20 May 2021

Making milk while the grass grows

LIC FarmWise® Consultant Darren shares tips for reaching your individual cow body condition score (BCS) targets and finishing the autumn season off in good condition - all while milking!

At last we have landed a kind autumn that has allowed farms to make milk while the grass grows! A pleasant change that we have not seen for the last four years.

This year the feed budgets and drying off decisions are not being dictated by average pasture covers (APC), but instead by cow condition (BCS) and days left to the start of calving.

It is tempting to milk on blindly, and certainly, there is more milk to be taken, but to the detriment of next season. This tail-end milk needs to be only taken from those cows in good BCS, or are later calvers.

BCS targets

Targets at calving are 5.0 BCS for MA cows and 5.5 BSC for first and second calvers. These are not just nice targets to achieve, but they should be the aim of every farmer at this time of year because it will affect your milk production and reproduction potential.

Studies have shown that the gain in milk production by calving cows who are at 5.0 BCS instead of 4.5 was worth about $40 per cow.

Another study also showed that cows calving at BCS 4.0 compared with BCS 5.0 resulted in a 7% less chance to be cycling at planned start of mating (PSM). Cows that have not started cycling at PSM have a 16% lower six-week in-calf rate and a higher empty rate of 6%.

And we have certainly seen some poorer reproduction figures this season.

So start with body condition scoring your herd to get a realistic understanding of condition of individual cows.

Dairy NZ’s booklet ‘Body Condition Scoring Made Easy’ will help to guide you in condition scoring. The app is also very useful and quick to use.

Targets for when a cow should be dried off will vary, depending on:

  • BCS at various dates
  • Age of animal
  • Date of planned start of calving
  • Possible feeding levels and types of feeds.

The table below outlines the number of days a cow requires to be dried off prior to calving to have any chance of gaining the 5.0 and 5.5 BCS targets at calving.

If a cows calving date is the 20 July, then the dry-off dates are as follows:

BCS table Autumn 2021

So if a cows in calving after the 20th of August, then you can add another 30 days to the above dates. This is why individual BCS of cows is important, not just the average of each herd.

By the middle of May you are likely to need all MA cows to be >4.0 BCs and all R3s to be >4.5 BCS to keep milking.

Remember, most cows will need restricted (low metabolisable energy and low protein feed) for 7-10 days to ensure they dry off cleanly. This can reduce BCS further. Maize rates do not need to be reduced through this process as this has low protein at 8-9% CP. But pasture rates will need to be reduced.

Feeding to gain BCS

To gain one BCS above maintenance requirements a Friesian cow will need to eat 160 kgs dry matter (DM) grass silage, 160 kgs DM maize silage or 125 kgs DM of PKE.

The following is the calculation for what a cows needs to be fed to gain 1 BCS.

  • A mixed-age cow dried off on 15 May, at 4.0 BCS and due to calve on 20 July, can only put on weight effectively up to about 3 weeks before calving.
  • She has 45 days to gain 1 BCS.
  • Maintenance for her through May and June will be about 8kg DM per day.
  • To put on 1 BCS with maize, she will need be consuming about 160kgs DM so allow for wastage.
  • Plan for 45 days to eat 160 kgs of extra feed, that’s 3.5 kgs per cow per day.
  • The total intake needed calculates to 11.5 kgs DM per cow per day before wastage. When allowing for wastage, this figure is closer to 13-14 kgs DM per day.

Feed budget

A feed budget will allow you to calculate how many more days you can milk for – do one from now through to 1 June, and another from calving through to your feed balance date.

Ring fence your winter supplements first before deciding what can be fed out this autumn.

The feed budget should include what BCS gains will be required from now to July. Do your feed levels support this? More importantly now in the middle of May, do you have enough days left to hit individual cow BCS targets?

If not, then you need to either secure more supplements, or dry off earlier this season to hit your APC and BCS targets that are so essential when setting up next season.