Abstract
The present study was performed to evaluate the effects of different concentration of rumen-protected methionine (RPMet) with a low level of crude protein (CP) using rumen simulation technology on many parameters. The experiment was assigned randomly into four treatments: (1) high protein diet (163.39 g/kg CP) without RPMet (HP); (2) low protein diet (146.33 g/kg CP) without RPMet (LP); (3) low protein diet, supplement with low RPMet (RPMet: 0.11 g/kg) (LPLMet); and (4) low protein diet, supplement with high RPMet (RPMet: 0.81 g/kg) (LPHMet), mixed with 20 g basal diet in each fermenter. Based on National Research Council (NRC) (Nutrient requirements of dairy cattle, National Academies Press, Washington, DC, 2001) recommendation for dairy ruminants HP diet was formulated as positive normal control and LP as a negative control. Results demonstrated that CP disappearance was found significantly higher (P < 0.05) in supplement groups compared with HP and found similar (P > 0.05) with LP. However, neutral detergent fiber (NDF) and gross energy (GE) were found a parallel among supplement groups compared to HP and higher than LP. Furthermore, microbial crude protein, total and short chain fatty acids were found similar in LPHMet and HP and found significantly higher than LPLMet and LP. The R. albus population of LPHMet found parallel to HP and pointedly higher than LP in a solid and liquid fraction. Daily production of ammonia nitrogen, total gas, and methane were higher in HP than LP, LPLMet, and LPHMet. Overall, results concluded that values of digestibility, rumen fermentation, microbial crude protein, and R. albus population were similar of LPHMet to that of HP group. However, production of ammonia-N, total gas, and methane volume were significantly higher in the HP group than LPLMet, LPHMet, and LP groups. In conclusion, rumen-protected methionine is a good feed supplement to low dietary protein in the level of 0.81 g/kg.
Highlights
Rumen environment quickly degrades free amino acids (AA) and could not maintain the performance of dairy ruminants
It became a growing objective to reduce crude protein (CP) in animal diets, with the supplementation of rumen-protected limiting amino acids to raise the quantity of metabolizable protein (MP) as it increases AA flow in the small intestine
neutral detergent fiber (NDF) and gross energy (GE) degradation of supplement groups were non-significant to high protein diet without RPMet (HP) positive control, while significantly higher (P < 0.05) to the low protein diet without RPMet (LP) negative control group
Summary
Rumen environment quickly degrades free amino acids (AA) and could not maintain the performance of dairy ruminants. AA and decrease blood urea nitrogen which is valuable for the reproduction and performance of dairy animals (Rhoads et al 2006). Increasing the level of limiting amino acids in the small intestine, resulting in increasing milk volume, protein, fat yields and reduces urine nitrogen (Zhang et al 2013; Abbasi et al 2017). Limiting AA flow methionine in the small intestine is considered the essential element for milk yield and milk protein production (Noftsger et al 2005). It became a growing objective to reduce crude protein (CP) in animal diets, with the supplementation of rumen-protected limiting amino acids to raise the quantity of MP as it increases AA flow in the small intestine. Decrease nitrogen losses, feed cost and global environmental pollution, without adverse impact on animal performance (Sinclair et al 2014; Guyader et al 2016)
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