an epidemiological study of listeriosis in dairy cattle

with the exception of silage eye cases. Cases of listeriosis in beef cattle were associated
with only two outcome variables (associated with overall and nervous signs) and the
rest were associated with one outcome variable (Table 4. 13). 5 of the 7 variables were
also significant in the univariate analysis. However, the use straw bedding in this model
was associated with a decreased risk of disease.
Table 4. 13. The agreement between the different outcome variables.
Predictor variables that O MC WC SE NS
increased the risk of disease
ring feeders for maize silage (indoor)* + + + + +
maize silage ad libitum (indoor)* + + + - +
cases of Listeriosis in beef cattle * + - - + -
maize silage in complete diet (indoor) - + - - -
cases of Listeriosis in sheep* - - - - +
decreased the risk of disease
big bale straw bedding - - - + -
straw bedding in cubicle* - + - - -
MC milking cows, WC winter cases, SE silage eye, NS nervous signs, + association with outcome
variables, - no association with outcome variables, * also statistically significant in univariate analysis
4. 4. Discussion:
A statistically significant association was found between 19 predictor variables
and the outcome variables using 3 separate models. In the first model major risk factors
were identified and these were investigated in more details in subsequent models. When
different outcomes were considered fewer predictor variables were associated with
cases of Listeriosis showing nervous signs than other outcomes, this may be due to fact
that a small number of farms reported cases of Listeriosis showing nervous signs. Of
these 19 variables 12 were also found to be significant in the univariate analysis. Cases
of Listeriosis in beef cattle and sheep, use of a mower conditioner, maize silage feeding,
big bale silage, storage of big bale outside uncovered, indoor feeding grass silage in ring