Genetic evaluation of length of productive life including predicted longevity of live cows (original) (raw)
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Genetic evaluation of longevity in dairy cattle
Applied Science Reports
Longevity is a highly desirable trait that considerably affects overall profitability. With increased longevity, the mean production of the herd increases because a greater proportion of the culling decisions are based on production. Longevity did not receive adequate attention in breeding programs because genetic evaluation for this trait is generally difficult as some animals are still alive at the time of genetic evaluation. Therefore, three basic strategies were suggested to evaluate longevity for cows: Firstly, cow survival to a specific age, which can be analyzed as a binary trait by either linear or threshold models. Secondly, estimating life expectancy of live cows and including these records in a linear model analysis. Thirdly, survival analysis: a method of combining the information of dead (uncensored) and alive (censored) cows in same analysis. This review represents an attempt to shed a light on different strategies of genetic evaluation of longevity in dairy cattle in most of developed countries.
Genetic Prediction Models and Heritability Estimates for Functional Longevity in Dairy Cattle
South African Journal of Animal Science, 2015
Longevity is a major component of the breeding objective for dairy cattle in many countries because of its high economic value. The trait has been recommended for inclusion in the breeding objective for dairy cattle in South Africa. Linear models, random regression (RR) models, threshold models (TMs) and proportional hazard models (PH) have been used to evaluate longevity. This paper discusses these methodologies and their advantages and disadvantages. Heritability estimates obtained from these models are also reviewed. Linear methodologies can model binary and actual longevity, while RR and TM methodologies model binary survival. PH procedures model the hazard function of a cow at time t derived from survival from first calving to culling, death or censoring. It is difficult to compare methodologies for sire evaluation and ranking across countries because of the variation in the definition of longevity and the choice of model. Sire estimated breeding values (EBVs) are derived differently for the models. Sire EBVs from PH models are expressed as deviations of the culling risk from the mean of the base sires, expected percentage of daughters still alive after a given number of lactations, expected length of productive life in absolute terms or as standard deviation units. In linear, TM and RR modelling, sire EBVs for longevity have been expressed as deviations of survival from the mean estimated with Best Linear Unbiased Prediction (BLUP). Appropriate models should thus be developed to evaluate functional longevity for possible inclusion in the overall breeding objective for South African dairy cattle.
Animal Science Journal, 2013
Genetic parameters for longevity in Slovenian Holstein (H), Simmental (S) and Brown Swiss (B) cattle were estimated with sire-mgs (maternal grandsire) model using survival analysis, applying a proportional hazard function following a Weibull distribution. Longevity was described as length of productive life (LPL), that is as number of days from first calving to the culling or to the moment of data collection (completeduncensored and censored records). Truncation date was January 1, 1991 while August 1, 2008 was date of data collection. Estimated sire variances were 0.050 (H), 0.021 (S) and 0.034 (B). Herd variances were 0.191 (H), 0.299 (S) and 0.318 (B). Heritabilities estimates were 0.161 (H), 0.064 (S) and 0.101 (B).
The genetic structure of longevity in dairy cows
Journal of dairy science, 2015
Longevity of dairy cows is determined by culling. Previous studies have shown that culling of dairy cows is not an unambiguous trait but rather the result of several reasons including diseases and selection decisions. The relative importance of these reasons is not stable over time, implying that genetic background of culling may vary over lifetime. Data of 7.6 million German Holstein cows were used to assess the detailed genetic correlation structure among 18 survival traits defined for the first 3 parities. Differences of genetic factors which determine survival of different production periods were found, showing a pattern with 3 genetically distinct periods within each parity: early lactation (calving until d 59), mid lactation (d 60 to 299), and late lactation (d 300 until next calving). Survival in first and later parities were found to be slightly genetically different from each other. The identified patterns were in good accordance with distributions of reasons for disposal, ...
