Why genetics may play a bigger role in breeding lameness

Good husbandry, environment and nutrition all play a part in controlling lameness in dairy cows. But new research has shown that genetics plays a bigger role than previously thought.

The research, carried out by the University of Liverpool, Scotland’s Rural College (SRUC) and the Royal Veterinary College, also shows that the British Genetic Lameness Index – the AHDB Lameness Advantage (LA) – can have a significant effect on disease eradication.

See also: How leg sensors helped control lameness in a dairy herd

It does this by reducing the tendency of cows to have the various causes of lameness, especially sole ulcers and sole bleeding or bruising.

“Many existing studies have shown the heritability of lameness to be between 1% and 20%,” says Georgios Oikonomou, professor of livestock health and welfare at the University of Liverpool.

Mr. Oikonomou was co-supervisor of this initiative of the Biotechnology and Biological Sciences Research Council (BBSRC).

Georgios Oikonomou © Matthew Barden

These low estimates – also sometimes expressed as 0.01-0.20 – have raised doubts about how quickly and effectively farmers could make improvements in lameness through animal husbandry.

But research has shown a much higher heritability for lameness, especially for sole ulcers, at 0.35 (or 35%), and sole hemorrhage at 0.29 (or 29%).

This puts lameness on a par with most conformation traits, which are generally easier to measure.

Additionally, by having a genomic index for LA calculated by AHDB for each animal involved in the trial, the researchers demonstrated that LA has a strong association with lameness later in life.

Genetic selection

In fact, the likelihood of a cow having sole ulcers decreased by 32% for every one point increase in LA in participating animals.

“To put this into context, a recent study reported a 20% reduction in the risk of sole ulcers in cows that were preventively trimmed before drying off,” Prof Oikonomou said, adding that the trimming of the feet was considered essential in the prevention of sole ulcers.

“For this reason, we advise growers to use LA as a genetic selection tool in the prevention of sole ulcers and bleeding,” he said.

“The cost of selecting high LA bulls is negligible compared to other interventions, which often include re-housing or increasing the frequency of foot trimming.

“And the magnitude of the potential reduction in sole ulcer incidence that could be achieved through genetic selection would result in substantial improvements in animal welfare and husbandry efficiency.”

High quality data

The researchers involved over 2,000 dairy cows in their study and recorded their lesions themselves, using the same trained veterinarian for each cow.

This gave a better and more consistent measure of the cows phenotype (her actual physical appearance or performance) and removed much of the so-called “noise”, which is created by other factors, including inconsistent scores. .

As a result, the researchers were able to create a higher quality dataset than had been achieved before.

Foot Cup Files

The trial showed that it was possible to use reliable lameness records for genetic selection to reduce hoof horn lesions, sole ulcers and sole haemorrhages.

“For genetic selection to work, we need big data,” says Professor Oikonomou. “The AHDB currently uses health data collected through milk recording in its calculation of LA, and it works very well.

“But this data may be incomplete or skewed towards the most serious causes of lameness. We can further improve the data set by using toe cup recordings. »

For this reason the Liverpool team, in conjunction with the AHDB, have partnered with foot trimmers through the National Association of Cattle Foot Trimmers and the Cattle Hoof Care Standards Board.

They are also collaborating with commercial software vendors including All4Feet, VetImpress and Hooftec to make foot cut data easier to access.

Their aim is to create a national database, merging records from different UK foot cutters which will be used for genetic evaluation of resistance to foot lesions.

“If we can get stalk-cut data from thousands of farms rather than hundreds, that will improve data quality and improve LA’s efficiency,” he says.

However, the challenge has been getting formal consent for data sharing, and he urges farmers to ask their trimmers or vets how they can give consent.

“We have to get over lameness, because it’s a welfare issue and a money issue,” he says.

“This needs to be addressed through better management, better housing and better feeding, but if we can breed a tougher cow, that gives us a head start.”

Target lameness

The lameness advantage score was developed by the AHDB in 2018, using records collected on farm software and collected via milk recording.

It was included in the UK’s national breeding target, the Profitable Life Index (PLI), in 2019.

Marco Winters, head of animal genetics at AHDB, explains that this means selecting bulls based on PLI will already help breeders reduce their cows’ tendency to lame.

“However, if producers want to target lameness specifically, they need to dig deeper into the components of the PLI and ensure they are choosing a bull with a positive lameness advantage. [LA] score,” he says.

“The Liverpool study showed that for every two point drop in lameness advantage, the risk of sole ulcers doubles,” he says. “It shows how effective reproducing can be for LA.”

“However, the study also demonstrates the benefits of more data and greater data consistency, which means the use of cut-toe records.

“We urge farmers to provide consent for the use of their data, as it will make the LA score more effective and allow them to induce natural resistance to lameness in their cows more quickly.”

Sole Ulcers and Sole Hemorrhage

Sole Ulcers

A sole ulcer is an area of ​​the damaged sole horn that has completely lost the corn tissue except for the corium (the tissue that produces new sole horn).

This happens when the structures supporting the pedal bone in the hoof weaken.

The bone can then move and sink, causing damage to the horn. As the sole wears away, the damaged horn area is exposed, leading to the development of an ulcer.

Sole hemorrhage

Sole hemorrhage, or sole bruise, is characterized by red and sometimes yellow marks or areas on the sole, and can occur where the sole is particularly thin.

It is caused by pressure on the corium, leading to damage to cells and blood vessels.

Inflammatory chemicals can cause permanent changes to the pedal bone, and possibly the digital cushion, leading to further episodes of bruising.

Sole hemorrhage is the usual precursor to sole ulcers.

Source: AHDB