Lameness is one of the most important problems of modern dairy farming with implications for production, reproduction, health, and welfare (Sprecher et al., 1997; Hernandez et al., 2001; Warnick et al., 2001; Juarez et al., 2003; O’Callaghan et al., 2003; Hernandez et al., 2005; Calderon and Cook, 2011). While 90% of all lameness cases originate from hoof lesions, not all hoof lesions cause lameness (Manske et al., 2002b). However, subclinical foot lesions significantly affect animal welfare (Bruijnis et al., 2012) and cause economic loss (Bruijnis et al., 2010).

The transition period is critical to the occurrence of hoof lesions (Cook and Nordlund, 2009). Around calving, heifers are exposed to stress caused by transitioning to a high-energy diet, change of housing and social groups, as well as social interactions among animals (Cook and Nordlund, 2009; Bergsten et al., 2015). The severity of subacute ruminal acidosis (SARA) in first-lactation cows, which are subjected to the same feeding regime, may vary due to several reasons, including differences in management factors and ruminal fermentation, and susceptibility or resistance to SARA (Kofler et al., 2023; Hartinger et al., 2024). Calving and lactation may result in claw horn disruption (CHD) lesions, the severity of which may increase with housing and nutritional conditions (Webster, 2001). Nonetheless, the ruminal acidosis (acute or subacute) and laminitis hypothesis describing the pathogenesis of CHD lesions is controversial in the current literature (Randall et al., 2018; Passos et al., 2023). Acute ruminal acidosis induced by oral oligofructose administration was followed by the establishment of the clinical and histological findings of acute laminitis (Danscher et al., 2009). Hovewer, Kofler et al. (2023) reported that the severity (light, moderate, and severe) of SARA cases induced by high levels of concentrate feed in first-lactation Holstein cows had no effect on the locomotion score and prevalence of claw lesions. The effects of nutrition on hoof health are related to the role of micronutrients in the maintenance of the structural integrity of the hoof rather than the laminitis hypothesis (Langova et al., 2020; Queiroz et al., 2021). Recent studies on the pathogenesis of CHD lesions in dairy cattle have investigated environmental and animal-based risk factors and alternative hypotheses that may explain associations previously identified in the literature (Randall et al., 2018; Laven and Laven, 2024). Major herd and animal related risk factors that cause predisposition to postpartum CHD lesions include hormone- and enzyme-induced deterioration of the supportive system of the hoof (Tarlton et al., 2002a,b; Knott et al., 2007), reduced thickness of the soft tissue of the claw sole (Bach et al., 2021), changes in the biochemical and physical structure of the digital cushion (Bicalho et al., 2009; Newsome et al., 2017; Wilson et al., 2021), altered metabolic status and lying behaviour (Sepúlveda-Varas et al., 2018), increased standing time and standing bout duration in early lactation (Eriksson et al., 2021), low body condition (Green et al., 2014; Lim et al., 2015; Randall et al., 2015), and decreased horn growth and increased hoof wear (Blowey, 2015) around calving.

While hoof lesions can develop in dairy heifers in the pre-calving period (Kofler et al., 2011; Randall et al., 2016), hoof lesions and lameness are most prevalent in early lactation (Cook and Nordlund, 2009; Mahendran et al., 2017). A prevalence of 48.7% has been reported for sole hemorrhages two months after calving (Drendel et al., 2005). High prevalences have been reported for white line lesions (72%) and sole hemorrhages (55%) in Danish Holstein heifers during 1–100 days of lactation (Capion et al., 2009). Similarly, 95% of dairy heifers were reported to display lesions on at least one claw between days 50 and 80 postpartum (Maxwell et al., 2015). Mahendran et al. (2017) reported a lameness prevalence of 12.2% at 29-42 days post-calving and 1.1% between 295 and 383 days post-calving. Thus, the prevention of foot lesions in heifers is a major critical control point of lameness control in dairy cattle (Bell et al., 2009).

