Colder temperatures over the last week have tempered grass growth rates, and some farmers are finding themselves tight enough for grass. However, with the weather warming up and now that we’re in May, grass will take off over the coming weeks.

This is both an opportunity and a threat. It’s a great chance to capitalise on the naturally high growth rates to reduce the amount of meal being fed, and to refill silage pits. Nitrogen will accelerate this growth rate, and it’s the cheapest way to rebuild silage stocks.

Some farmers are talking about feeding more ration to reduce what the cows are eating now, but it’s a very inefficient way of doing it.

Spreading one unit of nitrogen per acre per day for the next month will optimise growth at a time when nitrogen use efficiency is very high.

That means spreading 21 units/acre after grazing if cows are on a 21 day round. The rate can be turned down on clover paddocks later in the month.

Response to N

Every kilo of nitrogen applied per hectare now will probably grow over 35kg of grass per hectare, so the response is good. If nitrogen is costing say €1/kg, every additional kilo of grass grown costs about 3c/kg DM. If meal is costing €300/t, every 1kg is costing 30c/kg.

The other thing to keep in mind is that the substitution effect of meal is low. So for every 1kg of meal fed, it’s unlikely that cows will eat 1kg less grass. Their overall diet will increase and they might eat 0.5kg less grass.

Farmers have made great efforts to reduce nitrogen fertiliser use over the last few years which is noble, but in some cases unsustainable to support the stocking rate that is necessary to deliver an economic return.

Lower stocked and less intensive farms will get away with less nitrogen. If nitrogen is going to be spread, now is the time to get most value out of it.


Some farmers are reporting a sluggish start to the breeding season. The weather for the last week wasn’t ideal, with cold nights and some very wet days.

Cows are still under pressure, which could explain why bulling rates are a bit lower than they should be. Work out how many should be bulling per day by dividing 90% of the herd by 24 days.

This will tell you how many should be bulling per day to get 90% submitted over a 24 day period, as the normal cycle is anywhere between 18 and 24 days.

Stay with it and they will come in. Get the non-cyclers seen to as soon as possible. Those that have been breeding three weeks will know by now which cows haven’t been served, as will those that carry out pre-breeding heat detection.

Getting these cows scanned will help identify problems that can be rectified, such as cysts, uterine infections, etc. The vet can then prescribe hormone treatments to cows that require it, and it helps in bringing forward the AI date of these cows.

The other important animals to look after now are stock bulls. Get them out to good grass. Check feet and legs and get any issues rectified as soon as possible.

Avoid any doses or vaccinations in the run-up to service, as this may affect the bulls’ temperature and fertility.