Effects of dietary protein on ruminal fermentation, nitrogen utilization and crude protein maintenance in growing thai-indigenous beef cattle fed rice straw as roughage

Abstract

Six male growing Thai-indigenous beef cattle with Body Weight (BW) of 154±13.18 kg were randomly assigned in replicated 3 x3 Latin square design and fed with differences levels Crude Protein (CP) Total Mixed Ratio (TMR) diets. Crude Protein (CP) levels in diets were 4, 7% and 10% base on Dry Matter (DM), respectively. Dry Matter Intake (DM) increased iinearly (p<0.01) with increasing crude protein concentration. There was not significantly different (p>0.05) digestibility of DM, Organic Matter (OM), Acid Detergent Fiber (ADF) and Neutral Detergent Fiber (NDF). Ruminal ammonia nitrogen (NH3-N) concentration increased (p<0.01) with increasing CP level. Rumen pH, total VFA, acetate, propionate and buryrate were not affected by CP levels (p>0.05). Nitrogen (N) intake, urinary N excretion, N digestibility, N retention (g day-1) and N retention (Percentage of N intake) increased linearly with increasing dietary CP levels (p<0.05) and was affected significantly (p<0.01) by diet of CP levels, respectively. However, the fecal N excretion was not affected (p>0.05) by dietary CP levels. The CP for maintenance requirement in growing Thai-indigenous beef cattle was 3.54 g kg-1 BW 0.75 which was estimated by using linear regression ofN retention and N intake. © Medwell Journals, 2010.