Furosemide reduces the incidence of pulmonary hypertension syndrome (ascites) in broilers exposed to cool environmental temperatures.

The incidence of pulmonary hypertension syndrome (PHS; ascites) was evaluated in two experiments using broiler breeder male by-product chicks exposed after 3 wk of age to cool environmental temperatures (10 to 15 C). In Experiment 1, 3- to 6-wk-old birds were fed a grower diet to which 0 (Control), .001, .005, .010, or .015% furosemide had been added. All groups in Experiment 1 were fed a finisher ration containing no furosemide during Weeks 7 to 8. In Experiment 2, the Control group received no furosemide, a second group received .015% furosemide during the grower phase only (Weeks 3 to 6), and the third group received .015% furosemide during the grower and finisher phases (Weeks 3 to 8). Cumulative PHS mortality was significantly reduced by furosemide in both experiments. Compared with Controls, birds fed .015% furosemide did not have lower (P = .077) final body weights in Experiment 1 but did have significantly lower final body weights in Experiment 2. Lower levels of furosemide significantly reduced PHS mortality without reducing body weights. Furosemide did not improve feed conversion in either experiment. Neither body weight on Day 1 or 21 nor net Day 1 to 21 weight gain were predictive of susceptibility to PHS during the subsequent grower and finisher intervals in either experiment. On Day 55 of Experiment 2, large healthy birds fed .015% furosemide had significantly lower right:total ventricular weight ratios than control birds, indicating that furosemide reduced right ventricular hypertrophy, presumably by reducing pulmonary arterial pressure.