Prevalence of lesions associated with subclinical laminitis in dairy cattle.

Lameness is an important cause of reduced animal welfare and has been shown to cause substantial economical losses in dairy and beef-cattle herds. Lameness is perhaps one of the most important diseases of the modern dairy cow. Laminitis is a diffuse aseptic inflammation of the laminar corium of the hoof wall and, in the bovine definition, also includes the sole corium. There are various forms of laminitis: subclinical, acute or subacute, and chronic. Subclinical laminitis is the most common form of laminitis in dairy cows. For the study, we aimed to determine the prevalance of the lesions associated with subclinical laminitis in 1352 dairy cows from 132 cow barns in Elazig province between 2007 and 2008. Of the 1352 cows selected for the study, lameness was detected in 387 (28.6%). Of these lame cows, 320 (82.7%) had 591 lesions that could be associated with subclinical laminitis. Claw lesions were diagnosed on the basis of macroscopic examination before and after trimming to the correct claw shape. In this study, yellow discolouration and haemorrhage of the white line and the sole, separation of the white line, erosion of the heel, double sole, sole ulcers, flaky or chalky white powder on the sole, abscessed soles were considered lesions associated with subclinical laminitis. The most common lesions were separation of the white line (20.98%) and haemorrhage of the sole (20.31%). Consequently, in this study, it was found that causes of 82.7% of lameness showed in cattle in Elazig region was originated from subclinical laminitis-related lesions. INTRODUCTION Lameness is one of the most important causes of financial loss and distress in dairy cattle (1-4), and lesions in the claw are the most common visible pathology associated with lameness (5-7). Claw disorders cause over 90% of lameness in dairy cattle (8,9). Lameness is detrimental to animal welfare and is among the three most important diseases in the dairy industry after mastitis and fertility problems (10-12). Several studies in North America, the United Kingdom, and Scandinavia report a wide range in the prevalence of lameness in dairy cattle between herds, typically of the order of 10 to 55% of the herd affected (13-17). Laminitis has been described in many species, but is most common in the equine and bovine. Although bovine laminitis is most common in lactating dairy cows, it has been reported in all ages and both sexes. Laminitis is a diffuse aseptic inflammation of the laminar corium of the hoof wall and, in the bovine also includes the sole corium. There are various forms of laminitis: subclinical, acute or subacute, and chronic. Subclinical laminitis is the most common form of laminitis in dairy cows (18-22). In cattle, lesions in the sole are usually attributed to laminitis, include haemorrhages in the horn, double soles, ulcers in the sole and toe, haemorrhage and separation of the white line, as well as deformation of the whole surface (“dropped sole”) (23,24). Furthermore, lesions considered by researchers to be associated with subclinical laminitis include an inflamed coronary band, a sunken and rotated distal phalanx (25), abnormal horn formation with reduced hardness and strength (26-29), flaky or chalky white powder on the sole, deformed claws, horizontal grooves in the hoof horn (30), overgrown claws, abscesses of the white line and abscessed soles (31). Other authors used the term claw horn disruption (CHD) (13,32). Usually these lesions occur in the heel, i.e. in zones3, 4 and 6 (Figure 1). Claw disorders can be divided into three main categories according to their aetiology; infectious, metabolic, mechanical and traumatic. Infectious and partly infectious claw lesions such as digital dermatitis, heel-horn erosions and interdigital phlegmones are mainly influenced by the environment (30). The causes of CHD or laminitislike lesions are diverse. The incidence and severity of the lesions are influenced by external mechanical factors such as abnormal claw or limb