**4. Discussion**

414 A Bird's-Eye View of Veterinary Medicine

= 9.75, P = 0.021). But lactation stage between 1 to 90 days was significantly (χ2 = 9.06, P = 0.028) associated with subclinical laminitis. Failure to remove manure (more than one day) from the walk-alleys (r = 0.215, χ2 = 13.85, P<0.001), regular (2-4 times per day) concentrate feeding (r = 0.135, χ2 = 5.45, P = 0.0196) and lack of or inadequate mineral supplementation (r = 0.172, χ2 = 8.9, P = 0.0307) were all found to significantly have unconditional association with subclinical laminitis (Table 2). However stepwise logistic regression analysis (screening interactions of floor types, type of cubicle bedding, manure removal, concentrate feeding, type of forage and mineral supplementation) revealed that the most significant zero-grazing housing-and management-level contributor to the occurrence of subclinical laminitis was

regular concentrate feeding ( O.R. = 2.08, χ2 = 5.5, 95% C.I: 1.1 to 3.9, P = 0.0212).

of laminitis and related claw lesions in Nairobi and its environs

laminitis and related claw lesions in Nairobi and its environs

30.85, P<0.0001) (Table 3).

Farm variables χ2 r-value P-value Lack of manure removal 13.85 0.21 < 0.001 High concentrate feeding 5.45 0.13 0.0196 Lack of mineral supplementation 8.9 0.17 0.0307 Floor types 5.52 0.14 0.02381 Overstocking (fewer cubicles than cows) 6.2 0.14 0.1844 Type of cubicle bedding 7.2 0.15 0.5155 Presence of a curb 0.13 0.02 0.9361 Fodder type 3.26 0.1 0.5151 Table 2. Association of subclinical laminitis with possible risk factors in a study carried out in 300 dairy cows from 32 smallholder zero-grazing units to evaluate digital characteristics

Zero-grazing housing- and management-level risk factors that had unconditional association with chronic laminitis were revealed by descriptive statistics. These were overstocking (fewer cubicles than the number of cows) (r = 0.36, χ2 = 38.87, P<0.0001), presence or absence of cubicle bedding (r = 0.312, χ2 = 29.13, P = 0.0003), earthen floor (r = 0.203, χ2 = 12.33, P = 0.0151), presence of a high curb between walk-alley and the cubicles (r = 0.157, χ2 = 7.43, P = 0.0244), leaving manure (more than one day) in the walk-alleys (r = 0. 279, χ2 = 23.33, P<0.0001), regular (2-4 times per day) feeding with concentrates (r = 0.218, χ2 = 14.25, P = 0.0002), and regular (once per day) mineral supplementation (r = 0.321, χ2 =

Farm variables χ2 r-value P-value Overstocking (fewer cubicles than cows) 38.87 0.36 < 0.0001 Absence of cubicle bedding (bare concrete) 29.13 0.31 0.0003 Manure removal (infrequent) 23.33 0.28 < 0.0001 Earthen floor type 12.33 0.2 0.0151 High concentrate feeding 14.25 0.2 0.0002 Lack of mineral supplementation 30.85 0.3 < 0.0001 Presence of a curb 7.43 0.16 0.0244 Table 3. Association of chronic laminitis with possible risk factors in a study carried out in 300 dairy cows from 32 smallholder zero-grazing units to evaluate digital characteristics of

