Effect of ferric ammonium citrate in feedlot diets with varying dried distillers' grains inclusion on ruminal hydrogen sulfide concentrations and steer growth.J Anim Sci. 2016 Sep; 94(9):3894-3901.JA
Angus-cross steers (= 128) were used to examine the effects of supplementing ferric ammonium citrate (FAC; 300 mg ferric Fe/kg DM) to diets of 20, 40, or 60% dried distillers' grains plus solubles (DDGS) on growth performance, liver mineral and ruminal hydrogen sulfide (HS) concentrations, and carcass traits of finishing steers. Steers were blocked by initial BW (436 ± 10.6 kg) into pens of 4 and randomly assigned to 1 of 6 treatments (= 5 or 6 pens per treatment) including a 20, 40, or 60% DDGS inclusion diet with (+) or without (-) 300 mg Fe/kg DM from FAC. Liver biopsies (d -9/-10 and 96) and HS measures (d 0, 7, 14, 21, and 95) were determined from 1 steer/pen. Steers were harvested on d 102 and carcass data were collected. A treatment × month effect (≤ 0.006) was noted for ADG and G:F, in which the 20-FAC ADG and feed efficiency were greater (≤ 0.02) between d 0 to 28 but lesser (≤ 0.04) from d 29 to 56 than that of the 20+FAC steers. Final BW linearly decreased (< 0.01) as DDGS inclusion increased. Final BW tended to be greater (= 0.10) in the 60+FAC steers than in the 60-FAC steers, whereas final BW was not different (≥ 0.32) due to FAC supplementation in the 20 or 40% DDGS diets. A quadratic effect was noted for DMI (= 0.02), where 60% DDGS decreased DMI. Within the 20% DDGS diet FAC+ improved DMI (= 0.03) but had no effect within 40 or 60% DDGS inclusion. Ruminal HS concentrations were not affected (≥ 0.25) by FAC, but increasing DDGS linearly increased (< 0.01) ruminal HS values. Liver Cu was decreased (< 0.01) by FAC across all DDGS inclusions and tended to linearly decrease (= 0.06) with increasing DDGS inclusion, whereas liver Fe, Mn, and Zn were not altered (≥ 0.11) by DDGS inclusion. Liver Zn concentrations tended to be (= 0.08) or were (= 0.03) decreased by FAC supplementation within 20 and 40% DDGS, respectively. Increasing the inclusion of DDGS linearly decreased (= 0.04) HCW and quadratically affected marbling score where the 40% DDGS had the greatest (= 0.02) marbling scores. Supplementation of FAC within 60% DDGS improved (≤ 0.03) HCW and LM area. Marbling scores were greater (≤ 0.04) in 20+FAC and 40+FAC compared with 20-FAC and 40-FAC, respectively. In conclusion, although ruminal HS concentrations were not affected by FAC under the conditions of this study, supplementing FAC to diets containing 60% DDGS improved HCW and LM area, suggesting that FAC may be beneficial when dietary S concentrations exceed 0.5%.