Dairy advice: Reducing the risk of metabolic issues

The calving season is only a matter of weeks away and the risk of milk fever (hypocalcemia) and other metabolic issues may arise as calving starts.

The likelihood is that a lot of younger cows and heifers are going to be calving down first, which are not as ‘high risk’ as older cows in the herd.

In general, younger cows and heifers are not at risk when it comes to metabolic issues, but older cows and late-calving cows are at risk and as calving goes on, the risk increases.

Older cows tend to go in-calf somewhat later than younger cows and are at a high risk of getting milk fever as they can put on too much condition due to longer amount of time dry.

At this time of the year, the main focus is on getting cows calved and because of the demanding nature of this period, feeding dry cow minerals can be forgotten or overlooked.

The transition period for cows must be correct as any lapse in management may lead to metabolic issues and subsequently, poor animal performance throughout the lactation.

Preventing metabolic issues

During this time of the year, the focus can sometimes be completely on preparing for calves but it is crucial that dry cows are receiving the correct amount of minerals per cow, which should be about 100–120g/cow.

The dry cow mineral should have at least 22% magnesium (Mg) included and high levels of vitamin D of about 14,000 units or more – 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 sub-clinical milk fever;
• Ketosis;
• Retained cleanings;
• Low dry matter intake;
• Displaced abomasum;
• Fertility problems.

If dusting minerals on silage, minerals should be offered twice daily (60g/cow in two feeds) to try to ensure that intake is controlled and that all cows can have access to minerals.

This is particularly important where feed space is limited.

Daily magnesium supply from pre-calver mineral depending on magnesium inclusion level and feed rate is as follows:

Magnesium has an important role to play in supporting a number of the pathways in which calcium is mobilised – both from skeletal calcium reserves and re-absorption of dietary calcium.

Trace minerals like copper, selenium, zinc and so on should be fed from at least six weeks pre-calving in order to achieve adequate levels for when they are calving down.

Grouping cows

Some farmers benefit from running a freshly-calved group of cows where they are kept indoors and left apart from the milking herd for three to four days until the colostrum period is finished.

This should be continued so freshly-calved cows can 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, and if they are already over-conditioned, it may be difficult to rectify and should be managed and monitored at the point of calving.

If there has been a history of health issues, such as milk fever at calving, the mineral content of your silage should be tested.

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.

Milk fever can also result in reduced lactation performance and it can increase the incidences of slow or lazy calvings, retained cleanings and uterine infections due to impaired uterine contractions.

This can also cause muscle fractions to become impaired which reduces rumen motility and reduces dry matter (DM) intake and increased severity of negative energy balance (NEB).

This can all lead to reduced milk yield over the lactation and give rise to other metabolic disorders.

High incidences of mastitis in the first month after calving may also be associated with poor management of the cow’s transition period.