Hostname: page-component-cd9895bd7-mkpzs Total loading time: 0 Render date: 2024-12-28T14:37:54.239Z Has data issue: false hasContentIssue false
  • English
  • Français

Characterization of the variable cow's age at last calving as a measurement of longevity by using the Kaplan–Meier estimator and the Cox model

Published online by Cambridge University Press:  04 October 2012

S. L. Caetano ,
G. J. M. Rosa ,
R. P. Savegnago ,
S. B. Ramos ,
L. A. F. Bezerra ,
R. B. Lôbo ,
C. C. P. de Paz  and
D. P. Munari
S. L. Caetano
Affiliation:
Departamento de Ciências Exatas, Faculdade de Ciências Agrárias e Veterinárias (FCAV), Universidade Estadual Paulista (UNESP), CEP 14884-900, Jaboticabal, SP, Brazil
G. J. M. Rosa
Affiliation:
Department of Animal Sciences, University of Wisconsin, Madison, WI 53706, USA
R. P. Savegnago
Affiliation:
Departamento de Ciências Exatas, Faculdade de Ciências Agrárias e Veterinárias (FCAV), Universidade Estadual Paulista (UNESP), CEP 14884-900, Jaboticabal, SP, Brazil
S. B. Ramos
Affiliation:
Departamento de Ciências Exatas, Faculdade de Ciências Agrárias e Veterinárias (FCAV), Universidade Estadual Paulista (UNESP), CEP 14884-900, Jaboticabal, SP, Brazil
L. A. F. Bezerra
Affiliation:
Departamento de Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, CEP 14049-900, Ribeirão Preto, SP, Brazil
R. B. Lôbo
Affiliation:
ANCP – Associação Nacional de Criadores e Pesquisadores, CEP 14020-230, Ribeirão Preto, SP, Brazil
C. C. P. de Paz
Affiliation:
Departamento de Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, CEP 14049-900, Ribeirão Preto, SP, Brazil APTA – Agência Paulista de Tecnologia dos Agronegócios, CEP 14001-970, Ribeirão Preto, SP, Brazil
D. P. Munari*
Affiliation:
Departamento de Ciências Exatas, Faculdade de Ciências Agrárias e Veterinárias (FCAV), Universidade Estadual Paulista (UNESP), CEP 14884-900, Jaboticabal, SP, Brazil
*
† E-mail: danisio@unesp.fcav.br
Get access

Abstract

In most studies on beef cattle longevity, only the cows reaching a given number of calvings by a specific age are considered in the analyses. With the aim of evaluating all cows with productive life in herds, taking into consideration the different forms of management on each farm, it was proposed to measure cow longevity from age at last calving (ALC), that is, the most recent calving registered in the files. The objective was to characterize this trait in order to study the longevity of Nellore cattle, using the Kaplan–Meier estimators and the Cox model. The covariables and class effects considered in the models were age at first calving (AFC), year and season of birth of the cow and farm. The variable studied (ALC) was classified as presenting complete information (uncensored = 1) or incomplete information (censored = 0), using the criterion of the difference between the date of each cow's last calving and the date of the latest calving at each farm. If this difference was >36 months, the cow was considered to have failed. If not, this cow was censored, thus indicating that future calving remained possible for this cow. The records of 11 791 animals from 22 farms within the Nellore Breed Genetic Improvement Program (‘Nellore Brazil’) were used. In the estimation process using the Kaplan–Meier model, the variable of AFC was classified into three age groups. In individual analyses, the log-rank test and the Wilcoxon test in the Kaplan–Meier model showed that all covariables and class effects had significant effects (P < 0.05) on ALC. In the analysis considering all covariables and class effects, using the Wald test in the Cox model, only the season of birth of the cow was not significant for ALC (P > 0.05). This analysis indicated that each month added to AFC diminished the risk of the cow's failure in the herd by 2%. Nonetheless, this does not imply that animals with younger AFC had less profitability. Cows with greater numbers of calvings were more precocious than those with fewer calvings.

