Prevalence of Lameness in Dairy Cows and Associated Risk Factors at Hawassa Town Dairy Farms, Ethiopia

Lameness is one of the greatest constraints on the productivity, health, and welfare of dairy cattle. A cross-sectional study was carried out from March 2021 to September 2021 in Hawassa town with the aim of assessing the prevalence and identifying the associated risk factors of lameness in dairy farms. The study was conducted on 440 animals belonging to 19 randomly selected intensive dairy farms. Data regarding lameness and its possible risk factors were collected both at animal and farm level using a questionnaire. The results showed that the overall prevalence of lameness was 10.2% (n = 45/440). The association of lameness prevalence with various risk factors including milking status, exercise, age, parity, milk yield, and lactation stage was statistically tested using logistic regression model. There was a significant variation in the prevalence of lameness (P < 0.05) between cattle with different milking status, age, parity, milk yield, and stage of lactation by the univariable analysis result. According to the multivariable analysis, only milk yield and lactation stage were statistically associated with the occurrence of lameness. Milking animals (8%) had higher prevalence of lameness than nonmilking (2.2%). The occurrence of lameness increased with milk yield. The highest prevalence of lameness was recorded in the early stage of lactation. Lameness was more frequent in hind limbs (6.6%) than in forelimbs (3.6%). The main causes of lameness observed in this study were both claw overgrowth 10 (2.3%), unequal claw size 10 (2.3%), solar ulcer 8 (1.8%), interdigital necrobacillosis 2 (0.5%), interdigital hyperplasia 2 (0.5%), and digital dermatitis 1 (0.2%). There was no means of early lameness diagnosis in 94.7% of farms. Lameness was found to be an important disease in dairy cows at Hawassa town. Prevention and early diagnosis leading to prompt treatment of lameness in cows should be part of dairy farm management practice.


Introduction
Dairy production plays a crucial role in Ethiopian livestock farming.Te country possesses abundant and diverse livestock genetic resources, coupled with a variety of agroecologies suitable for dairy farming.Te rising consumer demand for milk and its derivatives, favorable market conditions, and close proximity to international markets underscore the signifcant potential and opportunities for the development of the dairy industry in Ethiopia [1].
Despite this substantial potential, the dairy sector has not reached the anticipated level of development, and the overall productivity of dairy animals remains low [2,3].Various challenges, including issues like lameness [4][5][6][7], contribute to this situation.Consequently, there is a shortage in the supply of dairy products, necessitating the country to expend foreign currency on importing them from abroad [2].
Lameness, characterized by a departure from the typical walking pattern due to lesions, defects, injuries, diseases, or other factors afecting the limb or other parts of the body, is typically accompanied by pain or a certain level of discomfort [8].Within the dairy industry, lameness stands out as a critical and pressing issue [9].It is acknowledged as the foremost challenge impacting productivity, health, and welfare in dairy cattle.
Lameness represents a crucial production disease in dairy cows with notable economic implications [10].In general, clinical incidences of lameness have a considerable negative impact on milk production, resulting in a reduction of 357 kg over a 305-day lactation period [11].Te onset of lameness is notably prevalent in the initial two months of a cow's frst lactation, and the alarming statistic that 50% of animals experience chronic lameness during their life underscores its severity [12,13].Lameness emerges as a signifcant risk factor for culling throughout the lactation period.Cows treated for foot and leg problems at the onset and in the second month of lactation face a culling risk six to twelve times higher than that of healthy counterparts [14].Beyond economic concerns, lameness in dairy cows raises serious welfare issues by causing pain and impeding the movement of the animals [15].
Bovine lameness, ranking third globally in modern intensive dairy production following reproductive failure and mastitis, leads to reduced milk production, enhanced treatment expenses, increased culling rates, and prolonged calving intervals [25].In Ethiopia, several studies highlight the signifcant impact of lameness in dairy cattle.An economic loss study conducted in Wolaita Sodo revealed that lameness resulted in a loss of 7.33 USD (125.30ETB) per cow, attributed to decreased milk output and treatment costs as documented by Kife [26].Additionally, Sulayeman and Fromsa [4] determined a mean reduction of 1.63 litres in daily milk yield per cow in Hawassa dairy cattle.Among the lameness-positive animals, eight out of 15 were milking cows, while the remainder were nonmilking.Te average daily milk production per cow decreased from 6.36 litres to 4.75 litres after the onset of lameness, indicating a mean loss of 1.63 litres in milk yield per cow per day.
Despite lameness posing signifcant economic losses and impacting the health and well-being of dairy cattle in Ethiopia, there is a scarcity of studies addressing the prevalence of lameness and its associated risk factors, particularly in Hawassa town.Furthermore, although lameness is infuenced by various modifable management practices, the last examination of lameness prevalence and associated risk factors for dairy cattle in Hawassa occurred in 2012 [4].Terefore, the present study aims to update the prevalence and associated risk factors of lameness in dairy farms located in Hawassa town.

