Effects of ammonia-treated maize on growth performance of beef cattle

High-moisture cereal grains are often treated with ammonia to prevent spoilage and for perceived animal performance advantages, but there are few reports on the effects of ammonia treatment of cereal on cattle performance. This study was carried out on 101 Charolais cattle to quantify the effects of feeding ammonia-treated maize on the performance of intensively fattened beef cattle. Animals were assigned to 16 pens in two sheds and all animals in each pen were fed on the same diet for 176 d. The cereal in the diets was either ammonia-treated maize (ATM) or untreated maize diet (UTM), formulated to be approximately isoenergetic and isonitrogenous. Cattle fed ATM had a lower feed conversion ratio (FCR) (6.14 ± 0.39 vs 6.49 ± 0.41 kg DM/kg BW; p = 0.011) and tended to have a higher average daily liveweight gain (ADG) (1.60 ± 0.10 vs 1.54 ± 0.10 kg/d; p = 0.060). The pH of the ruminal fluid at slaughter was higher (p < 0.001) in animals that were fed the ATM diet (6.35 ± 0.69) compared to those fed the UTM diet (5.46 ± 0.33). No differences were found in the concentrations of NH3 or total VFA in ruminal fluid between the two groups. The molar proportion of butyric acid from all VFAs was lower in animals fed ATM than UTM (14.69 ± 3.55% and 18.04 ± 2.97% respectively; p = 0.012), and the molar proportion of propionic acid was higher in the ATM than the UTM groups (22.14 ± 1.54% and 19.54 ± 1.72% respectively; p < 0.001). The ratio of acetic acid to propionic acid was significantly lower in animals fed ATM compared to those fed UTM (ATM vs UTM: 2.64 ± 0.26 vs 2.97 ± 0.29; p = 0.0038). Faecal starch was lower in cattle fed ATM than untreated maize (UTM) (14.73 ± 5.65 vs 18.14 ± 4.27% DM; p < 0.001). The pH of faeces in the ATM group was higher than that in the UTM group (4.75 ± 0.19 vs 4.55 ± 0.19; p < 0.001). In conclusion, ammonia treatment of maize resulted in increased ADG and decreased FCR, with reduced faecal starch concentration, suggesting possible gains in efficiency of starch utilisation