ESTRUS DETECTION BY USING VAGINAL CYTOLOGIC EXAMINATION IN MINIATURE SWINE

Vaginal smears were obtained from four Yucatan miniature swine daily f or 69 days and stained with hematologic stain. Epithelial cells were c ategorized as superficial, large intermediate, small intermediate, or parabasal. Leukocytes were also quantitated. External signs of estrus were recorded, including swelling, discharge, restlessness, or vocaliz ation. Mean age of three of the swine was 147 days at the beginning of the study. The fourth pig was 317 days old. The three younger swine h ad their first observed estrus at the age of 178 days (range, 167 to 1 96 days). Mean cycle length was 17 to 21 days. The moving mean leukocy te count (i.e., each value was averaged with the values for the previo us day and the following day) always exceeded the epithelial cell coun t (regardless of type), except during the 3 to 4 days when the pigs ex hibited external signs of estrus. Further, epithelial cells were at th eir peak during estrus, decreasing markedly during diestrus, and incre asing again during proestrus. The combined superficial plus large inte rmediate cell counts were significantly higher during estrus than duri ng diestrus or proestrus. We conclude that daily vaginal smears can be used to determine the stage of estrus in Yucatan pigs.