Lower food intake is a primary cause of reduced growth rate in growing pigs fed rapeseed presscake meal.

Rapeseed presscake meal (15% in the ration) of 0-varieties or a control diet (soybean meal instead of rapeseed presscake meal) was fed without or with thyroxine for 9-10 wk to growing pigs. Pigs fed rapeseed presscake meal developed hyperplastic goiter. Blood serum free thyroxine concentrations in rapeseed presscake meal-fed pigs were depressed, normal in thyroxine-supplemented pigs fed rapeseed presscake meal and above normal in thyroxine-supplemented controls, but serum free triiodothyronine concentrations were comparable in all groups. Feed intake and average daily gain were reduced in pigs fed rapeseed presscake meal, independent of oral thyroxine intake. However, in an additional experiment, in which food intake was comparable because pigs were pair-fed, average daily gain was similar. The data indicate that reduced growth performance of rapeseed presscake meal-fed pigs was primarily the consequence of decreased feed intake and that hypothyroidism was of lesser importance.