Furthermore, stepwise logistic regression analysis (testing interactions of all these unconditionally associated factors) pointed out the farm-level factors that most significantly The strength of this paper is elaborated by the important variations in housing designs, nutritional regimes and management protocol in these smallholder zero-grazing dairy units. The dairy production protocol in these units is so varied to the extent that they can further be subdivided into subunits. It is of paramount importance to note that the prevalent claw disorders affecting cows in these zero-grazing units are non-infective in nature and associated with laminitis syndrome. It is also worth noting that the lesions with high prevalence are mainly non-clinical with the highest proportion being subclinical laminitis. This could be attributed to presence of low-grade but persistent predisposing factors existing in these zero-grazing units that cause insidious claw damage eventually leading to clinical manifestations at an advanced stage that may already have caused irreversible changes in the claws particularly with effects of laminitis (Belge & Bakir, 2005; Nocek, 1997). The significance of high prevalence of subclinical laminitis in these zero-grazing production systems cannot be underrated since it serves as a major contributor to development of other more severe clinical claw lesions with far reaching effects such as sole bruising, heel erosion, white line separation, double soles and eventually chronic laminitis if early remedial measures are not instituted. Such outcomes have been reported previously (Nocek, 1997). A retrospective study carried out on the cases of cattle referred from the same area to the University of Nairobi Large Animal Hospital in the earlier years indicated that previously there was high prevalence of infective claw lesions and negligibly low prevalence of laminitis and associated lesions (Nguhiu-Mwangi, et al., 2008). The pattern of occurrence of claw lesions in the same area has remarkably shifted to high prevalence of non-infective

Risk (Predisposing) Factors for Non-Infectious

claw (Berry, 1999).

Claw Disorders in Dairy Cows Under Varying Zero-Grazing Systems 417

mechanical pressure on the solar corium due to excessive weight-bearing on the pedal bone and inadequate support of the corium by the horny capsule at the sole especially following thinning of the horn of the sole in laminitis (Baggott & Russell, 1981; Toussaint-Raven, 1973). Trimming tends to return the claw to near normal weight-bearing even at chronic stages of regular overgrowth (Weaver, 1993). However, when overgrowth is combined with chronic laminitis, the pedal bone undergoes irreversible alteration in its configuration within the claw capsule (Bargai et al., 1989; Greenough et al., 1990) and this result in poor prognosis.

It is prudent to conclude that regular examination is the most important way of ensuring good claw health. The most practical way to regularly observe the claws is during the milking times. Examination of the claws cannot be conclusive without trimming at least the horn of the sole. This is necessitated by the fact that lesions underneath the horn of the claws are not discernible externally until exposed by trimming (Nguhiu-Mwangi, 2007; Nocek, 1997). Such routine examination will help to recognize and manage claw disorders in the early stages before they progress to unmanageable chronic stages in which the claws are irreversibly damaged. Furthermore, the corium is the tissue that determines the health of the claw. It should therefore be protected from unnecessary insults by ensuring that it is adequately covered by sufficient claw capsule (hoof) thickness whose hardness is maintained by avoiding wet underfoot environment and that distribution of weightbearing is correctly maintained according to the relative hardness of various parts of the

Although regular concentrate feeding in these farms for each cow meant 2 to 4 times per day, nevertheless the feeding frequencies and amounts in each farm were inconsistent and this was similar for mineral supplementation. The results of this study indicated that most of the claw lesions encountered were related to laminitis in nature (Belge & Bakir, 2005; Nocek, 1997) and this could highly suggest the presence of predisposing risk factors in the smallholder zero-grazing units that were studied. Lactation period between 1 to 90 days is the time that subclinical laminitis is most prevalent. This could be attributed to the continuing effects of the transitional period of feeding with high energy concentrates that cause subacute ruminal acidosis and release of vasoactive agents, subsequently triggering laminitic processes (Donovan et al., 2004; Vermunt, 2004). The laminitic processes are further aggravated by the stress of heavy milk production during the first 90 to 120 days post-calving (Rowlands et al., 1985). Gradual progression of subclinical laminitis lesions culminates into chronic laminitis (Nocek, 1997), which could explain the reason for association between the later stages of lactation and chronic laminitis. The association between 3rd or higher parities with chronic laminitis agrees with previous findings by Sogstad et al. (2005) that most lameness is generally associated with third or higher parities. The habit of leaving manure in the walk-alleys for more than one day enhanced development of both subclinical and chronic laminitis. This could be attributed to persistent wetness that causes excessive softening of the claw-horn making it easily susceptible to horn-lesions. With softer solear horn, pressure insult from the ground is easily transmitted to the underlying solear corium which then becomes traumatized, resulting in laminitis.

