Wooden hoof blocks: are we using the right wood?

ABSTRACT

Aims

To investigate the association between the density of wooden hoof blocks and resistance to wear in pasture-based dairy herds, and to assess the density of commercially available wooden hoof blocks.

Methods

Three types of wooden hoof blocks with different densities (low, medium and high) were attached to 36 lactating dairy cows with parity ≤2 and sound locomotion (score ≤2 on a scale of 1–4). The height of wooden blocks was measured in three different regions, front, abaxial and caudal on Days 7, 11, 14, 18, 21, 25 and 28 after application. Due to the loss of low-density wooden blocks, the data for these blocks were analysed for only two measurements on Days 7 and 11. The data for medium and high-density wooden blocks were analysed from Days 7–25. A linear mixed model with repeated measures was used to analyse the repeated observations. Height, density and surface area of commercially available hoof blocks (n = 19) were measured and compared to the blocks used in this study.

Results

The magnitude of wear, in the front and the abaxial point of the blocks were greater in blocks made of low-density wood compared to those made of medium and high-density wood (p < 0.001). The amount of wear increased over time for all groups (p < 0.001). Wood density was negatively associated with wear and loss. Measurements of commercial wooden blocks revealed that the 13/19 (63%) had lower density and 12/19 (68%) less surface area than the wooden blocks with medium density used in this study.

Conclusion

In this study, the density of the wood was significantly associated with the longevity of hoof blocks when applied to hooves of pasture-based dairy cows.

Clinical relevance

The longevity of the wooden hoof blocks applied to treat lame cows plays a significant role in the healing of the claw horn lesions. The density of a wooden hoof block affects the rate of wear of the block, and this should be considered by manufacturers and those treating lame cows.

KEYWORDS:

• Lameness
• treatment
• density
• wear
• dairy cattle
• pasture

Introduction

Lameness indicates pain in the limb of the cow (Whay et al. 1997) and it is considered the most important welfare issue in the dairy industry (Webster 1986). Claw horn lesions causing lameness occur mainly on lateral claws (Amory et al. 2008) of the hind limbs (Cramer et al. 2008). It has been reported that even after preventative trimming, 70% of the total force on the hind limb can be carried by the lateral claws, and that this may contribute to a higher risk of injury to this claw (van der Tol et al. 2004).

There is limited evidence on the suitability and effectiveness of treatment for both sole ulcers and white line disease compared with therapeutic programs available for digital dermatitis (Potterton et al. 2012). Therapeutic value of hoof blocks has been suggested for hoof lesions such as sole ulcers and white line lesions (Toussaint Raven 1985). The injured claw is trimmed and a block affixed to the unaffected claw of the same foot to reduce the impact of weight on the affected claw (Horseman et al. 2013). The application of hoof blocks is suggested to expedite the recovery of hoof lesions (Blowey 1998). Blocks are commonly used; one review of the treatment of lameness in cattle reported that hoof blocks were applied to 86% and 87% of cows included that had sole ulcers or white line disease in these studies, (Potterton et al. 2012).

Pyman (1997) compared the therapeutic efficacy of different types of blocks versus the application of a bandage for the treatment of lame cows with axial wall crack, sole ulcer, white line disease, under-run sole and punctured sole. This work suggested a 66% recovery rate on Day 7 in cows treated with wooden blocks compared to 32% in cows treated with a bandage (recovery was based on cows having slight to no lameness during locomotion). However, there was no significant difference in the recovery rate between the two groups 14 days after treatment. The recovery rates for different types of lesions were not individually reported in this study. A randomised, controlled study compared various treatments for sole ulceration, white line disease and other claw horn lesions, where a locomotion score (LCS) of 0 (sound), 35 days after treatment was considered as a measure of successful treatment outcome (Thomas et al. 2015). This study demonstrated that therapeutic trimming, placement of a hoof block and administration of non-steroidal anti-inflammatories significantly improved treatment outcome compared to therapeutic trimming alone. Cutler et al. (2015) conducted a study to assess the effect of having a wooden hoof block for 28 days, on behaviour, milk production and locomotion of dairy cattle with no hoof lesions. They found minimal effect on these parameters from having blocks.

