Mechanism Research Of Guanidinoacetic Acid And Betaine On Lipid Metabolism And Protein Metabolism In Bulls

Guanidineacetic acid(GAA)is a precursor of creatine,which is the energy reserve of tissues and cells.Betaine(BT)provides methyl groups in the conversion of GAA to creatine.This study evaluated the influences of GAA or/and BT addition on growth performance,nutrient digestion,ruminal fermentation as well as lipid and protein metabolism in bulls.Forty-four Angus bulls(331 ± 13.6 days of age,433 ± 9.7 kg of body weight [BW])were blocked by body weight and then randomly assigned to one of four groups in a 2 × 2 factorial design.Betaine of 0 or 0.6 g/kg dry matter(DM)was added to diets containing 0 or 0.6 g/kg DM GAA,respectively.The experimental period was 80 days including 20 days of adaptation and 60 days of data and sample collection.(1)Effects of GAA or/and BT addition on growth performance,nutrient digestion,rumen fermentation and blood indexes in bulls.The interaction between GAA and BT was significant for 60 day body weight,average daily gain(ADG),feed efficiency(FE),the rumen numbers of Ruminococcus flavefaciens and Fibrobacter succinogenes and blood creatine content.Supplementary GAA or BT did not influence DM intake but increased apparent digestibility of DM,organic matter(OM),crude protein(CP)and acid detergent fibre(ADF).Digestibility of neutral detergent fibre(NDF)was increased by GAA inclusion but was unaltered with BT provision.Ruminal p H reduced but total volatile fatty acids and ammonia nitrogen elevated with inclusion of GAA or BT.Rumen short chain fatty acids percentages and fermentation pattern were not influenced by GAA.Dietary inclusion of BT increased molar proportions of acetate,valerate,isobutyrate and isovalerate as well as the ratio of acetate to propionate.Addition of GAA or BT increased activities of cellobiase,xylanase,α-amylase and protease and populations of total bacteria,cellulolytic bacteria and Ruminobacter amylophilus but did not affect Prevotella ruminicola.Addition of BT increased carboxymethyl-cellulase and pectinase activities and total fungi population.Serum contents of glucose,folate,arginine and methionine were unchanged but total protein increased with GAA or BT provision.Blood homocysteine content was unaffected by GAA but decreased with BT supplementation.(2)Effects of GAA or/and BT addition on fatty acid and amino acid composition of longissimus dorsi in bullsThe interaction between GAA and BT was not significant for fatty acid and amino acid composition in longissimus dorsi.Supplementary GAA did not influence fatty acid composition in longissimus dorsi but increased the content of arginine.Supplementary BT did not influence amino acid composition in longissimus dorsi but increased the content of C12:0 fatty acid.(3)Effects of GAA or/and BT addition on the metabolisms of lipid and protein in the longissimus dorsi of bullsGAA supplementation upregulated the expression of IRS2 and EHHADH which are according to the degradation of fatty acid,and also upregulated the expression of PPP2R2 C,UBE2D4 and RPS6KA1 which were according to the synthesis and metabolism of protein,but downregulated the expression of NOS3 which regulated the synthesis and metabolism of arginine.Supplemented with BT upregulated the expression of GLA which involved in the degradation of fatty acid but downregulated the expression of FADS1 which was a participant in lipid synthesis.Supplementary GAA and BT upregulated the expression of CPT1 B which regulated degradation of fatty acid,and upregulated the expression of SDS which promoted the synthesis and transformation of amino acid,but downregulated the expression of FADS1 and FADS2 which referred to lipid synthesis.(4)Effects of GAA or/and BT addition on lipid metabolism and protein metabolism in bull liver based on transcriptomeGAA supplementation downregulated the expression of CYP2E1 which was related with lipid deposition but upregulated the expression of PRSS2,CRYAB and SHMT2 which were according to the synthesis and metabolism of protein.Supplemented with BT downregulated the expression of TNC but upregulated the expression of GST,which were inhibited protein synthesis.Supplementary GAA and BT downregulated the expression of ELOVL2 and CYP8B1,which were according to the synthesis of fatty acid,upregulated the expression of SDS,GST and GPX3,which were according to the synthesis of protein.The data showed that 0.6 g/kg DM GAA or 0.6 g/kg DM BT addition improved growth performance and FE but supplementing GAA and BT together did not further increase the performance of bulls when compared with GAA or BT inclusion alone.The addition of 0.6 g/kg DM GAA can improve the content of arginine,and upregulated the expression of genes according to fatty acid degradation and protein synthesis in muscle,but downregulated the expression of genes according to lipid deposition,upregulated the expression of genes according to protein synthesis in liver.The addition of 0.6 g/kg DM BT can improve the content of C12:0,upregulated the expression of genes according to fatty acid decomposition,but downregulated the expression of genes according to lipid synthesis in muscle and protein synthesis in liver.In addition,0.6 g/kg DM GAA and 0.6 g/kg DM BT downregulated the expression of genes related to lipid synthesis and upregulated the expression of genes related to fatty acid decomposition and protein synthesis in muscle.The expression of genes related to fatty acid synthesis and liver injury was downregulated,and the expression of genes related to amino acid metabolism was upregulated.