Effect of beef cattle age, gender and barley grain processing method on rate and efficiency of gain and nutrient digestibilities
Rainey, Brian Michael.
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Three experiments were conducted to test the effects of animal age (cows vs. calves) and barley processing method (whole vs. rolled) on rate and efficiency of gain and diet digestibility when barley was fed as a supplement to medium quality grass hay. A fourth experiment was conducted to test the effects of differences in diet composition on ADG and carcass characteristics in early-weaned calves. No age x processing interactions (P > 0.05) were detected for OM, N, ADF or NDF digestibilities. Diet OM and N digestibilities were greater (P < 0.01) when consumed by calves compared to cows, but ADF and NDF digestibilities were similar between ages. A processing method x age interaction was measured (P < 0.05) for starch digestibility. Rolling the barley dramatically improved starch digestibility when fed to cows (71.4% vs. 23.3% for rolled vs. whole). For experiment two, animals fed the hay only diet had similar (P > 0.05) rates and efficiencies of gain as diets supplemented with barley. Barley processing had no effect (P > 0.05) on rate or efficiency of gain for cows or calves. Cows were less efficient than calves (12.6 vs. 7.6) when fed similarly formulated diets. Unlike experiment 1, no differences were measured for digestibility of OM, N, ADF, NDF, or starch due to animal age or grain processing method. For experiment 4, calves fed barley gained faster (1.29 kg.d-1 vs. 0.99 kg.d-1; P = 0.002) and had higher marbling scores (4.44 vs. 3.31 %EEF; P = 0.002) compared to calves fed wheat midds during the first 34 d after weaning. However, gains during the 90 d after weanining were nonsignificant (1.36 vs. 1.24 kg.d-1 for barley and midds respectively). Calculated final live weights and marbling scores after 217 d of consuming a common finishing ration were similar for barley-fed calves compared to wheat midds-fed calves. Results suggest processing of barley may be of greater value for mature cows compared to younger calves, and barley had a greater effect on changing calf body composition than wheat midds. Cost·kg-1 gain was similar for whole vs. rolled barley diets.