Feeding of Rapeseed Presscake Meal to Pigs: Effects on Thyroid Morphology and Function and on Thyroid Hormone Blood Levels, on Liver and on Growth Performance*

Abstract

Summary Effects of feeding soybean meal (SBM) or a mixture of SBM and 5%, 10% and 15% of either 0‐ and 00‐rapeseed presscake meal (RPM) on thyroid, liver and growth performance were studied in castrated boars. Goitrin (G) intake was closely correlated with total glucosinolate intake and blood thiocyanate concentration. In pigs fed 10% and 15% 0‐RPM refused feed was enhanced and daily gain decreased. Liver weight and DNA/total liver increased with increasing G intake. Thyroid weights increased up to a G intake of 4.6 mmol/d and then decreased with higher G intake. DNA content/g dry matter (DM) increased continuously and total thyroidal DNA content up to a G intake of 4.6mmol/l, indicating hyperplasia. Epithelial thickness increased up to a G intake of 13.3 mmol/d, whereas follicular area only up to an intake of 4.6 mmol G/d and then decreased, mirrored by a decrease of DM content. Thyroidal thyroxine (T4) and triiodothyronine (T3) content decreased with increasing G intake. Blood serum levels of T4 decreased with increasing G intake, whereas T3 levels only tended to decrease. Therefore, measured parameters differently reacted to different G intake. In groups fed high amounts of G, hyperplasia was not sufficient to maintain physiological circulating T4 levels, but enhanced thyroidal secretion T3 and/or extrathyreoidal T4 to T3 conversion obviously allowed maintenance of near normal circulating T3 concentrations and barely reduced growth rate despite marked hypothyroidism.

Detoxication of rapeseed meal by Rhizopus Oligosporus sp‐T3: A first step towards rapeseed protein concentrate

“…Phytic acid is found in the cotyledons of legumes or oilseeds; it forms insoluble complexes with minerals which are less available for digestion and absorption in the small intestine. Glucosinolates degrade to isothiocyanates, thiocyanates and nitriles in the presence of the seed enzyme myrosi-nase (EC 3.2.3.1); these are responsible for goitre formation, for liver and kidney dysfunction and reduced growth performance (Kroll & Przybilski, 1991;Spiegel et al, 1993). In spite of low levels of glucosinolates (Ͻ20 M g Ϫ1 ) in OO varieties, these antinutritional factors are responsible for rapeseed meal being unsuitable for human consumption (Vermorel et al, 1987) and constitute a major problem for human food use.…”

Piglet performance and physiological effects linked to reduced glucosinolate transformations in feed products based on rapeseed pressed cakes

“…Enlargement of thyroid glands, liver and kidneys has been reported in many animal studies after intake of high glc rapeseed meal, and this effect has especially been associated with high levels of progoitrin (Schone et al, ; Spiegel et al, ). The inclusion of RPC into the feed did increase liver size in piglets compared to the control group, as also found by others (Hulshof et al, ; Parr et al, ; Schone et al, ; Spiegel et al, ). This may be a result of nitrile formation in the rapeseed products, as intake of nitriles is associated with increased weight of kidney and lesions in kidneys and liver (Nishie & Daxenbichler, ).…”

“…The suggested tolerable level of 1-2 µmol glc/g feed in diets for monogastrics (European Food Safety Authority (EFSA), 2008) is usually met by using double-low Brassica napus L. rapeseed varieties that incur glc contents ranging from a few µmol/g seed up to 25 µmol/g seed (Eggum, Just, & Sørensen, 1985;Landero, Beltranena, Cervantes, Morales, & Zijlstra, 2011;Spiegel, Bestetti, Rossi, & Blum, 1993b;Zhou et al, 2016). The recommendable inclusion of RPC in feed may thus be limited to less than 10%.…”

Thyroid function, metabolic indices and growth performance in pigs fed 00-rapeseed meal

“…At the end of the finishing period, pigs fed 00-RPM had a significantly higher concentration of glucose and insulin in the blood than pigs fed SM. Spiegel et al (1993a) found lower concentrations of glucose in the blood of pigs fed 15% 0-RPM, but not in pigs fed 15% 00-RPM, and ascribed this to the lesser consumption of tasteless food, which also resulted in a decreased weight gain. We suppose that the increased level of glucose and insulin in our experimental pigs is, at least partly, a result of the well-balanced meal composition with regard to energy values, amino acids and a high content of essential fatty acids in rapeseed meal.…”

“…Investigations carried out on fattening pigs during the growing as well as the finishing period of feeding, have not given consistent results. The exception is the influence on the morphology and function of the thyroid gland Spiegel and Blum, 1993;Spiegel et al, 1993a;Lettner et al, 1996;Moreira et al, 1996;Schöne et al, 1996). Investigations are especially lacking as to the effect of feeding rapeseed meal on several metabolic processes.…”