1645 WS Effects of capsaicin source on blood capsaicin, glucose and insulin concentrations, rumen fermentation and nitrogen balance of sheep

This study evaluated the bioavailability of ruminally-protected capsaicin, and potential effects on rumen microbial fermentation, diet digestibility, and N retention of sheep. Twenty-one wether lambs (36.1 ± 1.0 kg BW) were used in 2 experimental periods (19 d each) based on BW (9 and 12 lambs in period 1 and 2, respectively). From d 1 to 7 of each period, lambs were adapted to indoor individual pens, and then moved to metabolism crates from d 8 to 19. Lambs were fed twice daily alfalfa hay and 1 of 3 supplements containing no capsaicin (CON), unprotected capsaicin (DCAP), or ruminally-protected capsaicin (RPCAP). On d 14 and 19, blood samples were collected at 0, 0.5, 1, 2, 4, 8, and 12 h, and on d 19 rumen fluid samples were collected 4 h after supplement delivery. Feces and urine were collected once daily for 5 d. The experiment was a randomized complete block, and the model included treatment, h, and treatment × h. Capsaicin was not detected in serum of lambs, and no treatment × h interactions (P ≥ 0.06) occurred for plasma glucose or insulin on d 14 or 19. Total VFA concentrations were lowest for DCAP, intermediate for RPCAP, and greatest for CON (P = 0.05). Acetate proportions (mol/100 mol) tended to be lower (P = 0.06) for DCAP than CON and RPCAP. Fecal excretions of DM, OM, NDF, and ADF were lower (P < 0.01), and DM, OM, NDF, and ADF digestibility (% of intake) were greater (P < 0.01) for lambs fed DCAP than CON and RPCAP. Nitrogen intake, fecal and urinary N, N digestibility, and N retention were not affected (P ≥ 0.15) by treatments. Greater differences in rumen VFA concentrations between DCAP and CON than RPCAP and CON suggest that shifts in microbial fermentation were greater when capsaicin was not ruminally-protected in a prill. Undetectable capsaicin in serum of lambs receiving capsaicin, and minimal effects of RPCAP on N balance indicates the concentration of capsaicin provided may not have entered systemic circulation. This could be due to potential microbial breakdown, inability to be absorbed, or rapid post-absorptive metabolism. Further work is warranted to develop a source of absorbable capsaicin that will withstand degradation in the rumen to allow an increase in blood capsaicin to serve as a potential anti-inflammatory supplement in ruminants.