Hoof blocks are manufactured from different materials. Plastic and rubber have been used along with wood. Unlike wooden blocks, plastic and rubber blocks are non-biodegradable and some tend to be lower and exhibit more signs of wear (Nuss and Tiefenthaler 1998). To the best of our knowledge, there are no published studies on the performance of wooden hoof blocks in pasture-based dairy cattle that provide data on the length of time it takes for the blocks to wear and fall off. The primary aim of this study was to investigate the association between the density of wood used in hoof blocks and resistance to wear in pasture-based dairy herds. The secondary aim was to assess the suitability of commercially available wooden hoof blocks in these terms. It is anticipated that clarifying the relationship between wood density and wear will facilitate hoof block selection to provide the required duration of protection (from weight bearing) that is sufficient for the recovery of claw horn lesions.

Materials and methods

Farm and cow selection

All methods were approved by the Animal Ethics Committee of the University of Sydney (Sydney, NSW, Australia). Thirty-six lactating dairy cows from a single pasture-based dairy herd located in the east coast of NSW, south-west of Sydney, fed a partial mixed ration and milked twice daily were enrolled in the study. Cows travelled on dirt tracks to different paddocks after each milking during the study period. The estimated mean walking distance was 2204.1 (min 320.8, max 3284.3) m/day. The surface of the holding yard was smooth concrete, with parallel grooves along the length of the yard and diamond grooving closer to the parlour entrance. The holding yard provided 1.95 m² of space per cow.

Cow selection criteria included parity ≤2 and LCS ≤2 and no history of lameness. The cows’ locomotion was scored on a scale of 1–4 using the method described by Ranjbar et al. (2016), after the morning milking, the day before the application of wooden blocks. Cows with a history of lameness during the current lactation were excluded from the study. Days in milk (DIM) and pregnancy status were recorded for each cow; however, pregnancy status was not used in the allocation of cows to the groups. Cows included in the study were kept as one herd to ensure that the walking distance from the milking parlour to the paddocks was similar between cows with different block types. The selected cows were matched for LCS and parity and randomly allocated to one of three groups each to receive wooden hoof blocks of different densities (low, medium, high). All the cows in each group had the same density block applied to their claw.

Body weight measurement

A weigh-tape (Coburn Weight-by-Breed Dairy Cow Tape, Wisconsin, USA) was used to estimate the weight of the cows at enrolment prior to the application of wooden blocks, however, this was not part of the group allocation criteria.

Experimental wooden hoof blocks

The experimental wooden blocks (133 mm long, 56 mm wide and 19 mm high with an estimated surface area of 64 cm²) were made of three different types of wood: flooded gum (FG; Eucalyptus grandis), blue gum (BG; Eucalyptus globulus) and ironbark (IB; Eucalyptus crebra) with identical shape, thickness and grooving pattern (Camden Cow Clogs, Camden, NSW, Australia).

The blocks were weighed using a calibrated scale (fx-1200i; A&D Company Ltd, Seven Hills, NSW, Australia) (Table 1). The blocks made from FG had a mean weight of 63.8 (min 58.2, max 71.1) g; BG 93.6 (min 92.1; max 94.7) g and IB, 126.8 (min 119, max 134.5) g. To measure the approximate density of the blocks in each group a single block from each group was chosen based on its proximity to the mean weight of the group. A cube of each type of block (1 cm³) was cut to measure the density of blocks using a modified hydrostatic weighing technique based on Archimedes’ principle (Hughes 2005). Based on the measured densities (Table 1) FG was determined to be low density, BG to be medium density and IB to be high density.

Table 1. Mean (SD) and range of weight of hoof blocks (n = 12) made of wood from flooded gum (Eucalyptus grandis), blue gum (E. globulus) and ironbark (E. crebra), density of the blocks and mean (SD) and range of dorsal and abaxial wall angles after application of the hoof block to the medial right hind claw of sound, pasture-based dairy cattle.

