Survival analysis in a buffalo herd located in well drained savannas, Guárico State, Venezuela

Abstract

The main objective was to identify animal outlets and to estimate survival curves based on 1198 records of birth, mortality and sales from Hato Barrancas, located in well drained savannas, Guárico State, Venezuela. Chi square test was used to find differences between years and sexes. Calving season, sex and breed were used as sources of variation to monitor survival. The data analysis involved Kaplan-Meier methodology, and Log-rank and Wilcoxon test to compare sources of variation. Sample was analyzed within four periods: calving to weaning; calving to 730 days old, weaning to 730 days old and calving to seven years old. Mortality until weaning was 10.1% and Murrah breed shows 59.38% higher than Mediterranean; while males were 147.7% superior to female. Period between weaning to 730 days old, showed an outlet highly affected by calving during rainy season (24.77%); where Murrah breed showed more outlet (61%) than Mediterranean. Differences by sex were 317% with males showing higher outlet. Period comprised within weaning to 730 days old reveals a 22.91% outlet, where animals calved in rainy season were 95.23% higher than those calved in dry season. Murrah breed had 105% superior outlet than Mediterranean. Finally, for period between calving and seven years old animals the outlet observed for females was 45.79%.

Keywords

• Survival analysis, Murrah, Mediterranean, Mortality