Spring grazing targets

With calving underway, getting cows out to grass will soon become a priority for many. Here’s a refresher on spring grazing targets.

Grazed grass is a valuable feed source for dairy cows in the spring. Cows will benefit far more from consuming grazed grass than silage to manage body condition score at this crucial time of year. Silage supplementation in February and early March has little effect on milk production at that point or for the remainder of the lactation. However, beyond this period, there is significant impact of silage supplementation on milk production for the lactation. Therefore, your spring grazing targets should prioritise this.

Opening targets and silage supplementation

Opening at a cover of more than 1,000kg DM/ha is important to ensure you will have enough grass for the first rotation. If opening cover is low, silage supplementation should be prioritised in the February period, when it has proportionally less of an effect on milk production. Some level of silage supplementation is hard to avoid during the spring period.

In terms of labour, it is also more efficient to supplement silage in the February period while the majority of cows are still calving than March. A silage budget should be carried out on farms as part of a feed budget, and good quality (>75% DMD) silage should be reserved in the yard for this.

Calving start date and compactness has a very large impact on the herd demand and the ability to meet the targets. Herds that calve too early will have a much higher demand and will result in big requirements for both forage and concentrate feed in the spring. Managing calving date should be included in the planning process for spring management.

• Open at AFC +1000kg DM/ha
• 30% area grazed 1st March? +7 to 14 days depending on farm type
• 60% area grazed 17th March? +7 to 14 days depending on farm type
• Finish the first rotation by 7th – 10th of April? +7 to 14 days depending on farm type

Spring rotation planner

The spring rotation planner (SRP) has been used successfully on many farms over the last 20 years to get grazing started while setting up the farm for second rotation. In recent years, many farmers have questioned its usefulness due to erratic spring weather events. While spring weather has become more variable with more severe extremes, changes in stocking rate and calving pattern are also causing farmers to question the SRP.

A key point here is to revisit the growth pattern of your farm (Grass reports - growth curve PBI) in spring and look for the date when you are, on average, hitting your demand comfortably. That is your end date on your SRP and can range from early April to early May depending on growth rates and demand.

Getting this date right is the key to setting the farm and the cow up to capitalise on high quality grass in early summer. If you are not measuring grass yet, a good way to identify if this is a problem on your farm is to review protein percentage on your co-op report in April and May. Where farmers tend to finish first rotation too early, silage will have to be fed in April to hold rotation length. Where this is a regular occurrence, you will see protein percentage will stagnate in April and recover in May if grass is being well managed at that point. If the opposite is the case and first rotation is being finished too late, protein will improve in April as grass will not be limiting but will stagnate in May as pre-grazing yields get too high.

More information on using the spring rotation planner to allocate grass is available here.

While the SRP is the tool that will allow you to set up the second rotation on the farm, a grass budget (PBI farm management) will help you ensure that the cow is on a rising plane of nutrition while doing so. The key to success is making sure both work together in unison.

Spring grazing planning:

• Decide on magic day based on data not tradition;
• Start with 600 AFC on that date in budget and work back;
• If is silage required, front load it in first 6 weeks.

The above was adapted for use on Teagasc Daily from the paper titled: ‘Future metrics for pasture production and utilisation on dairy farms’ by Áine Murray, Donal Patton, Laurence Shalloo, Ciaran Hearn, Michael Egan and Micheal O’Donovan and published in the Teagasc National Dairy Conference 2024 Proceedings. The full paper and presentation is available to view here.