| Summary: | 碩士 === 國立中興大學 === 動物科學系所 === 96 === The purpose of this study was to survey the nutritional status of selenium (Se) in lactating Holstein herds in Taiwan. The first survey was to understand the relactionship among the nutritional status of Se, somatic cell count (SCC) and composition of milk in three herds, from which the DHI data and samples of blood and milk were collected. There were determined of the Se concentrations in blood and milk, the activity of plasma glutathione peroxidase (GSH-Px), SCC and milk composition. It tended to be a negative correlation (r = -0.47, P < 0.1) between plasma GSH-Px activity (U) and SCC (105/mL). There was a correlation (r = 0.62, P < 0.01) between blood Se concentration (μg/L) and plasma GSH-Px activity (U). Another correlation (r = 0.68, P < 0.01) was observed between blood and milk Se concentration (μg/L). Thus, Se concentrations in milk may serve as a non-invasive indicator for rapidly depicting the Se nutritional status in cows. Survey 2 sampled 20 herds which were using lactating concentrates from ten feed factories. The samples collected from the herds were lactating concentrates, forages, TMR, faeces, urine and bulk tank milk (BTM). Additionally, blood samples were collected from 5 lactating cows randomly in each of the farms. The results showed that the mean of Se content (μg/kg DM) in the TMR was greater than that recommended by NRC (2001). It was a tendency of positive correlation (r = 0.43, P < 0.1) between the Se contents of lactating concentrates (μg/kg DM) and BTM (μg/kg). A correlation (r = 0.62, P < 0.01) was observed between Se content of TMR (μg/kg DM) and that of urine (μg/L). Se concentration (μg/L) in blood correlated (r = 0.69, P < 0.001) to that in urine. The Se concentration in milk or urine may be used for monitoring the nutritional status of Se in lactating Holsten cows. The Se content of TMR was more representative than that of estimate total ration in reflecting Se supply, and the Se content of TMR in most farms surveyed were out of the optimal range recommended by NRC. The contents of copper, calcium, zinc and molybdenum in TMR had the positive correlaction with the nutritional status of Se in the cows. Especially, the Se content in urine was affected by the mineral contents in TMR. The nutritional status of Se currently was not a decisive factor of affect SCC or milk composition in lactating Holstein cows in Taiwan. There were many cares that the dietary supply of Se for lactating Holstein cows in Taiwan was over or under the optimal range. Thus, how to correctly supplement Se in diets for lactating cows is still an important issue.
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