H. Kohsari - Department of Veterinary, Agriculture Faculty, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran.

Producing high-quality eggs is one of the aspects of rainbow trout breeding. Diets used vary among rainbow trout breeders and are usually not designed to optimize egg production. Although, the reduction of feeding is important due to the reduction of costs of production. The aim of the recent study was to investigate the effect of moderate food restriction on the reproductive performance of female rainbow trout. For this purpose, two feeding strategies were compared during the four months before the second reproduction. Females in the control group were fed ad libitum with a commercial trout diet. In the experimental group, females were fed ۷۵% of ad libitum (restricted feeding). An artificial photoperiod program was carried out in summer to trigger reproduction. At the end of the experiment, the weight of the females in the restricted feeding group was lower than females in the ad libitum group (p=۰.۰۴) whereas gonadosomatic index (GSI) and hatching rate of eggs in the females in the restricted feeding group was significantly higher than females in the ad libitum group. Females in the restricted feeding group produced larger eggs than females in the ad libitum group. They produced a lower number of non-viable eggs compared to the females in the ad libitum group too. The results of the study showed that feed intake of female rainbow trout broodstock can be reduced by up to ۲۵% without having a negative effect on egg production and quality.

Food restriction, Reproductive performance, Rainbow trout