**2. Study procedures**

#### **2.1 Geographical study area**

This study was carried out in the peri-urban areas of Nairobi, Kenya in a period of six months (partly during the long rainfall season and partly during the short rainfall season). This is a fertile agricultural zone with an altitude of 1798 metres above sea level and has an annual rainfall estimated at a maximum of 765 mm and a minimum of 36 mm in two distinct seasons, March to June (long rainfall season) and October to December (short rainfall season) respectively.

#### **2.2 Zero-grazing unit and animal selection**

394 A Bird's-Eye View of Veterinary Medicine

circumscribed excessive local loading, thus stimulating more horn production and enlarging of the claws. A positive correlation exists between the time cows spend on hard floors and development of claw horn lesions. This confinement further adversely affects behavior and welfare of cattle (Bergsten, 1994: Somers et al., 2003; van der Tol et al., 2003). These practices synergistically with high levels of concentrate diets exacerbate the occurrence of claw-horn disorders (Cook et al., 2004; Donovan et al., 2004; Nocek, 1997; Somers et al., 2005; Vermunt, 2004). Feeding cattle with diets that lead to low-grade prolonged lowering of rumen pH could result in an up-surge of lameness due to increased incidences of laminitis. Excessive feeding of rapidly fermented carbohydrates and finely chopped fodder silage enhance development of laminitis due to their tendency of initiating subacute ruminal acidosis (SARA), which is also aggravated by a fall in the ratio of concentrate to forage (C:F) (Vermunnt, 2004). However, supplementing cattle with minerals and vitamins tends to improve claw health and reduce likelihood of developing laminitis and sole lesions (Bergsten et al., 2003; Tomlinson et al., 2004). Previous publications based on retrospective data show that improvement of cattle housing in the zero-grazing units from earthen slurryladen floors to concrete floors, has led to a shifting from high prevalence of infective claw lesions and low prevalence of non-infectious laminitis related disorders to high prevalence of laminitis related disorders and low prevalence of infective claw lesions (Gitau, 1994;

In developing Kenya where this research on association between non-infective claw disorders and risk factors was carried out, increased human population has led to inevitable reduction in per capita land-holdings. This has invariably led to diminished grazing land and subsequently triggering an increase in smallholder zero-grazing dairy production units particularly for the low income households (Mutugi, 2004). Rearing of dairy cows in smallholder zero-grazing units in developing countries is inevitable since they are part of the livelihood of the high population of low class smallholder farmers. For example in Kenya, smallholder units contribute 80% of the national commercial dairy herd (Wanyoike & Wahome, 2004). These smallholder dairy production units in Kenya have varied designs and management practices. They are so varied unit to unit and sometimes within individual units that they can be further classified as subunits. They completely lack standardization of housing designs, nutritional regimen and management protocols (Nguhiu-Mwangi, et al., 2008). Prevalence of claw disorders in dairy cows raised under smallholder zero-grazing systems in Kenya and possible risk factors leading to development of these claw disorders has not been documented previously. Therefore, the study was carried out in Kenya to verify the types of claw disorders in dairy cows that are raised in the smallholder subunits under varied zero-grazing systems and to find out through statistical analysis whether there is any association between these subunit-level factors, animal-level factors and the claw

This study was carried out in the peri-urban areas of Nairobi, Kenya in a period of six months (partly during the long rainfall season and partly during the short rainfall season). This is a fertile agricultural zone with an altitude of 1798 metres above sea level and has an annual rainfall estimated at a maximum of 765 mm and a minimum of 36 mm in two

Mbithi et al., 1991; Nguhiu-Mwangi et al., 2009).

disorders.

