Long continued oestrogen administration to fowls

Abstract

Long continued administration of a substance (dienoestrol diacetate) having oestrogenic properties as a dietary additive to chickens from hatching over a period of 4½ years resulted in:—(1) an early, transient, hindrance to sexual development in both males and females,(2) a wide range of individual variation in response to the drug, shown i n the degree of feminisation of the plumage in males, and certain characteristics associated with egg laying in the females,(3) shell defects and related early embryonic deaths which could be attributed to an interference by the drug with development and differentiation of the oviduct.The birds were maintained throughout the experiment under two contrasting environments ‘natural’ and ‘constant’. In the former group two birds developed tumours (one a typical adenocarcinoma) while four of the ‘constant’ birds had adenocarcinomata on examination post-mortem. The incidence of the condition was much lower than that encountered in a previous experiment and suggested that the oestrogen employed was not of itself a carcinogenic agent.The primary function of the ovary was apparently unaffected and egg production to normal expected levels in both environments was attained.The disproportionally high number of hens dying with inspissated yolk i n the oviduct and/or free yolk in the abdomen emphasises the possible effect of oestrogen on oviduct development and activity.The danger of increasing the ‘load’ of oestrogens to susceptible individuals destined for breeding stock (and not short term administration of oestrogens for growth and ‘finishing’ of birds for slaughter) is referred to, and also its wider application were natural and synthetic oestrogenic substances in the diet to exceed a non-effective level.