The primary differences between summer and spring pastures are, in summer-dry regions, leaf emergence rate and pasture growth rates are slower due to reduced moisture. Therefore, slowing down the round, or increasing the number of days in the rotation to capture the three-leaf stage will help maximise growth during the summer and increase feed available in the autumn months. See leaf stage.
In summer-dry non-irrigated regions, high air temperatures and moisture stress can cause a build-up of dead material (stem and stalk) in the pasture base.
This may increase dry matter percentage and fibre content, but also reduces pasture quality; this needs to be considered when allocating daily pasture allowances.
For example, a mid-lactation cross-bred cow weighing 500kg LW producing 1.4kg MS and walking 2km over rolling terrain requires approximately 167MJ ME/day. This equates to:
16kg DM/cow/day - dry summer pasture in the Waikato with ME: 10.5 MJ
14kg DM/cow/day - irrigated pastures in the South Island with ME: 12.0 MJ
In irrigated areas, summer pastures are generally consistent with spring pastures.
Over-grazing pastures in summer depletes the a plant's energy stores primarily contained in the bottom 4cm of the plant.
This results in a lag in pasture regrowth when moisture become available, e.g. after the autumn rains. Severe or repeated overgrazing during this period can result in plant death which will have negative consequences for longer-term pasture persistence.
Manage pasture condition so when it rains pastures are in good shape to respond.
Options to reduce over-grazing include:
- summer crops
- reduce demand, e.g. culling low-producers
- using stand-off facilities
It's important that post-grazing residuals are no greater than 4.5 cm during summer. If higher residuals remain in summer, pasture quality will decline further and dead material in the pasture base will rot when it rains.
Additionally, in areas prone to facial eczema, leaving high residuals and increasing the amount of dead litter in the base of the sward will increase the risk of high spore counts and FE.
Options to avoid under-grazing:
- Check residuals after grazing and adjust allocation
- Measure pre-grazing covers
- Remove supplements.
Look after your irrigated pasture. If you are irrigating, regularly monitor soil moisture levels and consider signing up to NIWA FarmMet - a subscription weather forecast and information service.
Have a contingency plan for when water restrictions are applied. One option is to fully water the best part of your farm rather than poorly watering the whole farm. Irrigated crops can provide a high return.
More on managing water supply restrictions here.
During mid-lactation, energy is generally the limiting nutrient in a pasture-based system. Feeding an energy supplement in summer can be profitable - if it has been sourced and fed at a reasonable cost - and if pasture is not wasted; this will keep more cows milking for longer lactations.
As the dry matter content (DM %) increases in summer pasture (even under irrigation), more dry matter is available for the cows to eat compared to pasture at the same height in spring.
For most farms, protein will not be limiting production as crude protein content in pastures is rarely less than 16%. The requirement for a mid-lactation cow is 16% protein.
Protein may be limiting production where a low-protein supplement is fed, for example where more than 4kg of maize silage/cow/day is fed. A protein supplement being necessary or not will be dependent on the average protein content of the cow's diet especially if a high proportion of the diet is supplemented.
If protein is limiting production during the summer months in a pasture-based system, supplements high in undegradable dietary protein (UDP) are required to generate a milksolids response. Feeding supplements high in rumen-degradable protein (RDP) or non-protein nitrogen will not improve production.
Mineral supplementation in summer depends on the diet being fed and cow requirements. Compared with cow requirements, maize silage is low in Mg, Ca, P, and Na.
If more than 3kg maize silage is fed during mid/late lactation, minerals supplementation is recommended as an inexpensive insurance against possible deficiencies which can negatively affect production and increase the risk of metabolic disorders such as staggers. As the amount of maize silage in the diet increases, the requirement for certain minerals also increases.
Dry summer strategies
Use these strategies in summer dry to manage feed supply and look after the herd.
Be mindful of heat stress. Although heat stress effects are more severe in hot climates such as parts of America and Australia, dairy cows in some areas of New Zealand are affected by heat stress during summer. For symptoms of heat stress and to use the Temperature Humidity Index (THI) calculator see the heat stress page.
Tips for cool cows
When hot conditions are forecast some short-term solutions to reduce heat stress for cows and minimise milk production losses are to:
- graze cows close to the dairy to reduce walking distance for milking and let them move at their own pace
- milk cows later in the afternoon/early evening when the temperature has dropped
- use paddocks with shade or provide cows with access to well-ventilated and shaded housing facilities
- provide supplementary feed at night, so the extra heat generated by digestion occurs at the coolest time of day
- make sure cows always have good clean drinking water. Milking cows can drink over 100L of water per day in summer
- provide shade or use a sprinkler system in the dairy yard while the cows wait to be milked.
Use supplements wisely
Use supplements wisely if conditions get dry; feeding supplements keeps animals in production longer than would otherwise be possible in a dry summer.
- First and foremost earmark 10-14 days of supplement - for the period after rain occurs (approximately 100kg DM/cow) as there will be a lot of pasture decay and you will need something to keep your cows going while allowing pasture to recover.
- Supplements can increase stock water intakes - systems must be in place to cope with the increased demand; consider providing water in the yards to reduce the demand on troughs in the paddock after milking.
- Watch diet protein levels - offer pasture silage to milking stock first as it will have more protein than maize silage.
- Supplement requirements in your planning - avoid using supplements earmarked for winter; only use these supplements as a last resort after drying off the entire herd.
- If grazing turnips make sure you to offer enough turnips to meet cow energy demands and ensure all animals can feed at once.
- Supplement options - bought in supplements can be an option. Seek professional advice before using unfamiliar feed mixes on your stock.
Note: Supplements can be profitable providing you apply best practice management and purchase the supplement at the right price.
Only purchase and feed out supplements if you have:
- residuals below seven clicks or less on the rising plate meter (under 1500 kgDM/ha using the winter formula)
- determined the maximum supplement price you can afford to pay and still make a profit
- the ability to avoid feed losses and wastage when storing and feeding out the supplement.
Note: The immediate milk response is unlikely to fully cover the cost, but if feeding results in maintaining more cows in milk when it does rain.
A profitable return from supplements will depend on:
- quality supplement – higher energy and protein makes it more affordable
- the ability to store and feed the supplement without high wastage levels
- the likelihood that feeding supplement results in cows still milking later in the season
- grazing residuals being above or below desired levels. Is overgrazing already occurring?
Note: Not all feeds are the same in how much protein and fat they will produce for the same MS response, there are differences in the supplement amount required for BCS gain in dry cows. The Supplement Price Calculator takes these factors into account.
Although this has little affect on feed requirements, moving to once-a-day (OAD) or three times in two days can take the pressure off cows and staff as well as give managers more time to plan and manage.
Milking cows OAD may not be an option if the bulk SCC is over 200,000 before going onto OAD. Often the bulk SCC is a result of a small percentage of the cows with high counts. These can be dried off or milked twice a day to keep the bulk SCC under control.
For more information see the OAD milking section.
Dispose of known culls. Do this earlier rather than later. Cull on pregnancy diagnosis, production worth, and somatic cell count. The objective is to carry as many cows as practicable beyond autumn without jeopardising next season.
The aim of early culling and drying off of low-condition score and poor-producing cows is to keep as many cows as possible milking into autumn. This is important to capture any benefits from an autumn flush in pasture growth. The later the dry period breaks, the less likely a farm will capture the carryover benefits of any additional inputs and of keeping as many cows milking as possible.