Sixty-three cycling gilts were assigned randomly to be started on treatment on Day 13 of the oestrous cycle. Treatments consisted of the following—0, 50 and 150 mg of a dithiocarbamoylhydrazine (ICI 33828) and 0, 1000 and 2000 mg of iodinated casein (Protamone) in all combinations administered in 1 ·82 kg of feed per day for 10 days.
Iodinated casein significantly reduced gain in body weight while ICI 33828 had no significant effect. Only ICI 33828 significantly reduced feed consumption. Both iodinated casein and ICI 33828 at the higher doses significantly lengthened the interval from withdrawal to oestrus.
Iodinated casein, a hyperthyroid compound, failed to overcome the apparent hypothyroid effect of ICI 33828 on reproduction in the gilt under the conditions of this experiment.