The synopsis of this study was approved by the “Committee for the Purpose of Control and Supervision of Experiments on Animals” (CPCSEA) and Institutional Animal Ethics Committee (CPCSEA/IAEC/LA/SRSICAR-NDRI-2017/NO. 20).

The present study was conducted in Doddaballapura Taluk (13.292°N 77.543°E) of Bengaluru Rural District, located in south-eastern part of Karnataka, India during November 2017 - May 2018. The average temperature and humidity of the study area were 25° C (range: 22 to 29° C) and 61.25% (range: 49 to 75%) respectively during the study period. The number of animals reared by the farmers in the study area was two to five mature cows along with their progenies per smallholder unit. The mature animals were investigated in each household once during the study period to determine the risk factors associated with the incidence of lameness. The data were collected directly from farmers using a questionnaire.

Data collected using questionnaire included information on animal level and herd management level factors. Animal level observations included were breed, age, parity, lameness, body condition score (BCS), hoof disorders, hoof colouration, foot angle, hock injury, knee injury and animal hygiene score. Herd management level observations included were feeding and watering practices, the housing condition (tie-stall or free-stall), type of flooring (stone slab, cemented and kachha (earthen) and floor cleanliness score. A total of 204 crossbred dairy cattle comprising 127 Holstein Friesian (HF) crossbred and 77 Jersey crossbred dairy cattle were investigated during the study period regardless of their lactation status.

Chi-square test of independence was used to test the association between risk factors and the incidence of lameness. Binary logistic regression analysis was employed to find out the significant predictive risk factors of lameness and to determine adjusted odds ratio (OR) with 95% confidence interval for the subgroups of risk factors (Hosmer and Lemeshow, 2000). P values less than or equal to 0.05 was considered to be statistically significant. All the statistical analyses were done using IBM-SPSS Software 20.0.

All the statistically significant results are presented in Table 1. The overall incidence of lameness was found at 13.2%. The Holstein Friesian (HF) crossbred (18.1%) genetic group had significantly (p<0.01) higher incidence of lameness than Jersey crossbred dairy cattle (5.2%). This higher incidence in Holstein Friesian (HF) crossbred animals can be attributed to their selection for their high milk production trait which itself make them vulnerable to various production and reproduction related diseases and lameness is one out of them. Lohith et al. (2016b) also found a higher incidence of lameness in graded HF cattle followed by HF crossbred and Jersey crossbred respectively. Similarly, Bran et al. (2018) had also found that a higher incidence of lameness is associated with Holstein breed of cattle followed by crossbred dairy cattle and Jersey cattle respectively. Age of the cows had a significant effect on the incidence of lameness (p<0.01). It was found that as the age of the cows advanced greater than six years, they were found to have more incidence of lameness (36.0%) followed by cows under the age group less than 4-6 years (10.1%) and <4 years (10%). Findings of the present study are in agreement with a study conducted by Dembele et al. (2006) who found that as age advanced, the incidence of lameness increased and followed an inverted “U” shaped relationship with age and highest risk for cows becoming lame were in age 7-8 years. However, results of the present study are not comparable with the study conducted by Rowlands et al. (1985) where they found that the vulnerability of cows to lameness increased four folds for cows over 10 years of age. The reason behind this may be that, in the present study, there were only a few numbers of animals above 10 years of age. Cows having parity greater than three had significantly (p<0.01) higher incidence of lameness (21.4%) than those having parity ≤ 3 (7.5%). These results are in agreement with the previous reports that as the parity increases the chances of a cow becoming lame also increase (Solano et al., 2016).

However, Sadiq et al. (2017) had not found any significant association between parity and lameness. Tyagi et al. (2017) reported the highest incidence of lameness in cows having 1^st parity and lower incidence were found in cows having 2^nd, 3^rd, 4^th and 5^th parity respectively. Reason behind this can be that these studies were conducted in organized farm conditions where low producing animals or aged animals were culled periodically due to their reduced production potential, whereas the present study was carried out under field conditions where smallholder dairy farmers are not following rigorous culling due to economic reasons which might be the reason that in the present study the incidence of lameness was higher in cows having parity greater than three. Cows having body condition score lower than three had significantly (p<0.01) higher incidence (19.0%) compared to cows having a body condition score ≥3 (5.7%). Present study revealed that the animal having a lower body condition score (<3) were more prone to lameness and this variable was also found as a significant predictor of lameness in final logistic regression model, which indicates that cows with lower BCS (<3) are more likely to become lame and the findings are in agreement with previous studies who found strong association between low BCS and lameness in cattle (Randall et al., 2015; Lim et al., 2015; Singh et al., 2018; Sharma and Phillips, 2019) as BCS affect the thickness and quality of digital cushion (Bicalho et al., 2009). Dippel et al. (2009) found that cows having BCS greater than 3.5 had 0.39 lower odds of being lame. Sadiq et al. (2017) found no significant association between lameness and BCS. The difference might be due to the system of BCS used. Hoof examination of the cows revealed that the cows which were affected with the hoof disorders had significantly (p<0.01) higher incidence of lameness (35.5%) compared to cows with healthy hooves (3.5%). In the present study, it was also observed that 81.48% of lame cows suffered from at least one hoof disorder and maximum no. of hoof disorder per lame cow was two and the percentage of those cows was 14.8%. Similarly, Sadiq et al. (2017) found that 87.5% of the lame animals suffered from claw lesions and Moreira et al. (2018) found that hoof lesions were present in all the cows having lameness.