Study Area.
Te study was carried out in Hawassa town, which is located in Southern Ethiopia situated 270 km south of Addis Ababa.Te area has a latitude of 7 °3′ 0″ N and a longitude 38 °28′ 0″ E on the escarpment of the Great Rift Valley.Te altitude ranges from 1650 to 1700 meters above sea level.Te average annual rainfall of the study area ranges from 800-1000 mm, and the mean temperature ranges from 11.14 °C-29.1 °C.Te soil type of Hawassa town is lacustrine that is medium to fne textured and alluvial that includes clay, sand, and gravel.Te area is mainly covered by dry savanna and bush type of vegetation including mainly short grasses and shrubs and to some extent eucalyptus, oak, and other indigenous and exotic plants [27].Te total livestock population of the study area constituted 1,721,341 cattle, 228,941 goats, 457,465 sheep, 57,643 horses, 54066 donkeys, 725, 5540 poultry, and 44,492 beehives [28].

Study Animals.
Te study was conducted on 440 Holstein Friesian dairy cattle belonging to 19 farms kept under intensive management system in Hawassa town.Each animal was identifed by site of farm, age, parity, amount of milk per day, stage of lactation, and herd size using data fles from the dairy personnel.Te ages of the animals were determined primarily based on the information obtained from the animal owners and secondly by looking at the dentition pattern of the animals [29].Te foor system was concrete, and both roughage and concentrated feed were provided to the animals.All visited farms did not use bedding for their animals.All farms included in the study area have a practice of dung removal two or more times per day.

Study Design, Sampling Method, and Sample Size Determination.
A cross-sectional study was carried out from March 2021 to September 2021 in Hawassa town.According to the information obtained from the agricultural ofce of Hawassa town, the town has 157 dairy farms.A list of all 157 farms was prepared, and 19 farms were selected using a simple random sampling, lottery technique.All animals of each selected farm were included in the study.
Te sample size for the study was determined based on the description of Trusfeld [30] and considering as expected the prevalence of 50% as there was no previous study about prevalence of lameness in Hawassa town before this study, with the confdence interval of 95% and 5% required absolute precision.Ten, the minimum required sample size was calculated using the following formula: where N � sample size, P exp � expected prevalence, and d � required precision.By substituting the values in the formula and taking d � 0.05, Even though the calculated sample size was 384, the study was conducted on a total of 440 animals by adding 15% to increase the precision.

