Effect of different protein sources on the concentrations of small peptides in the rumen of sheep

The experiment was conducted to determine the effect of different protein sources on concentration of small peptides (Pro-Ala, Val-Val, Pro-Leu, Met-Met) in the rumen fluid of sheep. Four Inner Mongolia Sunite sheep fitted with permanent cannulas were used in a 4 x 4 Latin square design, and fed four different protein sources including soybean meal (SBM), casein (Casein), fish meal (FM) and corn gluten meal (CGM), respectively. The results showed that the concentration of Pro-Ala peaked in Casein, FM, CGM groups at 2 h after feeding, whereas the highest level was measured at 6 h after feeding in SBM group. Val-Val and Pro-Leu production were highest at 6 h after feeding Casein and CGM diets and 4 h after feeding SBM and FM diets, respectively. During 6 h after feeding the accumulative concentration of Pro-Ala (1.74 mg/l) and Pro-Leu (25.78 mg/l) in rumen was highest for the Casein diet. During the total sampling time, the highest amount of accumulated small peptides was measured for Pro-Leu, and lowest amount for Met-Met, which was independent of treatment groups. Experimental results proved that small peptides with N-terminal Pro and a hydrophobic structure could inhibit rumen degradation and may be available for post-ruminal absorption.