Incorrect feed allocation is most commonly caused by an incorrect break size. Knowing the crop face length and crop yield is vital to set break size.
To calculate the break size you need to know the number of animals and the kg DM/animal/
day to be offered (not intake, as not all of the crop will be utilised). The calculations are as follows:
Dry matter yield of crop ÷ 10000 m2 = dry matter yield/m2
kg DM allocated per animal = m2 required per animal
÷ DM yield per m2
No. animals in paddock x m2 per animal = m2 of area to be allocated
m2 to be allocated for the = width of the break
break ÷ face length
Dairy example of crop allocation
A 5 ha paddock of kale with a yield of 14 t DM/ha. 100 cows break fed offering them an allocation of 14 kg DM per cow/day. Of this 10 kg DM will come from kale and the remainding 4 kg DM from balage. The face length of the crop is measured at 200 m.
14,000 kg DM ÷ 10,000 m2 = 1.4 kg DM per m2
10 kg DM of crop ÷ 1.4 kg DM per m2 = 7.1 m2 per cow/day
100 cows x 7.1 m2 = 710 m2/break
710 m2 ÷ 200 m face length = 3.6 m break width
As an example, if the break width was incorrectly measured and was 0.5 m short, it would result in the cows being underfed by 1.5 kg DM per day.