Rapeseed meal-glucosinolates and their antinutritional effects. Part 5. Animal reproduction

Although there is no clear evidence to fully describe the mechanism involved in glucosinolate-related effects on animal reproduction, lowered fertility in animals fed diets with rapeseed meal (RSM) inclusion is related to glucosinolate content in the diet. Negative effects can result both from multidirectional action of glucosinolates, malnutrition of mother due to the thyroid dysfunction, transfer of goitrogenic compounds to foetus and reduced transfer of nutritive compounds (e.g. iodine) through the placenta. The degree of reproduction impairment depends both on glucosinolate content and on the type of animal. Pregnant female rats are sensitive to the presence of glucosinolates, and the first symptoms of fertility impairment and lowering of offspring survival rate may occur at low glucosinolate levels, e.g. with diets containing low glucosinolate rapeseed meal (LG-RSM). In the case of swine, the limiting value above which sows fertility may be impaired is 4 mumol of total glucosinolates per g diet and 8 mmol of daily intake of these compounds. Opinions on the permitted RSM inclusion in diet for hens are very divergent. Some authors recommend limiting of the RSM inclusion to 10%, while others did not find any lowering of egg production in hens fed with two- or three-fold greater RSM inclusion rates. Most long-term experiments with heifers, cows and ewes indicate that ruminants tolerate the level of glucosinolate in LG-RSM although feeding this fodder as the only high-protein concentrate component may lead to impaired fertility.