In this article, Richard Gibson of CAFRE provides advice for dairy farmers, covering grazing management for first rotation, fertiliser application for first-cut silage, and full and partial grazing cows.
I recently took up the post of dairying development adviser for South Antrim, where I will facilitate Business Development Groups and work with dairy farmers in CAFRE’s eastern dairy team.
Previously, I worked with Aurivo Co-op as a farm liason officer for Northern Ireland. I provided daily support to farmers, covering total bacteria counts, somatic cell counts, thermodurics, antibiotics and milk compositional quality.
Furthermore, I was also responsible for coordinating all Aurivo suppliers in the Red Tractor Quality Assurance Scheme.
Grazing management for the first rotation
Managing grass at turnout can be critical in dictating the rest of the grazing season, ensuring both surplus and deficit of grass supply does not become a significant issue.
Regular walking of the grazing platform should already have taken place and should continue throughout April. This will give a picture of grass growth and grazing covers.
As ground conditions allow, get as many cows out to grass as possible after morning milking, initially for a few hours. Gradually increase the number of cows going to grass to coincide with improved conditions and grass growth.
Depending on the calving pattern and yield of the herd, cows that are producing less than 30 litres of milk per day and confirmed in-calf should be turned out first. This will help ensure maximum milk yield is maintained and to remain feed efficient.
For a spread calving herd, batch cows depending on milk yields:
|Grazing full-time||Lowest yielding/late lactation cows|
|Grazing by day and housed at night||Mid-lactation cows|
|Housed full-time||Freshly calved/highest yielding cows|
For the full-time grazing group, the maintenance plus (M+) will depend on the grass supply and quality.
For the partial grazing or full-time housed groups, the ration M+ should be formulated so that the group’s lowest yielding cow is not overfed. The M+ will change as cows are moved from housing through partial grazing to full-time grazing.
Aim for pre-grazing covers of 2,800-3,000 kg dry matter (DM) per hectare and post-grazing of 1,500-1,600 kg DM per hectare. Although grass analysis may vary, generally speaking, DM intake will be higher than silage, with crude protein and ME also higher than most first cuts.
At turnout, reduce the protein percentage of the diet accordingly.
Benefits of spring grazing – advice for dairy farmers
Assuming silage ME of 11 MJ/kg DM, protein of 14%, and a DM intake of 14 kg per cow per day, you will need to fed a 30-litre cow 7.2 kg of a 19% protein dairy ration to meet her energy and protein needs.
Partially grazed cows
Recent grass analysis indicates excellent quality, with 12.5 MJ/kg DM and 19.8% protein.
Moving to partial grazing on a sward like this, where the cow eats 5 kg DM of grass and can access silage of the quality above, can result in significant savings.
To achieve a similar energy and protein intake to support the 30-litre production, you will need to feed 6.5 kg of a 16% protein dairy ration.
In summary, six hours grazing using the assumptions above will:
- Save 5 kg DM per cow per day of silage (seven tonnes fresh per week for a group of 50 cows);
- Secondly, save 0.7 kg of meal per cow per day (245 kg per week for a group of 50 cows);
- Reduce meal protein requirement from 19% to 16% resulting in significant cost savings;
- Increase milk from forage by 1.6 litres per cow per day.
Full-time grazing, where possible, will allow half concentrate input for a 30-litre cow and further, reduce the protein concentration of the feed. This will result in additional savings at a time when the milk: meal price ratio is squeezing margins.
Fertiliser applications for first cut silage
A splash-plate application of 33 cubic metres per hectare (3,000 gallons per acre) of cow slurry in early March will have supplied enough phosphate and potash for first cut silage at soil indices of 2+ for phosphate and potash.
To note, nitrogen (N) is the key to silage yield and quality. Nutrient requirement for first cut on dairy farms is 120 kg N per hectare (96 units per acre).
Given that slurry will have supplied 30 kg per hectare (24 units per acre), this leaves a requirement of 90 kg per hectare (72 units per acre) of nitrogen for you to apply using chemical fertiliser.
A general guide to nitrogen uptake is 2.5 kg N per hectare (2 units per acre) per day from the date of application.
For example, a silage field with 90 kg N per hectare applied on April 1st will be ready for cutting on May 7th without any excess nitrate remaining in the grass.