differences (P ≥ 0.13) observed in either experiment for growth performance due to bunk management. In Experiment 1, OVF steers had greater (P = 0.001) DMI during adaptation; however, overall DMI was not different (P = 0.14) between treatments. In Experiment 2, DMI (d 0 to 104) tended to decrease (P = 0.09) with greater MDGS inclusion. Hot carcass weight, ribeye area, marbling score, and quality grade were not affected (P ≥ 0.48) by either bunk management or MDGS inclusion. In Experiment 2, back fat (1.30 vs. 1.17 ± 0.042 cm) and yield grade (3.2 vs. 3.0 ± 0.11) were greater (P = 0.03) for CON steers compared with OVF but were not affected (P = 0.59) by MDGS inclusion. In Experiment 1, H₂S tended (P = 0.07) to be greater in steers on OVF compared with CON. In Experiment 2, bunk management strategy did not impact (P = 0.82) H₂S concentrations. There was a MDGS inclusion × day interaction for H₂S with steers fed 50% MDGS having greater (P < 0.01) H₂S concentrations compared with steers fed 25% MDGS on d 28 and 35. Bunk management strategy during adaptation did not impact growth performance but did reduce intake in Experiment 1. Yield grade decreased when OVF bunk management was applied throughout Experiment 2. Response of H₂S concentrations in the rumen were variable and likely influenced by inconsistencies in bunk management and resulting DMI during the early portions of the feedlot study.

Keywords: beef cattle; bunk management; hydrogen sulfide; modified distillers grains with solubles.

Figure 1.

Change in ruminal H₂S concentrations (g/m³) caused by divergent bunk management treatments: CON = control, bunks devoid of feed prior to next feeding; OVF = over-fed, bunks containing >2.54 cm of feed at time of next feed delivery. P-Values: bunk management, P = 0.07; day, P < 0.01; bunk management × day, P = 0.30). Superscripts indicate means within a day differ P ≤ 0.05). Concentrations of ruminal H₂S measured via rumenocentesis on H₂S detector tubes (Gastec, Kanawaga, Japan).

Figure 2.

Change in ruminal H₂S concentrations (g/m³) caused by increasing dietary modified distillers grains with solubles (MDGS) inclusion during dietary adaptation to final finishing diet. Treatments were 25MDGS = 25% MDGS DM basis, and 50MDGS = 50% MDGS inclusion DM basis. P-Values: MDGS inclusion, P < 0.01; day, P < 0.01; MDGS × day, P < 0.01). Superscripts indicate differences within day between treatments (P < 0.01). Concentrations of ruminal H₂S measured via rumenocentesis on H₂S detector tubes (Gastec, Kanawaga, Japan).