**2. Study procedures** 

**2.1 Geographical study area** 

Evaluation of 32 smallholder zero-grazing dairy units purposively selected was done, in which cows were also examined for lameness and claw lesions. The zero-grazing units selected were those with 5-20 adult dairy cows. The farmers owning most of the zerograzing units were skeptical and hesitant to allow their dairy units evaluated or their cows examined. This was the reason for purposive selection of the zero-grazing units used in this study. The cows that were included in the study of claw lesions were those that had calved at least once with parities ranging between first and fourth. Those with 3rd and 4th parities were 60% and those with 1st and 2nd parities were 40% of the total population examined. All the selected cows whether lame or non-lame were examined. All the cows that had the study criteria were tagged with serial numbers 1, 2, 3, to n, where n was the serial number of the last cow being selected in the zero-grazing unit. To avoid biased numbering of the cows, assigning of serial numbers was randomly done by an independent worker employed in the zero-grazing unit. Then the author did the systematic selection of individual cows from the serialized groups by picking every second cow from the serial numbers. For example in the serial n1 to n10, if the first cow selected was n1, the next serially selected would be those with odd serial numbers (n1, n3, n5, n7, and n9). But if the first cow selected was n2, the next serially selected would be those with even serial numbers (n4, n6, n8 and n10). The serial numbers of the first cow selected was alternated between n1 and n2 from one zero-grazing unit to the next. Therefore, the cows selected in any zero-grazing unit were all those with either odd or even serial numbers.

#### **2.3 Study design and data collection**

The data were collected in a cross-sectional study in which each smallholder zero-grazing dairy unit was visited only once. During the single visit, the zero-grazing unit was evaluated and data recorded on possible risk factors of claw conditions. The selected cows were also evaluated for claw lesions as well as animal-level risk factors of claw lameness conditions. Data on animal-level risk factors were collected by the author administering questionnaires to the farmers or to the persons employed to manage the zero-grazing units as respondents before examination of each cow. These data included breed of the cow, parity, milk yield per day and lactation stage. The questionnaires were structured with simple "Yes" or "No" and "I do not know" responses to minimize variations and information bias from the respondents. From the 32 smallholder zero-grazing units, 300 dairy cows were examined for claw lesions and animal-level risk factors. Out the 300 cows, Friesians were 76% (228), Ayrshires 20% (60) and the remaining 4% (12) were a mixture of Guernsey and Jersey. Data from unit-level risk factors were collected during visitation to each of the 32 smallholder zero-grazing units. Some of the data (housing and stall design, number of cubicles, type of cubicle bedding, type of floor, presence or absence of a curb (kerb) at the rear end of the cubicles, lunging space, bob zone, presence or absence of neckbar over the feeding bunk/trough and adequacy of feeding space) were collected through observational (qualitative) method. Other data such as curb height and height of neck-bar from the top surface of feeding trough were collected through actual measurements, while

Risk (Predisposing) Factors for Non-Infectious

between the smallholder zero-grazing units.

had very low prevalence of 4.7% (Table 1).

Laminitis-related disorders

Laminitis-related claw deformities

Non-laminitis lesions

in Kenya.

**3.1 Prevalence of claw disorders found in the study** 

**3. The study findings** 

Claw Disorders in Dairy Cows Under Varying Zero-Grazing Systems 397

with in the analysis but they were minimal because of some similarities in the management

The results of this study revealed that cows from the varied smallholder zero-grazing dairy units had a high (88%) prevalence of claw lesions, 69% of which did not manifest lameness but had subclinical disorders and only 31% were lame. Some of the cows had more than one claw disorders concurrently. Laminitis had the highest prevalence (70.3%), with subclinical laminitis at 49.3% and chronic laminitis at 21%. Other non-infectious claw disorders with high prevalence were sole bruising (erosion) at 45%, claw overgrowth at 30%, heel erosion at 27.3%, white line separation at 18% and underrun (double) soles at 17%. Infective lesions

Claw lesions Number of cows (n = 300) Prevalence (%) Subclinical laminitis 148 49.3 Chronic laminitis 63 21.0

