The use of urea treated wheat straw in complete feed blocks and determining its effect on fattening performance of male calves

The aim of this study was to investigate the effect of urea treated baled wheat straw on fattening performance of male calves. The bales of wheat straw were treated with urea solution to contain 45% water and 4.5 % urea and were kept under plastic sheet for one month. Then the plastic was removed and samples of treated straw were taken for chemical analysis and in vitro studies. Bio-availability of the straws to rumen microbes was investigated using in vitro Gas Production and Nylon Bag Techniques. Effect of treated wheat straw on fattening performance of male calves was assessed using 20 heads of Montbeliard male calves in 120 days of fattening period. Animals were divided in two equal groups with 10 animals per each. The diet of both groups contained 70% concentrate, 20% wheat straw and 10% alfalfa with the exception of substitution of treated wheat straw in the diet of treatment group. The content of CP (14.7%) and metabolizable energy (2.40 Mcal/Kg) in both of the diets were equal. Animals were fed twice a day and total feed consumption was recorded daily. Animals were weighed every month after 14h of feed and water deprivation. The results showed that urea treatment decreased NDF (from 85 to 79 percent) and increased ADF content (from 54 to 57 percent) but the differences were not significant. Results of in vitro gas production showed that there was a significant difference (p0.05) in volume of gas production between the untreated and the treated straws. Urea treatment significantly (p0.05) increased the fermentation characteristics of b (from 60.95 to 63.45 percent) and c (from 2.77 to 3.67 percent) and metabolizable energy (from 3.92 to 5.09 Mj/Kg). Significant increase (p0.05) was observed in potential degradation (from 55.78 up to 70.51 percent) and factor of b (from 45.62 up to 54.33 percent) in the treated sample but changes in a and c factors was not significant. Urea treatment did not affect average daily gain and voluntary feed intake but significantly (p0.05) improved feed conversion ratio (from 8.14 to 7.51).