We are now into the middle of April, which means cows are getting close to their peak milk production and grass intake can be put under pressure as April grass supplies can often struggle to keep up with demand.
The weather in March and the start of April has been very good and, with a bit of rain forecasted, hopefully grass growths can avoid any pinch in grass intakes this month.
When grass does not meet the herd’s demand, performance can be negatively impacted and body condition can deteriorate as the cow is approaching peak milk production and edging closer to the breeding season.
As many herds will be starting their second rotation, the transition can be difficult with insufficient grass growth rates to meet the herd’s demand, potentially closing off areas for silage ground and reaching maximum stocking rate hindering supplies.
Grass intake
Herds need to be offered 18-20kg of dry matter (DM)/day of grass, from cover of 1,400kg DM/ha to drive on milk solids through maximised grass quality and maximised dry matter intake (DMI), according to Teagasc.
Paddock size can really hinder a cow’s DMI and has been a limiting factor on many farms for quite some time now, as paddock sizes have not increased at the same rate as dairy herds have expanded.
Paddocks that allow for 36 hours of grazing should be implemented where possible to allow for full herd nutrition, as many farms will have 25-30 paddocks, which is well above the theoretical ideal number of 14-16 paddocks.
Milk production can be compromised when cows have to moved midday as paddocks fall between one and two grazings or between two and three grazings.
In order to work out what your paddock size should be, farmers should use the following calculation: Cow numbers X 19kg of grass (may vary between herds) X 1.5 days = cow requirement for three grazings ÷ 1,400 (pre-grazing yield) = the size of paddock in hectares to accommodate three grazings.
Example: 120 cows X 19kg DM grass X 1.5 days = 3,420 ÷ 1,400kg DM/ha = 2.44ha paddock required. (The kilos of grass DM allocated may vary from herd to herd).
The pre-grazing yield should ideally be 1,400–1,500kg DM/ha to achieve a balance for optimal cow nutrition and sward regrowth.
Post-grazing residuals should be between 4-4.5cm to maintain intake and subsequent sward quality.
Plan for April
If grass supply on the farm is tight as it is, farmers should maintain a consistent, if not increasing, supply of grass to the herd in the lead-up the start of the breeding season.
The body condition score (BCS) of the cow cannot afford to drop at this stage as the cow needs a minimum of 2.75 body condition score (BCS) to get back in calf as, with anything less, conception rates will begin to be impacted.
Any cow that is below a BCS of 2.75 or nearing 2.5 BCS should be considered for once-a-day (OAD) milking for the next few weeks to reduce their energy output and is the quickest way of replenishing condition rather than meal feeding.
As April moves on and cows are reaching peak milk production, farmers need to question whether they can grow enough grass to meet the herd’s demand.
To calculate the herd’s demand, calculate the herd’s DM allocation x the stocking rate (SR).
For example, if you take the above example with a 19kg of DM/cow allocation x 3 livestock units (LU)/ha = 57kg DM/ha of a demand.
This means that over a 21-22-day grazing rotation, you need a growth of 57kg DM/ha/day to meet the 1,400kg DM/ha pre-grazing cover.