	Flooded gum	Blue gum	Ironbark
Weight (g)
Mean (SD)	63.8 (4.5)	93.4 (1.2)	126.5 (5.8)
Range (min, max)	58.2–71.1	92.1–94.7	119.0–134.5
Density (kg.m^3)^a	547.3	771.4	1124.3
Density classification	Low	Medium	High
Dorsal wall angle (^o)
Mean (SD)	51.5 (3.3)	52.3 (4.1)	50.7 (2.7)
Range (min, max)	44.7–57.2	41.0–57.0	47.1–55.8
Abaxial wall angle (^o)
Mean (SD)	75.8 (5.4)	78.4 (4.7)	79.4 (2.8)
Range (min, max)	62.4–85.6	62.4–85.6	76.4–86.4

^a The density of a single block of each type was measured which was selected to be near the mean weight of all blocks of that type.

Application of blocks and measurement of wooden block height

Hoof blocks were attached to the medial claw of the right hind foot. The right hind feet were randomly selected at the outset by the toss of a coin and the medial claw was selected as claw lesions are more common in lateral claws of hind feet. No cows were excluded due to lesions on the medial claw. Claw trimming and application of wooden blocks were conducted in a hydraulic trimming crush (WOPA Constructie, Harreveld, Netherlands), by a skilled and experienced study investigator. The medial claw was initially trimmed and prepared for the application of wooden blocks using the Dutch trimming method (Toussaint Raven 1985). The wooden blocks were affixed to the claws using Mini-Moo Gloo Bovine Blocking Adhesive (www.moogloo.ca). The blocks were lined up flush at the toe and were slightly overhanging at the heel. To avoid the interference of glue with the measurement of amount of wearing during the study, we attempted to avoid having excessive glue on the toes, abaxial edges, and heels by scraping off the glue from those areas while the glue was still wet.

The height of affixed blocks was measured during milking time on Days 7, 11, 14, 18, 21, 25 and 28 in the milking parlour. The height of the blocks was measured at the tip of the hoof (front), at an area correlating with Zone 2 and 3 (abaxial) as defined by Leach et al. (1998) and at the back of the block (caudal). The amount of wear on Day 7 was calculated based on the height of the block at the start of the study (19 mm) minus the measurement of the block on Day 7. The subsequent amount of wear was calculated based on the previous measurement minus the new measurement of the height of the block. Since we were unable to measure the axial edge of the block, we opted to measure the abaxial angle as an indication of changes to the axial edge of the blocks (Figure 1). The dorsal and abaxial wall angles were recorded using a digital inclinometer (Shahe Co., Hebei, China).

Figure 1. Diagram showing measurement of the abaxial wall angle using an inclinometer. Arrows show that wear of the abaxial wall of the block increases the abaxial wall angle.

Evaluation of commercial hoof blocks

In order to compare and assess characteristics of the wood used in some of the commercially available blocks, nineteen blocks were sourced from Australia (n = 7), Iran (n = 4) and the United Kingdom (n = 8). The surface area, weight and densities were measured as described for the experimental blocks above.

Statistical analysis

Sample size estimation

Sample size estimation for longitudinal linear model slope power calculation (Diggle 2002) showed that 12 cows per group would have 80% power to determine the difference between groups with an alpha level of 0.05.

Descriptive statistics

Data were initially explored graphically to determine the distribution, trend of changes and missing observations of measured variables. A complete dataset was used for the statistical analysis after excluding cows with missing data (e.g. cows that had lost their hoof blocks during the study).

Linear mixed model with repeated measures

A linear mixed model with repeated measures was used to analyse the repeated observations of height of the blocks at front, medial and caudal points on Days 7, 11, 14, 18 and 25 and abaxial wall angle.

