Milk fever (hypocalcemia) is a metabolic disorder where the cow’s blood calcium levels drop, typically within 24 hours after calving.
With the calving season is only around the corner or underway for many for autumn calving herds, the risk of milk fever and other metabolic issues increases.
The likelihood is that a lot of the younger cows and heifers will be calving down first, due to synchronisation programmes and/or the ability of younger cows and heifers to be fit come breeding and to hold to first service.
In general, younger cows and heifers are not at risk when it comes to metabolic issues, unlike older cows and late calving cows.
Generally speaking, a lot of the older cows will take that bit longer to go back in calf when compared to the younger and more fertile cows in the herd.
These cows are at a high risk of getting milk fever due to their parity, and in some cases build too much condition due to a longer dry period.
Many farmers will know the impact of having a cow down with clinical milk fever, but sub-clinical milk fever can also result in reduced lactation performance.
It can cause a cow to have slow or lazy calvings, retained cleanings, and uterine infections due to impaired uterine contractions.
The cow may have poor muscle function, leading to reduced rumen motility and resulting in a supressed dry matter intake and negative energy balance (NEB).
NEB and reduced intake will impact on milk yield and further increase the likelihood of metabolic disorders such as ketosis or displaced abomasum.
Any form of milk fever is a gateway for other diseases and issues throughout the lactation, as high incidences of mastitis in the first month after calving may be associated with poor transition cow management.
Preventing milk fever
It is crucial that dry cows are receiving the correct amount of minerals per cow, which should be about 100-120g/cow every day, especially during the cows’ transition period three weeks pre and post calving.
The aim should be to have 22% magnesium included in the dry cow mineral with high levels of vitamin D of at least 14,000 units – older cows are going to need high levels of vitamin D to prevent milk fever.
Cow health problems from inadequate mineral supplementation include clinical and subclinical milk fever; ketosis; retained cleanings; low dry matter intake; displaced abomasum; and/or fertility problems.
To ensure that each cow is receiving their adequate mineral intake every day when you are dusting minerals onto their feed, it should be done twice a day with 60g/cow in each feed – this ensures all cows have access to minerals and is crucial where feed space is the limiting factor.
Trace minerals like copper, selenium, zinc, etc., should be fed from at least six weeks pre-calving in order to achieve adequate levels for when they are calving down.
Running a freshly calved group of cows where they are kept indoors and left separate from the milking herd for three to four days until the colostrum period is finished is beneficial, to allow them to get that bit of extra nutrition and care.
Later calving cows should be restricted to 10-11kg DM in November to keep body condition score (BCS) under 3.5.
If they are already over-conditioned, it may be difficult to rectify and should be managed and monitored at the point of calving.
Over-conditioned cows should be separated and their feed restricted, and mainly fed a fibre-rich diet, so their condition is controlled.
Silage should be tested regardless but especially if there has been a history of health issues, such as milk fever at calving, as testing the mineral content of your silage could help rectify any potential causes.
Testing silage for winter milk herds is fundamental in ensuring that cows are getting adequate feed through silage and an appropriate amount of meal is fed to bridge the nutritional gap.
This will ensure cows are fed properly to support production but not over fed, which can be costly.
High potassium (K) silage can often be the cause of the problem, so the farmer should target a low K silage of less than 2.2% from four weeks pre-calving.
A high calcium bolus with vitamin D is recommended instead of straight calcium bottles under the skin for the purpose of preventing milk fever at the point of calving.
