Effects of fenfluramine on body weight, feed intake, and reproductive activities of broiler breeder hens

Inherited overfeeding and fattiness reduce laying performance in broiler br eeder pullets. Although feed restriction is used to compensate for overeati ng and weight gain, this management practice leads to increases in BW varia tion, labor cost, and bird stress. Dietary supplementation of anorectic age nts, such as fenfluramine, may be an alternative. Anak female prebreeder he ns (19 wk of age; n = 10 per group) were treated as follows: daily oral adm inistration of 5, 10, 20, or 40 mg DL-fenfluramine/kg BW or saline with foo d provided for ad libitum intake or administration of saline and feed restr iction. Daily feed intake (FI), laying rate, egg composition, and BW were m easured. At 40 wk of age, adipose tissue and ovary weights were measured. F enfluramine depressed (P < 0.05) BW and FI in a dose-dependent manner, but was less effective in reducing BW than feed restriction. Suppression of FI occurred in two phases: a dynamic phase, coinciding with the rapid growth p hase, during which FI declined progressively and a static phase during whic h FI reached a plateau at a significantly low level until the end of the ex perimental period. Egg production peaked first in saline-treated hens fed f or an libitum intake, but soon after started to decline. In all fenfluramin e-treated and feed-restricted hens, egg production peaked 3 to 4 wk later a nd remained high until the end of the experiment. There were no differences in egg and egg component weights among the experimental groups. Abdominal adipose tissue weight was reduced by fenfluramine in a dose-related manner, and its weight in the group treated with the highest dose was similar to t hat of feed-restricted hens. In these two groups, ovarian weight was signif icantly higher than in the saline-treated hens fed for ad libitum intake, a nd a small, nonsignificant increase in ovary size was observed in groups tr eated with the two median doses of fenfluramine. The effect of fenfluramine on egg production was similar to that of feed restriction, but it was not dose-dependent and, thus, not directly related to its leaning effect. In br oiler breeder hens, oral fenfluramine may be used for chemical feed restric tion and diminution of fattiness without reducing egg production relative t o manually feed-restricted hens.