Vet’s Vision Phil Rennie Tauranga Vets

With calving in full swing it will soon be 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, referred to as ICR.

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. One way to improve this is by cleaning up cows with an infected uterus – also known as ‘dirty cows’.

Endometritis cases

‘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 had a twin birth. In saying this even cows that had 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 in-calf rates 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.

-  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 show cows checked and treated between days 14-28 after calving respond better to treatment than those treated later.

Cows calved less than 14 days with vaginal discharge are not classified yet as ‘dirty’ because flecks of pus in the discharge at this time may reflect normal involution. Therefore, batch testing of cows within the 14-28 day post-calving window appears to be the most effective approach as it treats cows earlier. This allows them to return to normal uterine health quicker and get back in-calf earlier.

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 two to four weeks 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 what the best course of action is for your herd.