Sole bruising 135 45.0 Heel erosion 82 27.3 White line separation 54 18.0 Underrun (double) soles 51 17.0 Sole ulcer 8 2.7 sole foreign bodies 1 0.3

Claw overgrowth 91 30.3 Claw horn deep horizontal grooves 53 17.8 Flattened claws (reduced toe angle) 36 12.0 Splayed toes 26 8.7 Concaved dorsal claw wall 15 5.0 Corkscrewed claws 14 4.7

Claw infective lesions 14 4.7 Claw traumatic lesions 2 0.7 Growths in the foot soft tissues 2 0.7

(NB: *Some of the cows had more than one claw disorders concurrently, hence percentage totals of more than 100*). Table 1. Prevalence of claw disorders and lesions and their prospective risk factors as found during a cross-sectional study in dairy cows in varied smallholder zero-grazing dairy units

Among the cows that had chronic laminitis, 85% had more than two other concurrent claw disorders such as underrun (double) soles, sole bruising, heel erosion and white line separation. In addition, all the cases of chronic laminitis invariably had one or more ways in

the rest (frequency and amount of concentrate feeding , mineral supplementation, type of fodder, and frequency of manure removal from the walk-alleys were collected by the author interviewing the farmers or the persons managing the zero-grazing units. All the data both for animal-and unit-level risk factors were entered into the questionnaires using codes adopted at the pre-coding stage during an initial pilot study in 5 sample smallholder zerograzing dairy units.

#### **2.4 Examination of the cows for claw lesions**

Each cow was examined for general lameness using universally described locomotion scoring system (Sprecher et al., 1997). Data on claw disorders were collected by examining each claw on each cow. Each cow was restrained in a standing posture in a restraining area (crush). The limbs were lifted one at a time by tying with a rope and fastening the rope to an overhead pole or cross-bar. In that raised position, each claw was thoroughly washed with soap and water and examined for any lesions particularly on the weight-bearing surface. About 1-2 mm thickness of the horn of the sole was trimmed-off using a sharp quitter knife to expose any underlying lesions particularly sole haemorrhages. Trimming did not reach the level of corium and therefore no pain was caused on the cows. In cases with painful claw conditions, foot anaesthesia using 2% lignocaine hydrochloride was applied to allow painless manipulation. The lesions found on each cow were recorded.

#### **2.5 Data management and analysis**

The data were entered and stored in Microsoft Office Excel 2003. After verification and validation of data, they were imported into SAS© 2002-2003 (SAS Institute Inc., Cary, NC, USA). Descriptive statistics were computed for cow-level and unit-level risk factors. The prevalence rate of each claw disorder was calculated independent of other claw disorders. The prevalence of each claw disorder was calculated as the number of cows affected by the specific claw disorder or lesion (nCL) divided by the total number of cows (300) examined, and then multiplied by 100.

$$\text{Prevalence (\%)} = \frac{n\text{CL}}{100} \text{x100} \tag{1}$$

Chi-square (χ2) statistics were used to determine unconditional associations between all risk factors and the claw lesions. An association was considered significant at the level of p<0.05. Chi square values were determined using 2 x 2 contingency tables constituting 2 rows and 2 columns. In these associations the Chi square calculations were determined by evaluating each risk factor (variable) against each claw disorder (outcome) on the cow. The degrees of freedom (df) in each case was standard, being calculated by:

$$[(\text{row-1}) \times (\text{columns-1})] \text{ } \text{hence } [(\text{2-1}) \times (\text{2-1})] \tag{2}$$

Therefore, df was 1 for each association test. Multiple logistic regressions were done through a step-down regression in which the risk factors that made the least variation to the occurrence of the claw lesions were eliminated one at a time through consideration of their odds ratios. Only the factors that were found to influence the occurrence of claw lesions significantly were retained in the model. The effects of confounding risk factors were dealt with in the analysis but they were minimal because of some similarities in the management between the smallholder zero-grazing units.
