[en] The effects of high level of rapeseed meal in the diet on the concentration of antinutritional
factors (glucosinolates metabolites) in blood plasma, milk and thyroid were studied in 90 ewes.
From the 100th day of gestation, ewes bearing two foetuses were divided into three groups and
were fed with pasture hay ad libitum and 500 g/d of diet containing 0 or 40% rapeseed meal
obtained from either Apex or Synergy variety. During the 47 first days of lactation, 1200 g/d of
the same meal were given. Thereafter, during 3 weeks, the ewes were only fed with hay. Blood
and milk samples were taken fortnightly for the determination of SCN- and 5-vinyl-1,3-
oxazolidine-2-thione (5-VOT) concentrations. One ewe from each group was slaughtered at the
end of rapeseed meal distribution and another one three weeks later for thyroid analyses. SCN-
and 5-VOT concentrations in blood plasma increased significantly (P<0.05) and regularly until
one month of rapeseed supplementation to the withdrawal of rapeseed in the diet. One to three
weeks after the end of rapeseed meal distribution, the SCN- and 5-VOT plasma concentrations
came back at the basal level. Some changes were also observed for SCN- and 5-VOT contents
in milk. The results indicated a great capacity of the ewes to excrete SCN- and 5-VOT by the
milk. A 5-VOT accumulation was observed in the thyroid according to the level of progoitrin in
the diet, but no SCN- accumulation. The 5-VOT concentration in thyroid of the ewes fed during
three weeks with hay came back to zero. The thyroid analysis showed the reversible aspect of
the thyroid hypertrophy due to 5-VOT accumulation.
