Mm. Mcallister et al., EVALUATION OF RUMINAL SULFIDE CONCENTRATIONS AND SEASONAL OUTBREAKS OF POLIOENCEPHALOMALACIA IN BEEF-CATTLE IN A FEEDLOT, Journal of the American Veterinary Medical Association, 211(10), 1997, pp. 1275
Objectives-To measure concentrations of thiamine in blood and sulfide
in ruminal fluid in cat-tie with polioencephalomalacia (PEM) and to ev
aluate temporal associations between PEM and risk factors. Design-Epid
emiologic analysis. Sample Population-14 steers with acute signs of PE
M, 26 clinically normal steers, and records of ail cattle in a feedlot
for the past 6 years. Procedures-Concentrations of thiamine in blood
and sulfide in ruminal fluid were measured. Values were compared betwe
en healthy steers that had been in the feedlot for 3 weeks or 2 months
. Records were used to estimate the incidence of PEM and the time when
cattle were at greatest risk of developing PEM. Results Thiamine conc
entrations in steers with PEM were within reference ranges. Healthy st
eers had significantly greater sulfide concentrations 3 weeks after en
tering the feedlot, when the incidence of PEM was greatest, than 2 mon
ths alter entering the feedlot, when risk of developing PEM was low. T
hiamine concentrations were within reference ranges at these times. An
nually recurrent outbreaks of PEM during the summer began after initia
ting use of a water well containing a high content of sulfate. Clinica
l Implications-Excessive ruminal sulfide production is an important fa
ctor in the pathogenesis of PEM, without concurrent thiamine deficienc
y. Most cases of PEM developed between 15 and 30 days after introducti
on to a high-sulfur diet. When water is an important source of dietary
sulfur, risk of PEM may increase during hot weather.