Bovine lameness in small-scale dairy farms in Kikuyu division, Kiambu district, Kenya
Lameness is one of the three most important causes of economic loss inwestern European and North American dairy farms (Weaver, 1986). The current trend towards intensive dairy farming and the importation of exotic breeds of cattle in Kenya's small-scale farms may be accompanied by similar lameness problems. Since these small-scale farms are collectively the largest dairy producers inthe country (Stotz, 1983), dairy cattle lameness would result in a significant reduction in the national dairy output. A prospective study was therefore carried out to estimate the incidence and to investigate the risk factors of dairy cattle lameness in these farms. One hundred farms were selected at random from the registers of three Dairy Societies. Out of these, 78 participated in the study. The farms were visited twice; first in March and then in June, 1993. During the farm visits, all cattle in the farm were examined for clinical lameness and digital lesions. Data on housing, management, nutrition and signalment of cattle were collected through questionnaires administered during the visits. Farm, individual animal, and digit factors were assessed for their association with lameness using logistic regression. The housing system and the type and condition of the floor were considered at herd level; while age, breed, heart girth, parity, reproductive status and stage of lactation were considered at the individual animal level. The site (fore or hind; left or right; medial or lateral) and conformation of the digits were considered at the digit level. The incidence of lameness during March to June 1993 was estimated at 1.46% per month. The incidence increased with increased confinement of cattle. It was 0.76% per month in cattle kept in pasture 24 hours a day, 1.46% in cattle kept in pastures during daytime and 2.14% in those housed 24 hours a day. Interdigital cleft lesions (wounds, necrobacillosis, fibromas and dermatitis) had the highest incidence (4.54%) followed by heel erosion (4.43%) and loss of solear concavity (flat soles, 1.63%). Interdigital lesions (wounds and necrobacillosis) comprised 51.5% of clinical lameness cases while hoof overgrowth comprised 15.2%. Other, less frequent types of clinical lameness were sandcracks (6%), digital sepsis (6%) and sole ulcers (3%). Hind limbs were involved in 63.6% while fore limbs were involved in 18.2% of the clinically lame cattle. However, all the digits were simultaneously affected with heel erosion in 91.9%, flat sole in 70.0% and hoof overgrowth in 46.7% of the affected cattle. Variance component analysis indicated that variation between individuals was relatively more important in explaining the occurrence of lameness (Variance component = 88.5%) than that between herds. In the logistic regression models, confinement 24 hours a day (OR = 2.9; P = 0.0157), the Jersey breed (OR = 5.2; P = 0.0087) and the early lactation period (OR = 5.9; P = 0.0421) were associated with clinical lameness. Increasing length of the dorsal hoof wall, which was often accompanied by a shallower heel (r -0.27; P = 0.0001) and a small dorsal angle (r = -0.40; P = 0.0001), was strongly associated with clinical lameness (each centimetre increased the odds of lameness by a factor of 16.9; P = 0.0001). Jersey cattle had significantly smaller dorsal angles (P 0.0328) and longer dorsal walls (P = 0.0007) than other breeds. The incidence reported in this study is likely to be an underestimate as some cases occurring between the farm visits (about 3 months) may have been missed. Between-herd variation was relatively unimportant in explaining the occurrence of lameness probably because of small herd sizes (median = 2) and the relatively common management systems. It may also be that the individual animal factors are the ones that determine the animals ability to adapt to the various environmental and management factors. Breed, stage of lactation and digital conformation, which were associated with lameness in this study, are probably some of the determinants. The Jersey breed, which was a risk factor for lameness, had uniquely shaped digits as determined by the hoof measurements. This unique shape was associated with lameness and other digital lesions, and may therefore be the cause of the increased susceptibility of this breed. Digital conformation appeared to depend on individual-animal factors such as heart girth, body score and parity, indicating a possibility that change in digital conformation may be primary to development of digital lesions and, subsequently, clinical lameness. However, hoof measurements were taken at the time of examination, and it cannot be determined whether abnormal hoof measurements preceded or followed lameness. Further longitudinal information is required to elucidate the causal association.
Department of Clinical studies, University of Nairobi