EFFECTS OF INCREASING PHOTOPERIOD LENGTH AND ANTICOCCIDIALS ON PERFORMANCE AND HEALTH OF ROASTER CHICKENS

Male broiler chickens were raised to 63 days of age under different lighting and anticoccidial treatments. A constant light program was compared with two interrupted and increasing-light programs in which the photoperiod length was 6 hours between 7 and 14 days of age and then increased gradually to continual light by 49 days of age in the first program and more gradually to 18 hours by 49 days of age in the second program. By 63 days of age, the increasing light programs significantly increased body weight gain and decreased feed/grain ratio, but not significantly. The increasing light programs reduced the incidence of skeletal disease from 7.56% to 2.88% in the first program and to 3.53% in the second program, reduced the incidence of acute death syndrome from 5.94% to 3.317% in the first program and to .65% in the second program, and reduced total mortality from 18.81% to 11.71% in the first program and to 11.38% in the second program. The lighting programs had no effect on the incidence of ascites and right heart failure, the ratio of right ventricular weight to total ventricular weight, the incidence of clinical and subclinical tibial dyschondroplasia, and the number of cartilaginous and osseous nodules in the lungs. The anticoccidials compared were monensin and amprolium/ethopabate, from 0 to 35 days of age. These treatments had no significant direct effects on anv of the parameters measured.