Let the cows tell you how good the diet is

Spending time watching cows chewing the cud will tell a lot about dairy cow diets according to Tom Hough, Technical Manager with NWF Agriculture.

Mr Hough believes that variable quality silages are one of the main reasons that cows are milking worse than expected in many cases this winter, due to the low dry matters and high fibre levels in many first cuts.

“It is proving a real challenge to get some cows to produce milk this winter,” comments Mr Hough.  “Cows seem to be lazy due to the older, more mature grass silages on offer. Faced with high NDF, low ME forage, cows are spending too much time cudding and not getting much back in return.”

Mr Hough advises farmers to set time aside to watch cows chewing as this can give a good indication of possible deficiencies in the ration.

“A cow normally chews each cud 50 to 70 times with each cud-chewing period lasting half an hour or more. The cow should be lying down for around three quarters of this time.  At any one time over 50% of the cows lying down should be chewing their cud, rising to as high as 90% in the two hours immediately after feeding.”

A chewing rate of below 50 cuds per mouthful suggests the diet is short in fibre while a cudding rate of over 80 would indicate the diet could contain too much long fibrous material such as straw or long chopped grass silage.  Alternatively a high rate may indicate that the diet is too acidic and that the cows are trying to produce more saliva to buffer the diet.  High yielding cows produce about 300 litres of saliva per day when cud chewing is optimal.

“Where cows have a high chewing rate per mouthful, we would recommend putting the diet through a Penn State Separator to identify whether the problem is particle length or diet acidity.  The separator can also be used where cudding rate is low to check if the diet is short of fibre.

“Many sieved diets this year have too much material in the top, long material sieve and intakes have been improved by adjusting the physical structure of the ration. In one herd just replacing long straw with chopped straw increased yields per cow by over 2 litres per day.  Where the physical breakdown of the diet is adequate and cows still have a high cud rate, then we have seen a good response to rumen buffers, in particular NWF Stable Rumen Pak.

“By spending a few minutes a day checking on cudding rate, farmers can get an early impression of what the cows think of the diet on offer and make changes as necessary to improve performance,” Mr Hough concludes.