Spring management

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.

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 the APC at calving section on the pasture assessments page.

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 overallocating 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 overallocated, there will also be negative effects on subsequent pasture quality and re-growth.
• Avoid underallocating 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

Supplements

Decisions to use supplement feed during this period should consider the severity and duration of the feed deficit and the predicted response to supplement. Find out when supplements should be introduced as a tool to help maintain a slow rotation.

Ensure all feed allocated to your herd is of high quality this spring. High quality pasture contains more energy than many supplements. Scrutinise any supplement use – ensure you are getting a real benefit. Use supporting resources to ensure your information is correct.

Look for every opportunity to reduce wastage when feeding supplements; this improves milk production responses and helps bring down the cost of the feed eaten. It also makes feed reserves last longer.

When grazing residuals are less than seven clicks on the rising plate meter (1450kg DM/ha), supplements are an option. The return from supplements depends on the payout, the severity and length of time of the feed deficit, and the quality and utilisation of the supplement as shown in Table 1.

In addition to the main minerals that may be required in early lactation (calcium, and magnesium) five trace elements 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.

Pasture surplus

Identifying and managing pasture surplus early and maintaining good quality pasture through good grazing practices is key to maximising late spring and summer milksolids production.

After balance date, the feed wedge is the best tool to manage pasture. A feed wedge shows the current pasture situation by ranking the paddocks based on average pasture cover. It allows you to make proactive decisions to manage a surplus or deficit.

• Data for a feed wedge should be obtained from a weekly pasture assessment where pasture is measured.
• Pastures are then ranked from highest to lowest. Adding a target line makes it clear where there is likely to be a surpluses or deficit in feed.
• The wedge identifies the grazing plan for the next round in terms of the sequence in which paddocks will be grazed.
• A feed wedge allows you to identify and anticipate a surplus (or a deficit) 10-14 days in advance

Identifying a pasture surplus

Surplus management is one of the greatest skills of pasture management and is critical to maximise pasture eaten and feed quality. A temporary pasture surplus, if not managed, allows ryegrass to grow to form stem and seed head, resulting in lower pasture quality.

Pasture management in late spring is based around providing high-quality feed to the cows. Grazing residuals drive pasture quality, and when growth exceeds demand, residuals will rise unless this surplus is managed.

Surplus management is all about anticipation. To get surplus management right requires weekly pasture assessment to predict feed surpluses before they happen.

Identifying pasture surplus early allows better management of a surplus, including decisions around rotation length, removal of supplements and the number of paddocks to shut up. It also provides time to organise a contractor and therefore better control silage quality.

It is critical to anticipate in advance the length of the closed period and associated risks. These include:

• Shutting up too much area for too long and restricting future milk production (higher risk with higher stocking rates).
• Managing silage quality. After the pasture has passed target grazing residuals, the quality will decline at an average rate of 0.3 MJME/kg DM for each week of closure. Try to harvest silage within 42 days of the last grazing.

For information, see the surplus management page.

Pasture silage

Pasture silage is an important source of supplementary feed on New Zealand dairy farms. The better the silage’s quality, the higher the milksolids (MS) production and body condition score (BCS) gain in cows.