The block types (groups) and days were the fixed-effect terms, and cow was the random effect term: $y_{ij}=\text{β}0+\text{β}1X{1}_{ij}+\text{β}2X{2}_{ij}+{\mu }_j+{ϵ}_{ij}$In this case, y_ij is the response variable (hta: height of block at front point; htb: height of block at abaxial point; htc: height of block at caudal point; and the abaxial wall angle), for the ith cow on the jth day. β0 (intercept) is the overall mean of outcome variables, and β1 to β2 are the fixed-effect coefficients of intervention (groups) and time (days), respectively. In this model, X1_ij to X2_ij are the variable values for the fixed-effect terms (group and day), μ_j is the random effect of individual observations, and ϵ_ij is the residuals (error term). The statistical analysis was conducted using R software (R Development Core team 2014, R Foundation for Statistical Computing, Vienna, Austria).

Since the majority of cows in the FG group lost their hoof blocks during the first 2 weeks of study, we analysed the height of blocks (i.e. wear-off data) for two separate periods and groups, to ensure there were sufficient and balanced numbers of observations between the groups to warrant statistical analysis. The first analysis was conducted on Days 7–14 on all three groups of cows, and the second analysis was conducted from Days 7–25 on cows with BG and IB blocks.

Results

Descriptive statistics of cows in each group, such as DIM, LCS, parity and milk yield, are presented in Table 2. Rain fell (22 mm; Bureau of Meteorology; www.bom.com.au) once during the study. Following application of the blocks, the mean dorsal wall angle for all cows was 51.5 (min 41.0; max 57.5)°. This was consistent with the recommended angle of 50° (Archer et al. 2015) to minimise the risk of abnormal wear induced by hoof block application. The mean dorsal wall angle for FG, BG and IB groups was 51.5°, 52.3° and 50.7°, respectively (Table 1).

Table 2. Mean (SD) and range of days in milk, milk production and body weight of dairy cows (n = 12 per group) which had hoof blocks made of either flooded gum (Eucalyptus grandis), blue gum (E. globulus) or ironbark (E. crebra) wood applied to the medial right hind claw along with the number of cows receiving each type of block which were parity 1 or 2 or currently pregnant and which had a locomotion score (LCS) of 1 or 2.

	Flooded gum	Blue gum	Ironbark
Days in milk
Mean (SD)	221.4	208	217.3
Range (min, max)	65–335	36–420	37–341
Reproductive status
Parity 1	8	7	6
Parity 2	4	5	6
Pregnant	8	9	10
Locomotion score (1–4^a)
LCS 1	9	8	7
LCS 2	3	4	5
Body weight (kg)
Mean (SD)	647.3 (68.4)	593.8 (55.9)	608.3 (58.1)
Range (min, max)	501, 735	501, 735	506, 679
Milk production (L/d)
Mean (SD)	21.8 (4.2)	20.8 (3.7)	20.4 (3.2)

^a Locomotion scoring as described in Ranjbar (2016).

The total number of blocks lost during the study is shown in Table 3. In the FG group (low density) 60% of the cows lost their hoof blocks by Day 14 and 90% by Day 18. This was greater than the frequency of losses in BG (medium density) and IB (high density) groups. Approximately 50% of cows in BG and IB groups lost their hoof blocks by Day 21 and 28, respectively.

Table 3. Number of cows which had which had hoof blocks made of either flooded gum (Eucalyptus grandis), blue gum (E. globulus) or ironbark (E. crebra) wood (n = 12 per group) applied to the medial right hind claw that lost their block at different days after the start the study.

Day of study	Flooded gum	Blue gum	Ironbark
3	2	0	2
7	0	0	0
11	0	1	0
14	6	3	2
18	3	2	2
21	1	1	0
25	NR	0	0
28	NR	0	2

NR = no cows remaining in the study.

