scholarly journals Genetic evaluation for functional longevity in Polish Simmental cattle

2017 ◽  
Vol 62 (No. 7) ◽  
pp. 276-286 ◽  
Author(s):  
M. Morek-Kopeć ◽  
A. Zarnecki
Keyword(s):  
Fixed Effects ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Average Length ◽  
Selection Index ◽  
Herd Size ◽  
Genetic Evaluation ◽  
Productive Life ◽  
Stage Of Lactation ◽  
Fat Yield

The Weibull proportional hazards model was applied for genetic evaluation of functional longevity in Polish Simmentals. Data consisted of production and disposal records for 12 527 Simmental cows, daughters of 294 sires, calving for the first time from 1995 to 2014 in 286 herds. Length of productive life of cows was calculated as number of days from the first calving to culling or censoring. Average length of productive life of 4462 cows with complete (uncensored) survival records was 1198 days (39.3 months); mean censoring time for the remaining 8065 cows was 1093 days (35.8 months). Functional longevity was defined as length of productive life corrected for production. The model included time-independent fixed effect of age at first calving, time-dependent fixed effects of year-season, parity-stage of lactation, annual change in herd size, relative fat yield and protein yield, and random herd-year-season and sire effects. Likelihood ratio tests showed a highly significant impact of all fixed effects on longevity, except for relative fat yield. Estimated sire variance was 0.069, resulting in the equivalent (accounting for censoring level) heritability of 0.09. Standardized relative breeding values (RBV) ranged from 71 to 139 (mean 101.4, SD 9.12). Average reliability of RBVs was 0.47. Moderate heritability supports the possibility of effective selection for functional longevity, which will be included in the total selection index for Polish Simmentals.

scholarly journals Genetic evaluation of the functional productive life in Slovak Simmental cattle

2013 ◽  
Vol 56 (1) ◽  
pp. 797-807
Author(s):  
E. Strapáková ◽  
J. Candrák ◽  
P. Strapák ◽  
A. Trakovická
Keyword(s):  
Milk Production ◽  
Herd Size ◽  
Genetic Evaluation ◽  
Independent Effect ◽  
Proportional Hazard ◽  
Productive Life ◽  
Stage Of Lactation ◽  
Standard Deviations ◽  
Weibull Proportional Hazard ◽  
Maternal Grandsire

Abstract. Genetic evaluation of sires based on length of functional productive life of their daughters was carried out using a Weibull proportional hazard sire-maternal grandsire model. The data consisted of 214634 registered Slovak Simmental cows with censoring of 21.34%. Besides the random sire and maternal grandsire effects, the model included time dependent effects parity × stage of lactation interaction, within-herd standard deviations of milk production, herd × year × season interaction, change of herd size with respect to the previous year, and time independent effect age at first calving. Within-herd, the standard deviations of milk production had the most important influence on functional productive life. The highest risk of culling was found in cows with the lowest milk production class (uncompleted lactation). Risk of culling decreased with an increasing milk production class. Estimated heritability of functional productive life was 0.05 on the original scale. Breeding values of sires expressed as a risk ratio of their daughters were between −0.57 and 0.53.

scholarly journals ESTIMATING PANEL DATA DURATION MODELS WITH CENSORED DATA

2008 ◽  
Vol 24 (5) ◽  
pp. 1254-1276 ◽  
Author(s):  
Sokbae Lee
Keyword(s):  
Panel Data ◽  
Fixed Effects ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Unobserved Heterogeneity ◽  
Right Censoring ◽  
Duration Models ◽  
Finite Sample ◽  
Asymptotically Normal ◽  
Monte Carlo Studies

This paper presents a method for estimating a class of panel data duration models, under which an unknown transformation of the duration variable is linearly related to the observed explanatory variables and the unobserved heterogeneity (or frailty) with completely known error distributions. This class of duration models includes a panel data proportional hazards model with fixed effects. The proposed estimator is shown to be n1/2-consistent and asymptotically normal with dependent right censoring. The paper provides some discussions on extending the estimator to the cases of longer panels and multiple states. Some Monte Carlo studies are carried out to illustrate the finite-sample performance of the new estimator.

