Blood biochemistry, thyroid hormones, and performance in broilers with ascites caused by caffeine.

Previously, we demonstrated that caffeine, a natural alkaloid, stimulates increased incidences of pulmonary hypertension syndrome (ascites) in broilers. The present study was designed to evaluate the ergogenic effects of caffeine on broiler performance and blood parameters. One-hundred-and-ninety-two Ross 308 male broiler chicks were randomly assigned at one d of age to 16 pens with 4 treatment groups. On d 3, the drinking water was supplemented with caffeine at levels of zero, 12.5, 25, and 50 mg/kg BW/day. Caffeine supplementation linearly improved (P < 0.01) body weight gain (BWG) and the feed conversion ratio (FCR); however, feed intake was not affected by caffeine (P > 0.05). On d 28, increasing caffeine supplementation caused linear reductions in plasma albumin, total protein, globulin, and triglyceride concentrations, and caffeine supplementation increased plasma uric acid concentrations (P < 0.05). On d 42, caffeine did not consistently affect plasma albumin, globulin, triglyceride, total protein, uric acid, or urea concentrations (P > 0.05), whereas plasma glucose concentrations increased linearly with increasing caffeine levels (P < 0.05). Plasma T4 concentrations were not affected by caffeine (P > 0.05), but plasma T3 concentrations were reduced by caffeine supplementation on d 28 and 42 (P < 0.05). The T3:T4 ratios also were reduced by caffeine supplementation on d 42. Skin temperature was not influenced by caffeine supplementation (P > 0.05). There was a negative correlation between thyroid hormone concentrations and BW on d 42 (P < 0.05). It can be concluded that caffeine supplementation at the levels of 12.5 to 25 mg/kg BW/day increased BWG, decreased FCR and T3, and significantly altered blood biochemistry parameters.