Are you underutilising your grazing

Published 13 February 15

Are you underutilising your grazing? Challenging your paddocks - part two

Once you have grown it, are you challenging the grass enough nutritionally? Asks Piers Badnell, DairyCo technical extension officer.

How much grass is worth nutritionally depends on how much cows eat and what quality it is, plus the cow’s requirements. The calculation and comments below are aimed at the middle to higher yielding herd which is grazing the less than 30 litres, in-calf cow. The calculations are the same for the grass based genetics animal (with differing cow weights and constituents – see chapter 7 Feeding+ (link) to alter for your cow). These animals tend to have a higher drive to graze, are more robust and are not tempted by buffer, thus making them better grazers. But all cows can graze if trained.

A 600Kg cow requires 70 MJ of ME for maintenance. She will require 5.3MJ ME per litre for a 4% fat and 3.3% protein litre of milk. So if this cow consumes 10Kg DM of 12 ME grass this will give her 120 MJ ME. Take off 70 MJ for maintenance and that leaves 50 MJ ME. Divide this by 5.3 and this equals 9.43 litres of milk. If she consumes 16Kg DM, grazing at 12 ME, this gives her 192 MJ ME. Take her maintenance of 70 MJ from this and that leaves 122 MJ ME. Divide this by 5.3 and this equals 23 litres of milk. Source DairyCo Feeding+ manual chapter 7.

Can a cow eat 16Kg DM of grazing in a day? The answer is yes, some herds get to 17 or 18Kg DM a day. But she needs training to graze well. That means when grass supply is not limited, not filling her with buffer. It also means giving her plenty of time to do it, as she can only bite so many times per minute. If she is stood twice a day in a collecting yard for four hours then she won’t have the time.

In order to get these type of intakes we have to present the cow with a quality, and accurately allocated, area. She will also have to have an edge to her appetite when she goes out to graze. She is very unlikely to achieve these intakes if it is hammering down with rain, but if it is dry, and the DM of the grass is in the low to mid-twenties, and she does not to have to walk miles, and has the time to graze, the potential for high DM intake is there.

Some work done at SRUC in Dumfries, on dry matter intakes in wet and dry weather, showed that for late lactation 20 litre cows, on autumn grass intakes on dry days was 15Kg DM, whilst on wet days it had fallen to 8-10Kg DM.

Another way of putting this is in the slide below, which Alicia Newport (LIC Consultant) presented at the Pasture to Profit Conference last autumn (11th November 2014).

LIC table

 

Alicia suggested that UK grazing farmers were best compared to Southland in New Zealand, as the climates were far more comparable. As such, if we compare the % imported feed are we under utilising our grazing?

The challenge is there. Make sure your paddocks are both performing well and being utilised fully. As the table above shows, farmers in New Zealand’s Southland are achieving higher solids on less imported feeds, can we do the same?