Copper and iodine in pig diets with high glucosinolate rapeseed meal. 3. Treatment of rapeseed meal with copper, and the effect of iodine supplementation on trace element status and some related blood (serum) parameters

Abstract

In a 15-week experiment with 50 growing pigs, 5.5% soya-bean meal (SBM) was replaced by 8% rapeseed meal (RSM) (5.5% glucosinolates in the dry matter) or 8% RSM treated with Cu 2+ (RSM Cu 2+) (glucosinolates not detectable). The RSM diets were given without I supplementation or they were supplemented with 0.0625 to 1 mg I kg −1. The control animals received the SBM diet with 0.125 mg I kg −1 feed. After 4, 10 and 15 weeks, the red blood cell (RBC) count, the haemoglobin (Hb) content, and the haematocrit (Hc) as well as the Cu, Zn, Fe content and the alkaline phosphatase (AP) activity were determined in blood and serum. The Cu, Zn, Fe and Mn content of the liver and the rib was determined in 21 animals of selected groups (SBM diet, RSM or Cu 2+ treated RSM with or without 0.5 mg supplementary I kg −1 diet). The untreated RSM without additional dietary I induced I deficiency. In these hypothyroid pigs the bone and serum Zn content and the serum AP activity were significantly reduced. The Zn and Mn contents of the whole liver were lowered, but its Cu content was at least doubled ( P < 0.05). Owing to the enlargement of liver by RSM antinutritive compounds it is less valid to give the trace element concentration per unit liver weight solely. A reduction of the RBC count, Hb and Hc of the blood occurred only in the case of high glucosinolate RSM feeding without I supplementation. This mild anaemia of I deficient pigs was not accompanied by a changed serum or liver Fe content. In addition to the I effect a reduced glucosinolate load by Cu 2+ treatment of RSM increased the Zn content and the AP activity of the serum significantly. These criteria should be used to evaluate low glucosinolate RSM from new winter varieties.