These findings agree with previous reports (Borderas et al., 2004; Vermunt, 2004).

The association of high concentrates feeding with subclinical and chronic laminitis as well as with sole bruising and white line separation is attributed to SARA and production of

laminitis related lesions since the adoption of confinement of cattle in zero-grazing housing units, whose floors are concreted hence improving on hygiene (Nguhiu-Mwangi, et al., 2009). With the likelihood of improved cleanliness and hygiene of the modern type of cattle houses, the prevalence of infective claw lesions is bound to continually decline.

The importance of the claw lesions prevalent in the cows in these zero-grazing units is that they mainly affect the horn of the claw. When the horn is affected, the claws become vulnerable to many types of insults because it interferes with the protection of the interior parts of the claws. The effects on the horn are due to the fact that in these lesions there underlies the laminitis syndrome as the cause or sequel of the lesions. During this laminitis syndrome, the damaged corium produces poor quality horn that is softer than normal as previously reported (Baggott & Russell, 1981; Nocek, 1997; Weaver, 1979). This explains why the whitish soft crumbling horn was seen in some claws with chronic laminitis in this study. The softer low integrity horn of the sole and the heel predisposes these sites to bruising and erosion, hence the high prevalence of sole bruising and heel erosion. Since the horn quality is poorer in chronic laminitis, sole bruising and heel erosion become more severe during that phase of laminitis. The softened horn easily undergoes bacterial erosion and necrosis (Nocek, 1997) particularly when combined with other physical factors that cause horn softening such as accumulation of slurry on the floor of the cow house (Baggott & Russell, 1981). Sole bruising and heel erosion were found to be deeper and affecting more weight-bearing zones of the claw when the corium was more damaged. When these two lesions are spread more widely on the weight-bearing surface of the claw, it also means they involve the horn more deeply. This makes the prognosis poor because trimming-off the eroded horn leaves very thin layer of normal horn (Nguhiu-Mwangi, 2007) through which external insults easily traverse and damage the underlying corium further. However, when sole bruising and heel erosion are diagnosed early, the necrotic eroded horn can effectively be trimmed-off and the claws dipped in or sprayed with antimicrobial chemicals with either 5% formalin solution or 5-7% copper sulphate solution.

Alterations in the shape of the claws in chronic laminitis has been reported previously (Greenough, 1987; Nocek, 1997) and is attributed to disruption in growth of keratinized horn (Nocek, 1997). This shape alterations associated with chronic laminitis are severe, irreversible and render reshaping of the claw difficult; hence they give chronic laminitis poor prognosis (Baggott & Russell, 1981; Nguhiu-Mwangi et al., 2008). This explains why attempts made to manage deformity conditions by trimming claws of the affected cows during this study, proved to be of little benefit. Therefore, the finding of irregularly shaped (unusual flattening, widening, concaving and rippling of the dorsal wall) claws in chronic laminitis is an indication of poor prognosis (Nguhiu-Mwangi et al., 2008) and attempts to manage them by trimming are therefore only palliative and short-lived. Ignorance and negligence of claw trimming practices in the zero-grazing units that were included in this study have been major cause and an aggravating factor in the progression of claw disorders to chronic stages. This contributes to long-term claw damage and worsens the prognoses (Nguhiu-Mwangi, 2007). It has been shown that trimming of hooves leads to lower locomotion scores and reduced clinical lameness (Manson & Leaver, 1988). When claws are excessively overgrown, weight-bearing is shifted towards the proximal parts near the heel bulb. These parts have softer and weaker horn that inadequately protects the underlying corium (Collins-née Hedges et al., 2004). Excessive claw overgrowth then leads to undue

laminitis related lesions since the adoption of confinement of cattle in zero-grazing housing units, whose floors are concreted hence improving on hygiene (Nguhiu-Mwangi, et al., 2009). With the likelihood of improved cleanliness and hygiene of the modern type of cattle

