Dairy management: calving, grazing and getting fertiliser spread

Aidan Brennan has some advice for farmers in the throes of the busiest weeks of calving

Aidan Brennan

5 February 2025

Calving The next few weeks will be the busiest in terms of calving. At this stage, all anyone can do is go with it, but there are a couple of things to keep in mind:

Calving

The next few weeks will be the busiest in terms of calving. At this stage, all anyone can do is go with it, but there are a couple of things to keep in mind:

The single-most important thing a farmer can do is to ensure the newborn calves have enough colostrum. Get 3l of good-quality colostrum into them as soon as possible after being born. The stomach tube is the quickest method.

Clean out calving pens regularly, particularly large group pens. The build-up of cleanings, womb fluids and dung creates a cesspit for bacteria and infection to thrive. Remove all the bedding and start again every few days. It will help prevent mastitis in cows.

Feed additional magnesium pre-calving to prevent milk fever and other metabolic disorders. Most dry cow minerals contain magnesium, but the cow requirements increase prior to calving. Sweetened cal-mag or mag flakes should be sprinkled on the silage or fed in the water for a week or more prior to calving. Spreading 60g per cow per day of sweetened cal-mag (33% magnesium) will supply an extra 20g of magnesium. Magnesium flakes are generally lower in magnesium, at 12%, so to get 20g of magnesium you would need to feed 170g of flakes on the silage or in the water. Some farmers mix the flakes with meal.

Nobody can stay going all day and all night for long periods. Rest will need to be prioritised at some point. Some good farmers that operate on their own will do a final check at 10pm or 11pm and then get to sleep until 5am or 6am and go again. Getting six or seven hours of sleep will mean more work is done during the day and better decisions are made. The vast majority of cows will calve fine by themselves anyway.

Grazing

The weather forecast is looking good, with little or no rain forecast for the next 10 days or so. Despite a good bit of rain over the last few weeks ground conditions are really good in most places for the time of year. So there will be good opportunities for most farmers to get cows out and fertiliser spread. The benefits of getting cows out to grass is enormous, from a cost, but also a productivity perspective. Cows will produce more milk and lose less body condition because the diet will be more balanced from an energy in/energy out perspective. The other thing to remember is that the more area grazed in February the more grass there will be in April. The target is to graze 30% to 40% in February, a bit less on colder or later farms.

Fertiliser

While the forecast is dry, it is also set to get a bit colder. This might put some people off spreading fertiliser if soil temperatures aren’t above six degrees, etc. In my view the risk of losses is low and it is better to have the nitrogen out and ready to be taken up by the plant when ground warms up. We are now approaching mid-February, not mid-January so I think its time to be getting nitrogen out, especially on fields with new grass that’ll respond well. The advice is to go with 20 to 23 units/acre of nitrogen on fields that didn’t get slurry.