Dairy farmers will be able to reduce the organic nitrogen excretion rates of their dairy cows if they feed low crude protein in dairy ration.

Under new measures being implemented by the Department of Agriculture, farmers will be able to opt-in to lower organic nitrogen excretion rates based on crude protein in meal fed.

The reduction in the nitrogen excretion rate will be tiered based on the level of protein in the feed and will apply to herds in each milk yield band.

The lower the protein in the feed, the greater the reduction in nitrogen excretion rate.

For a herd in the middle band, the current excretion rate is 92kg N/ha whereas under the new measures, that will fall to 90kg where 15% crude protein meal is fed, 89kg where 14% crude protein meal is fed and 87kg where 13% crude protein meal is fed.

The finer details are yet to be announced but it is expected that the annual crude protein level of the concentrate will be determined by the weighted average during the year.

This means that herds that feed, say, 16% or 18% crude protein meal in spring will need to feed significantly lower crude protein in the summer months if they are to avail of the reductions to excretion rate.

Changes to the nitrogen excretion rates of young calves and yearling heifers are also being made.

What the changes mean

Together with the changes to the cow excretion rates, a typical dairy farm with 100 acres and 80 dairy cows, along with 20 of each age group of heifers and that is selling beef calves at one month of age, will see a reasonably significant reduction in annual nitrogen excretion rates as a result of the changes.

If this farm feeds 14% crude protein feed on average over the year, then the annual excretion rate per hectare will fall from 228kg N/ha to 216kg N/ha, a 5% reduction. This farm moves from a situation where it was exceeding the new 220kg N/ha limit to now being under the limit.

For the same farm that is in the high band, the nitrogen excretion rate per hectare will reduce from 256kg N/ha to 238kg N/ha.

Further reductions in cow numbers or additional land would be required in order to comply with the 220kg N/ha limit.