In the present study, the hoof disorders were found as a significant predictor for lameness in the final logistic regression model, which indicates that cows with hoof disorders are more likely to become clinically lame. Hoof colour was found to have a significant effect (p<0.01) on the incidence of lameness. It was observed that animal with white coloured hooves had a higher incidence of lameness (41.2%) followed by mixed coloured (12.31%) and black coloured hooves (9.4%).

In present study lighter coloured claws were found to suffer more with lameness compared to mixed and darker coloured claws respectively and the present finding is in agreement with Chesterton et al. (1989) who revealed that less pigmented hooves (more common in Friesian cattle) were more prone to lameness compared to the darker coloured hooves. He also found that Jersey cattle tend to have harder foot and was less prone to lameness. In the present study, 83.58% of Jersey crossbred cows had black hooves compared to 39.37% of HF crossbred cows. The stronger hooves may be the reason behind the lower incidence of lameness in Jersey crossbred cows. Similarly, it was also observed by Sogstad et al. (2011) that the cows with lighter colour claws were more likely to suffer from certain claw lesions like sole haemorrhages and white line disease compared to darker claws and similarly the cows with mixed coloured hooves were more likely to suffer from sole haemorrhages and corkscrew claws compared to darker claws. In this study, the author reported no significant associations of other claw disorders with claw horn colour. It suggests that the composition of the darker claws is much harder than the light coloured claws. Cows having shallow foot angle had significantly (p<0.05) higher incidence (19.0%) in comparison to those cows having intermediate foot angle (9.21%). Lohith et al. (2016a) in crossbred cattle reported a higher incidence of hoof lesions in cows having intermediate foot angle followed by very steep and in very low foot angle. The reason behind variation with respect to the findings of the present study might be due to less number of observations in a very low foot angle and evaluation of animals for clinical lameness in the present study whereas

Lohith et al. (2016a) have associated this factor with the incidence of hoof disorders and they did not scored the cows for lameness. Cows with injured hock condition had significantly (p<0.01) higher incidence of lameness (48.3%) compared to cows having normal hock condition (10.5%). Similarly, cows with injured knees also had significantly (p<0.05) more incidence of lameness (21.6%) compared to those with normal knees (10.5%). In the present study, hock injury was found as a significant predictor of lameness in crossbred dairy cattle. Cows with injured hocks had more lameness compared to cows having clinically normal hock conditions and it is in agreement with previous reports which states that hock lesions are associated with an increased risk of lameness (Brenninkmeyer et al., 2012; Nash et al., 2016; Sadiq et al., 2017; Sharma and Phillips, 2019). Hock injuries are associated with hard abrasive flooring (Nash et al., 2016; Mostafa and Maharan, 2016). In the present study also the majority of animals were kept on hard flooring (stone slabs and cemented flooring). Similarly, cows with injured knees also had more lameness compared to cows had clinically normal knee conditions.

Our results are in agreement with previous studies (Mostafa and Maharan, 2016; Sharma and Phillips, 2019). Mostafa and Maharan, (2016) reported that concrete flooring in barns was a predisposing factor for injured knees in both tie-stall and free-stall systems where they observed a higher incidence of knee injury in both tie-stall and freestall barns. This can be attributed to the hardness of the stone slabs and cemented floors and the involvement of forelimbs which occurs first whenever animal rises and sit and can be the reason behind significant association among lameness and knee injury in the present study. Type of flooring was also found to have a significant (p<0.01) effect on the incidence of lameness. Results in the present study revealed that Cows kept on cemented floors had a higher incidence of lameness (44.8%) followed by cows kept on stone slabs (8.2%) and the incidence of lameness was nil in animals kept on kachha floors.

