Longitudinal assessment of intensively reared dairy heifer claw growth and corkscrew shape development.

As the future of the dairy herd, heifers represent a large investment; however, compromised claw health poses a significant risk to their productivity and longevity. Issues with mobility can be influenced by foot growth and shape, with corkscrew claw conformations now reported in heifers. This study aimed to assess claw growth of precalving heifers, along with claw shape observations. A convenience sample of 20 preconception heifers from a single fully housed dairy herd in the UK, milking 2,500 cows, were recruited, aged between 249 and 265 d. They were restrained in a crush and had their feet measured, with the horn marked at the dorsal and lateral heel wall to allow growth and wear measurements to be taken every 90 d. An additional 250 heifers aged between 267 and 437 d were recruited for visual claw shape observations. All 8 claws of each heifer were scored every 90 d for claw shape, following a visual guide based around dorsal and axial wall positions, over a total of 5 visits. In the heifer cohort having their feet measured, the dorsal wall was always longer than the heel wall (mean 67.6 mm [SD 9.9 mm] compared with 43.7 mm [SD 9.2 mm], respectively). Length of the claws and rate of growth at both the dorsal and heel positions reduced between visits 4 and 5 when heifers were about to or had already calved and entered the milking herd, with increased wear (0.25 mm/d) and reduced growth (0.13 mm/d). Claws with shape score 1 (scissor claw) had longer dorsal walls 68.9 mm (95% CI 64.2-73.6 mm) than other claw shapes. Although only 10% (2/20) of the heifers developed score 2 corkscrew claw shapes, they did have higher rates of growth (2.1-2.2 mm/90 d more), and reduced wear (2.2-10.1 mm/90 d less) compared with shape scores 0 and 1. With regard to observed foot shape, only 24.4% of heifers maintained a foot shape score 0 throughout the whole study period, suggesting more attention should be paid to maintaining an optimal heifer foot shape before entry into the lactating herd. The foot shape of the heifers was dynamic, with individual claws able to transition from one shape score to another between visits. The main transitions were from a score 0 to a score 1 scissor claw, with an increase in transitions to score 2 corkscrew claws over time, suggesting a cumulative deterioration in claw shape. Twenty-one heifers transitioned from a score 2 corkscrew claw shape back to a score 1 or 0, suggesting that some mild to moderate dorsal wall deviations can rotate back to a more anatomically normal state. Overall, we found that minor changes to dorsal wall alignment of claws (scissor claws) did not necessarily lead to development of corkscrew claw foot shape in heifers, but use of early pregnancy foot inspections before calving, particularly focusing on the medial claws of heifers, may be of benefit in maintaining good claw conformation in precalving heifers.