Housing in free stalls forces cattle to walk on hard, wet, slippery, and manure-contaminated concrete floors for routine daily activities including feeding, milking, finding a resting area, and social behavior (Bergsten et al., 2015). This increases the exposure of cattle to adverse environmental factors such as traumas due to suboptimal flooring and increased standing time on concrete floors, and thereby, increases the risk of lameness (Cook and Nordlund, 2009; Akköse and İzci, 2017). Previous studies have shown that the prevalence of lameness is associated with the bedding material used for dairy cows (Webster, 2001; Cook, 2003; Cook et al., 2004; Barberg et al., 2007). Good stall comfort could prevent lameness by improving the resting time, decreasing the standing time and avoiding the exposure of cattle to adverse environmental effects. It also complements the treatment of foot diseases by reducing the pain of lame animals and improving their living conditions (Cook and Nordlund, 2009).

Webster (2002) reported that the housing of heifers in straw yards (SY) during the last month of gestation and the first two months of lactation significantly reduced the occurrence of sole hemorrhages (SH) and white-line hemorrhages (WLH) compared with housing on concrete floors in free stalls during the same period. Laven and Livesey (2004) determined that the prevalence of SH and WLH during the last four weeks of gestation and the first 12 weeks postpartum was lower in cows housed in straw yards compared with those housed in mat- and mattress-based free stalls. Livesey et al. (1998) reported that Holstein heifers diagnosed with SH and WLH before calving, after being housed in either free stalls or SY during the previous trimester and 12 weeks postpartum, displayed an increased severity of SH and WLH in response to being housed in free stalls and a decreased severity of WLH in response to being housed in straw yards.

The results of previous research on hoof horn haemorrhage in heifers have contributed to a better understanding of CHD by showing the major involvement of housing conditions and the relatively less importance of postpartum nutrition. Furthermore, these results have revealed that parturition serves as an important risk factor for CHD, and through interaction, heightens the effects of other risk factors involved (Laven and Laven, 2024).

In this study, we hypothesized that improving housing comfort (straw yard > mattress > mat) throughout the last month of gestation would decrease the severity of hoof lesions in the postpartum period. Thus, the present study was aimed at the assessment of postpartum hoof lesions in dairy heifers kept under different housing conditions during the last month of gestation (but under similar housing conditions in the postpartum period).

Research on animals was conducted according to the Ethics Committee of the Selçuk University, Faculty of Veterinary Medicine (2016/2).

The AFC ranged from 24.0 to 41.2 months, and the 100-day milk production of the first-calving heifers ranged from 1051.0 to 2800.0 L (Table 1). The AFC and 100-day milk yield did not differ among the groups.

Table 1

Parameter	Group	n	Mean±SEM	Median	Minimum	Maximum
MY	MAT	12	1959.4±157.6	1895.0	1092.0	2800.0
	MATR	12	2228.4±63.8	2200.0	1975.0	2590.0
	SY	12	2011.6±142.9	1964.5	1051.0	2770.0
AFC	MAT	12	27.1±0.7	26.5	25.0	32.8
	MATR	12	30.3±1.7	28.0	24.6	41.2
	SY	12	28.2±1.2	27.1	24.0	38.0

MAT - mats; MATR - mattresses; SY - straw yard; MY - 100-day milk yield; AFC - age at first calving; SEM - standard error of the mean.

We detected SH, WLH, and HHE at 60 and 90 DIM in all heifers. The prevalence of SH at 60 DIM was significantly higher in groups MAT and MATR compared with group SY (P = 0.003). On the other hand, we did not observe any differences for the prevalence of SH at 90 DIM and the prevalence of WLH at 60 and 90 DIM among the three study groups postpartum. The distribution of SH and WLH scores determined in groups MAT, MATR, and SY at 60 and 90 DIM are presented in Figure 1.

Figure 1 SH - sole hemorrhages; WLH - white-line hemorrhages; DIM - days in milk.

While the mean severity score of SH at 60 DIM was significantly higher in group MAT (P<0.001) and MATR (P = 0.002) compared with group SY, no difference was observed between groups MAT and MATR. The mean severity score of SH at 90 DIM was similar in groups MATR and SY, but significantly higher in group MAT (P = 0.005). In group MAT, the mean severity score of SH remained similar during the period from 60 to 90 DIM (2.25 and 1.92, respectively; P>0.05). On the other hand, in group MATR, the mean severity score of SH significantly decreased during the period from 60 to 90 DIM (from 1.92 to 0.92; P<0.001). In group SY, the mean severity score of SH was observed to remain similar between 60 to 90 DIM (0.75 and 0.92, respectively; P>0.05). Furthermore, during the period between 60 to 90 DIM, the mean severity scores of WLH were determined to have significantly decreased in all groups.

