In pasture-based systems, an optimum balance exists between daily pasture allocation and intake, and whole season performance. To achieve post-grazing residuals in spring (7-8 clicks), and promote maximum pasture growth and quality from the remainder of the season, a compromise is made between pasture growth and utilisation, and individual cow dry matter intake.
Using the Spring Rotation Planner
The spring rotation planner provides guidelines for allocating pasture to cope with the growing milking herd and the shrinking dry herd. It helps to manage the speed of the first grazing rotation after calving, control the rate of pasture cover decline, minimise deficits and manage pasture quality.
Average Pasture Cover at calving
Achieving your target average pasture cover (APC) at calving is important for meeting feed demand, and for pasture growth rate and quality. APC at calving will determine how cows are fed for the first two months after calving, For more info see APC at Calving.
Graphing the average pasture cover you are targeting for your farm at any time between PSC and balance date means you can adjust your spring rotation planner for seasonal conditions that impact on pasture cover.
You can create an average pasture cover graph as part of the spring rotation planner tool.
Feed allocation from start of calving
From the start of calving the priorities are firstly the colostrum cows (as these are most prone to metabolic problems) then the milkers followed by the springers and dry cows. The fastest way to have metabolic problems like milk fever or ketosis is to have well fed springers and then underfed colostrum cows.
Feed intake potential at calving is significantly less than intake potential at peak. Cows can reach their peak milk production per cow in as little as 4 weeks after calving but peak dry matter (DM) intake potential is not reached until 7-10 weeks after calving.
Although there are some good rules of thumb for individual cow intake, the best indicators to use collectively to determine if feed allocation and intake are adequate in a pasture-based system are:
- Post grazing pasture residuals
- Changes in milk production and composition
- Cow behaviour
Control of DMI in the early lactating cow involves many complex processes. There are several key animal and farm system factors that affect a cow’s intake or drive to eat. These include:
- cow size and breed
- stage of lactation
- grazing time and behaviour
- physiological feedback
- feeding system
- pasture quality
Using pasture residuals (the pasture remaining after a grazing event)
Pasture residuals are a good indicator of the adequacy of pasture offered (pasture allowance). Decisions on pasture allowance should focus on future pasture growth and quality, and optimising whole season performance. There is a compromise between future pasture growth and utilisation, and individual cow intake.
- Avoid over allocating pasture: Achieve target residuals of 14-1500kgDM/ha with no clumps in the first rotation. In addition to high energy pasture being wasted when pasture is over allocated, there will also be negative effects on subsequent pasture quality and re-growth.
- Avoid under allocating pasture: If post-grazing residuals are less than target, this indicates the cows are being underfed. Restricting pasture allowance to less than minimum cow requirements in early lactation will cause an immediate drop in milk production but the impact on whole season depends on timing, severity, and duration of the restriction. From a pasture perspective, there are no lasting negative impacts of grazing lower than target residuals once in early spring, provided pastures are given time to recover before the next grazing.
Trials indicate cows (calving at appropriate BCS) can recover from a short-term moderate feed restriction in early lactation (75% of requirements/ residual 2.7cm for 14 days) with no negative effects on whole season production. If the restriction is more severe or the restriction lasts for a longer period, then there are both short and long term negative effects on milksolid production.
See Pasture allocation for more information.
Sequence of events following on from over-allocation of pasture
Decisions to use supplement feed during this period should consider the severity and duration of the feed deficit and the predicted response to supplement.
Feed additional minerals if required during spring
In addition to the main minerals that may be required in early lactation (calcium, and magnesium) there are five trace elements that are likely to be deficient in grazing dairy cows and are recommended for supplementation for 2-3 weeks pre-calving until 4 months post-calving.
These are copper, cobalt, selenium, iodine, and zinc. Consult a veterinarian to determine mineral requirements in your herd.