Breeding for longevity and survival in dairy cattle
Thc aim of dairy cattle brceding should be to improvc lifetime profit, rattrer than longevity in itsclf. It is most likcly, though, O16t traits rhar dercrmine longevity will be selccad for, and thus the ability to livc longer will improve. Health and rcproductive traits are describcd as the most imporrant in dercrmining longevity. The main focus of the articlc is on describing methods used as indicators of longevity: sayabilities, sundval scores, and failure time analysis. Mcasurcs of prcduction ard involuntary cdting (c.g. mastitis, reproduaion) are suggested for usc as selection criterion, if measured in the population. If not, other indicalor traits, such as somatic cell counts, could bc used irsrcad. If no or few hcalth and reproduction traits arc available in a population, breeding values for length of pmductivc lifc adjustcd for thc within-herd milk production deviuion, analyzed with failure time analysis' could bc used as a complement to milk production.
Journal of dairy science, 2001
Genetic evaluation of sires for functional longevity of their daughters based on survival analysis has been implemented in the populations of Braunvieh, Simmental, and Holstein cattle in Switzerland. A Weibull mixed sire-maternal grandsire survival model was used to estimate breeding values of sires with data on cows that calved since April 1, 1980. Data on Braunvieh and Simmental cows included about 1.1 million records, data on Holstein cows comprised about 220,000 records. Data contained approximately 20 to 24% right-censored records and 6 to 9% left-truncated records. Besides the random sire and maternal grandsire effects, the model included effects of herd-year-season, age at first calving, parity, stage of lactation, alpine pasturing (Braunvieh and Simmental), and relative milk yield and relative fat and protein percentage within herd to account for culling for production. Heritability of functional longevity, estimated on a subset of data including approximately 150,000 animal...
Advances in Dairy Research, 2014
Longevity of productive life in dairy cattle is a characteristic difficult to evaluate. This measurement is complicated, in part, because the phenotype is expressed late in the life of the animal, but also because the methods of evaluation are complex. The molecular bases of longevity are still far from being fully understood, although some genes begin to be associated with this characteristic. In this short communication will be discussed the criteria for selection in dairy cattle and to report some studies evaluate the molecular bases of longevity; your progress and current perspectives of selection by genic information.
Understanding the genetics of survival in dairy cows
Premature mortality and culling causes great wastage in the dairy industry, as a large number of heifers born never become productive or are culled before their full lactation potential is reached. The objectives of this study were to characterize survival and estimate genetic parameters for alternative longevity traits that considered (1) the survival of replacement heifers and (2) functional longevity of milking cows in the UK Holstein Friesian population, using combined information from the British Cattle Movement Service and milk recording organizations. Mortality of heifers was highest in the first month of life and was proportionately highest in calves born during winter months. Heifer mortality tended to decrease with age until about 16 mo onward; it then gradually increased, expected to be associated with culls due to reproductive failure or problems during pregnancy and calving. In milking cows, days of productive life (DPL) was analyzed as an alternative to the current trait lifespan score. Cows that died in 2009 on average lived for 6.8 yr with an average production of 4.3 yr. Heritability estimates were low for both heifer and cow survival and were ~0.01 and ~0.06, respectively. The positive genetic correlation between heifer survival with lifespan score (0.31) indicates that bulls that sire daughters with longer productive lives are also likely to have calves that survive and become replacement heifers. However, the magnitude of the genetic correlation suggests that survival in the rearing period and the milking herd are different traits. Genetic correlations were favorable between DPL with somatic cell count and fertility traits indicating that animals with a longer productive life tend to have lower somatic cell count, a shorter calving interval, fewer days to first service, and require fewer inseminations. However, an antagonistic relationship existed between DPL with milk and fat yield traits.
Genetic evaluation of longevity in Italian Brown Cattle Breed
Description of genetic evaluation for longevity in Italian Brown population is presented. A total of 49,520 records of first parity cows, born from 1983 to 1986, were used to analyse longevity, type and production traits and to estimate genetic parameters. Functional longevity was defined as total production days (lifetime) adjusted for within herd-year-season class deviation from average herd milk yield (linear and quadratic effects). Genetic parameters were estimated using a REML multiple trait sire model procedures that considered the fixed effects of herd, stage of lactation, age at the first type scoring, interaction between calving year and type classifier, and time interval between milking and type scoring. Heritability values were 0.24, 0.06 and 0.04 for milk yield, true and functional longevity, respectively. Genetic correlations between milk yield and functional longevity was negligible. Longevity exhibited positive genetic associations with udder depth (0.43), rear teats ...