Effects of Partial and Full Feed Restriction on the Plasma Levels of Thyroid Hormones and Testicular Activity in the Male Air-breathing Catfish, Clarias gariepinus during Different Phases of the Breeding Cycle

The effects of partial and full feed restriction on the plasma levels of thyroxine (T4), triiodothyronine (T3) and
testicular activity were studied in the male air-breathing catfish, Clarias gariepinus. Partial and full feed
restriction for 3 weeks significantly decreased the plasma T4 levels during the progressive and breeding phases,
and decreased the plasma T3 levels only during the breeding phase. However, full feed restriction for 3 weeks
increased plasma T3 levels and T3/T4 ratio during the quiescent, progressive and regressive phases. Histologically,
3 weeks of partial and full feed restriction markedly reduced the testicular activity during the progressive and
breeding phases. These results indicate that partial and full feed restriction adversely affects the thyroid
hormonogenesis and testicular activity in a phase-dependent manner in C. gariepinus.