Genetic relationship between clinical mastitis, claw disorders and exterior traits in Holstein cattle

The paper deals with the genetic relationships between clinical mastitis (CM) nad foot and claw diseasesúdisorders in Holstein cattle, including their genetic relationship to he exterior traits. A dataset included 9,512 cows of Holstein cattle from 7 farms collected betwen the year 1999 and 2015. Lactational incidence rates for clinical mastitis ranged from 31.5% to 50.1% according to parity and from 1.6 to 2.2 cases of clinical mastitis per lactation affected with clinical mastitis. The lactational incidence rates for foot and claw diseases/disorders ranged from 37.6% to 66.2% and from 1.7 to 2.4 cases of foot and claw diseases/disorders per affected lactation. CN traits were defined either as binary 0/1 (CM0/1) or as a number (NCM). Three groups of foot and claw disorders were defined: skin diseases, including digital and interdigital/superficial dermatitis, and interdigital phlegmon; claw disorders including ulcers, white line disease, double sole and horn fissures; and overall foot and claw disorder comprising all the recorded disorders, all groups defined as 0/1 occurence per lactation. The following type traits scored on a 9-point scale were analyzed: body condition score, stature, angularity, fore udder attachment, rear udder height, udder depth, rear udder width, central ligament, teat length, front teat placement and rear teat position; rear legs rear view, rear leg set (side view), foo angle and locomotion. Genetic parameters for the analyzed traits were estimated using bivariate linear animal models that included the random additive genetic effect of animal (A) and the permenent environmental effect of cow (PE) and fixed effects according to the analyzed traits. Coefficients of heritability for both the clinical mastitis and the groups of foot and claw disorders were about 0.10. Gebetic correlations between both evaluated types of health disorders were 0.03-0.09. The exterior traits that showed a stronger genetic relationship with clinical mastitis (CM0/1; NVM) were the udder traits: fore udder attachment (-0.25; -0.22), udder width (0.21; 0.33) and udder depth (-0.34; -0.35); but also traits such as body condition score (-0.26; -0.15) and angularity (-0.18; -020). The genetic correlations between the exterior traits of feet and legs and foot and claw diseases/disorders were within the range of 0.03 to 0.45 (absolute values). They differed within the assessed groups of foot and claw diseases/disorders. For skin diseases, there was a strong genetic relationship to the rear legs rear view /-0.35) and too locomotion (-0.46). On the contrary, claw disorders had a stronger genetic relationship to the rear leg set (side view) (0.41) and to the foot angle (-0.25). We assume that our findings wil allow composing healh index including the health of the udder and health of the feet and legs.