Genetic parameters for digital dermatitis and correlations with locomotion, production, fertility traits, and longevity in Holstein-Friesian dairy cows.

Heritability of digital dermatitis (DD) and correlations between DD and type traits related to legs and feet were estimated from a linear animal model. Data comprised 93,391 national type evaluation records of pedigreed first-lactation Holstein-Friesian cows that calved from 2002 through 2006. At the time of classification, cows were housed in different housing systems (i.e., cubicles, straw yards, slatted or loafing yards) and on pasture. The type traits evaluated were locomotion score (LOCO), rear legs side view (RLS), foot angle (FA), bone quality and leg and feet composite (L&F). In addition, cows were examined for DD lesions at classification. The relationships among these type traits, lifespan (LS), production (milk and fat), fertility (calving interval and 56-d nonreturn) and DD were examined by estimating the approximate genetic correlations from sire estimated breeding values. The study also evaluated the association between DD and the housing systems as well as the general conditions of the farm flooring where classification took place. In general, cows on pasture were less susceptible to DD than cows in other housing systems, whereas the association between DD and the flooring conditions was counterintuitive. Heritability estimate for DD was 0.011 on the 0/1 scale, which is equivalent to 0.029 on the assumed underlying normally distributed scale. Bone quality, LOCO, and L&F had moderate to high negative genetic correlations with DD, indicating that flatter, more refined bones, higher LOCO, and better L&F were associated with less incidence of DD. The genetic correlations between DD, RLS, and FA were not significantly different from zero. Digital dermatitis had moderate but negative genetic correlations with LS and milk and fat, suggesting that breeding for resistance to DD will result in an increase in both longevity and production. Cows affected with DD had a slightly shorter calving interval than healthy cows, an association found to be mediated through the reduced milk yield of these cows. Generally, the type traits included in this study had low genetic correlations with production and fertility traits whereas the associations between these traits and LS ranged from moderate to high. This indicates that good locomotion, straighter RLS, steeper FA, better L&F, and flatter, more refined bones are associated with increased longevity.

Genetic analysis of locomotion and associated conformation traits of Holstein-Friesian dairy cows managed in different housing systems.

The objectives of this study were to determine the influence of housing on lameness-related linear and composite traits, and to estimate heritabilities of the traits and correlations among them. Data comprised 156,770 national type evaluation records of pedigreed first-lactation Holstein-Friesian cows that calved from 2000 through 2006 and were classified in different housing systems--cubicles, straw yards, slatted or loafing yards, and on pasture. Locomotion score (LOCO), rear leg, side view (RLS), foot angle (FA), bone quality (BO-NEQ), legs and feet (L&F), and mammary composite (MAMM) were the traits measured. Data were analyzed by REML, using an animal model. In general, cows in grazing systems had better locomotion, straighter RLS, steeper FA, flat and more refined bones, better L&F, and better mammary systems compared with cows housed in other systems. Estimates of heritability ranged from 0.11 for LOCO to 0.31 for MAMM. Bone quality had the highest heritability (0.23) of the traits associated with L&F. Genetic associations between BO-NEQ and LOCO, L&F, and MAMM were moderate to high (0.30 to 0.50), but estimates between BONEQ and RLS and FA were not significantly different from zero. Locomotion score had a very high genetic (0.98) and phenotypic (0.78) correlation with L&F, indicating that both traits are genetically the same. On the basis of the genetic parameters, including BONEQ in a selection index as a predictor of longevity is promising, but further information on its association with longevity is required.

Risk factors and milk yield losses associated with lameness in Holstein-Friesian dairy cattle.

Weekly locomotion scores on a scale of 1 to 5 were used to investigate the relationship between cattle lameness, management systems and the impact of lameness on milk production. The data were 14026 locomotion scores from 248 Holstein-Friesian cows. Cows were managed in two groups, XE (high-concentrate feed and housed indoors all year) and XM (low-concentrate feed and outdoors in summer). Analysis was performed using residual maximum likelihood. Results indicated that the most significant variables affecting locomotion were time of year when the animal was locomotion scored and management group. Cows scored during February and August had increased locomotion problems. Cows in the more intensively managed group had significantly poorer locomotion compared with those in the more extensive group. Older animals were more susceptible to lameness than heifers. Body weight, body condition score and days in milk (DIM) also accounted for significant variation in locomotion score. Poor locomotion was associated with a significant reduction in the milk yield of later lactation cows. There was a significant difference in the shape of the lactation curve depending on whether or not the cow was lame during lactation. Average persistency was greater for the group of cows never lame throughout lactation compared with those lame before 60 DIM.