Don’t get caught out spring calving herds told

Block calving herds which examine cows post calving, to pick out potential cases of endometritis (whites) for early treatment, could benefit from more days in milk. One New Zealand (NZ) study, involving nine herds and 2780 cows,  showed that simply blanket treating all at-risk cows (see box) yielded an extra 10 days of lactation.

Endometritis is a chronic low-grade infection of the uterus lining, usually with no obvious symptoms apart from some occasional discharge. Cows that are most likely to develop endometritis can be predicted by looking at their history around calving and labelled at-risk. Yet only around half of at-risk cows end up with endometritis, said vet Rachel Risdon of Westpoint Veterinary Group in Cornwall, talking at a farmer meeting this week. “Treating only the positive cows in the trial was highly effective and, in one study, resulted in an extra 20 days in milk,” she added. 

Although most cows – over 90% - have some uterine infection after calving, that’s normal and they usually self-cure within three weeks, she explains. However, typically 15% of cows in a herd are affected with endometritis. It may sound a small percentage until you realise these cows can’t get back in-calf until their infection is cleared up. UK research shows that even when successfully treated, these animals have 20% lower conception rates, take 30 days longer to conceive and are 3% more likely to be culled for failure to conceive than unaffected animals. Mrs Risdon revealed NZ data which shows that at-risk factors lead to high final empty rates: cows with retained foetal membranes up to 25%; difficult calvings over 15% and cows calving twins around 15%. “Clean cows in our study took an average of 25 days to conceive, whereas dirty cows took 68 days,” she said.

Financial losses depend on treatment costs, milk yield losses and the impact on fertility. In the UK, direct costs of treatment and reduced milk yield from late calving are at least £60/cow, while indirect costs of extra inseminations, a longer calving interval and increased culling rate are more than £70/cow. This all goes to show that diagnosing endometritis on time is particularly important in a block-calving herd, remarked Mrs Risdon. “Cows which have infection in their uterus are not going to cycle, or will take longer to do so. And there isn’t time for this in block calving. Some 60% of cows not seen bulling 10 days before the planned start of mating (PSM) are infected with endometritis. The risk is, therefore, an increased culling rate due to more cows empty at the end of mating, or an extended calving block.”

Looking at cows 4-5 weeks before PSM gives them time to be treated, recover and start cycling before routine pre-mating heats and checks. “Cows will clean up in 1-2 weeks and then need time for their hormones to kick in,” she added. With so many cows calving at once, finding out whether they are clean or dirty is made simple by conducting a Metricheck test on the whole herd.  This is a job that’s easily done at milking explained Mrs Risdon. This New Zealand tool is a stainless steel rod with a rubber cup at the end which identifies dirty cows because it gathers a sample of mucus from the vagina, near the cervix where infection tends to be. Vets can give training in how to use it and interpret the results, she said.

“Spray-mark cows with their score (see box) then draft them out, check their history and see if they have calved long enough to be treated. Unless the herd is very tightly calving and there are no tail end cows, you will need to do a second round of Metricheck to catch the next batch of calvers. Problem cows can be presented to the vet for full diagnosis and treatment.”

Work from the UK, US and New Zealand shows the best time to treat dirty cows is about 21 to 35 days after calving. In the Kiwi trial, Mrs Risdon reported that treating cows with retained foetal membranes, that had had a dead calf, or vaginal discharge, one month before PSM led to an increase in four-week and eight-week in-calf rates. “It got cows pregnant faster – up to 13 days sooner for cows with retained cleansing. What is more, it was economically sensible to undertake the treatments.”

She went on to point out to the audience that the only licensed antibiotic – given as a washout – to treat endometritis is cephapirin (Metricure®). It is effective in killing most of the common bacteria causing the infection. In the NZ study, working on a 15% endometritis rate in a typical 300-cow herd (ie. 45 cows), the return per extra day in milk was $6.84 or £2.97 (2.3NZ$=£1). This was based on production of 1.2kg milksolids/cow/day and a milk price of £2.43/kg milksolids. Treatment cost £10.86/cow. “When all 45 cows were blanket treated, this produced a total of 450 days (45 cows x 10 days) extra in milk worth £1,338. After treatment costs (£489) this left a benefit of £849.50.  It would not be unreasonable to expect similar figures in the UK.”

RISK FACTORS FOR ENDOMETRITIS

• Difficult calving
• Twins
• Retained foetal membranes
• Milk fever
• Ketosis
• Displaced abomasum
• High milk protein %
• Caesarean
• Cows in negative energy balance

METRICHECK DISCHARGE SCORES

0 = no discharge

1 = clear

2 = mucus + flecks of pus

3 = mucopurulent

4 = purulent

5 = foul