SHORT NOTE (NOTA CORTA) STAYABILITY IN THE HERD AND CULLING CAUSES OF BOARS IN FOUR PIG FARMS OF YUCATAN, MEXICO (PERMANENCIA EN EL HATO Y CAUSAS DE DESECHO DE VERRACOS EN CUATRO GRANJAS PORCINAS DE YUCATÁN, MÉXICO)

SUMMARY The stayability and causes of culling of boars in four pig commercial farms in Yucatan, Mexico were studied. The get-in and get-out dates of the boars corresponded to the period of March 1994 to June 2007. Stayability was defined as the number of days between the first service of the boar (approximately 8 months) until its culling or end of the study. Information on 169 boars of which 147 were culled and 22 were in service at the end of the study was investigated. Stayability curves of the boars were obtained by survival analysis. The risk of culling of the boars between farms was determined by the Cox proportional-hazards regression method. Stayability curves between farms were statistically different (P<0.05). The longest stayability belonged to boars of farm A and the shortest to boars of farm B. The hazard risks were 6.26, 2.16 and 1.93 times greater for the boars from farms B, C and D, in comparison with boars from farm A. The main causes of culling were: old age and loss of sexual appetite (22.5 and 12.4%).