Effect of type traits on functional longevity of Czech Holstein cows estimated from a Cox proportional hazards model

Abstract

Relationships between conformation traits and functional longevity in Holstein cows were evaluated using survival analysis. Functional longevity was defined as the number of days between the first calving and culling; that is, length of productive life. The data set consisted of 116,369 Holstein cows that first calved from 2003 to 2008. All cows used in the analysis were scored for conformation between d 30 and d 210 of their first lactation. The data included 48% censored records. Analyses were done separately for 20 linear descriptive type traits, 6 composite traits, and height at sacrum measured in centimeters. Cox proportional hazard models were fitted to analyze data. The hazard function was described as the product of a baseline hazard function and the time-independent effects of age at first calving and sire (random), and the time-dependent effects of stage of lactation and lactation number, herd, year and season, herd size, and 305-d milk production. The strongest relationship between a composite trait and functional longevity was for dairy form, followed by udder and final score. Among the descriptive type traits, the strongest relationships with longevity were found for body condition score, angularity, traits related to udder attachment, and udder depth. Foot and leg traits showed substantially lower effect on functional longevity, and the effect of foot angle was minimal. Functional longevity declined with decreased body condition score of cows. Cows with deep udders had significantly lower functional survival compared with cows with shallow udders. In addition, weak central ligament was associated with significant reduction of cow longevity. For dairy form and angularity, cows classified as very good were the worst with respect to longevity, whereas cows classified as poor were the best. An intermediate optimum was evident for rear legs rear view and rear legs set (side view), whereas cows with sickled legs had lower longevity than cows with straighter legs.

Genetic Prediction Models and Heritability Estimates for Functional Longevity in Dairy Cattle

“…Dadpasand et al (2008) observed a slightly different order for the risk of culling, which ranged between 0.78 and 1.73 for fore udder attachment, 0.89 and 1.64 for udder depth, 0.98 and 1.26 for fore teat placement and 0.75 and 1.07 for suspensory ligament, against a reference score class of 5 within the score range of 1 to 9. Udder depth has been reported to have the highest relative contribution to survival likelihood, and therefore had the highest effect on cow survival after correction for milk production (Bünger & Swalve, 1999;Caraviello et al, 2003;Zavadilová et al, 2011). Dadpasand et al (2008), Sewalem et al (2005a) and Caraviello et al (2003;2004b) reported an intermediate optimum for udder depth, implying that cows with very deep or very shallow udders were at high risk of being culled from the herds.…”

“…The relative contribution of udder-type traits to risk of culling and hence likelihood of survival has been well documented (e.g. Bünger et al, 2001;Dadpasand et al, 2008;Zavadilová et al, 2011). Some researchers have listed udder traits as having a significant impact on longevity.…”

“…The conditions to which animals are exposed are time dependent. Nor can linear models account optimally for time dependency of variables or non-linearity in data (Vukasinovic, 1999;Caraviello et al, 2004a;Zavadilová et al, 2011). Nevertheless, linear models have been used to evaluate binary survival and absolute longevity in a number of studies (e.g.…”

“…Predictor traits may be included in net merit indices on their own or in combination with direct longevity, as in the USA, France and Belgium (Forabosco et al, 2009). Recent studies have evaluated dairy form, body capacity, conformation score, rear leg set, hock quality, rump angle and udder traits as early predictors of functional longevity (Zavadilová et al, 2011;Zavadilová & Štípková, 2012). The positive correlations between some of these traits and longevity imply the possibility of predicting longevity from other structural traits.…”

“…When plotted, longevity data are characteristically skewed to the left because a larger proportion of cows are usually in early lactation (Caraviello et al, 2004b). Environmental factors that influence an animal's risk of culling at any given time may differ dramatically, based on prevailing conditions, and will probably change throughout its lifetime, rendering the factors time dependent (Caraviello et al, 2004a;Zavadilová et al, 2011;Flynn, 2012). In any instance, survival data will have complete and incomplete records.…”