Comparison of the three types of wooden blocks on Days 7 and 11 showed that the amount of wear at the front part of FG blocks was greater than that for BG and IB blocks (Table 4; p < 0.001). The mean heights of BG and IB blocks at the front of the block were 4.82 (SE1.07) mm and 6.12 (SE1.07) mm greater than FG blocks, respectively, indicating an association between density and wear: blocks characterised as higher density (BG and IB) wore less than lower density (FG) blocks. The amount of wear also increased over time for all groups (p < 0.001). Similarly, the magnitude of wear of BG (3.11 mm) and IB (4.68 mm) blocks was less than FG blocks at the abaxial point of the blocks, which also increased during the period of study (p < 0.001). The heights at the caudal point of the BG blocks were similar to those in FG group (p = 0.322) but differed from the height of IB blocks 2 weeks after affixing the blocks.

Table 4. Results of linear mixed model of height measured at three points (front, abaxial, caudal) on wooden hoof blocks, on Days 7 and 11 after application. Blocks were made of flooded gum (FG; Eucalyptus grandis; low density), blue gum (BG; E. globulus; medium density) or ironbark (IB; E. crebra; high density) wood (n = 12 per group) and applied to the medial right hind claw of dairy cows. Least square mean (LSM) estimates of the height (mm) on day 7 after application are also shown.

Measure point	Coefficient (SE)	P-value^a	LSM height (95% CI)
Front
FG	Ref		10.29 (8.62–11.97)
BG	4.82 (1.07)	<0.001	15.12 (13.65–16.59)
IB	6.12 (1.07)	<0.001	16.42 (14.96–17.88)
Days	–0.58 (0.08)	<0.001
Abaxial
FG	Ref		11.48 (9.56–13.40)
BG	3.11 (1.23)	0.019	14.60 (12.90–16.29)
IB	4.68 (1.23)	0.001	16.17 (14.49–17.85)
Days	–0.61 (0.09)	<0.001
Caudal
FG	Ref		12.17 (9.78–14.56)
BG	1.55 (1.53)	0.322	13.72 (11.62–15.83)
IB	3.77 (1.53)	0.022	15.95 (13.85–18.05)
Days	–0. 63 (0.07)	<0.001
Abaxial wall angle
FG	Ref		75.12 (72.41–77.83)
BG	4.07 (1.73)	0.028	79.20 (76.82–81.57)
IB	4.79 (1.72)	0.011	79.91 (77.58–82.25)
Days	0.13 (0.23)	0.556

^a Significance of difference in height between group or over time.

Ref = reference category.

In the second analysis, the height of BG and IB blocks were compared from Day 7–25 (Table 5). There was no statistical evidence of a difference (p = 0.236, Table 6) in wear of BG and IB blocks at the front point (A) or that the height of the caudal points of IB blocks was greater than the BG blocks (p = 0.055).

Table 5. Results of linear mixed model of height measured at three points (front, abaxial, caudal) on wooden hoof blocks, on Days 7, 11, 14, 18, 21 and 25 after application. Blocks were made of blue gum (BG; E. globulus; medium density) or ironbark (IB; E. crebra; high density) wood (n = 12 per group) and applied to the medial right hind claw of dairy cows. Least square mean (LSM) estimates of the height (mm) on day 14 after application are also shown.

Measure point	Coefficient (SE)	P-value^a	LSM height (95% CI)
Front
BG	Ref		11.66 (10.07–13.26)
IB	1.30 (1.05)	0.236	12.96 (11.39–14.54)
Days	−0.61 (0.03)	<0.001
Abaxial
BG	Ref		11.45 (10.14–12.76)
IB	1.90 (0.87)	0.044	13.35 (12.05–14.65)
Days	−0. 54 (0.02)	<0.001
Caudal
BG	Ref		11.15 (9.60–12.69)
IB	2.13 (1.03)	0.055	13.28 (11.74–14.83)
Days	−0.48 (0.01)	<0.001
Abaxial wall angle
BG	Ref		78.56 (76.94–80.17)
IB	0.59 (1.05)	0.579	79.16 (77.61–80.71)
Days	−0.06 (0.06)	0.314

^a Significance of difference in height between group or over time.

Ref = reference category.

Table 6. Weight, density, height and surface area of commercial wooden hoof blocks sourced from Australia, United Kingdom (UK) and Iran (IR).

