520. The effect of feeding iodinated casein and L-thyroxine upon the health, reproduction and yield of a dual-purpose breed of cattle and a purely dairy breed

Abstract

1. Iodinated casein or L-thyroxine, under the conditions of this experiment, had no adverse effect on the general health of a dual purpose (Red Poll) or a dairy breed (Ayrshire) of cattle.2. The treatment did not increase the total milk or butter-fat production.3. The treated animals did significantly better than the controls in one lactation only and in the following variables only: (a) daily milk yield adjusted for pre-treatment differences—Red Polls, lact. 1; (b) milk yield for duration of treatment adjusted for pre-treatment differences—Red Polls, lact. 1.