The Department of Agriculture, Food and the Marine (DAFM) has confirmed that the nitrogen (N) excretion rate for dairy cull cows defaults to the value for cattle over two years-of-age.
This means that for a cull cow which moves off farm to a non-milk producing herd, the cow defaults to a nitrates excretion rate of 65kg N/head/year.
Essentially this means that cull cows purchased for fattening will not remain at the same nutrient excretion rate based on the respective band.
Cull cows
From January 1, 2023 the organic N value of dairy cows is determined by milk yield with dairy cows placed in three bands.
Prior to this, all cows were given a N value of 89kg.
These changes impacted on the organic stocking rate of dairy holdings, with some farms moving into derogation.
Bands Milk yields Excretion rate Band 1 <4,500kg of milk 80kg organic N/cow Band 2 4,500-6,500kg of milk 92kg organic N/cow Band 3 >6,500kg of milk 106kg organic N/cow
The introduction of banding has meant that the maximum stocking rate for a farm with cows that are placed in Band 3 is reduced by 19.1% (assuming the farmer cannot rent or buy land).
Meanwhile, for farmers that are placed in Band 1, the maximum allowable stocking rate could increase by 11.3%.
Although the organic stocking rate of dairy cows moved to a non-milk producing holding is reduced to 65kg of N, DAFM stated that a dairy cull cow that remains in a milk-producing herd is considered to be a dairy cow regardless of her lactation status.
She is allocated a nutrient excretion rate based on the respective band declared for that herd as per department legislation, which means that these cows will have an organic N value of between 80kg and 106kg depending on which band the herd is in.
But DAFM noted that these cows which remain on the holding are included in determining the average milk yield/cow in the herd.