なたね油粕と乾燥甲状腺剤との併用がひなの発育および甲状腺に及ぼす影響

Abstract

Three feeding experiments have conducted in order to examine the interrelationship of growth depressing factor and goitrogenic factor in rapeseed oil meal. Day old White Leghorn female chicks were divided into six or eight lots of 25 each. One lot was fed on soybean oil meal diet as a control and other lots were fed on 15% rapeseed oil meal diet with various levels of dried thyroid powder (Thyradin). At the termination of eight or ten weeks feeding period, three chickens representing each lot were killed for thyroid examination.Feeding of rapeseed oil meal diet resulted in an obvious enlargement and marked histological changes of thyroid gland. Degree of enlargement of thyroid was not the same in three experiments and was most severe in Experiment III and was slightest in Experiment I. But thyroid of chickens fed on rapeseed oil meal diet containing 10mg% Thyradin were normal or nearly normal on both size and histological feature in all experiments.Body weight gain was depressed by feeding of rapeseed oil meal diet. Degree of depression was most severe in Experiment III and slightest in Experiment I, which was in parallel with the tendency of enlargement of thyroid. The addition of Thyradin on it resulted in an increase of gain in Experiment I and II, but it was not found any apparent effect of Thyradin in Experiment III.Feed consumption did not change by feeding of rapeseed oil meal diet in Experiment I and it decreased considerably in Experiment II and III. The addition of Thyradin on it showed an increase of feed consumption in Experiment I and II but did not show any apparent effect in Experiment III.Feed efficiency was depressed by feeding rapeseed oil meal diet on almost same degree in three experiments and it was not affected by the addition of Thyradin.The results of these three experiments suggested that it should be taken into account not only body weight gain but also feed consumption and feed efficiency in considering the effects of rapeseed oil meal on growth of chickens. And it was also guessed that in the rapeseed oil meal, the factors which affected thyroid weight and feed consumption in chickens might be identical or in close relationships and that the factors which affected thyroid weight and feed efficiency in chickens might be different from each other.