How a dairy farm pilot tackled conception and culling rates

Giving repeat breeders a holding injection after service has improved conception rates and reduced forced culls at New Manor Farm in Somerset.

Like many dairy farmers, Martin Hawkins was frustrated with the number of “good” cows that were failing to get pregnant after three or more services and had to be culled to maintain efficiency.

“It’s when you lose the good ones that it’s a problem, as you’ve got less choice over which cows to get rid of,” Martin explains. That means retaining a higher number of less efficient animals.

See also: High-yielding herds top efficiency stakes – but beware of low fertility

According to Kingshay’s Dairy Costings Focus Report 2023, fertility issues account for 24.9% of herd culls, with repeat breeders making up 6.3%.

Having to serve cows multiple times also represents a significant drain on funds, with Kingshay putting the cost of an extended calving interval at £5.89 a cow a day over 365 days.

With the cost of infertility clear, and the number of repeat breeders at about 15% in his 850-cow herd, Martin was keen to address the issue.

The farm team was already practising a high standard of herd fertility management (see “Herd fertility fundamentals at New Manor Farm”), but there were still 15% of cows requiring three or more services and, therefore, at risk of culling.

On-farm trial opportunity

Vet Paddy Gordon of Shepton Vets says even if good fertility management is in place, repeat breeders will always be a problem, partly because some cows are naturally less fertile.

He suggested Martin take part in an on-farm pilot using the gonadotropin-releasing hormone (GnRH) off licence after service, as a means of maintaining a pregnancy.

Paddy had read a Spanish study from the University of Lleida, where the use of the GnRH dephereline at two-and-a-half times the conventional dose, five to seven days after service, had resulted in a pregnancy rate of 39.1%. This compared with 28.6% in non-treated repeat breeders.

The dosage, and the time it was given, set this study apart from previous work, and he was keen to see if such a strategy had a role to play on his clients’ farms.

GnRH is naturally produced by the pituitary gland and stimulates the release of luteinising hormone (LH), which promotes the production of progesterone.

High levels of progesterone in early pregnancy are needed for embryo growth and establishment and maternal recognition of pregnancy, says Paddy.

Martin Hawkins and vet Paddy Gordon © Aly Balsom

Improved conception rate

Nineteen cows that had failed to hold were enrolled onto the study (see “Pilot study – cost benefits at New Manor Farm”). Nine out of 19 held. “That’s not only a positive outcome, but we’re also achieving normal conception rates of 45% in those animals,” says Paddy.

Martin adds: “For that group of animals, it’s very high. I was quite surprised to get so many in-calf, and the ones you’d given up on.”

At about £9 for the treatment, he says the cost is “negligible,” particularly as some (or all) of those nine cows would have been culled.

In addition, he believes this should help environmental targets because fewer herd replacements will need to be kept on farm.

Paddy is keen to get more of his clients involved in using this to get cows in-calf at the optimum time.

“We want a calf a cow a year. To achieve that, we need most of our cows to get pregnant between 50 and 150 days after calving. There’s a window of opportunity to get that cow in-calf.

“The economic benefit would be significant, as we’ll retain those cows in the herd and get them in-calf at a reasonable time to maintain production,” he explains, adding that milk production will show a more marked decline after 200 days.

Cows conceiving after 200 days are more likely to be fat at the next calving as a result of relative overfeeding during their extended lactation, he adds.

Careful targeting

Martin says missing that optimum window leads to a “vicious cycle” of cows getting fat and having calving issues and reduced fertility.

However, both stress that using a GnRH holding injection is not the answer to poor management. “If you’ve got other problems in the herd, it won’t fix them,” he says.

Paddy agrees: “It’s about targeting the right cows and addressing the fundamentals of fertility, and not using this as a sticking plaster but maintaining good animals in the herd.