The importance of the claw lesions prevalent in the cows in these zero-grazing units is that they mainly affect the horn of the claw. When the horn is affected, the claws become vulnerable to many types of insults because it interferes with the protection of the interior parts of the claws. The effects on the horn are due to the fact that in these lesions there underlies the laminitis syndrome as the cause or sequel of the lesions. During this laminitis syndrome, the damaged corium produces poor quality horn that is softer than normal as previously reported (Baggott & Russell, 1981; Nocek, 1997; Weaver, 1979). This explains why the whitish soft crumbling horn was seen in some claws with chronic laminitis in this study. The softer low integrity horn of the sole and the heel predisposes these sites to bruising and erosion, hence the high prevalence of sole bruising and heel erosion. Since the horn quality is poorer in chronic laminitis, sole bruising and heel erosion become more severe during that phase of laminitis. The softened horn easily undergoes bacterial erosion and necrosis (Nocek, 1997) particularly when combined with other physical factors that cause horn softening such as accumulation of slurry on the floor of the cow house (Baggott & Russell, 1981). Sole bruising and heel erosion were found to be deeper and affecting more weight-bearing zones of the claw when the corium was more damaged. When these two lesions are spread more widely on the weight-bearing surface of the claw, it also means they involve the horn more deeply. This makes the prognosis poor because trimming-off the eroded horn leaves very thin layer of normal horn (Nguhiu-Mwangi, 2007) through which external insults easily traverse and damage the underlying corium further. However, when sole bruising and heel erosion are diagnosed early, the necrotic eroded horn can effectively be trimmed-off and the claws dipped in or sprayed with antimicrobial chemicals with either

Alterations in the shape of the claws in chronic laminitis has been reported previously (Greenough, 1987; Nocek, 1997) and is attributed to disruption in growth of keratinized horn (Nocek, 1997). This shape alterations associated with chronic laminitis are severe, irreversible and render reshaping of the claw difficult; hence they give chronic laminitis poor prognosis (Baggott & Russell, 1981; Nguhiu-Mwangi et al., 2008). This explains why attempts made to manage deformity conditions by trimming claws of the affected cows during this study, proved to be of little benefit. Therefore, the finding of irregularly shaped (unusual flattening, widening, concaving and rippling of the dorsal wall) claws in chronic laminitis is an indication of poor prognosis (Nguhiu-Mwangi et al., 2008) and attempts to manage them by trimming are therefore only palliative and short-lived. Ignorance and negligence of claw trimming practices in the zero-grazing units that were included in this study have been major cause and an aggravating factor in the progression of claw disorders to chronic stages. This contributes to long-term claw damage and worsens the prognoses (Nguhiu-Mwangi, 2007). It has been shown that trimming of hooves leads to lower locomotion scores and reduced clinical lameness (Manson & Leaver, 1988). When claws are excessively overgrown, weight-bearing is shifted towards the proximal parts near the heel bulb. These parts have softer and weaker horn that inadequately protects the underlying corium (Collins-née Hedges et al., 2004). Excessive claw overgrowth then leads to undue

houses, the prevalence of infective claw lesions is bound to continually decline.

5% formalin solution or 5-7% copper sulphate solution.

mechanical pressure on the solar corium due to excessive weight-bearing on the pedal bone and inadequate support of the corium by the horny capsule at the sole especially following thinning of the horn of the sole in laminitis (Baggott & Russell, 1981; Toussaint-Raven, 1973). Trimming tends to return the claw to near normal weight-bearing even at chronic stages of regular overgrowth (Weaver, 1993). However, when overgrowth is combined with chronic laminitis, the pedal bone undergoes irreversible alteration in its configuration within the claw capsule (Bargai et al., 1989; Greenough et al., 1990) and this result in poor prognosis.

It is prudent to conclude that regular examination is the most important way of ensuring good claw health. The most practical way to regularly observe the claws is during the milking times. Examination of the claws cannot be conclusive without trimming at least the horn of the sole. This is necessitated by the fact that lesions underneath the horn of the claws are not discernible externally until exposed by trimming (Nguhiu-Mwangi, 2007; Nocek, 1997). Such routine examination will help to recognize and manage claw disorders in the early stages before they progress to unmanageable chronic stages in which the claws are irreversibly damaged. Furthermore, the corium is the tissue that determines the health of the claw. It should therefore be protected from unnecessary insults by ensuring that it is adequately covered by sufficient claw capsule (hoof) thickness whose hardness is maintained by avoiding wet underfoot environment and that distribution of weightbearing is correctly maintained according to the relative hardness of various parts of the claw (Berry, 1999).