While the mean severity score of WLH at 60 DIM was significantly higher in group MAT, compared with groups MATR and SY (P<0.001) (Table 2); no difference was detected among the groups at 90 DIM. Ordinal logistic regression showed that the AFC and 100-day milk yield did not affect the severity of SH and WLH.

Table 2

Hoof lesion	Group	n	Time			P-value
			At 60 DIM	At 90 DIM	Total	Time	Group	Group × Time
SH	MAT	12	2.25±0.18A	1.92±0.19A	2.08±0.13	0.017	<0.001	0.015
	MATR	12	1.92±0.19Aa	0.92±0.15Bb	1.42±0.19
	SY	12	0.75±0.28B	0.92±0.26B	0.83±0.19
	Total	36	1.64±0.17	1.25±0.14
WLH	MAT	12	1.92±0.15Aa	0.83±0.11b	1.38±0.15	<0.001	<0.001	0.009
	MATR	12	1.17±0.13Ba	0.75±0.14b	0.96±0.10
	SY	12	0.92±0.08Ba	0.50±0.15b	0.71±0.10
	Total	36	1.33±0.10	0.69±0.08

MAT - mats; MATR - mattresses; SY - straw yard; DIM - days in milk.

In the present study, 92% (33/36) of the animals were diagnosed with mild (1) HHE at 60 and 90 DIM. It was observed that HHE developed in parallel with the junction of the hoof with the skin and had progressed downward to the heel with the growth of the hooves (Figure 2). No differences were observed among the study groups for the prevalence and severity of HHE in the postpartum period. Clinical lameness (LS ≥3) was not detected in any of the groups throughout the study period.

Figure 2

Hemorrhage in the sole of the hoof is an indication of serum and erythrocyte leakage from the capillary bed of the corium to the claw horn (Bergsten et al., 2015). As is the case with other CHD lesions, hoof hemorrhages generally occur during the transition period and become visible within a period of 8-12 weeks (Leach et al., 1997; Chapinal et al., 2009). In agreement with previous research (Leach et al., 1997; Webster, 2002; Chapinal et al., 2009), the heifers in all three study groups presented with hoof hemorrhages of varying severity at 60 and 90 DIM.

It is indicated that functional hoof trimming contributes to the prevention of hoof diseases and the improvement of the hoof structure (Manske et al., 2002a; Sadiq et al., 2020). Throughout the study period, the hoof lesions of each animal were assessed after performing functional hoof trimming. In the present study, no CHD lesion, except for SH and WLH, having been detected in the animals, was attributed to the beneficial effects of functional hoof trimming.

Previous studies have indicated that WLH are observed as of the second week postpartum and occur earlier than SH (Kempson and Logue, 1993; Leach et al., 1997). As the earliest hoof examinations were performed at 60 DIM in our study, no data was obtained on this particular aspect.

Previous epidemiological research has demonstrated that the prevalence of hoof lesions tends to increase during the first few months after calving. In a study in Holstein heifers, Capion et al. (2009) determined that the prevalence of moderate and severe SH and white line lesions increased from the last four weeks of gestation to 200-250 days postpartum (SH: 27% vs. 56%; WLH: 44% vs. 70%). Randall et al. (2016) indicated that the prevalence of sole lesions (sole hemorrhage and sole ulcers) in dairy heifers increased up to a level of 97% from the prepartum period to the fourth month postpartum. In the present study, the prevalence of SH was determined to have increased up to 100% by 60 DIM in groups MAT and MATR, and up to 83.3% by 90 DIM in group SY. Furthermore, the prevalence of WLH was ascertained to have increased up to 100% in group MAT, 91.7% in group MATR, and 75% in group SY by 60 DIM. These results comply with those of previous reports. The findings of the present study suggest that the transition from heifer to lactating cow (including calving, changes in housing, BCS, feeding, time budgets, etc.) and the occurrence of hoof lesions are associated with each other.

