Effects of swine husbandry on the incidence of congenital malformations: a matched-paired study☆

Abstract One hundred case-control herds were evaluated to determine the possible association between congenital malformations and husbandry practices in two subpopulations of Missouri swine. The etiology of the malformations in these populations was thought to be primarily environmental. General geographic environment and herd size, two variables considered to be related to both the exposure (husbandry practices) and disease (congenital malformations), were used in matching the case-control herds. A total of 32 swine husbandry variables including breeding practices, feeding practices, use of drugs, and water source were evaluated. Only five of the variables were significant ( P = 0.10). This, however, is not considered unusual when 32 variables are tested, even if the null hypothesis is true. Therefore, in the future, environmental studies of swine birth defects may be confined to factors in the natural environment rather than the man-made environment (husbandry).