Although regular concentrate feeding in these farms for each cow meant 2 to 4 times per day, nevertheless the feeding frequencies and amounts in each farm were inconsistent and this was similar for mineral supplementation. The results of this study indicated that most of the claw lesions encountered were related to laminitis in nature (Belge & Bakir, 2005; Nocek, 1997) and this could highly suggest the presence of predisposing risk factors in the smallholder zero-grazing units that were studied. Lactation period between 1 to 90 days is the time that subclinical laminitis is most prevalent. This could be attributed to the continuing effects of the transitional period of feeding with high energy concentrates that cause subacute ruminal acidosis and release of vasoactive agents, subsequently triggering laminitic processes (Donovan et al., 2004; Vermunt, 2004). The laminitic processes are further aggravated by the stress of heavy milk production during the first 90 to 120 days post-calving (Rowlands et al., 1985). Gradual progression of subclinical laminitis lesions culminates into chronic laminitis (Nocek, 1997), which could explain the reason for association between the later stages of lactation and chronic laminitis. The association between 3rd or higher parities with chronic laminitis agrees with previous findings by Sogstad et al. (2005) that most lameness is generally associated with third or higher parities. The habit of leaving manure in the walk-alleys for more than one day enhanced development of both subclinical and chronic laminitis. This could be attributed to persistent wetness that causes excessive softening of the claw-horn making it easily susceptible to horn-lesions. With softer solear horn, pressure insult from the ground is easily transmitted to the underlying solear corium which then becomes traumatized, resulting in laminitis. These findings agree with previous reports (Borderas et al., 2004; Vermunt, 2004).

The association of high concentrates feeding with subclinical and chronic laminitis as well as with sole bruising and white line separation is attributed to SARA and production of

Risk (Predisposing) Factors for Non-Infectious

**5. Conclusion** 

the subclinical phase.

**6. Future research** 

**7. Acknowledgements** 

113-132

66

Alberta, Canada. pp 207

**8. References** 

Claw Disorders in Dairy Cows Under Varying Zero-Grazing Systems 419

The smallholder zero-grazing dairy units in the peri-urban areas of Nairobi, Kenya have uniquely wide variations in their production systems with respect to housing designs, nutritional regime and management protocol. From the statistical associations in this study, it can be concluded that the cow-level factors that strongly contribute to the development of claw lesions are 3rd or higher parities and being in the lactation period between 1 to 90 days. The farm level factors that strongly enhance claw lesion development are frequent high concentrate feeding, lack of regular mineral supplementation, both concrete and earthen floors, overstocking, the presence of a curb between walk-alley and cubicles, and leaving manure in the walk-alley for a long time. These associations are supported strongly by statistics that indicate the direction and strength of the relationship. It can also be concluded that non-infective claw disorders in dairy cows particularly the disorders related to laminitis are insidious in nature, which gradually but progressively damage the integrity of the claw. The subclinical occurrence of these disorders makes them subtle and careful early diagnosis so that remedial measures can be instituted early before these irreversible damages have occurred is essential. The fact that a cow does not show signs of lameness does not necessarily imply her claws are sound, but only calls for further careful scrutiny. Claw trimming is one of the major ways of discerning these underlying claw disorders at

Due to the wide variations in the smallholder production units in the study area, there is a need to carry out a controlled experimental study to further elucidate these risk factors. A comparative study should also be carried out in Kenya to establish if similar risk factors exist in the large scale better managed farms. Each of the risk factors incriminated in the

We are grateful to the Deans Committee, University of Nairobi, Kenya for providing a

Baggott, D.G. & Russell, A.M. (1981): Lameness in cattle. *British Veterinary Journal* vol.137, pp