Hoof lesions that occur around calving are indicated to become more severe with adverse environmental factors such as hard flooring (Proudfoot et al., 2010). In the present study, as all three study groups were exposed to uniform nutrition, housing, and management conditions after calving, the differences detected among the groups for the severity of the hoof hemorrhages were attributed to possible previous traumas during the prepartum period.

Cattle prefer to lie on softer surfaces and tend to stand for longer periods in less comfortable areas (Wagner-Storch et al., 2003; Cook and Nordlund, 2009). Mat-based free stalls offer a lower level of comfort in comparison to mattress-based free stalls and are considered to resemble concrete floors (Wagner-Storch et al., 2003). Cattle housed in SY display longer lying times on straw (Singh et al., 1993; Phillips and Schofield, 1994), and their hooves are exposed to less mechanical stress from the flooring when standing on straw (Singh et al., 1993). Therefore, cattle housed in SY present less severe hoof lesions (Webster, 2002; Laven and Livesey, 2004; Bergsten et al., 2015).

In the present study, the mean SH severity score was significantly lower in group SY at 60 DIM and significantly higher in group MAT at 90 DIM. Furthermore, from 60 to 90 DIM, the mean SH severity score was observed to remain similar in group SY, to decrease to a level similar to that of group SY in Group MATR, and to remain significantly higher compared with the other two groups in group MAT. On the other hand, the mean WLH severity score was found to be significantly higher in group MAT at 60 DIM. These findings demonstrate that, in group MAT, which was housed under less comfortable conditions in the last month of gestation, the hooves of the heifers were exposed to adverse flooring effects, whilst in group SY, the heifers were affected only mildly by the flooring. In the present study, group SY having displayed significantly lower levels for both the prevalence and mean severity score of SH at 60 DIM compared with the other two groups, and a significantly lower mean SH severity score at 90 DIM compared with group MAT, shows that the housing of dairy heifers in SY during the prepartum period significantly reduces the severity of hoof lesions in the postpartum period.

Heel horn erosion is generally described as an infectious foot disease, to which environmental conditions associated with poor hygiene cause predisposition (Enevoldsen et al., 1991; Knappe-Poindecker et al., 2013; Bergsten et al., 2015). Offer et al. (2000) reported that the severity of HHE increased during early lactation and decreased during late lactation. Chapinal et al. (2010) indicated that the severity of HHE was significantly higher in mid-lactation compared with early lactation and the prepartum period. We consider that, due to decreased hoof growth and the growth of poor-quality hoof tissue during the calving period (Blowey, 2015), the invasion of infectious agents, including Dicherobacter nodosus, in the heels becomes relatively easier, and thereby, the prevalence of HHE increases in mid-lactation, depending on environmental hygiene. We observed that, between 60 to 90 DIM, 92% of the animals had developed HHE, which were localized in parallel with the coronary band and progressed downward over time with the growth of the hooves. In view of the softest region of the hoof tissue being the heel, it is most probable that, during the postpartum period, insufficient and weak hoof tissue growth occurs mainly in the heels. The location of HHE detected in the present study clearly demonstrated that the insufficient growth and poor quality of newly grown tissue are both influential on the development of such lesions. On the other hand, the severity of HHE remaining the same throughout the three-month period after calving suggested that the use of footbaths on the farm where the present study was conducted may have prevented the increase of the severity of these erosions. Footbaths may serve to harden the hooves and control the microbial population present on the hoof (Cook, 2017).

Animals in all three groups, at 60 and 90 DIM, were graded as either score 1 or score 2. The lameness scores assigned, not being high, was attributed to the regular practice of functional hoof trimming and effective footbath treatment having prevented the development of lameness.

The housing of dairy heifers in straw yards during the last month of gestation aiming to provide improved flooring and bedding conditions significantly decreases the severity of SH and WLH. Since 92% of the dairy heifers showed HHE in parallel with the coronary band after parturition, we believe that there may be a relationship between calving and the development of HHE.