Step-by-step guide to carrying out IVF on cows

A growing number of cattle breeders are using in vitro fertilisation (IVF) to maximise pregnancy rates.

This is the process of harvesting oocytes from donor cows, and creating embryos by fertilising the oocytes with semen in a petri dish.

The embryo is then implanted into a recipient (otherwise known as surrogate cow), or they can be frozen indefinitely. 

See also: Embryo transfer ‘a faster way to boost beef herd genetics’

Cumbria-based Paragon Veterinary Group has seen embryo production increase at least six-fold in the since its Activf-ET programme began in 2013 and they explained how the process works.

Read the step-by-step guide to using IVF and case study at Trueman Limousins in County Down below.

How the procedure works

The first stage is the key addition to conventional embryo transfer. Eggs are removed from the donor cow’s ovary before the ovary naturally releases the oocyte down the fallopian tube.

Using a process called trans-vaginal recovery, IVF works by first removing the dominant follicle in the ovary, allowing the rest to grow.

In a normal pregnancy, the dominant follicle inhibits the rest – otherwise a cow could end up developing dozens of calves in the womb, she adds. With IVF, all follicles are left for six days to develop uninhibited within the ovary in a process called dominant follicle regression (DFR). 

Ooctye development

1 Dominant follicle regression

The donor cow is given a local anaesthetic and cleaned with a mild disinfectant and saline solution. This can happen on the farm or at the Paragon facility.

2 Ultrasound needle

An ultrasound-guided needle enters the ovary to remove the dominant follicle and stimulate super-ovulation.

3 Super-ovulation

a three-day course of follicle stimulating hormones (FSH) is administered to stimulate ovaries to produce more oocytes.

Oocyte collection

4 Ovum pick-up (OPU)

The donor cow is brought into the crush collection facility, where the temperature is at 27-32C. Oocytes are harvested via trans-vaginal recovery, averaging 10 eggs per collection, and the eggs are matured for 20 hours.

5 Insulated chambers

Eggs are placed into insulated chambers at 37C to mimic a cow’s body temperature.

Fertilisation

6 Fertilisation occurs with semen

7 Embryos

Resulting embryos are matured for a week in the laboratory, passing through eight different maturation liquids (medias) mimicking the changing pH and gas levels inside the uterus.

8 Embryos can be transferred directly or frozen indefinitely

Recipient and donor management advice

General guidelines

Recipient cow or heifer

Avoid lush, wet grass – if grazing, buffer-feed if possible. Indoor recipients achieve 5-10% better pregnancy rates that those managed at grass. Bought-in stock should have six weeks to settle into new farm. Recipients should be managed as a group and major changes (such as spring turn-out and autumn housing) should be avoided for six weeks pre- and-post transfer. Good body condition score is essential – 2.5 minimum. A long fibre-based diet of hay, big bale silage or straw should be fed. Low-protein coarse mix as a supplement is preferable (although not barley). Sugar beet pulp can deliver energy and fibre – and be used as a mineral carrier. Routine treatments (worming, vaccination, foot trimming) should be avoided at this time.

Cows Cows calve easier and so the process can be preferred in beef breeding or with low calving ease bulls. Works best on fourth-calvers or younger. Select cows with no reproductive or health issues. Synchronise cow after peak yield as stress of lactation can reduce pregnancy rates.  Pregnant cows can be collected from until about the fourth month of pregnancy. Maiden heifers Heifers average 5-10% better pregnancy rate, compared with cows. Should be at least 15 months old, cycling regularly and weigh 350kg (depending on the breed)

IVF stages – fortnight timelines

Donor cow			Laboratory			Recipient cow
Day 1	Day 2 to 6	Day 7	Day 7/8	Day 8	Day 8 to 15	Day 15
DFR	Superovulation after three-day FSH course	OPU	Egg maturation 20-24 hours	Fertilisation	Maturation in incubator	Must be used within 24 hours if fresh in cow seven days after heat

Benefits of using IVF

• 50% of usual amount of semen needed. Half a straw can inseminate around six or seven donors
• About 10 eggs per collection. About 73% of these will be fertilised
• Then 43% will become a viable and freezable
• Fresh pregnancy rate = 58%
• Frozen pregnancy rate = 57%

Breeding benefits

Problem breeders can be salvaged because they can be used as a donor if, for example, they have:

• Uterine damage
• Fallopian tubes blocked
• Scarring

Extend breeding life:

• Collection possible from 10 months to 20 years old and above
• Ovaries can be recovered from abattoir

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Case study: Henry Savage, Trueman Limousins, Altnamackin, County Down

At Trueman Limousins, where a 70% pregnancy rate is the target for heifers, success with IVF and conventional embryo transfer work hinges on diligence around three key areas – condition, nutrition and regime.

• Condition: Heifers must be well-fleshed but not too fat. Too much weight is an “uphill struggle” and should mean heifers are ruled out of embryo transfer work. With reference to fatness classifications on the Europ grid, Mr Savage targets 3s.

• Nutrition: Energy levels must be kept high, with no sudden changes in diet in the two months leading up to oocyte collection and embryo transfer.

• Regime: Quality semen must be used, and optimum care taken of semen and embryos to maximise conception.

IVF contenders must be mature cows with calves on the ground of exceptionally high genetic merit that may be experiencing breeding difficulties, explains Mr Savage.

Two cows have been through the IVF process successfully so far – a 16-year-old, from which three calves were produced, and a six-year old with a retained membrane, which produced four calves via IVF. 

This summer a third dam is being put forward. She had a mummified calf inside her, of which only three-quarters was removed. 

IVF nutrition: supplementing grass/silage in summer/winter

Donors: five weeks out

• Flax oil: 50-60ml daily
• Dried sugar beet: 1-1.5kg a head a day
• High-energy/low-protein pre-calving nuts (40-50% maize, 14%CP): 1-1.5kg a head a day
• Pre-calving minerals. Mixed with sugar beet and pellets or placed on to silage

Recipients: six to seven weeks after transfer

• Broadly the same protocol
• One difference is that double the amount of flax oil is used (100ml a head a day)
• Cows are scanned at seven weeks and then transitioned on to standard heifer diet if pregnant.

“We focus on energy levels and a rising plane of nutrition,” Mr Savage says. “We have a regime we think works and we wouldn’t change it. We achieved five pregnancies from seven embryos with our last recipients and generally find higher success rates with heifers, while cows, as you would expect, might manage 50% success.

“Semen quality is hugely important and the number of times the straw goes in and out of liquid nitrogen has an effect, as does having older semen – there are so many variables.

“I’m investing in a new turner for the farm this year and this is mainly because I want to produce better-quality dry silage to support cow condition and improve fertility.”