Lameness of dairy cattle : factors affecting the mechanical properties, haemorrhage levels, growth and wear rates of bovine claw horn : a thesis presented in partial fulfilment of the requirements of a doctoral degree in Animal Science, Massey University, Palmerston North, New Zealand

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Lameness is one of the main economic and welfare issues faced by the global dairy industry. It mainly affects the hind claws and the main causes / types are; claw horn lesions of the sole and white line (WL), along with foot rot (NZ) and digital dermatitis (UK). This thesis aims to apply and develop mechanical tests to determine the effect of dietary supplements, animal breed and number of days postpartum (dpp) on claw horn (CH) mechanical properties. Supplementation with live yeast (UK) significantly increased the puncture resistance (PR) of sole horn (P<0.05), level of mean sole haemorrhage percentage, total combined lesion score (TLS) and wear rates (P<0.10), while increasing daily mean milk yield, total milk fat and protein without significant increases in feed intake, providing an increase in feed conversion efficiency. In growing (NZ) dairy cattle PR was lower in 1, 2 (WL) compared with sole (4 and 5) while zones 4 and 5 did not differ significantly. Dairy breed (NZ) affected the PR of the CH, significantly (P<0.001) lower PR in CH of Friesian (all 5 IFM regions) compared with Friesian X Jersey (FxJ). Lactating dairy heifers (partition 22 to 24 months) from 0 to 160 d pp showed that the breed did not significantly affect the; number, percentage or TLS of sole or WL lesions, with the exception of 160 dpp where Friesian heifers had significantly (P<0.05) higher WL and sole lesions compared with FxJ. Mechanical properties (PR) of CH, declined significantly with increasing number of days post partum (dpp), while EM was significantly stiffer at 30 d pp compared with 120 dpp. PR was reduced significantly by increasing lesion score (LS), but was not confirmed by Vickers hardness and EM results. Hydration of CH significantly lowered EM compared to dried horn or horn at physiological moisture content. Short term (200 d), neither the form (zinc as salt or complexes with yeast) not level of zinc (At 1.0 or at 0.3 of NRC recommended levels (RL)) did not significantly affect; locomotion score; growth and wear rates; claw measurements and sole and WL lesions were not significantly effected by form or level of supplemental zinc up to 150 d pp. Overall, the number of days pp (dpp) significantly increased the level of sole and WL lesions, and reduced CH PR and elastic modulus (EM).
Lameness in cattle, Dairy cows, Dairy cattle, Diseases