Proportional hazard models associated with the survival of dairy goats reared in a tropical environment

Abstract

Increasing the functional life of a doe in order to keep the most productive females in the herd as long as possible can result in a reduction of replacement costs because of the better utilization of the animal in the production system. Thus, the objective was to evaluate the influence of environment effect, and morphometric and type traits on the culling that limits the stay of a doe of an exotic dairy goat breed reared in a tropical climate in the herd (stayability). The data utilized in the present study had information of 1439 Saanen does, born between 2000 and 2015, from 17 herds. The stay in the herd for longer than 28 months of age (STAY28), that is lack of culling, was defined as successful; the does’ records were then not censored (C = 1). On the other hand, does kept in the herd for less than 28 months had their records censored (C = 0), once we considered that she still would kid. Does sold to other farmers were considered censored. Information regarding birth year, birth season, herd, six morphometric traits, and 12 visual appraisal-scored traits were evaluated. The Cox proportional hazard rate and the Kaplan-Meier models were fitted to analyze the data. Birth year, body length, rump width, feet and legs soundness, udder, and teat conformation were the traits that affected STAY28. For each birth year, body length, and rump width, reductions of 4 %, 2 %, and 5 % were observed on the culling hazard of a doe, respectively. Does with great scores for traits related to the mammary system were prematurely culled from the herd. In conclusion, STAY28 can be used as a selection criterion based on the aforementioned morphological and type traits, since it is effective to early detect individuals that will stay longer and more productive in a herd. Therefore, these traits should be considered in breeding programs.