Data Collection.
A semistructured questionnaire which contained both animal and farm level questions was developed to collect data.Data regarding foor type, frequency of dung removal, and production status, animal's age, sex, lactation stage, type of feed, and site of lesion were collected.Te questionnaire was developed based on previous studies [4,31].In order to assure the quality of the data, a pretest of 2 Veterinary Medicine International data collection instrument was carried out on 5% of the total sample size outside the study area.Furthermore, all the animals in the selected farms were carefully observed and clinically examined for lameness.During the examination, the study animals were allowed to move and observed for any symptom of abnormal gait as described by Shearer et al. [32].
2.5.Data Analysis.Te data collected in the paper format was transferred to and stored in Microsoft Excel database.Stata/MP software version 16 was used for the analysis of the data.Te prevalence of lameness was presented using descriptive statistics.Logistic regression model was used to check the association of the abovementioned potential risk factors with the occurrence of lameness.Pearson's chisquare test was used to evaluate the association of diferent variables with the prevalence of lameness with treatment practice.In all statistical analysis executed, 95% confdence level and 5% precision were used and P value of less than 0.05 was considered as statistically signifcant.2).

Prevalence of Lameness with Associated Risk Factors.
Table 3 displays the outcomes of a univariable logistic regression examination regarding the occurrence of lameness in dairy cows, considering diferent risk factors.With the exception of the permission for dairy animals to engage in exercise (P > 0.25), all the factors explored in the research, milking status, age, parity, milk yield, and lactation stage were determined to be statistically signifcant (P < 0.25).All the independent variables that demonstrated signifcance in the initial univariable analysis underwent an assessment for colinearity using Kruskal gamma statistics.Variables with gamma values falling between −0.6 and +0.6 were deemed suitable for inclusion in the multivariable logistic regression model.Consequently, milk yield and lactation stage were selected for the multivariable analysis.Both variables incorporated into the multivariable model, namely, milk yield and lactation stage, exhibited signifcance (P < 0.05) (Table 4).Te Hosmer-Lemeshow goodness-of-ft test indicated that the model adequately fts the dataset (χ 2 � 0.732; P � 0.866).

Prevalence of Lameness and Limbs
Afected.We also described the proportion of lameness associated with the type of limbs.Lameness was observed due to problems from both limbs.However, hind limbs were more prone to lameness than forelimbs (Table 6).

Practice of Early Lameness Detection and Treatment.
Out of the 19 farms observed, only one farm had the practice to detect early signs of lameness.Te incidence of lameness in dairy cows is notably higher (10.59%) in farms lacking means for early recognition compared to those with such capabilities, where lameness is recorded at 7.7% (Table 7).Most of the treatments were carried out by veterinarians (16/ 19).Te prevalence of lameness in dairy farms where farmers are responsible for treatment (11.11%) surpasses that in farms where veterinarians handle treatment (10.03%) (Table 7).Te treatment success in the study area was 100%.Ten cows were culled in the last two years due to lameness.

