Cox-Lognormal Model to Assess Longevity in Curraleiro Pé Duro Cattle Breed from the Semiarid Region of Brazil

Abstract

Cattle of the Curraleiro Pé Duro breed are characterized as very docile and exceptionally rustic animals. They are animals gradually adapted to low quality native pastures, drought conditions, high temperatures and other adverse factors, resulting in the formation of bovine herds adapted and resistant to the unfavorable conditions of the Brazilian hinterland. In this context, the objective of this work was to use the survival analysis methodology with a Cox-lognormal proportional hazards model, to assess the stayability in the herd, considering the failure as the inactivity of the bovine being caused by death or sale, using information from 102 Curraleiro Pé Duro cattle born in the period from 2005 to 2014 in an experimental field of Embrapa Meio-Norte located in São João do Piauí. The Cox-lognormal proportional hazards model considered, among the analyzed covariates, the season of birth, sex and weight at 365 days as significant. There was a predominance of birth in the dry season (July to December). It was observed that the cattle that longer remained in the herd were born in the dry season, were male and weighed less than 95 kg at 365 days, justified by the absence of parasites, availability of pasture for the mother during the pregnancy period, carcass evaluation, sale, slaughter and reproduction. The Cox-lognormal proportional hazards model proved to be adequate in the adjustment of the statistical model to estimate the stayability in the herd, with censorship related to the inactivity of the Curraleiro Pé Duro breed.