Abstract: The objective of this study was to evaluate ruminal peptide and ammonia nitrogen concentrations and Crude Protein (CP) degradation in Holstein steers fed diets differing in concentrate to alfalfa hay ratios. Four rumen fistulated Holstein steers (216±27 kg, body weight) with were used. Animals fed 7 kg of Dry Matter (DM) of diets differing in concentrate (155 g CP kg 1 of DM; 30% maize, 34% barley, 8% soybean meal, 5% sugar beet pulp, 10% wheat bran, 12% cottonseed meal, 0.3% CaCo3, 0.5% mineral and vitamin premix, 0.2% salt) to alfalfa hay (155 g CP kg 1 of DM ) ratios as 60:40 (C60:L40), 70:30 (C70:L30), 80:20 (C80:L20) and 90:10 (C90:L10) in a 4�4 Latin square design (28 days of each period). Steers fed the experimental diets as total mixed ration twice daily at 0800 and 2000 h. Ruminal fluid was taken, by suction, via rumen fistula on days 24 to 28 of each period. Then, pH and NH3-N, soluble protein-N and peptide-N concentrations were determined. In addition, in situ CP and DM degradation kinetics of various feeds (alfalfa hay, barley grain, soybean meal and fish meal) were determined. Ruminal pH and ammonia-N concentration were significantly affected by the treatments and sampling time (p< 0.05). Ruminal pH and ammonia-N concentration decreased from 6.48 (C60:L40) and 19.86 (C70:L30) to 5.86 (C90:L10) and 14.81 (C90:L10), respectively, when level of concentrate was increased from 60 to 90% (p< 0.05). Results indicated that the ruminal peptide-N and soluble protein-N concentrations were not significantly influenced by the diets and sampling time. In steers fed a high concentrate:alfalfa hay ratios (C80:L20), ruminal peptide-N concentration was lower than those fed C60:L40 and C70:L30. In general, ruminal soluble protein-N was high in samples taken before feeding, intermediate at 6 h and low at 4 h after feeding. The results showed that the DM and CP degradation parameters of the feeds evaluated in the present experiment are influenced by the diet composition. It was concluded that the extent of ruminal CP degradation was affected by rumen pH.
A.R.Vakili , M. Danesh Mesgaran , A. Heravi Moussavi , R.Valizadeh and M. R. Nassiry , 2007. Ruminal Peptide and Ammonia Nitrogen Concentrations in Holstein Steers Fed Diets Differing in Concentrate to Alfalfa Hay Ratios . Journal of Animal and Veterinary Advances, 6: 392-398.