An improved model for the French genetic evaluation of dairy bulls on length of productive life of their daughters

2005 ◽  
Vol 80 (3) ◽  
pp. 249-256 ◽  
Author(s):  
V. Ducrocq
Keyword(s):  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Analysis Model ◽  
Genetic Trend ◽  
Hazard Functions ◽  
Stage Of Lactation ◽  
Dairy Bulls ◽  
Estimated Breeding Values ◽  
Improved Model ◽  
Efficiency Of Selection

AbstractFunctional longevity of dairy cows has been routinely evaluated in France since 1997 using a survival analysis model. Recently, we proposed a genetic trend validation test that could be used before including national data in an international evaluation of bulls on longevity of their daughters. Its application to the French Holstein data revealed a large overestimation of the genetic trend. It was found that the bias is the result of a change in the baseline hazard rate over time. A new proportional hazards model is proposed which accounts for this change. In the new model, the baseline is described as a stratified, piecewise Weibull hazard function within lactation, i.e. a function of the number of days since the most recent calving. Stratification is within year and parity. Different Weibull hazard functions are used over four periods: 0 to 270 days, 271 to 380 days, 381 days to day when dried, dry period until the next calving. The non-genetic effects included in the model were slightly different from the previous one. In particular the interaction effects between the within herd-year class of production and lactation number × stage of lactation on the one hand and year-season were accounted for. The estimated genetic variance was smaller than with the old model. The new genetic trend is almost flat. An illustration of the efficiency of selection on the estimated breeding values for longevity is presented.

scholarly journals Genetic evaluation for length of productive life in Slovak Pinzgau cattle

2008 ◽  
Vol 51 (5) ◽  
pp. 438-448 ◽  
Author(s):  
G. Mészáros ◽  
C. Fuerst ◽  
B. Fuerst-Waltl ◽  
O. Kadlečík ◽  
R. Kasarda ◽  
...  
Keyword(s):  
Milk Production ◽  
Proportional Hazards ◽  
Genetic Evaluation ◽  
Data Set ◽  
Final Model ◽  
Breeding Values ◽  
Age At First Calving ◽  
Clear Tendency ◽  
Productive Life ◽  
Increasing Risk

Abstract. The proportional hazards method was used to estimate breeding values for functional length of productive life within the endangered Slovak Pinzgau population. The analyzed data set contained 21,985 cows, daughters of 254 sires. The risk of culling was higher for cows with lower milk production relative to herd average, higher age at first calving and in herds decreasing in size. In the first lactation the culling risk was highest at the beginning, and decreased during lactation. From second lactation onwards an increasing risk was observed. The effect of breed composition was found insignificant, and was not included into final model. A heritability of 0.05 was estimated for functional length of productive life. The average reliability of estimates was 0.25. No clear tendency in average breeding values by year of birth of bulls was observed.

scholarly journals Genetic evaluation for longevity of Croatian Simmental bulls using a piecewise Weibull model

2013 ◽  
Vol 56 (1) ◽  
pp. 89-101
Author(s):  
S. Jovanovac ◽  
N. Raguž ◽  
J. Sölkner ◽  
G. Mészáros
Keyword(s):  
Milk Production ◽  
Weibull Model ◽  
Fixed Time ◽  
Herd Size ◽  
Genetic Evaluation ◽  
Genetic Trend ◽  
Data Set ◽  
Breeding Values ◽  
Age At First Calving ◽  
Productive Life

Abstract. Genetic evaluation of sires for functional longevity was conducted using survival analysis techniques. The data set consisted of 49 659 Simmental cows with first calving from 1997 to 2008. A piecewise Weibull sire model was used to estimate breeding values of 251 bulls for functional length of productive life of their daughters. The model was stratified by parity i.e. a separate baseline hazard was computed for each stratum. Besides the random sire effect, the model included the fixed time independent effects of age at first calving, herd size and region as well as the time dependent effects of relative milk production and year*season of first calving. The highest impact on longevity was found for relative milk production. Cows with the lowest milk yields were at approximately 2.7 times higher risk of culling compared to cows with average milk production. Effects of age at first calving, herd size and country region had lower impact on longevity. Sire variance was 0.023 which results in a heritability of 0.06 for functional length of productive life. The average approximate reliability of estimated breeding values was 0.49. Genetic trend showed no clear tendency by year of birth of bulls.