Discussion
Te current investigation revealed a lameness prevalence of 10.2% in dairy farms located in Hawassa town.Tis study highlights a signifcant and widespread occurrence of lameness in the study area, emphasizing the need for appropriate preventive and therapeutic measures.Notably, this prevalence is higher than the fndings reported by Lobago et al. [33] who documented a lameness rate of 7.7% in clinically examined dairy cattle under urban and peri-urban production systems in the Addis Ababa milk shed.Similarly, Kife [26] reported a lower lameness prevalence of 4.0% in Wolaita Sodo.In contrast, our study's prevalence is lower than that reported by Abunna et al. [31] in Bishoftu, where lameness was recorded at 13.9%.Moreover, the prevalence of lameness found in the present study is lower than that reported in other countries, such as 36.8% in England and Wales [34] and 28.5% in Canada [35].Te variations in lameness prevalence among our study and those conducted in diferent countries could be attributed to diferences in the management system, climate, study duration, cow productivity, and the methods employed for lameness detection and prevention.Geographical disparities and seasonal fuctuations in the Veterinary Medicine International incidence and prevalence of lameness are also evident, as indicated by Espejo et al. [36].
In the current study, the lameness prevalence varied among the farms, ranging from 0% to 33.3%, and there was a statistically signifcant correlation between the prevalence of lameness and the examined farms (p < 0.05).Te difference in the prevalence of lameness between the farms might be due to the diferences in management system and awareness of the negative impact of lameness.
Tis study examined the risk factors associated with lameness, considering both milking and nonmilking cows.Te prevalence of lameness in milking cows was 35 (8%), while, in nonmilking cows without pregnancy, it was 10 (2.2%).Te higher prevalence in milking cows is likely linked to the mobilization of fat from various tissues to support milk production, as suggested by Green et al. [37].Consequently, the hypothesis was formulated that elevated milk yield may result in thinner digital cushions, exposing cows to conditions such as sole ulcers and white line disease [38].Te present study strengthened this hypothesis by evidencing that milk yield is signifcantly associated with the occurrence of lameness.
A higher prevalence of lameness, specifcally 10.2%, was recorded in animals aged greater than two years compared to animals aged less than two years, where the prevalence was 0%.Te fndings of our study align with those of Manske et al. [39] who observed an increase in lameness with advancing age.
Te occurrence of lameness in this study was higher in animals that yield more than 16 litters of milk per day (44.4%)compared to those produce less than 16 litters, and these might also be due to the loss of minerals such as calcium that have a great role in the strength of bone in animals.
In this study, the occurrence of lameness and the limbs afected was signifcantly associated, indicating that lameness was most common in hind limbs than in forelimbs possibly due to the fact that the hind legs were often contaminated with manure and kept wet.Hedges [40] also reported that on average, approximately 80% of lame cows are lame in the hind limbs.Singh et al. [41] also reached to similar fndings from Punjab where the distribution of lameness in cattle was 28.9% in forefoot, 54.7 in hind feet, and 16.3% in both fore and hind feet.Te same authors have 4 Veterinary Medicine International also recorded more frequent foot abnormalities in the hind (80%) than in the fore (20%) feet in bufaloes.Sadiq et al. [42] suggested that there was no signifcant link between the prevalence of lameness and parity.In contrast, our study demonstrated a noteworthy connection between lameness occurrence and parity.Te higher prevalence in animals with more than two parities is believed to be attributed to their prolonged exposure to uncomfortable barn conditions and the absence of early lameness detection methods on the farm.
Van Amstel and Shearer [43] asserted that confnement on hard surfaces alone is sufcient to induce a mechanical form of laminitis, leading to subsequent claw overloading.Similarly, Barker et al. [34] found that housing dairy cows for 61 days or more were a signifcant risk factor associated with lameness prevalence in dairy herds in England and Wales.In contrast, Bicalho et al. [38] highlighted that lameness in dairy cows can manifest at any point during lactation, similar to many other diseases.
According to the present study, lesions that were found causing lameness were sole ulceration 8 (1.8%), digital dermatitis 1 (0.2%), claw overgrowth 10 (2.3%), unequal size claw 10 (2.3%), and interdigital hyperplasia and interdigital necrobacillosis 2 (0.5%).Highly prevalent lesions causing lameness in this study were unequal claw size and claw growth, and this might be due to lack of exercise and poor practice of hoof trimming.

Conclusion and Recommendations
Te present study indicated a high and wide distribution of lameness that varied among the farms.High occurrence of lameness was recorded in cows with milking status, early lactation period, increased parity, and high milk yield.Te present study showed that hind limbs of dairy cattle are more prone to foot lesions than the forelimbs.Poor means of recognizing early cases of lameness in the farms were another fnding of the study.Terefore, providing awareness to farmers on the risk factors of lameness and management systems of dairy cattle is crucial to minimize lameness which is a serious welfare and economically important disease of dairy cows.

Table 1 :
Gender and educational level of farm workers.

Table 2 :
Te prevalence of lameness in the individual examined farms.

Table 3 :
Univariable logistic regression analysis of risk factors for the occurrence of lameness in Hawassa city dairy farms.

Table 4 :
Multivariable logistic regression analysis of potential risk factors for the occurrence of lameness in Hawassa city dairy farms.

Table 5 :
Lesions that caused lameness in dairy cows in Hawassa town.

Table 6 :
Te prevalence of lameness and limbs afected in dairy cows in Hawassa town.