By Debbie James

A dairy farmer is making informed breeding decisions that reduce calf mortalities and improve fertility by screening his high genetic merit dairy herd for inherited mutations.

Richard Pilkington runs a herd of 275 pedigree Holsteins at Shordley Hall, a Farming Connect focus farm near Wrexham.

The all-year round calving herd produces 10,900 litres at 3.8 per cent butterfat and 3.15 per cent protein.

When three calves suddenly died at around three months old, the circumstances of their deaths pointed to a genetic mutation known as haplotype cholesterol deficiency (HCD), a defect in which calves are born without cholesterol in their cells. 

Mr Pilkington and his wife, Ruth, embarked on a project in conjunction with Farming Connect to identify which animals in their Aintree herd were carriers of HCD and also those that carried any of five fertility haplotypes (HH) – haplotypes present within the DNA of the black and white breed.

Owen Tunney of Willows Vets took hair follicle samples from 200 cows and youngstock for genotyping.

The tests revealed carriers – the highest genetic merit female tested was carrying the HCD and a fertility haplotype – but carrier status does not mean that Mr Pilkington won’t breed from these animals.

By selecting non-carrying sires he can prevent these haplotypes from being passed to offspring by selecting sires that don’t carry the HCD mutation. For a calf to be a defective carrier, the HCD mutation must occur in both parents and there is then a one in four chance that their offspring will inherit the fault.

Half of AI bulls currently have their haplotype status published. In the top ten proven bulls for Profitable Lifetime Index (PLI), two are carriers of HCD but these bulls will have a significant impact on the genetic gain of UK herds.

Rhys Davies, Dairy Technical Officer at Farming Connect, who co-ordinated the project, says they should not be disregarded due to their carrier status.

“Likewise, knowing the statuses of any resulting females from these bulls, will allow for peace of mind when planning future matings,’’ he says.

Mr Pilkington plans to continue genotyping every female heifer calf for recessive disorders because he says it will help him improve his herd further.

“We can now manage our breeding around this. There is nothing wrong with an animal with a haplotype but by knowing they have got one of these it gives us the full picture. We can manage them to avoid future grief.’’

At around £33 per animal, he says the test isn’t cheap but when balanced against the cost of sexed semen and selecting which animals to breed heifers from according to haplotype, he believes it is a sound investment.

The outlay will also be clawed back by preventing calf mortalities due to HCD, he adds.

“It costs a lot to rear a heifer replacement. To lose an otherwise healthy animal at three months old when you have put all that cost in is very frustrating.’’

Heat detection collars have been used in the herd since 2009 and this has improved fertility but identifying heifer replacements with fertility haplotypes should lift this further, Mr Pilkington reasons.

Knowing the HH status of bulling cows and heifers can result in fewer repeats and straws to conception and lower the calving index – the index at Shordley Hall is 391.

Mr Pilkington’s aim is to breed robust cows with lower stature and uses sires that average a Profitable Lifetime Index (PLI) in excess of 700.

“Our goal is to further improve the herd to produce a robust type of cow with good health traits that still produces the same amount of milk and components.

“We don’t want to forego type because we have invested a lot of time in putting type into these cows.’’