Block	Weight (g)	Density (kg/m^3)	Height (mm)	Surface area (cm^2)
Australia 1 (Large)	73.6	513.3	19.4	70
Australia 2 (Small)	74.8	735.7	19.4	57.5
Australia 3	73.5	727.0	18.7	50.5
Australia 4	57.7	767.3	21.8	53.5
Australia 5	113.5	714.3	22.7	79.5
Australia 6	157.2	828.6	28.3	75.5
Australia 7	134.6	1016.4	20.3	78
UK 1 (Large)	67.7	755.6	24	58
UK 2 (Small)	91.5	842.9	19.8	49
UK 3	75	709.1	23.1	55.5
UK 4	68.4	797.0	19.5	50
UK 5	78	673.9	19.8	69
UK 6	108	801.1	24.3	62
UK 7	81.2	749.1	18.9	68.5
UK 8	46.7	709.1	14.3	54.5
IR 1	62.8	784.4	22	52.5
IR 2	74.9	719.8	26.8	51.5
IR 3	62.2	672.9	21.5	53
IR 4	81.6	804.5	27.4	49.5

Measurement of 19 commercially available wooden hoof blocks sourced from Australia, Iran and the United Kingdom showed that the mean estimated surface area of these blocks was 59.8 (min 49, max 79.5) cm², mean density was 753.8 (min 5,13.3, max 1,016.4) kg/m³ and mean height was 21.7 (min 18.7, max 24) mm (Table 6). Thirteen of 19 (68%) blocks had a smaller surface area than the blocks applied to the cows, and 12/19 (63%) had a lower density than the medium density blocks.

Discussion

This study was conducted to investigate the association between the density of wooden hoof blocks and the amount of wear in these blocks when applied to non-lame lactating dairy cows.

Although the sample size of 36 cows chosen for enrolment, was selected on the basis of the results of a power analysis, at the time of the first measurement (Day 7) 4/36 (11%) cows were missing their block (Table 3). The proportion of cows that lost their block before the first measurement was similar to that reported in a recent study on wooden blocks applied to cows in a freestall dairy (10%; Cutler et al. 2015). However, our results were lower than an earlier pasture-based study (Pyman 1997) who reported 17.9% loss of blocks by Day 3. Early loss of up to 20.1% of wooden blocks has been reported by Nuss and Tiefenthaler (1998). In our study 8/12 (67%) FG blocks were lost by Day 14. The greater loss of FG blocks compared to IB or BG blocks could be due to the rainfall of 22 mm after the day of application of blocks, making paddocks and track conditions wet and muddy. Cows in all groups were exposed to similar environmental conditions, however, differences in moisture absorption related to density, may have been a factor (Okoh 2014). More than half of the medium (BG) and high-density (IB) block groups were lost by Day 21 and 28, respectively. This was similar to the study of Pyman (1997) where a loss of 49.7% by Day 14 and 70% by day 30 was reported.

Comparison of the three types of blocks on Days 7 and 11 showed that, blocks with higher density remain attached to the hoof for a longer period of time, but also wear more slowly providing longer elevation of the opposite claw. However, comparison of wear of the medium (BG) and high (IB) density blocks from Days 7–25 failed to find evidence of a difference in wear for these two types of hoof block. We believe that the small sample size and the high percentage of lost blocks during the later stage of the study limited our ability to determine and quantify other risk factors that may contribute to the magnitude of wear. The resilience of the higher density blocks compared to low-density blocks demonstrate that these blocks will be able to provide better support for up to 4 weeks, consistent with the time required for healing of claw lesions (Sala et al. 2008).

The objective of applying hoof blocks is to relieve weight bearing on the diseased claw during the healing process. The capacity of the block to relieve weight bearing will be influenced by the longevity, wear characteristics and height of blocks. A number of studies have examined the time taken for hoof lesions to heal. It has been reported that 50 days is required to form a solid layer of horn over sole ulcers (Lischer et al. 2002). The rate of healing and the outcome of treatment may also be influenced by ancillary treatments. The study of Thomas et al. (2015) found a statistically significant difference in the time to sound locomotion (Score 0) after treatment (56.1 vs. 24.4%) when non-steroidal anti-inflammatory therapy was administered in addition to the application of a wooden block (Thomas et al. 2015). In a subsequent study (Thomas et al. 2016) chronically lame cows were observed to recover over 28 days. While a specific time interval to healing after the application of hoof blocks has not been well defined Sala et al. (2008) recommend support be provided for approximately 4 weeks.

