Phenotypic and genetic analyses of claw lesions in TMR Holstein herds in South Africa

Abstract. Claw lesions in dairy cattle pose a significant risk to dairy farmers worldwide in terms of animal welfare concerns and economic profitability. However, the use of different data sources, classification systems, and definitions of reference groups limits the comparison across herds and decreases the usability of the recordings for phenotypic and genetic analyses. In South Africa, information on claw lesions is not routinely collected by dairy farmers and data are limited to hoof trimmers recording lesions during preventative trimming or as needed by producers. Records of the most common claw lesions scored by a local hoof trimmer in five Holstein herds between January 2014 and December 2023 were used, including interdigital phlegmon (F), heel horn erosion (E), sole ulcers (SU), sole haemorrhage (SH), and two combined traits, one representing digital and interdigital dermatitis (DDID) and the other representing white line disease and white line separation (WLDS). The majority of lesions recorded were infectious (40.87 %), with DDID showing the highest incidence (39.58 %). Phenotypic associations may provide valuable information for hoof trimmers regarding the practical prevention, management, and treatment of lameness on-farm. A large, statistically significant odds ratio of 4.39 exists between DDID and E (95 % confidence interval: 3.55 to 5.43, P<0.0001). Within the non-infectious lesions, SH is moderately positively associated with total non-infectious lesions (|ϕ|=0.43, P<0.01) and the occurrences of SU and WLDS are both strongly positively associated with total non-infectious lesions (|ϕ|=0.54, P<0.01 and |ϕ|=0.58, P<0.01, respectively). In addition, the relationships observed among non-infectious lesions (SH, SU, and WLDS) are moderate to strong. The occurrence of DDID is moderately positively associated with the occurrence of infectious lesions in the front feet (|ϕ|=0.39, P<0.01) and strongly associated with the rear feet (|ϕ|=0.89, P<0.01). The occurrence of WLDS is moderately positively associated with the occurrence of total non-infectious lesions in the front feet (|ϕ|=0.37, P<0.01), with a stronger correlation with the occurrence of non-infectious lesions in the rear feet (|ϕ|=0.46, P<0.01). The occurrence of non-infectious lesions in the rear feet is moderately associated with the occurrence of SU (|ϕ|=0.42, P<0.01) but strongly associated with SH (|ϕ|=0.57, P<0.01). Heritability estimates ranged from 0.02 for DDID to 0.08 for the total lesions category (representing the presence or absence of at least one claw lesion on any foot). Phenotypic correlations and heritability estimates indicate that claw lesion data have the potential to be used for genetic evaluation of hoof health; therefore, the simplification and standardization of hoof lesion data collection should be encouraged.