Protein Sources for Growing Beef Steers Fed with a Diet Based on Corn Silage

This study was conducted to determine the effect of different protein sources in growing beef cattle (25 Aberdeen Angus steers) fed with a corn silage based diet on daily live weight gain (DLWG), dry matter intake (DMI) and feed conversion (FC). Five treatments with different supplies of crude, degradable and metabolizable protein (MP) were used. The treatments were formulated with different protein sources to provide different rate and extents of protein degradation, as follow: a negative control (T0) without protein supplements and below animal requirements, urea (T1), soybean meal (T2), whole cotton seed (T3) and a positive control (T4), which include a mixture of protein sources in excess of animal requirements. The treatments were planned to be isoenergetics (2.63 Mcal ME kg -1 DM) and also T1, T2 and T3 were isoprotein. The data were analyzed statistically by ANOVA. The DGWG were significant different 730, 869, 1006, 946 and 979 g.day-1 for T0, T1, T2, T3, and T4 respectively. The main differences in DMI were obtained in the isoprotein treatments. Exceeding the animal requirements of metabolizable protein to achieve a suitable nitrogenous supply to rumen did not produce any improvement in the animal performance. The supply of nitrogenous in diets based on corn silage improves the DLWG and FC. This effect was higher with the use of true protein