Effect of rapeseed feedstuffs with different glucosinolate content and iodine administration on gestating and lactating sow.

In two experiments with a total of 60 sows during late pregnancy and at 28 days of lactation, diets containing rapeseed were compared with rapeseed free diets (control). In Experiment 1 dietary content of solvent extracted rapeseed meal was 250 g/kg (10 mmol glucosinolates/kg diet), in Experiment 2 diets containing 100 g/kg rapeseed were tested (2 mmol glucosinolates/kg diet). During late pregnancy all sows received 150 micrograms supplementary iodine/kg diet. In lactation, different subgroups received different rates of iodine administration (Exp. 1:0, 100 or 1000 micrograms/kg diet; Exp. 2: 0, 150 or 300 micrograms/kg diet). Rapeseed feeds had no significant effect on feed intake, body weight of sows and rearing parameters in both experiments. There was a tendency (8%) toward lower litter weight at weaning in Exp. 1. Sow diets without supplementary iodine but containing glucosinolates (via rapeseed meal, rapeseed) caused significant reduction in thyroxine serum concentration of piglets, whereas this hormone did not change in sow serum. Thiocyanate was significantly increased in the serum of mothers. The minor increase of thiocyanate concentration of milk and piglets' serum points to negligible transfer of rapeseed glucosinolate degradation products to offspring. However, the milk iodine concentration was significantly decreased due to glucosinolates, and this seems to be the reason for impaired iodine and thyroid hormone status of piglets from sows given rapeseed feeds.