Factors influencing length of productive life and replacement rates in the Bruna dels Pirineus beef breed

2004 ◽  
Vol 78 (1) ◽  
pp. 13-22 ◽  
Author(s):  
J. Tarrés ◽  
P. Puig ◽  
V. Ducrocq ◽  
J. Piedrafita
Keyword(s):  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Mean Value ◽  
Time Dependent ◽  
Beef Breed ◽  
Productive Life ◽  
Average Value ◽  
Hazards Model ◽  
Calving Difficulty ◽  
Calving Intervals

AbstractAn analysis of the length of productive life in the Bruna dels Pirineus beef breed was performed with a non-parametric approach giving an average value of 9 years of productive life, and a corresponding replacement rate of 11%. Using a proportional hazards model stratified by herd, the influence of calf birth weight and weight gain until weaning, calving difficulty, calving interval and age at first calving on length of productive life were studied. Two models were explored: the first one included time-dependent variables taking the current value of the covariate at each calving date, while the second one also comprised time-dependent interactions between the value of the covariate of the current calving and its mean value during the last (up to) three previous calvings. Results from the first model showed that the risk of culling increases with very high ages at first calving, increasing calving difficulties, very large calf birth weights, very small weight gains until weaning and very long calving intervals. Furthermore, results from the second model showed that these increases also depend upon a sequence of values for the same covariate in previous calvings. Finally, these higher risks of culling implied lower survival functions that increased replacement rates but only slightly decreased average performances.

Mortality, wastage, and lifetime productivity of Bos indicus cows under extensive grazing in northern Australia. 1. Seasonal mating in the speargrass region

1995 ◽  
Vol 35 (3) ◽  
pp. 285 ◽  
Author(s):  
PK O'Rourke ◽  
G Fordyce ◽  
RG Holroyd ◽  
ID Loxton
Keyword(s):  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Bos Indicus ◽  
Herd Size ◽  
Northern Australia ◽  
Hazards Model ◽  
Specific Mortality ◽  
Wastage Rate ◽  
Very High ◽  
Genotype Effects

Mortality and wastage rates and lifetime productivity for seasonally mated, Bos indicus cows were studied over 8000 cow year records from 1972 to 1992 at Swan's Lagoon in the subcoastal speargrass region of North Queensland. The proportional hazards model was used to estimate age-specific mortality and wastage rates, adjusted for cohort and genotype effects. The 1970-72 cohorts had an average mortality of 1.7% (range 0-4.2%), with this low overall rate tending to increase with age. The average mortality rate for the 1973-87 cohorts was 1.2% (range 0.5-2.6%), with no pattern with age. For 1970-72 cohorts, the average wastage rate was 8.9% and ranged from 2.1 to 18.3% with no clear age pattern. However, there was a clear age pattern for the 1973-87 cohorts, with an average wastage rate of 9.2% comprising very high rates (27.5%) for 2-year-olds and low rates (2.8-8.9%) for 3-7-year-olds, increasing to 11.9% for 8-year-olds and 14.2% for 9-year-olds. The heifer replacement rates to maintain a stable herd size were 17.5 and 19.2% for the 2 herds. Lifetime productivity was very low, with 1970-72 cohorts rearing 3.3 calves over 4.7 years at a rate of 57.5% calves per year, and 1973-87 cohorts rearing 3.1 calves over 4.9 years at a rate of 45.0% calves per year. Total weaner weights reared up to 10 years of age were 578 kg for 1970-72 cohorts and 315 kg for 1973-87 cohorts. However, variability between individual cows was high, indicating scope for selection based on productivity, provided that better performing cows can be identified from predictors early in life.

Mortality, wastage, and lifetime productivity of Bos indicus cows under extensive grazing in northern Australia. 2. Continuous mating in the semi-arid tropics

1995 ◽  
Vol 35 (3) ◽  
pp. 297 ◽  
Author(s):  
PK O'Rourke ◽  
RM Sullivan ◽  
JA Neale
Keyword(s):  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Bos Indicus ◽  
Herd Size ◽  
Replacement Rate ◽  
Hazards Model ◽  
Wastage Rate ◽  
Breeding Herd ◽  
North Western ◽  
Semi Arid

