RAPESEED MEAL-GLUCOSINOLATES AND THEIR ANTINUTRITIONAL EFFECTS .5. ANIMAL REPRODUCTION

Although there is no clear evidence to fully describe the mechanism in volved in glucosinolate-related effects on animal reproduction, lowere d fertility in animals fed diets with rapeseed meal (RSM) inclusion is related to glucosinolate content in the diet. Negative effects can re sult both from multidirectional action of glucosinolates, malnutrition of mother due to the thyroid dysfunction, transfer of goitrogenic com pounds to foetus and reduced transfer of nutritive compounds (e.g. iod ine) through the placenta. The degree of reproduction impairment depen ds both on glucosinolate content and on the type of animal. Pregnant f emale rats are sensitive to the presence of glucosinolates, and the fi rst symptoms of fertility impairment and lowering of offspring surviva l rate may occur at low glucosinolate levels, e.g. with diets containi ng low glucosinolate rapeseed meal (LG-RSM). In the case of swine, the limiting value above which sows fertility may be impaired is 4 mu mol of total glucosinolates per g diet and 8 mmol of daily intake of thes e compounds. Opinions on the permitted RSM inclusion in diet for hens are very divergent. Some authors recommend limiting of the RSM inclusi on to 10%, while others did not find any lowering of egg production in hens fed diets with two- or three-fold greater RSM inclusion rates. M ost long-term experiments with heifers, cows and ewes indicate that ru minants tolerate the level of glucosinolate in LG-RSM although feeding this fodder as the only high-protein concentrate component may lead t o impaired fertility.