Getting autumn transition cow management right

By Ruairi McDonnell, Independent consultant

There have been some great advances in transition cow management (TCM) in recent years. The three weeks pre and post calving are a very metabolically challenging period for cows and errors or incorrect management during this time can have significant financial consequences for the whole season. About 80% of disease costs are incurred in the four weeks post calving, so it’s worth taking steps to minimise this on your farm. Many people will have cows calving in the next three weeks or so, and even if you have not implemented any TCM strategies on your farm it’s still not too late.

The following table shows what a successful integrated TCM program should look like (expressed as percentage of cases of calving cows within 14 days of calving), and the thresholds above which you should seek help.

What does the research on TCM tell us?

The transition diet is defined as the cow’s diet for the last three weeks of gestation. The dietary cation/anion difference (DCAD) of the transition diet is a major factor affecting milk fever incidence. The transition diet should have a negative DCAD; target -50 mEq/kg DM or lower. The challenge on Australian farms is that the commonly used forages typically have a positive DCAD, especially if it is hay or silage that has been heavily fertilised with potassium or effluent. A further complication is that post calving, the lactating cows actually require a diet with a positive DCAD!

How do I measure the DCAD of the diet?

You will need to do mineral analysis of the forage used to feed your transition cows. Most feed labs will report the DCAD as part of the results in a mineral analysis.

What if I haven’t got time to do a comprehensive mineral analysis on my transition cow forage at this stage prior to autumn calving?

If you don’t have time at this stage to do a mineral analysis (it can take 2-3 weeks to get the results), then it may be wise to consider lead feeding anyway, as an insurance policy. Published book values for mineral levels in silage and hay are extremely variable and of limited use in determining a TCM strategy. However, if you know that the hay/silage was cut from a paddock that received a lot of potassium fertiliser or effluent, the chances are it will have a highly positive DCAD. Save this for lactating cows if possible.

The other option is to just offer 2-3 kg of a commercial lead feed supplement in the three weeks pre-calving regardless of the forage testing. These supplements generally include anionic salts which help generate a negative DCAD in the transition diet.

Why should I worry about DCAD of the transition diet anyway?

Research has shown that providing an optimum transition diet in the last 3 weeks pre calving will reduce milk fever incidence, increase milk solids production, decrease culling and improve herd fertility, all of which will save you money.

Do I need to worry about other minerals in the transition diet?

Yes – calcium, magnesium and phosphorus levels in the transition diet are all linked to milk fever incidences. The transition diet should contain 0.4-0.6% DM as calcium. Post calving, the cows demand for calcium increases dramatically, therefore the lactating cow diet should contain 0.8- 1.2 % DM as calcium. Transition diets should also contain 0.45% DM as magnesium and less than 0.4% DM as phosphorus to minimise the risk of milk fever.

Can’t I just feed the milker concentrate ration to the transition cows?

No, this is not recommended. Many lactating cow concentrate supplements contain added sodium bicarbonate, which has a positive DCAD of over 10,000 mEq/kg DM. Never feed anything containing sodium bicarbonate to transition cows.

How long should I lead feed transition cows?

Research shows the maximum benefit is obtained with 3 weeks of lead feeding. Having accurate calving dates via pregnancy testing is the best
way to manage the transition and avoid feeding transition cows for too long or too short a period.

What about heifers, should they be included?

Yes it is recommended – 80% of Australian farmers that lead feed also provide it to their heifers. While milk fever risk is lower in heifers, lead feeding still allows the rumen to adapt.

Does the decision to lead feed depend on my production system and how much concentrate I feed post-calving?

To an extent, yes. If you are a low input producer that only feeds a max of 3-4 kg concentrate /cow post calving, then there is obviously less need to have the rumen adapted to higher levels of concentrate intake post calving. However, the problem of feeding highly positive DCAD forages to transition cows will still exist, even if you are a lower input producer.

So supplementing transition cows with anionic salts via drinking water or lick-drums is likely to still be beneficial in this instance to reduce milk fever risk post-calving.

For more information on Transition Cow Management please visit the Dairy Australia webpage. Dairy Australia also publishes a Feed Value Index (FVI) every year. Access the latest report at https://bit.ly/GippslandFVI2021