Friday, March 29, 2024

Keeping hooves in top condition

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The impacts of lameness on farm performance can be far-reaching, from loss of milk production to poor reproductive performance to lower staff morale.
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The good news is that diagnosing the cause of lameness in a herd is relatively easy. By observing cows walking, and picking up and examining any affected foot, a picture can soon be constructed of where potential problems might lie.

The anatomy of a cow’s hoof is deceptively complex. The hoof “capsule” is made up of the medial (inner) and lateral (outer) claws, with the interdigital space between. Each claw horn is actually different types of horn knitted together; the wall, the sole, and the join between these two, called the white line simply because that’s what it looks like.

Dr Jean Margerison, a senior lecturer in animal science at Massey University who has spent more than a decade studying lameness in dairy cattle in New Zealand and the United  Kingdom, said a combination of claw horn disorders and cow handling are the main cause of lameness for dairy farmers in this country.

The wall horn – the part of the claw horn seen from the side view when a cow is standing normally – is the hardest. The white line horn is a narrow band that bonds the wall horn with the relatively more flexible sole horn. This white line and any bruised sole horn are the weakest parts of the claw horn, particularly susceptible to injury when cows are pushed up too tightly with a backing gate or on raceways.

The two main categories of disorder are sole bruising and white line damage. Margerison said sole bruising is initially caused by the pedal bone coming down inside the capsule and creating pressure against a hard surface.

“It mainly happens around calving – all the ligaments that support the pedal bone in that capsule are slackened and loose, and the impact occurs.”

Although all cows experience the ligament relaxing at calving, she said heifers suffer the most as they transition from minimal mob pressure and no exposure to concrete to life in the milking herd.

The sole bruising occurs at calving and then grows out – Margerison likened it to a bruise under a fingernail that grows out over time. Overseas research suggests the maximum amount of bruising is visible 120 days after calving. She said that in the UK context, bruising had usually subsided by 160 days after calving but in NZ that period was extended to 220 days after calving.

“In NZ we’re getting more bruising and it is going on for longer.”

While bruising on its own can cause some discomfort, it also increases the risk of sole puncture. Research supervised by Margerison indicated that bruising decreased sole horn strength – the greater the bruising, the less resistance to puncture.

“So we have cows with bruised feet for a long time,” she said.

“All it takes is for someone to push them along the tracks and they stand on stones they would not normally stand on – and you have got lame cows.”

She warned that it’s impossible to prevent the initial bruising at calving, but that good management and infrastructure could minimise the risk of puncture and subsequent infection.

Walking cows to the dairy at such a pace they can pick where they place their feet, combined with best practice operation of any backing gate (taking up space rather than bulldozing forward) would be the first ports of call. Making sure concrete areas like holding yards and feedpads are kept free of stones and cleaned regularly was also crucial.

White line horn is the softest part of the claw horn so is still susceptible to penetration by sharp objects. Any damage can easily lead to a secondary infection. Unlike sole horn, it can be damaged by torsion or twisting forces.

Margerison said the twisting forces could be generated by cows exiting a rotary dairy or even through poor use of the backing gate – anywhere cows are forced to turn in a relatively tight space. She pointed out that cows’ physiology was not suited to walking backwards or tight turns.

A simple way of reducing white line damage was to place a mat that would soften the underfoot conditions where the twisting motion occurs, such as where cows leave the rotary platform.

For both sole horn and white line damage, sensible animal handling practices and basic infrastructure management offer easy opportunities for reducing the incidence of lameness onfarm.

Another cause of lameness starting to develop in NZ is digital dermatitis. Though still uncommon, it occurs in the interdigital space between the two claws.

The bug – spirochete – that causes this survives in manure. Margerison warned that once cows have digital dermatitis it can only be controlled rather than cured. Regular cleaning of feedpads and housing minimises the chances of infection.

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