How Fat Are Your Cows?

In many parts of the UK cows are entering the winter in very good condition.  This is unlikely to be the case for herds in southern England following the severe shortage of grass from the August drought.  However the important thing is to assess YOUR cows ASAP, particularly spring calvers.  (It is likely you will already be aware of the condition of autumn calving cows which appear to have again suffered from higher levels than normal of calving difficulties due to being overfat.)

If your cows are fatter than normal ie above a condition score of 3 and are beginning to show fatty patches around the tailhead then you need to take action now.

Daily Liveweight LOSS Needed To Lose 1 Condition Score

* NOT recommended

The table shows the daily liveweight loss cows need to achieve if they are to lose 1 unit of condition score before calving.  The rate of liveweight loss obviously depends on:

• Size of the cow with bigger cows needing to lose more fat/liveweight per day and
• How early calving starts next spring.

Hence a small 500 kg cow only needs to lose 0.36 kg per day if she is not due to calve until next April.  If however she is due to start calving in January this doubles to 0.72 kg per day.

For the larger cow calving in January the figure is a massive 1.15 kg liveweight loss per day!  While all of us will have seen the occasional cow “melt rapidly” SAC do not feel such high levels of weight loss can be recommended over a period of months and therefore SAC has restricted its maximum liveweight loss to 1 kg per day.

(It is important to remember that these liveweight losses relate to the cow’s own bodyweight and not her actual liveweight which includes the calf inside her.  Hence if cows are fed rations to achieve the target liveweight losses in the table their actual weight loss will be lower as the calf inside them grows.)

Why It’s Important To Act Now

The table clearly shows the importance of:

• Assessing the condition of your cows ASAP.
• Where cows are excessively fat (or thin) splitting them off into a separate group so they can be fed/managed appropriately ASAP.

As an example we can compare taking action now on a very fat, 700 kg spring calving cow compared with waiting until after the festive season.  Acting now would require a daily liveweight loss of just -0.5 kg per day but waiting until January doubles this to 1 kg weight loss per day.  This of course assumes the cow doesn’t gain even more weight/condition over the rest of the autumn.  (The same problem occurs with extremely thin cows needing to put on a lot of condition before they calve.)

Another way to help slim cows is to outwinter them so they use some fat for warmth in cold, wet windy weather and to make sure they get as much exercise as possible.  But DON’T give them ad-lib silage, just a good mineral/vitamin supplement.

Basil Lowman, basil.lowman@sac.co.uk.