Keywords

beef cattlecow's age at calvingCox modelKaplan–Meier estimator
Type
Breeding and genetics
Information
animal , Volume 7 , Issue 4 , April 2013 , pp. 540 - 546
Copyright
Copyright © The Animal Consortium 2012

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bertazzo, RP, Freitas, RTF, Gonçalves, TM, Pereira, IG, Eler, JP, Ferraz, JBS, Oliveira, AIG, Andrade, IF 2004. Genetic parameters of longevity and productivity of Nellore females. Revista Brasileira de Zootecnia 33, 1118–1127.CrossRefGoogle Scholar
Boligon, AA, Albuquerque, LG, Mercadante, MEZ, Lôbo, RB 2010. Study of relations among age at first calving, average weight gains and weights from weaning to maturity in Nellore cattle. Revista Brasileira de Zootecnia 39, 746–751.CrossRefGoogle Scholar
Buzanskas, ME, Grossi, DA, Baldi, F, Barrozo, D, Silva, LOC, Torres Júnior, RAA, Munari, DP, Alencar, MM 2010. Genetic associations between stayability and reproductive and growth traits in Canchim beef cattle. Livestock Science 132, 107–112.CrossRefGoogle Scholar
Cox, DR, Hinkley, DV 1974. Theoretical statistics, 1st edition. Chapman and Hall/CRC, New York, NY, USA.Google Scholar
Ducrocq, V, Casella, G 1996. A Bayesian analysis of mixed survival models. Genetics Selection Evolution 28, 505–529.Google Scholar
Formigoni, IBV, Silva, JA, Brumatti, RC, Ferraz, JBS, Eler, JP 2002. Economic aspects of stayability as selection criterion in beef cattle industry in Brazil. Paper presented at the 7th World Congress of Genetics Applied to Livestock Production, Montpellier, France.Google Scholar
Gehan, EAA 1965. Generalized Wilcoxon test for comparing arbitrarily singly censored samples. Biometrika 52, 203–213.Google Scholar
Grossi, DA, Venturini, GC, Paz, CCP, Bezerra, LAF, Lobo, RB, Oliveira, JA, Munari, DP 2009. Genetic associations between age at first calving and heifer body weight and scrotal circumference in Nelore cattle. Journal of Animal Breeding Genetics 126, 387–393.Google Scholar
Hosmer, DW, Lemeshow, S 1999. Applied survival analysis: regression modeling of time to event data, 1st edition. John Wiley and Sons, New York, NY, USA.Google Scholar
Kaplan, EL, Meier, P 1958. Nonparametric estimation from incomplete observation. Journal of the American Statistical Association 53, 457–481.Google Scholar
Lawless, JF 1982. Statistical models and methods for lifetime data, 1st edition. John Wiley and Sons, New York, NY, USA.Google Scholar
Mantel, N 1966. Evaluation of survival data and two new rank order statistics arising in its consideration. Cancer Chemotherapy Reports 50, 163–170.Google ScholarPubMed
Mwansa, PB, Crews, DH Jr, Wilton, JW, Kemp, RA 2002. Multiple trait selection for maternal productivity in beef cattle. Journal of Animal Breeding Genetics 119, 391–399.Google Scholar
Peto, R, Peto, J 1972. Asymptotically efficient rank invariant test procedures (with discussion). Journal of the Royal Statistical Society: Series B Statistical Methodology 34, 187–220.Google Scholar
Prentice, RL 1978. Linear rank tests with right censored data. Biometrika 65, 167–179.Google Scholar
Schoenfeld, D 1982. Residuals for the proportional hazards regresssion model. Biometrika 69, 239–241.Google Scholar
Sölkner, J 1989. Genetic relationships between level of production in different lactations, rate of maturity and longevity in a dual purpose cattle population. Livestock Production Science 23, 33–45.Google Scholar
Struthers, CA, Kalbfleisch, JD 1986. Misspecified proportional hazard models. Biometrika 73, 363–369.CrossRefGoogle Scholar
Therneau, T 2011. Survival: survival analysis, including penalised likelihood. R package version 2.36-5. Retrieved April 4, 2011, from http://CRAN.R-project.org/package=survivalGoogle Scholar
Van Melis, MH, Eler, JP, Oliveira, HN, Rosa, GJM, Silva, JAV, Ferraz, JBS, Pereira, E 2007. Study of stayability in Nellore cows using a threshold model. Journal of Animal Science 85, 1780–1786.Google Scholar
Van Melis, MH, Eler, JP, Rosa, GJM, Ferraz, JBS, Figueiredo, LGG, Mattos, EC, Oliveira, HN 2010. Additive genetic relationships between scrotal circumference, heifer pregnancy, and stayability in Nellore cattle. Journal of Animal Science 88, 3809–3813.Google Scholar
Vanzin, IM 2000. Inseminação artificial e manejo reprodutivo dos bovinos. Retrieved May 7, 2011, from http://www.inseminacaoartificial.com.br/estacao_reprodutiva.htmGoogle Scholar
Werth, LA, Azzam, SM, Kinder, JE 1996. Calving intervals in beef cows at 2, 3, and 4 years of age when breeding is not restricted after calving. Journal of Animal Science 74, 593–596.CrossRefGoogle Scholar