Vet's vision with Phil Rennie Tauranga Vets

With calving well progressed on many farms, it’s now time to think about next season’s reproductive targets and getting those same cows back in-calf.

For the New Zealand dairy industry, the national in-calf goal is to achieve at least a 78 per cent six-week In-Calf Rate.

This is regularly achieved by the top 25 per cent of Kiwi farmers. The main drivers of six-week ICR are the three-week submission rate and conception rate – and, one way to improve this is by cleaning up cows with an infected uterus – also known as ‘dirty cows’.

Endometritis

‘Dirty cows’ have a condition called endometritis where the lining of the uterus is inflamed, and pus produced within the uterus discharges into the vagina. White vulval discharge may sometimes be seen at milking time for instance.

Cows deemed ‘at risk’ of developing endometritis either had dead calves, assisted calvings, retained afterbirth, milk fever or twin births.

In saying this even cows that have normal non-assisted calvings with no metabolic disease can also develop endometritis – therefore, ideally the whole herd should be checked to ensure these cows are not missed either.

New Zealand and overseas studies have shown the following associations:

Cows with endometritis have 15-20 per cent lower six-week ICRs than those without endometritis.

Cows with endometritis have 10-20 per cent higher empty rates. If they do conceive, they have an increased calving-to-conception interval, typically two to three weeks later but can be up to 26 days longer. And reduced days in milk will impair herd performance.

Detection and treatment

Cows can be given a quick and practical check by using a metricheck device for evidence of infected vaginal discharge. The traditional approach has been to check the ‘at risk’ cows about 35 days prior to the planned start of mating.

Using that approach typically shows up to 10 per cent of a herd to have infection. Subsequently, Australasian studies along with a recent NZ study show cows checked and treated between days seven-28 after-calving respond better to treatment than those treated later. Cows calved less than seven days with vaginal discharge are not yet classified as ‘dirty’ because flecks of pus in the discharge at this time may reflect normal involution. While treating cows earlier is the most effective approach, all infected cows will benefit from treatment with a return to normal uterine health, hence getting back in calf earlier than if left untreated.

In summary treatment of metricheck positive cows early in lactation provides the most benefit. Improved reproductive performance is seen in cows that are examined and treated within one month after calving. If investigation is delayed, cows with endometritis do not tend to ‘self-cure’ and become much harder to diagnose. A proactive approach is recommended, so feel free to talk to your local large animal vet for more information and discuss the best course of action for your herd.