Effects of short-term supplementation of dairy cow diets with surplus selenium and rapeseed meal on milk and blood selenium levels

We studied the effects of short-time dietary supplementation with surplus selenium (Se) on Se con - centrations in milk and blood of dairy cows fed a diet containing rapeseed meal. e experiment was designed as a 4 × 4 Latin Square with four three-week experimental periods. Two groups of dairy cows received a mixture contain- ing rapeseed meal (RM) while in another two groups RM was replaced by soybean meal (SM). In each pair of the experimental groups, one mixture was supplemented with selenised yeast (RM Se , SM Se ; 0.5 mg of Se per 1 kg of dry matter). e following parameters were evaluated: concentration of Se in milk; concentration of Se in whole blood; activity of glutathione peroxidase (GSH-Px) in whole blood; concentration of iodine in milk; triiodothyronine (T 3 ) and thyroxine (T 4 ) plasma concentration. e supplement of Se significantly increased its content in milk of dairy cows fed diets containing either RM (+29.5 µg/l; RM Se vs. RM 0 ; P 0.05) while in groups without Se supplement the Se contentration was significantly lower by 5.62 µg/l ( P < 0.01). As far as milk Se was concerned, the interaction of factors under study was statistically insignificant. e intake of RM in the diet resulted in a decreased concentration of iodine in milk both in animals receiving a diet with selenised yeast and without it (-134.0 µg/l, RM Se vs. SM Se , P < 0.01 and -145.1 µg/l, RM 0 vs. SM 0 , P < 0.01, resp.). Feeding of RM did not influence the concentration of Se in blood, GSH-Px activity in blood and plasma concentrations of T 3 and T 4 .