| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Animal Science, McGill University, Ste-Anne-de-Bellevue, Quebec, Canada, H9X 3V9
Survival analysis methodologies were used to study herd life in Canadian Holstein cows. Herd life was de- fined as true herd life or the length of time between first calving and censoring. True herd life adjusted for 305-d milk production was defined as functional herd life. Lifetime records (censored or completed) were from 331,147 Holstein cows registered in the Programme d'Analyse des Troupeaux Laitiers du Que'bec (PATLQ) that calved for the first time between March 1, 1981 and March 31, 1995. The Weibull (proportional hazards) model used to analyze true herd life and functional herd life contained a Weibull baseline hazard function and the time-dependent effects of year of first calving, lactation number by stage of lactation, annual change in herd size and herd-year (random), and the time-independent effects of the milk recording option (supervised or not) and age at first calving. The model for functional herd life included also the time-dependent effect of herd-year-parity class of 305-d milk production. Genetic differences between sires with regard to the hazard function of their daughters was clearly demonstrated. The hazard rate followed a different pattern in later lactations, particularly in the first 240 d in milk. Older age at first calving was found to be associated with higher risks of culling. Changes in herd size had a small impact on the hazard function of animals. The hazard decreased as production of the cow increased. Heritability in the log scale was 0.09 for true herd life and 0.08 for functional herd life, but when heritability was expressed on the original scale, the estimates for the two traits were 0.19 and 0.15, respectively. The difference in the median survival between a bull with an estimated transmitting ability of 0.6 and another bull with an estimated transmitting ability of 1.3 was 690 d or 1.7 lactations. Rank correlations between the official estimated transmitting abilities for true herd life and functional herd life and those obtained in this study were 0.62 and 0.66, respectively.
Key Words: survival analysis • herd life
Submitted on November 13, 1998
Accepted on June 9, 1999
This article has been cited by other articles:
|
|
 |
|
  Y. Terawaki and V. Ducrocq Nongenetic effects and genetic parameters for length of productive life of Holstein cows in Hokkaido, Japan J Dairy Sci, May 1, 2009; 92(5): 2144 - 2150. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. L. de Maturana, E. Ugarte, and O. Gonzalez-Recio Impact of Calving Ease on Functional Longevity and Herd Amortization Costs in Basque Holsteins Using Survival Analysis J Dairy Sci, September 1, 2007; 90(9): 4451 - 4457. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Terawaki, T. Katsumi, and V. Ducrocq Development of a survival model with piecewise weibull baselines for the analysis of length of productive life of holstein cows in Japan. J Dairy Sci, October 1, 2006; 89(10): 4058 - 4065. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. B. Garcia-Peniche, B. G. Cassell, R. E. Pearson, and I. Misztal Comparisons of Holsteins with Brown Swiss and Jersey Cows on the Same Farm for Age at First Calving and First Calving Interval J Dairy Sci, February 1, 2005; 88(2): 790 - 796. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Sewalem, G. J. Kistemaker, V. Ducrocq, and B. J. Van Doormaal Genetic Analysis of Herd Life in Canadian Dairy Cattle on a Lactation Basis Using a Weibull Proportional Hazards Model J Dairy Sci, January 1, 2005; 88(1): 368 - 375. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. R. Southey, S. L. Rodriguez-Zas, and K. A. Leymaster Competing risks analysis of lamb mortality in a terminal sire composite population J Anim Sci, October 1, 2004; 82(10): 2892 - 2899. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