Bargai, U, Pharr, J.W.& Morgan, J.D. (1989) radiographic changes in chronic laminitis

Belge, A. & Bakir, B. (2005). Subclinical laminitis in dairy cattle: 205 selected cases. *Turkish* 

Bergsten, C. (1994). Haemorrhages of the sole horn of dairy cows as a retrospective indicator

*Journal of Veterinary and Animal Science*, vol. 29, pp 9-15

*Proceedings of the 8th International Symposium on Disorders of Ruminant Digit and International Conference on Bovine Lameness*. Saskatoon, Saskachewan, and Banff,

of laminitis: an epidemiological study. *Acta Veterinaria Scandinavica*. Vol.35, pp 55-

current study needs individual experimental evaluation.

proportion of financial support to carry out the study.

vasoactive substances. This initially triggers development of subclinical laminitis as has been reported previously (Cook et al., 2004; Vermunt, 2004). Subclinical laminitis then predisposes the cow to other claw lesions (Nocek, 1997). Failure or inadequate supplementation of the cows with mineral mixtures was associated with enhanced development of subclinical and chronic laminitis as well as white line separation. This finding conforms to the reports stating that trace-minerals reduce claw lesion scores (Tomlinson et al., 2004) and biotin supplementation reduces macro-cracks in the claws (Higuchi & Nagahata, 2001). The positive association between overstocking and chronic laminitis may be attributed to the long hours of standing because of fewer cubicles. Standing for long periods causes prolonged pressure injury to the solear corium, thus being an exacerbating factor to the development of claw lesions as reported previously (Leonard et al., 1994). Further to this, the presence of a high curb between the walk-alley and the cubicles was found to be one of the main factors enhancing occurrence of chronic laminitis. This factor may possibly cause additional stress to the claws as the cow enters or disembarks from the cubicle, as has been suggested by others (Leonard et al., 1994; Philipot et al., 1994). Eventually it contributes to compromise of the entire phenomenon of "cow comfort" and some cows prefer standing on the free alleys to occupying the cubicles. Standing for long periods in the free walk-alleys causes further stress to the corium.

The results of this study also found that housing cows on earthen (bare soil) floors was an important risk factor for development of chronic laminitis. This is possibly due to the fact that such floors have soft (yielding) surfaces which tend to promote overgrowth of the claws for lack of constant hoof-wear (Rhebun & Pearson, 1982). Claw overgrowth and change in its angle result in redistribution of weight-bearing that subsequently overloads specific zones of the claw particularly during locomotion (Van der Tol et al., 2003). Consequently, these effects predispose the affected claws to development of laminitis and other claw lesions (Neveux et al., 2006; Sagues, 2002). However, earthen floors were found to be protective against occurrence of sole bruising. This could be attributed to the floor being soft, yielding and non-abrasive which closely relates to a previous report by Somers et al. (2003) stating that cows raised on yielding straw-yard surfaces were found to have very low prevalence of claw disorders. Chronic laminitis is the only claw disorder that showed a significant difference between cows in zero-grazed and in pasture-grazed farms with higher prevalence in zero-grazed cows. The hard concrete surface that was more common in the zero-grazed farms, probably combined with regular concentrate feeding, could have contributed to the difference in the prevalence rates of chronic laminitis between zerograzed and pasture grazed farms (Bergsten, 1994; Somers et al., 2003; Vokey et al., 2001).

Absence of cubicle bedding and presence of bare concrete in the cubicles was found to be associated with occurrence of chronic laminitis. Some of the cubicles were narrow in such a way that cows remained in a standing posture even within the cubicles. This act of standing in the cubicles further prolongs the cumulative period of stress exerted on the claws while on concrete. The consequence of this stress is the increased incidence of claw lesions, particularly laminitis (Bergsten & Herlin, 1996; Somers et al., 2003). Good concrete (non-slip, without defects or loose stone pebbles) was protective against heel erosion probably due to the absence of traumatic edges. The non-slip nature of the floor would also prevent abrasive trauma on both the heel and sole.