These results are in agreement with previous studies which reports that concrete flooring is associated with lameness (Nash et al., 2016; Mostafa and Maharan, 2016). Concrete flooring causes excessive and uneven wear of hooves which leads to more skin breaks and increases chances of infections and also increases impact forces which predispose increased damage to corium (Fayed, 1997). Concrete flooring does not provide sufficient friction thus causing poor traction in floors and poor hoof grip with the ground (Van Der Tol et al., 2006). Therefore, grooving of floors is also recommended for maximizing traction in floors and to minimize wear and damage in hooves. Stone slabs have more roughened surface which may have better friction and provide better grip and traction, however, there is the risk of wear and skin breaks due to its hardness and uneven surface. This better grip and traction to hooves can be the reason behind fewer incidences in case of stone slabs flooring compared to cemented floors. Bovine hooves are well adapted to kachha floors because earthen floors provide better comfort to hooves due to its consistency and due to this there was no case of lameness observed under this category of flooring. Cows with dirty hygienic scores had significantly (P<0.01) higher incidence of lameness (22.9%) compared to those with clean hygienic scores (8.2%). Under herd-level risk factors, cows under dirty flooring conditions had significantly (p<0.05) higher incidence of lameness (17.5%) compared to clean flooring condition (6.4%). In the present study, cows with lower hygienic scores had a higher incidence of lameness in comparison to cows with clean hygienic condition which is in agreement with the findings of previous studies (Kara et al., 2011; Relun et al., 2013; Sadiq et al., 2017) that cows with dirty body conditions and very dirty leg hygienic conditions had increased risk of being lame.

Recently, Sharma and Phillips (2019) have also found a significant association between dirty udder conditions and lameness prevalence in 54 shelters (Gaushalas) in India. This dirtiness of the cows could be associated with the dirty flooring conditions in the farms and it is also found in the present study that dirty floor conditions had a significant influence on lameness. It was reported previously that exposure of cattle hooves to manure slurry on the floor and dirty leg conditions increases the claw conformational changes leading to lameness and also had a deleterious effect on claw health (Relun et al., 2013).

In a recent study done in Zimbabwe revealed that the cow cleanliness was found to be significantly (p<0.001) associated with manure accumulation in cattle enclosures and was found to be significantly (p<0.001) associated with lameness also (Matore et al., 2018). This indicates that the dirty flooring and dirty animal hygienic conditions supplement the deterioration of claw health and increase the lameness. Cows kept under free-stall housing conditions had significantly (p<0.01) higher incidence of lameness (46.7%) compared to cows who were kept on tie-stall housing conditions (7.5%). These results are in agreement with several previous studies which reports that cows reared under free-stall housing had higher incidence of lameness compared to tie-stall housing (Cook, 2003; Phillips and Morris, 2001). However, in contrary to the present study, Kara et al. (2011) reported that locomotion score in cows which were housed in free-stall was significantly lower than tie-stall on concrete bedding. The difference in findings may be due to different flooring material being used in the present study i.e. stone slab flooring in tie-stall houses and cemented flooring in free-stall houses in the study area. This indicates that the stone slabs flooring has less harmful effect on hooves in comparison to cemented flooring.

A final binary logistic regression model was developed had 91.67% accuracy, 93.01% sensitivity and 77.8% of specificity (Table 2). The model showed a reasonably good fit. Hoof disorders, BCS, parity, animal hygiene, hock injury and foot angle were six final explanatory variables present in the model (Table 2).

Results of the model revealed that the explanatory variables like hoof disorders (OR = 16.98; 95% CI = 4.67-61.66), BCS (OR = 6.99; 95% CI = 1.72-28.37) and hock injury (OR = 11.99; 95% CI = 3.243-44.337) were the significant (p<0.01) predictors of lameness (Table 3). Cows with hoof disorders had seventeen times more chances of becoming lame than those cows having normal hooves. Cows with lower BCS (<3) had seven times more chances than those having BCS ≥3. Cows with injured hocks had 12 times more chances of becoming lame than those have normal hocks. In the present study, the variables like parity, animal hygiene and foot angle were not the significant (p> 0.05) predictor of lameness (Table 3).

The recorded incidence estimates indicate that Holstein Friesian crossbred dairy cattle are more prone to lameness than Jersey crossbred dairy cattle. The animal level risk factors like the advancement in age and parity, lower body condition score, hoof disorders, white-coloured hooves, shallow foot angle, injured hocks and knees and animal hygiene had a significant association with lameness. The herd level risk factors like dirty flooring conditions, freestall housing conditions and cemented flooring also had a significant association with lameness. It is concluded that hoof disorders, hock injuries and lower BCS can be used as a significant predictor of lameness in crossbred dairy cattle.