Lameness in dairy cattle has been associated with many causes, including prolonged standing on concrete, excess carbohydrates in feed, wet environments, and stress from poor handling, but in dairy cattle there is one crucial factor which is the most important and that is calving.
Calving massively increases the risk of claw horn disease – non-infectious lameness such as white line disease and sole bruising. Environments and diets that increase lameness risk in calved heifers have no such effect in heifers of the same age that are not pregnant or calving. Additionally, when pregnant heifers are reared in cubicles (free-stalls) with concrete passageways there is little evidence of damage to the hoof but if they are kept in cubicles after calving, hoof horn haemorrhages – the first stage of claw horn disease – become much more common. Calving is a trigger that allows other factors, such as prolonged standing on concrete, to have an impact on lameness.
So what’s happening? As part of the process of calving there are changes in the pelvic ligaments that allow the calf to be born more easily. These changes are not limited to just the pelvis but happen throughout the body, including in the feet. It is these changes that mean a calving cow is at increased risk of developing the initial changes, which will eventually result in clinical lameness.
The pedal bone (P3) (the last bone in the limb) is supported by a ligament attaching it to the wall, and also by a mix of connective tissue and fat. At calving these relax and allow the pedal bone to move.
Calving itself doesn’t produce the haemorrhages; the decreased support for P3 means it is easier for outside factors to produce haemorrhages.
In the left-hand picture, the attachments are tight and the range of movements of the hammock is small. In the right-hand picture, the attachments are loose and small movements by the occupant lead to big movements of the hammock. Severe stresses, such as wind, can produce movements large enough to lead to significant injury!
Stresses that wouldn’t cause significant problems in mid- to late-lactation cows can cause damage in early lactation which ends up as claw horn disease. Because the ligament laxity effects last for 4-6 weeks; it is crucial that stresses are minimised from four weeks before to six weeks after calving to reduce lameness.
Under New Zealand conditions, this means minimising time spent standing on concrete, on the feedpad or collecting yard, minimising walking distances particularly on poorly-maintained tracks, and avoiding stressors such as underfeeding, changing groups, and pushing and shoving from dominant cows.
This is particularly important for heifers because they, and their hooves, haven’t experienced the stresses associated with being milked before so when the system goes wrong they’re often the worst-affected group. In large herds, it might pay to milk a separate heifer group with just a few cows to guide the heifers through the process.
It is important to realise claw horn disease is a slow disease so problems at calving might not be seen as lameness until five months later. The damage to the horn-producing tissue from the pedal bone can take up to a month to become significant enough to affect horn production and once horn production is affected it can take months before the damaged horn becomes weight-bearing and claw horn disease is observed
Calving and lameness are closely linked because calving increases the impact of almost all risk factors for lameness. If you focus on reducing lameness risk factors during the late dry period and the first six weeks after calving, this will have a significant impact on the number of lame cows in your herd.
