A comparison between maize and grain sorghum as a concentrate source in fattening diets for beef cattle.
The influence of replacing 0%, 50% and 100% of the maize meal (Pioneer 432) with bird resistant (SSK52) and non-bird resistant (NK 283) grain sorghum, respectively, in a high concentrate diet (80% concentrate and 20% maize silage dry matter) was investigated. The replacement of maize meal with a 50% non-bird resistant + 50% bird resistant grain sorghum mixture in the diet was also investigated. The crude protein content of the diets was approximately 11% on a dry matter basis. Six groups, each consisting of 40 eighteen-month-old Simmentaler steers, were used. All steers were slaughtered after a 105 day finishing period. In a metabolism study each of the six diets was also fed to a group of 4 steers in two replicates. The replacement of maize meal with both types of grain sorghum in the diet resulted in a highly significantly (P ≤0,01) lower apparent digestibility of both dry matter and gross energy. likewise, a significant (P ≤0,05) and highly significant (P ≤0,01) decrease in apparent digestibility of protein occurred when maize meal was replaced with either non-bird resistant or bird resistant grain sorghum, respectively. A higher dry matter intake by steers on the grain sorghum diets resulted in some compensation for the lower digestibility. Nevertheless, an 11% and 50% reduction in efficiency of feed conversion to carcass mass of steers was observed when maize meal was totally replaced by non-bird resistant or bird resistant grain sorghum, respectively. From the results it was concluded that for the successful use of especially bird resistant grain sorghum in finishing diets for cattle the digestible protein content of the diet should probably be corrected.