Selenium (Se) is an essential mineral for animal
health. Deficiencies result in white muscle
disease (WMD), retained placenta, and ill thrift in
cattle. These health problems are known to occur
in some northern California herds. This survey was
initiated to provide knowledge on the epidemiological
features of Se deficiency in cattle in this region.
Blood samples were drawn from 10 cows on each
of 10 ranches in each of the northern 22 counties.
Whole blood Se and glutathione peroxidase (GSH-Px)
activities were determined, and these values were
statistically compared with each other and with data
obtained by questionnaire. The latter included
information on animal diseases, soils, forages, and
general ranch descriptors like elevation and rainfall.
The GSH-Px spot test produced either a positive
(+), negative (-) or intermediate (+/-) enzyme
activity classification for each cow. Herd
classification was identified as + or - if > 70%
cow-values fell in that class, otherwise it was identified
as +/-.
The overall geometric mean blood-Se value was
47.6 ng/ml. Regressions of individual and herd
GSH-Px-class against blood-Se values produced
r = .75 and r = .82, respectively. Significantly
low blood-Se levels were recorded in herds with:
1) negative GSH-Px values, 2) past histories of WMD
and ill thrift, 3) predominantly hay diet, 4) pregnant
and early lactating cows, and 5) pure bred
cows. The Se status of herds using Se-salt blocks
was not different from non-supplemented herds. Descriptive
ranch variables did not reliably assess
the Se status of herds in this study
