The dairy industry needs to “wake up” to the dangers of using genomic bulls on maiden heifers, according to a breeding specialist.
Munster AI’s Doreen Corridan claimed that more heifers are experiencing difficult calvings this year because both farmers and farm advisors ignored best practice by mating low reliability bulls with maiden heifers.
“I’m hearing about a lot of calving difficulties and Caesareans in heifers that were carrying calves by some genomic bulls that have since topped the latest spring AI list,” said Ms Corridan.
Among the farms that are facing culling first calvers due to problems this spring was the Greenfield demonstration farm in Kilkenny. Management there decided to use two genomic bulls on maiden heifers in an effort to accelerate EBI gain in their 2015 calf crop.
“It was our own mistake and we definitely won’t be doing it again,” said Teagasc specialist on the Greenfield project, Abigail Ryan.
She added that the risks associated with using genomic bulls on maiden heifers were considered worthwhile last year because of the sires’ very high EBIs and low calving difficulty scores. However, the plan has backfired, with two heifers subjected to Caesareans likely to be culled this year.
“We ended up with two Caesareans out of the 89 heifers that have calved down so far this spring. They’re barely milking now and I’d say they’ll be culled, even though they were smashing heifers. We jacked a good few of them too, but these animals are all doing fine now,” she said.
Teagasc research has shown that every Caesarean can end up costing the farmer over €700 in dead calves, higher culling rates, lower milk yields, labour, and veterinary costs.
“We cost Caesareans at six hours in labour for the farmer and a minimum of €160 for the vet,” said Teagasc geneticist, Donagh Berry.
“We also assume that the cow has a 5pc higher chance of dying, and 25pc more likely to be barren. There’s also the cost of the calf and the loss of 600kg of milk.”
Even calving interventions that don’t require a vet cost farmers dearly.
“What we class as severe assistance by the farmer will result in a 5pc increase in barreness, 50kg less milk and additional hours of labour. That’s going to be close to €150 per cow,” said Mr Berry.
Doreen Corridan believes that genomic proofs are not as accurate on calving difficulty as other production traits. This may be partly due to the subjective nature of scoring calving difficulty for farmers at a time when they are under severe workload stress.
“Gene Ireland is the only way that we can get accurate information on crucial issues such as calving difficulty and congenital defects,” said Mr Berry.
“It ensures that we have a minimum number of animals in commercial situations where the farmer has no vested interest in playing with the figures.”
Ms Corridan’s advice for farmers is never to use a bull on maiden heifers that has a calving difficulty index of more than 2pc, or a calving index reliability that is lower than 90pc.
“Yes, you are compromising your genetic gain, but at least you are guaranteeing that your heifers survive into cows.
“A lot of Teagasc advisors were mating genomic bulls with maiden heifers. Both they, and some farmers, need to cool the jets on the chase for elite EBI calves,” she said.