Abstract
The objective of this study was to investigate the metabolism of inorganic and organic Se sources at different dietary Se levels in lactating goats and dairy cows. The study consists of two experiments on goats dosed singly, either orally with grass sprayed with Na275SeO3 one week before cutting, intraruminally (I.R.) with Na275SeO3, or intravenously (I.V.) with Na275SeO3 or 75Se-selenomethionine. Follow-up periods were from 15 to 28 d long. Dietary Se levels were 0.05, 0.22 and 0.34 mg/kg DM. Values for 75Se absorption, excretion in milk, urine and faeces, 75Se activity in plasma, erythrocytes and hair are presented. In another experiment lasting 539 d, 48 dairy cows were fed either Na275SeO3 or grass silage sprayed with Na275SeO3 one week before cutting. Dietary Se levels were from 0.03 to 1.8 mg/kg DM. Se content in milk, plasma and erythrocytes, and GSH-Px activity in erythrocytes and plasma are given. True absorption of 75Se was 63 % and 65 %, and excretion of 75Se in milk 4 % and 7 % in the goats dosed I.R. with Na275SeO3 and orally with 75Se-labeled grass. The effect of dietary Se content was non-significant. After I.V. dose, 3.6 % and 33 % of 75Se was excreted in milk in goats dosed with Na275SeO3 and 75Se-selenomethionine, respectively, Na275SeO3 being eliminated mainly via urine. In cows receiving selenium as Na275SeO3, milk contained 0.011, 0.011, 0.016 and 0.020 mg Se/l at dietary Se levels 0.11, 0.17, 0.42 and 0.68 mg/kg DM, respectively. In cows receiving Se-sprayed silage, milk Se content was 0.023, 0.020, 0.029 and 0.040 mg/l when the diet contained 0.09, 0.20, 0.45 and 1.20 mg Se/kg DM. Se incorporated into silage was more efficient (p
Highlights
The selenium content of feed and food grown in Finland has been well below the accepted dietary requirements (Sippola 1979, Varo & Koivistoinen 1981)
The present study addresses the metabolism of selenium in tissues closely related to selenium absorption and excretion in lactating animals
For the intravenous dose the goats were catheterized in Vena jugularis (Cavafix 1.4 mm catheter). 75Se-selenomethionine at a dose of 2.56 MBq was introduced through the catheters and to ensure proper flushing of the catheter syringes were filled twice with blood drawn from the catheter and reemptied into the vein
Summary
The selenium content of feed and food grown in Finland has been well below the accepted dietary requirements (Sippola 1979, Varo & Koivistoinen 1981). Investigations of plant uptake of various seleno compounds were succesfully carried out by Dr Toivo Yläranta Based on his results, it was concluded that sodium selenate would be the most suitable form of selenium to be added to fertilizers given prevailing conditions in Finland (Yläranta 1984a). Introduction of the intraruminal dose for goat 1 failed as the dose was probably introduced into the rumen or abdominal wall. For introducing the intravenous dose the goats -were catheterized in Vena jugularis (Cavafix 1.4 mm catheter) 20 hrs before dosing. After dosing the syringes were filled twice with blood drawn through the catheter and reemptied into the vein to ensure proper flushing of the catheter
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