Hoof blocks should have sufficient height to reduce the likelihood of weight bearing on the injured claw. In our study, the mean height of low-density wood (FG) hoof blocks was worn to less than 40% of the original height (19 mm) by Day 11, which makes them an unsuitable block to be used for the treatment of lame cows. The height of the medium (BG) and high-density (IB) blocks were 50% of their original height by Days 14 and 21, respectively. The results of our study indicate the medium-density blocks (BG) are superior to the low-density blocks (FG). While the high-density blocks (IB) had the best wear characteristics, the plank of wood used to manufacture these blocks is not available in a thickness of more than 19 mm (pers. comm.).¹ The findings of our study suggest wooden hoof blocks with 19 mm height may not be sufficient to prevent weight bearing by the diseased claw for 4 weeks. This is in agreement with the study by Nuss and Tiefenthaler (1998), where it was suggested that blocks with heights >25 mm are preferred especially for more severe claw lesions. However, to the best of our knowledge, there are no studies on the height of the block required to provide support for the duration of the suggested 28-day treatment.

The distribution of wear across the more dense blocks (BG and IB) was more even, maintaining a more consistent abaxial wall angle compared with the low-density block (FG). The low-density blocks (FG) showed a tendency to wear on the abaxial edge increasing the abaxial wall angle, hence tilting the foot. The cows enrolled in our study had sound locomotion; however, lame cows have imperfect locomotion, due to pain and lower nociceptive threshold (Laven et al. 2008). This may influence the magnitude and extent of wear at different regions of the wooden hoof blocks. This puts emphasis on the importance of the wooden block characteristics used in the treatment of lame cows. More studies are needed to determine wear patterns in lame cows with different hoof lesions.

There are a variety of wooden hoof blocks of different shapes, sizes and densities available around the world. In the assessment of the wooden blocks sourced from manufacturers in Australia, Iran and the United Kingdom, we found that 68% of blocks had a smaller surface area than the blocks tested in the study, and 63% had a lower density than the medium density blocks. Sixteen (84%) of the blocks had a lower height than the 25 mm suggested by Nuss and Tiefenthaler (1998). Given the lower density and height of the commercial blocks tested, it appears likely that many of these blocks would be unlikely to provide relief for the recommended 4 weeks. Of the commercial blocks evaluated, those with a larger surface area, manufactured for larger cows, were made of lower density wood than smaller blocks. This is likely to predispose to rapid wear and potential early loss.

Conclusions

Wooden hoof blocks have been used to treat lame dairy cows for more than 60 years; however, little attention has been paid to the characteristics of this important ancillary tool. The density of the wood used in manufacturing wooden hoof blocks was found to be positively associated with longevity, wear and subsequently the angle of the foot. The majority of the commercially available blocks tested were of low density, which was associated with excessive wear and short longevity. Considering the healing time of lesions and the difference in wear between types of wood, our study highlights the importance of establishing criteria in manufacturing and choosing wooden hoof blocks. Further studies are needed to investigate the optimal density, height, and shape of wooden hoof blocks used for the treatment of lame cows under different management conditions. There is a diversity of hoof block products on the market and it is inappropriate to assume the performance of the different products are the same.

Acknowledgements

The authors would like to thank Mr Greg Johnston (Camden Cow Clogs, Camden, NSW, Australia), for providing the hoof blocks and advice on the types of wood, Associate Professor Tina Bell for her assistance with the measurement of wood density and Mr. Gavin Moore for providing the study farm and cows.

Notes

1 G Johnston, Camden Cow Clogs, Camden, Australia