GAA, fermentation and nutrient flow
Eight dual-flow continuous culture fermenters were used in 2 periods (7 adaptation and 3 sampling days) to evaluate the effect of guanidinoacetic acid (GAA) on rumen microbial fermentation and nutrient degradability in dairy and beef cattle. The study was conducted as a completely randomized block design. Treatments (n = 4) were arranged in a 2 × 2 factorial, with factors being the type of fermentation conditions: beef (pH between 5.5 and 6.5; diet 10:90 forage:concentrate, 163 g/kg CP and 176 g/kg aNDFom) or dairy (pH between 5.8 and 6.8; diet 50:50 forage:concentrate, 171 g/kg CP and 300 g/kg aNDFom); and GAA: 0 vs. 2 g/l/d. Temperature (38.5ºC), liquid (0.10 h-1) and solid (0.05 h-1) dilution rates were kept constant. Diets (90 g/d DM) were fed in 3 portions/d. Effluent samples were collected from a composite of the 3 sampling days, and bacteria were isolated on the last day of each period from fermenters for microbial composition analysis. Fermenter samples were taken 3 h after the morning feeding of sampling days for microbiome analysis. Fermentation data were analyzed with the PROC MIXED of SAS and the microbiome diversity and composition were carried out using various libraries/packages in R-Studio. Significance was set at P < 0.05. No differences were observed in true OM degradation. Degradation of aNDFom, the proportions of acetate and butyrate, the acetate to propionate ratio, NH3-N concentration, the flow of total and ammonia N, the efficiency of microbial protein synthesis, and alpha and beta bacterial diversity indexes were higher in dairy than in beef. Total VFA and the propionate proportions were higher in beef than in dairy fermentation conditions. The addition of GAA increased NH3-N concentration, and the flow of total and ammonia N. Microbial degradation (g/kg DM) of GAA was higher in dairy (698) than in beef (63) fermentation conditions. Supplementation of GAA did not affect rumen microbial fermentation.
Calsamiglia, Sergio and Temmar, R. and Kihal, A. and Rodríguez-Prado, M. E. and Inhuber, V. K., Evaluation of Guanidinoacetic Acid in Dairy or Beef Fermentation Conditions on Rumen Microbial Fermentation and Nutrient Flow from a Continuous Culture System. SSRN 2023 (in press). DOI: 10.2139/ssrn.4467116