Genetic evaluation of susceptibility to clinical mastitis in Spanish Holstein cows

Abstract

This study had 3 objectives: to estimate genetic parameters and predict sires' transmitting abilities for clinical mastitis in a Spanish Holstein population, to propose a methodology for comparing models with different response variables by using a cost-based loss function, and to evaluate alternative genetic evaluation models by using this methodology. On-farm records for clinical mastitis from herds in 3 Spanish regions were analyzed as a binary trait (CM) and as number of episodes (NCM) per lactation. Linear and probit models were fitted for CM, whereas linear and Poisson models were used for NCM. Predictive ability of the models was evaluated by using the average predicted residual sum of squares from cross-validation and an alternative cost-based loss function. The loss function for model comparison was calculated by using average mastitis costs depending on the NCM and average cost per infected lactation. The average cost per infected lactation was $345.58, whereas the cost per lactation ranged from $204.86 to $985.44 for lactations with 1 to 5 cases, respectively. Management and hygiene practices on individual farms had a large impact on clinical mastitis because the herd-year variance was larger than that of other random effects considered. The sire variance was significantly different from zero, confirming that genetic variation exists for clinical mastitis. Estimates of heritability for CM using the linear and probit models were 0.07 and 0.10 on the underlying scale, respectively. For NCM, the estimate of heritability for the linear model was 0.10 and estimates for the Poisson model evaluated at the mean and the median of lambda on the underlying scale were 0.09 and 0.07, respectively. Regarding ranking of sires, the definition of response variable (CM or NCM) was of greater importance than the choice of statistical model. Cross-validation results indicated that models with the best fit for CM and NCM were the probit model and the linear model, respectively. However, a comparison across all models using the alternative cost-based loss function showed that using NCM as a response variable with a Poisson model provided the most accurate predictions of future costs associated with clinical mastitis.

Estimation of economic values and financial losses associated with clinical mastitis and somatic cell score in Holstein dairy cattle

“…Comparisons of milk losses v. treatment costs as a proportion of total losses per CM case in different countries are summarized in Table 8. In this study and in those of some others, milk revenue losses accounted for a higher proportion of total mastitis costs than veterinary expenses (Kossaibati and Esslemont, 1997;Wolfova et al, 2006;Bar et al, 2008;Pé rez-Cabal et al, 2009). In contrast, veterinary costs made up a higher proportion of mastitis costs than milk losses in Denmark, India, Sweden and The Netherlands dairy herds (Nielsen 1994;Sasidhar et al, 2002;Wolfova et al, 2006;Svensson and Hultgren, 2008;Huijps et al, 2008).…”

Genetic parameters for production, health, fertility and longevity traits in dairy cows

“…Estimates were generally higher when repeated cases of mastitis or lameness within parities were accounted for, as more variability is observed among cows. Definition, as either a binary or count trait, has been found to have differing impacts on sire rankings (Pé rez-Cabal et al, 2009;Vazquez et al, 2009), and it has been suggested that the definition should depend upon the selection goal. Pé rez-Cabal et al…”

Multiple trait genetic evaluation of clinical mastitis in three dairy cattle breeds

“…So on the long term, consequences of CM for breeders are increasingly detrimental. Although management and hygiene practices on farms have a large impact on CM (Pérez-Cabal et al, 2009;Vazquez et al, 2012), genetic selection for mastitis resistance is also a solution to be considered for improvement of UH. For example, Nordic countries have included mastitis in their genetic evaluation since 1978 and have shown that improvement of resistance to mastitis as a result of genetic selection is effective (Heringstad et al, 2003).…”