Solvent-Extracted Rapeseed Oil Meal as a Protein Source for Pigs and Rats: Iii. Blood Serum Protein Bound Iodine, Standard Metabolic Rates, Thyroid Activity, Adrenal and Gonad Weights

Serum protein bound iodine (P.B.I.) levels in rats’ blood were generally not changed by feeding solvent-extracted rapeseed oil meal (R.O.M.) in the diet. Serum P.B.I. levels in pigs’ blood were reduced as the levels of dietary R.O.M. increased. There was a decrease in standard metabolic rate of rats after they had received R.O.M. in replacement for 50 or 100 per cent of the soybean oil meal in the diet (7.8 to 15.6 per cent R.O.M. in the total diet) for a 2-week period.The thyroid glands of rats receiving high levels of dietary R.O.M. for 4 weeks were increased in weight 52 to 105 per cent over those receiving no R.O.M. Moderate hypertrophy was evident at 3 weeks and there was a regression of the hypertrophy at 9 weeks. Histological examination of the glands showed extreme hyperplasia and almost complete lack of colloid in the follicles after 4 weeks on diets containing R.O.M. but a return to more normal activity after 9 weeks. Pigs at market weight of 200 pounds had only limited, but significant, thyroid hypertrophy when fed the same levels of R.O.M. as were fed to the rats.Adrenal and gonad weights did not differ for rats or pigs fed varying levels of R.O.M. The ratio of thyroid weight to body weight was higher for female than for castrate male pigs. The ratio of adrenal weight to body weight was higher for female than for male rats.