Logistic regression was used to examine factors associated with the formation of ovarian
cysts. The model included lactation length, parity and weaning-estrus interval. In order to
do so, lactation length was broken down into four categories: (1) shorter than 14 days, (2)
from 14 to 16 days, (3) from 17 to 19 days and (4) longer than 19 days. The 17–19 days
category was used as the standard, because this is the category representing the average
lactation length in both farms. Parity categories used were: gilts, primiparous and multiparous.
Multiparous females were considered as the standard because they were the most
representative group of females. The weaning-estrus interval was divided into three categories:
(1) shorter than 3 days, (2) from 3 to 6 days and (3) longer than 6 days. The second
category was considered the standard duration because it represents the average weaning
to estrus interval. The odds ratios were obtained from this analysis. As gilts did not have
a previous lactation and weaning to estrus interval, they were excluded from lactation length
and weaning to estrus interval analysis.