With fertility management which delivers a regular calving pattern one of the fundamentals of dairy farm profitability, a milk sample-based pregnancy test could become an increasingly valuable tool in the armoury. Hannah Park reports.
Good herd fertility is a major profit driver on dairy farms, a cornerstone to good management being effective heat detection protocols alongside finding non-pregnant cows as soon as possible after service.
Speaking in a recent Cattle Information Service (CIS) and US vet services company IDEXX-organised webinar, veterinary consultant Owen Atkinson said pregnancy testing therefore is, and will continue to be, an important component of this.
In addition to palpation and ultrasound to perform pregnancy diagnosis, he encouraged farmers and vets to embrace new technology which can determine the pregnancy status of a cow using a milk sample.
The sample is tested for pregnancy associated glycoproteins (PAGs) which are only produced in the presence of a live foetus, to detect whether the animal is pregnant or not.
Going into more depth about the fundamentals behind pregnancy efficiency, Mr Atkinson said how important maximising heat expression and detection was in achieving good results.
Achieving a 40 per cent conception rate, 65 per cent heat detection rate to give an overall 26 per cent pregnancy rate were reasonable targets, he added, for an all-year-round calving herd to be hitting or aiming
Improving the heat detection, Mr Atkinson said, is where most gains are to be had for the majority of farms.
“To do that, maximising heat expression is absolutely key,” Mr Atkinson added.
“Facility design, floor surface, having space and so on all have a part to play, but essentially poor health events will influence heat expression.”
Highlighting this Hilary Dobson, Emeritus professor at the Institute of Veterinary Science, University of Liverpool, presented research which pitted lameness second only to caesareans in a list of disruptors to fertility in cattle.
Mastitis and low body condition scores were also highlighted, alongside calving-associated issues including endometritis, retained foetal membrane and dystocia.
Mr Atkinson said: “Minimising lameness is absolutely key to maximising heat expression and therefore heat detection.
“In terms of maximising heat detection, combining the use of technology alongside visual checks from a herdsperson is the most sensible approach.”
Finding open cows as soon as possible after service is also key, said Mr Atkinson.
Pregnancy testing is generally done via rectal palpation and ultrasound alone at present, however with research, also highlighted by Prof Dobson, suggesting embryo loss can continue to occur beyond 28 days post-insemination, this may result in open cows slipping through the net and continuing through lactation
Using PAG testing, she added, milk samples can be tested from 28 days post-insemination to find non-pregnant cows and throughout gestation to confirm pregnancy status given that PAGs are only produced in the presence of a live foetus.
To minimise the economic effect of embryo death, she suggested taking two PAG samples within a 30-60 day interval and continued to explain that, given PAG values in milk start to increase as the pregnancy progresses,
PAG testing could also be used to monitor foetal death, with problems identified if the second sample is lower than the first.
Offering his opinion on a vet’s perspective of PAG testing as an alternative to rectal examinations, Mr Atkinson said it was hypothetically, less stressful for the cow and farmer as well as being accurate and time efficient.
“It avoids time involved with cow segregation and is less dependent on highly skilled veterinary resource.”
He added that he felt the role of the farm vet was continuing to evolve, from reactive, to more recently task-based work and what it might look like in the future.
Mr Atkinson said: “There is an evolution and vets are increasingly moving into a herd health leadership role alongside operations and data management. The time spent on-farm, therefore, needs to be cost and time efficient.”