1221
SELENIUM CONCENTRATION IN BLOOD, MILK AND URINE IN GRAZING JERSEY HERDS IN COSTA RICA
The aim of this study was to determine the concentration of selenium (Se) in blood, milk and urine in grazing Jersey cows. The study was conducted on four commercial dairy herds in the highlands (≈ 2250 m of altitude) of Cartago, Costa Rica. Cows were intensively grazing kikuyu grass (Kikuyuocloa clandestina) and daily supplementation consisted of concentrate according to milk yield (1kg concentrate : 3kg of milk). Blood samples were taken from the coccygeal vessels, milk samples were collected during milking from the milk yield measure container and urine was obtained using rubbing stimulation. A total of 102, 139 and 87 samples of blood, milk and urine respectively were collected and analyzed. Atomic absorption spectrophotometry was used to determine Se concentration. Soil was sampled in each farm in order to determine Se and sulfur (S) concentration and their associations with average Se in blood, milk and urine. A soil borer was used to obtain 20 subsamples per sample; those subsamples were collected drilling the soil surface to a depth of 10 cm. Se an S concentration in soils was analyzed using atomic absorption spectrophotometry and Ca(H2PO4)2∙H2O 0.008M 10:25 extraction, respectively. Average blood, milk and urine Se concentration are shown in Table 1.
Table 1. Selenium concentration in blood, milk and urine in four grazing Jersey herds. |
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Herd |
Se in blood (µg/L) |
Se in milk (µg/L) |
Se in urine (µg/L) |
1 |
41.12 |
32.61a |
200.27ab |
2 |
108.11 |
66.57b |
263.05a |
3 |
69.44 |
32.94a |
47.48bc |
4 |
41.44 |
22.35a |
28.35c |
a, b Means in the same column not sharing a common superscript are different (P < 0.05) |
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Se in soils of farms 1, 2, 3 and 4 were 98, 78, 144 and 345 µg/kg respectively, S concentration in soil was 74, 35, 57 and 32 mg/L in the same order. No association was obtained between average Se concentration in the animal fluids and the soil Se or S concentration. Se concentration in blood was correlated to Se concentration in milk (r = 0.31, P < 0.01). Differences between Se concentrations in milk among herds suggest that it could be related to supplementation on each farm. Results also indicate that high values of selenium in urine in some of the farms could imply a poor utilization or excessive supplementation of this mineral with associated economic costs. More research should be done in a wider population to support these findings.
Keywords: Jersey cows, Selenium, Soil