Understanding inflammation around calving
Fort Atkinson — Inflammation is a key and common problem in early lactation cows.
Up to 73 percent of dairy cows battle inflammation during their transition period, Dr. Barry Bradford, Kansas State University, said during the November "Hoard's Dairyman Webinar" sponsored by Virtus Nutrition and co-hosted by Steve Larson, Hoard's Dairyman, and Dr. Mike Hutjens, University of Illinois.
"If we can solve this problem, we can really improve the sustainability of our dairies," he said.
One of the big frustrations is that inflammation is not any one thing. "It is a big mix of different issues, all combined at the same time," Bradford said, calculating the mix at about 40 percent metabolic disorders and 60 percent infectious.
In many instances, it is likely both factors feeding together.
Studies show cows with metritis are more prone to develop ketosis and mastitis, while cows with ketosis are significantly more likely to develop metritis and mastitis.
Suppressed immune function contributes to infectious disorders, he explained. Infections promote metabolic disorders and metabolic problems increase infection risk. It could be that inflammation provides a mechanistic link.
If that's true, Bradford said, it could lead to new ideas on how to disrupt those pathological processes.
Inflammation and transition
Inflammation is associated with immune activation or tissue damage, swelling, pain and fever as the cow's body responds to illness, accidents or infections.
Research grouping cows by degree of inflammation found that only 5 percent of cows with the lowest degree of inflammation experienced any kind of transition disorder, compared to 45 percent of cows with the highest level of inflammation.
Summarizing multiple studies comparing herdmates, Bradford said cows with biomarkers tied to poor immune function and higher risk of infection had a four-fold increase in the risk of metritis, a 40 percent decreased risk of conception in the first 150 days in milk and, in one study, a 2,000 pound decrease in milk yield.
"So the associations here look pretty ugly in terms of all the major outcomes that we're worried about in the lactation," he noted.
There are long-term negative consequences of these disorders, Bradford said, citing studies that suggest cows with mastitis in early lactation lose about 1,100 pounds of milk over the whole lactation, while cows with metritis or ketosis in early lactation likely lose 700-800 pounds of milk.
"But even more consequential, economically, is their risk of leaving the herd early," he added. Such cows are 1.5-3.5 times more likely to be culled before having their next calf.
Causes of inflammation
Many studies on many cows in many countries provide strong evidence that all transition cows deal with systemic infection. "Even healthy cows show a ten-fold increase in the biomarker of systemic inflammation," Bradford said.
However, the magnitude or degree of infection varies tremendously by cow. Those with the biggest disease challenges took two or three times longer to return to normal than healthier cows, meaning they were showing signs of chronic or subacute inflammation for 2 to 3 weeks instead of 5 to 7 days.
One of the big questions is the cause of transition inflammation. Studies show mastitis, even though it is a local infection of the mammary gland, causes systemic inflammation that affects all the organs of the cow's body.
It is the same with metritis. "Pretty clearly, these local infections can cause systemic inflammation," Bradford said.
He made the point that uterine involution is clearly involved in the mix, although how is not clear. One question researchers would answered is if the degree of inflammation witnessed in the healthiest cows necessary to make sure that uterine involution progresses as it should.
Chicken or the egg
One of the biggest questions is how to sort out cause and effect. "Does inflammation cause disease or does disease cause inflammation?" Bradford asked.
His research on whether repeated inflammatory signals would alter metabolism found inflammation decreased dry matter intake and lowered milk yields.
"This ties in with the idea that, perhaps, these mild levels of inflammatory responses are problematic for cows in terms of adequate feed intake and hitting peak milk yield quickly," he noted.
The No. 1 factor in predicting which cow will have transition disorders is excessive body condition score. "We think that contributes to metabolic problems and to immunity challenges," he said.
Inflammation around calving is a sign of disrupted health and needs to be addressed.
"I am a big believer in treating inflammation, if it improves outcomes," Bradford said.
However, be aware that blocking inflammation by pharmaceutical means close to calving can raise the risk of retained placentas and metritis, likely because the drugs interrupt the normal process of giving birth.
"Clearly, if we're too good at blocking too much inflammation right around this window we can cause problems," he pointed out.
In light of this information, Bradford's study of two anti-inflammatory drugs on multi-parous cows did not administer the drugs until 24 hours postpartum after placentas had been delivered.
Unfortunately, the strategies used in the study are not approved for commercial use. "There is no FDA approval for these uses at this time, but we investigated this trying to understand what are the long-term implications of inflammation in this window of time and, by trying to block it, uncover some really potent whole lactation impacts," he explained.
Although return to pregnancy was not affected, the data revealed an 11 percent increase in whole lactation milk yield with three doses of one drug and a 12 percent increase in whole lactation milk yield and better herd retention with a single dose of another drug. Return to pregnancy was not affected with either.
The results were exciting. "Not only are we seeing increased milk yield, but some hints at better health or, at least, better retention in the herd," Bradford said.
Perhaps it's not the big spike in inflammation at the beginning of lactation that's the problem.
"Maybe this spike for a day or two is necessary to get the uterus behaving in the right direction," Bradford suggested. We even have some hints that it may be involved in helping the cow adapt metabolically.".
However, he concluded, when inflammation stays higher and longer, it can lead to poor feed intake and negative energy balance, metabolic disease and infertility.