The effect of processing type of straw on degradability, diet digestibility and Holstein bulls performance

The study was conducted to investigate the effect of urea treatment method of wheat straw on degradability، digestibility and the fattening performance of male calves fed treated straw. In a completely randomized experiment with 3 treatments، 18 Holstein bulls (with average body weight 224. 72 ± 20. 45 kg) was assigned to 1 of 3 treatments: 1) 40% normal untreated straw; 2) 40% whole bale treated straw with 5% urea (WSBP); or 3) 40% chopped straw treated with 5% urea (OSBP). The average DM degradability of untreated and treated straw at zero time was 16، 20 and 22%، respectively that were significantly different (p<0. 05) between the treatments. The treatment resulted in a significant increase (p<0. 05) in effective rumen degradability of DM at various outflow rates. The average apparent digestibility of DM was 44. 9، 48. 4 and 48. 8% in treatments 1، 2 and 3 respectively that was not significantly different between treatments. The average daily gain (698، 881 and 882 g/d، respectively) and daily DMI (8. 8، 10. 2 and 10 kg/d، respectively) were significantly (p<0. 05) higher for WSBP and OSBP compared with un-treated straw diet. Further، the required time to achieve 200 kg weight gain reduced. In general، considering the similar results of treating straw on the diet digestibility and animals performance، and being easy of whole bale straw treating، this method is recommended for farmers.