Mortality and wastage rates and lifetime productivity were studied over 4800 cow years from 1981 to 1990 with continuous mating and minimal management in the semi-arid tropics at Kidman Springs, Northern Territory. The proportional hazards model was used to estimate age-specific mortality and wastage rates, adjusted for cohort effects. Annual breeder mortality rate averaged 11.5%, with similar rates in the range 9.0-12.0% for 2-9-year olds, increasing to 15.5% for 10-year-olds, 17.9% for 11-year-olds, and >20% for older cows. A further 20.8% of the cows that calved failed to rear the calf to branding. Wastage included mortalities and physical culls but minimal discretionary culls based on reproductive performance or maximum age. The wastage rate averaged 16.7%, ranged from 11.1 to 14.4% for 2-9-year-olds, increased to 21.1% for 10-year-olds and 34.3% for 11-year-olds, and exceeded 50% for older cows. The heifer replacement rate to maintain a stable herd size was 16.3%. Typical lifetime productivity up to 10 years of age in this harsh north-western environment was 3.1 calves reared over a lifetime of 6.5 years in the breeding herd, at a rate of 44.5% calves per year. Timing of first pregnancy was identified as a useful predictor of lifetime productivity when overall productivity was low. Cows that were lactating as 2-year-olds reared 4.0 calves in their lifetime up to 10 years of age, cows pregnant at this age reared 3.2 calves, and non-pregnant cows reared only 2.6 calves.

scholarly journals Analysis of longevity in the Slovak Pinzgau population – extension to the animal model

2013 ◽  
Vol 58 (No. 7) ◽  
pp. 289-295 ◽  
Author(s):  
G. Mészáros ◽  
O. Kadlečík ◽  
R. Kasarda ◽  
J. Sölkner
Keyword(s):  
Animal Model ◽  
Milk Production ◽  
Fixed Effects ◽  
Herd Size ◽  
Size Change ◽  
Breeding Values ◽  
The Third ◽  
Stage Of Lactation ◽  
Increased Risk ◽  
High Age

Breeding values for length of productive life in Slovak Pinzgau cattle were estimated using survival analysis. As the results were corrected for milk production, the final breeding values represented the ability of cows to avoid culling from reasons other than milk production. In addition to the relative milk yield, the risk of culling was also studied in connection with the herd and year of calving, parity and stage of lactation, herd size change and age at the first calving. Among the fixed effects, the low milk production, high age at the first calving, and decreasing herd size were associated with increased risk of culling. The risk was non-linear for parity &times; stage of lactation classes, decreasing within the first parity and increasing during later parities. Two genetic random effects were considered in separate models: the sire of the cow and the animal itself, both with the corresponding pedigree records up to the third generation. The genetic effects were estimated in separate runs, but the rest of the model remained unchanged. Heritability was h<sup>2 </sup>= 0.08 for sire model, confirming the results of an earlier study in the Slovak Pinzgau population. The computational feasibility of the animal model for estimation of breeding values for cows was confirmed in this study. The new breeding values could be computed for each cow, accounting for all relationships within the population. The estimated heritability for the animal model was h<sup>2 </sup>= 0.11, which should be used later on for animal breeding purposes. &nbsp;

scholarly journals Estimation of breeding values for functional productive life in the Slovak Holstein population

2014 ◽  
Vol 59 (No. 2) ◽  
pp. 54-60 ◽  
Author(s):  
E. Strapáková ◽  
P. Strapák ◽  
J. Candrák
Keyword(s):  
Herd Size ◽  
Proportional Hazard ◽  
Breeding Values ◽  
Productive Life ◽  
Stage Of Lactation ◽  
Weibull Proportional Hazard ◽  
Season Interaction ◽  
Maternal Grandsire ◽  
Genetic Standard Deviation ◽  
Interaction Change

Genetic evaluation of length of functional productive life was carried out using a Weibull proportional hazard sire-maternal grandsire model. The database included 405 624 Holstein cows with 19.24% censoring. The analyzed effects were parity &times; stage of lactation, within-herd standard deviations of milk production, herd &times; year &times; season interaction, change of herd size with respect to the previous year, age at first calving, and sire and maternal-grandsire effects. Parity &times; stage of lactation had the most important influence on functional productive life. The results of the analysis confirmed more intensive selection at the beginning of each lactation, whereby the risk ratio increased with each other lactation. Heritability of functional productive life was 0.13 on the original scale. Breeding values of sires were expressed as relative breeding values with a mean of 100 and genetic standard deviation of 12. &nbsp;

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