News & Advice

What’s new with dirty cows?

Aug 5, 2017 | Dairy, Dairy Farm Reproduction

Katrina Roberts, Anexa FVC Herd Health Veterinarian

Dirty cows have a post-calving infection in their uterus termed endometritis. 
Until recently in New Zealand we haven’t had an idea of the true extent of endometritis in the national herd. In the 2015 mating, our research team Cognosco worked with Dairy NZ in this field, and some of our Anexa FVC herds were involved in the study. 
Nationally 1806 cows from 100 herds were checked 30 days before their herd PSM. The prevalence of metri-check positive (score 2 or more) cows was 25%. As expected cows that were metri-check positive had lower conception rates, three and six week in-calf rates, with increasing score (more pus) having a bigger impact on these outcomes. 
Previous research has shown dirty cows take 2 to 3 weeks longer to get in calf and have empty rates 10-30% higher than clean cows. 

Herd level prevalence of endometritis varies hugely, some herds with only a couple of dirty cows and some at 30-50%. We do not understand all the risk factors for endometritis, but once we get to this time of year, it’s too late to prevent. The best we can do for these cows is find them and treat them. This gives these cows the best chance of conceiving early in the mating period. 
There will be cows in the herd more likely to develop endometritis. This group of animals are known as ‘At Risk’ cows and includes any animal that has had retained foetal membranes (RFM), twins, milk fever, an assisted calving and/or a dead calf. However, there are cows with no health issues recorded that are also diagnosed with endometritis on metri-check. In fact, 71% of metri-check positive cows come from non-at-risk cows! 
Metri-checking is a simple and cost-effective method for finding dirty cows and studies have shown better responses to treatment when cows are detected and treated earlier. Recent New Zealand research indicates that the in-calf rates of cows diagnosed metri-check positive and treated were higher when herd was metri-checked in batches i.e. cows with endometritis detected earlier and treated earlier leading to better reproductive outcomes (9.6% higher 6 week in calf rates) than the traditional whole herd metri-checked in one batch before PSM. This is consistent with the anecdotal evidence we have seen in herds that batch metri-check, more cows treated but better in-calf rates in the treated cows. In order for the batch metri-check system to work, cows need to be clearly marked based on their calving date. Cows can be checked in batches from two weeks after calving. 
If the whole herd is to be metri-checked in one go, it needs to occur at least 35 days before the start of mating to give the treated cows time to cure before mating starts. 
There is a positive return on investment to whole herd metri-checking in herds where there are more than 2% of dirty cows, which is probably >95% of herds! 

There are options for treating the dirty cows. The most common is an intrauterine antibiotic with a nil milk withholding. Talk to your Vet about metri-checking and treatment options. Is there room for gains to be made in this area on your farm? 

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