Effects Of Palm Acid And Folic Acid On Growth Performance And Lipid Metabolism Gene Expression In Growing Holstein Dairy Bulls

The objective of this study was to determine the effects of palm acid(PA)and folic acid(FA)on growth performance and lipid metabolism gene expression in growing Holstein dairy bulls.Sixteen Chinese growing Holstein dairy calves with 10 mouths of age and 298.1 ± 3.5 kg of body weight were assigned to one of four groups in a randomized experimental design with a 2(diet of without PA or diet of 3% dry matter [DM] PA)× 2(3.6 mg FA per kg diet DM or 3.6 mg FA as rumen-protected folic acid [RPFA] per kg diet DM)factorial arrangement.The results showed that:(1)PA significantly reduced average daily weight gain(ADG)(P<0.05);RPFA significantly increased ADG,reduced feed conversion ratio(FCR)(P<0.05).(2)PA or RPFA significantly reduced the rumen molar ratio of acetic acid,the ratio of acetic acid to propionic acid,the concentration of ammonia nitrogen,rumen enzyme activity,rumen bacteria quantity and concentration of urinary excretion of purine derivatives(P<0.05).(3)PA significantly reduced nutrient digestibility of DM.(P<0.05);RPFA significantly increased nutrient digestibility of DM.(P<0.05).PA or RPFA significantly reduced urine nitrogen and total excreted nitrogen,and significantly increased the ratio of nitrogen retained to intake nitrogen(P<0.05).(4)PA or RPFA significantly increased the concentrations of serum albumin,total protein,folate,and growth axis hormone,decreased the concentrations of urea nitrogen and homocysteine(P<0.05);PA significantly increased serum concentrations of free fatty acids(NEFA),triglycerides,total cholesterol(TC),high-density lipoprotein(HDL),?-hydroxybutyric acid(BHBA)and acetoacetic acid(ACAC)(P<0.05);RPFA decreased the concentration of NEFA,TC and BHBA and increased the concentration of very low density lipoprotein(VLDL)(P<0.05).(5)PA or RPFA significantly increased the expression of the genes of liver growth axis hormone and receptor and phosphatidylinositol 3 kinase/protein kinase B-mammalian rapamycin target protein(PI3K/AKT-m TOR)(P<0.05);PA significantly increased the expression of the genes of the peroxisomal proliferator-activated receptor ?(PPAR?)pathway and the AMP-activated protein kinase(AMPK)pathway,and significantly decreased the expression of the genes of folate metabolism;RPFA significantly increased the expression of the genes of PPAR? pathway gene and folate metabolism,and significantly decreased the expression of the genes of AMPK pathway(P<0.05).(6)PA significantly reduced the expression of the genes of growth axis hormone and receptor,PPAR? pathway,AMPK pathway,PI3K/AKT-m TOR pathway genes and folate metabolism;RPFA significantly increased the expression of genes of these pathway(P<0.05).(7)The interaction effect between different palm acid level and FA administration mode was observed on growth performance,rumen metabolism,gene expression of lipid metabolism in liver and intramuscular(P<0.05).In conclusion,Dietary supplementation with PA or RPFA increased liver protein synthesis and lipid metabolism gene expression and nitrogen utilization.RPFA can significantly improve the adverse effects caused by the addition of PA,increase the lipid metabolism gene expression of liver and intramuscular,enhance the growth performance in growing Holstein dairy bulls.