Necrotic enteritis was reproduced in broiler chickens by mixing cultures of Clostridium perfringens in the feed. Mortality due to necrotic enteritis was higher among chickens fed rations based on wheat, rye, barley, and oat groats than among chickens fed corn-based rations. Addition of pentosanase to a wheat-based diet did not affect the level of mortality due to necrotic enteritis. Addition of pectin and guar gum to different rations severely reduced growth rate and eliminated necrotic enteritis from test birds. Addition of glucose to a corn-based diet caused a small increase in mortality due to necrotic enteritis.

Three experiments were conducted to examine the impact of changing photoperiod length on the performance of chicken broilers. Effect of long, constant (23-h) photoperiod length (23H) was compared with treatments where photoperiod increased from 6 to 23 h abruptly after 21 days (6H) or gradually during the experiment (INC). The 6H program was used in all three experiments, whereas the INC treatment was included only in Experiment 3. Differences between total body weight gains of birds in the 6H and 23H treatments were inconsistent and small in the three experiments. In Experiment 3, there were no differences between total body weight gains for INC, 6H, and 23H treatments. Feed-to-gain ratios for 6H broilers were significantly superior to those for birds on the 23H treatment for Days 0 to 21 (all experiments), Days 21 to 42 and Days 0 to 42 (Experiment 2), and inferior for Days 21 to 42 (Experiment 3). The INC treatment was significantly superior to the 23H program for all time periods and to 6H birds for Days 21 to 42 and Days 0 to 42. The 6H treatment significantly reduced the incidence of leg abnormalities in comparison with the 23H program in all experiments; the INC and 6H treatments were equal in incidence in Experiment 3. When data from the three experiments were combined, mortality due to sudden death syndrome and other causes for the 6H treatment was significantly lower than that of the 23H program; values for the 6H and INC treatments were not different in Experiment 3.(ABSTRACT TRUNCATED AT 250 WORDS)

1. Broiler performance and health were compared from 0 to 42 d for lighting programmes consisting of near-continuous light 23L:1D (23L), a lighting programme where photoperiod gradually increased from 6 to 23 h between days 4 and 35 (INC) or an increasing-lighting programme with 1 h of light mid-way through the scotophase (INC + 1). 2. The increasing lighting programmes reduced growth rate and increased gain:food ratio from 0 to 21 d; INC + 1 growth rate was intermediate to the 23 L and INC treatments. From 0 to 42 d there were no differences in growth rate or gain:food ratio among lighting treatments. Males grew faster, ate more food and converted food more efficiently than females. 3. The increasing-lighting programmes (INC and INC + 1) resulted in less skeletal disease than the 23L control. The incidence of sudden death syndrome (SDS) and mortality other than SDS were numerically lower for the increasing lighting treatments. More males died as a result of SDS and were affected by skeletal defects than females. 4. In terms of health, increasing lighting programmes were superior to near-continuous light for broiler chickens.

A study was completed to characterize the electrocardiographic (ECG) patterns of male broiler chickens. Data were collected from 300 commercial broilers. ECG readings were collected from all birds between 12 and 15 days of age and then twice more at 10-day intervals. The measurements. included heart rate and rhythm, QRS complex duration, amplitude and mean electrical axis (MEA), incidence of ascites and incidence of sudden death syndrome (SDS). Eight birds died from SDS and 4 birds died from ascites. Twelve birds were condemned for ascites at the processing plant. The overall population heart rate declined with age. Birds that died of SDS had a higher heart rate, whereas those that developed ascites had a lower heart rate than the remainder of the population. The normal MEA was found to be between 0 degree and 180 degrees. On average 30% of birds showed left or right QRS axis deviation, and this pattern was observed in 14 of the 16 birds that developed ascites. Several types of cardiac arrhythmias were observed, the most common being premature ventricular contractions (PVC). The incidence of PVC increased with age, ranging from 1% at 12-15 days of age to 8.9% at 32-35 days of age. QRS axis deviation was present in 5 SDS birds. It is concluded that some 30% of the broiler flock tested was at risk of developing heart failure or heart-related disease.

The incidence of cripples among broiler chickens kept until 74 days of age was greatest in chickens fed ad libitum and kept in batteries. The incidence was lower in chickens kept in floor pens and was reduced by feed restriction. Crippling was due to long-bone distortion, rupture of the gastrocnemius tendon, and spondylolisthesis. Long-bone distortion was the most common defect and could be divided into valgus and varus deformation. The former was more important in chickens less than 7 weeks of age, and the latter was more important in older chickens. Tibial dyschondroplasia was found in some chickens with long-bone distortion, and the possible significance of this abnormal cartilage as a cause of long-bone distortion is discussed.