| dc.description.abstract | 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. | en |
