Effects Of Rumen-protected Pantothenate Supplement On Ruminal Fermentation,Nutrient Digestion And Metabolism In Beef Cattles Based On Different Dietary Protein Level

The objective of this study was to evaluate the optimum supplementation of rumen protected pantothenate(RPP),reveal the mechanism of pantothenate on promoting the growth of beef cattle based on different protein content diets by determining rumen fermentation,nutrient digestion and metabolism,and blood metabolites.Four ruminally cannulated Blonde d’ Aquitaine and Simmental crossbred first generation growing beef steers with 12 months of age and 268.7± 3.56 kg kg of body weight were assigned to a 4×4 Latin square design experiment.The treatments were:control(without RPP),low RPP(LRPP),medium RPP(MRPP)and high RPP(HRPP)with 0,0.32,0.48 and 0.64 mg RPPA per kg dietary DM based on different protein content diets(high protein diet[HPD],177.2 g/kg of CP;medium protein diet[SPD],156.3 g/kg of CP;low protein diet[LPD],129.8 g/kg of CP),respectively.The results show that:① For growing performance,regardless of the dietary protein levels,average daily gain(ADG)increased with increasing RPP supplementation and was higher for MRPP than for control(P<0.05),while feed conversion rates(FCR)decreased(P<0.05).② For ruminal fermentation,either based on the high or low level protein diet,ruminal pH was not effected by the supplemention of RPP.However,ruminal pH was significantly decreased for MRPP than for control based on SPD(P<0.05).Irrespective of the ration,the total volatile fatty acids was higher for MRPP than for control(P<0.05),but NH3-N was lower for MRPP than for control(P<0.05).In addition,irrespective of the ration,the dry matter(DM),neutral detergent fiber(NDF)and acid detergent fiber(ADF)of corn silage as well as the DM and crude protein(CP)of the mixed concentrate were significantly increased for MRPP than for control(P<0.05).The ruminal cellulolytic bacteria and protein degradation bacteria populations increased with altering the dose of RPP in three diets(P<0.05),and further stimulated the activites of ruminal cellulolytic enzyme.Only in HPD,ruminal protease activity was higher for MRPP than for control(P<0.05).Additionally,no matter what kinds of diet,the urinary excretion of purine derivatives was higher for MRPP and HRPP than for control(P<0.05).③ For nutrient digestion and metabolism,nutrient digestibility,N reteention and N utilization increased with increasing supplementary RPP and were higher for MRPP than for control based on different diets.④ Blood concentrations of glucose,albumin and pantothenic acid as well as activities of 3-hydroxy-3-mthylglutaryl-coenzyme A synthetase(HMGCS),pantothenate kinase(PANK),acetyl CoA and acyl carrier protein(ACP)increased with increasing RPP supplementation and was higher for HRPP than for control(P<0.05)in all different diets.Blood activities of glutamic-pyruvic transaminase(GPT)and glutamic-oxaloacetic transaminase(GOT)were increased with with increasing RPP supplementation in HPD and SPD diet,and were greater for MRPP than for control(P<0.05),but no significant difference in LPD diet.In conclusion,rumen microflora was improved,digestibility of dietary nutrient and production performance of growing beef cattle coule be improved by the supplementary pantothenate at 0.48 and 0.64 mg RPPA per kg dietary DM rather than control group and 0.32 mg RPPA per kg dietary DM in different protein content diets.However,the difference between MRPP and HRPP is not significant.The results indicated that the optimum dose of RPP is 0.48 mg RPPA per kg dietary DM based on different protein content diets.