Winter pasture management

Winter management is about setting pasture up for spring and protecting pastures from pugging.

Winter offers an opportunity to reset the residuals' level for the coming season and ensure leaf growth is promoted in the base of the sward.

Pasture management (June to August)

Grazing management during winter is about transferring autumn and winter grown pasture into early spring to achieve target average pasture cover (APC) at calving and meet the feed requirements of the milking herd.

This is achieved by lengthening the rotation in late autumn and winter, beyond the time taken to grow three new leaves.

Moist, cool conditions mean tiller death is low. Ryegrass is forgiving of stress, such as severe grazing, except where high soil moisture leads to pugging damage.

Good management to improve persistence involves:

• Grazing at the 3-leaf stage. In the North Island, rotation lengths may need to be more than 60 days to meet feed cover targets.
• Use the spring rotation planner to manage the transition from winter to spring and ensure appropriate covers are reached in spring.
• Winter is the time of year where grazing below 7 clicks/1500 kg DM/ha does not appear to damage ryegrass growth.

Poor management that will reduce persistence includes:

• Pugging (reduces tiller density and allows weed ingress, reduces subsequent pasture production). Consider standing cows off on races/feed pads.
• Grazing at high stock density on wet soils (reduces subsequent pasture production by up to 45% the following year).
• High farm covers in August (leads to shading and loss of tiller density).

Rotation length

It is important to determine the leaf stage of your own pastures. Leaf appearance rates mainly depend on temperature and water availability with leaves taking longer to appear in colder temperatures or where water is limited.

The following table shows the approximate leaf appearance rates for different regions in autumn; this can be used as a guide to determine rotation length.

Minimum rotation length (e.g. two leaf stage): Time taken for one leaf to fully grow x 2Maximum rotation length: Time taken for one leaf to grow x3

To determine the leaf stage of your own pasture, collect 10 tillers and compare  the leaf stages with the grazing pocket guide pages 10 & 11.

Recommended grazing residuals

Winter is the time of the year where grazing below seven clicks does not appear to damage ryegrass regrowth. Grazing as low as 2.5 cm or 1200 is possible without reducing pasture regrowth. This is because stubble energy reserves are higher due to slower plant growth and less energy use at night due to the colder temperatures.

Wet weather management

Wet weather during the autumn and winter months increases the potential pugging damage to pastures as soils become waterlogged.

Pugging can impact on farm profitability through:

• Reduced pasture yield – between 20% and 80% for four to eight months
• Restricted pasture intake affecting cow body condition and potentially mating performance
• Soil compaction and structural damage.

Quick tips to avoid pugging damage

• Build pasture cover before the wet period
• Graze paddocks vulnerable to wet conditions early (e.g. autumn)
• Take cows in and out of different gateways
• Start grazing from the back of the paddock
• Use on-off grazing with a well-designed and managed stand-off area.

On-off grazing

On-off grazing is the most effective grazing strategy for minimising pugging damage. It involves having stock on pasture or crop for short periods of time. For the rest of the time use a well-designed and managed stand-off area.

• Cows can consume their daily intake in 6-8 hours so can be stood off paddock if necessary to avoid damage
• Alternative places to stand cows off include - races (confine cows to limit damage), paddocks that have been identified for regrassing, yards (ensure that they are stone-free to minimise lameness)
• Ensure cows have enough space to lie down - at least 3.5m2 per cow if on woodchip, sand or concrete for up to two days; at least 5m2 on woodchip or sand for more than two days; and m2 if on crops or feed-out paddock.

Block grazing with temporary fencing

Shift stock regularly (twice per day) and back fence to reduce excessive treading.

• Make breaks as square as possible. Avoid strip grazing. Long, thin breaks encourage stock to walk up and down the fence line. Use electric fences to break rectangular paddocks into squares
• Start grazing from the back of the paddock. Long grass gives some protection against soil damage when stock or vehicles are driven over it. Also it is easier to get stock to move to fresh pasture by walking over pasture rather than over pugged, muddy soil
• Have several entrances to a paddock so that stock can walk over a different route each time they enter and leave. Consider having a gate in each paddock corner, dropping fences, and leaving grassed laneways to avoid walking over grazed areas
• Use a temporary back fence to prevent stock from back grazing and causing further damage to the previously grazed pasture. However, ensure stock have access to water, especially if hay or other dry feeds are being fed out
• Give a bigger break at night to reduce stocking intensity. Also, start a 24-hr break in the evening, so that it will be daylight when pasture cover becomes low and damage is more likely to be observed
• Use electric fences to protect damaged or sensitive areas such as bare patches, seeps and wetter soils.

Sacrifice paddock

A sacrifice paddock is one way farmers choose to manage their cows and pasture when there are no purpose built stand-off facilities, or where off-farm grazing is not an option.

A sacrifice paddock can take the pressure off the rest of the farm by allowing grass cover to build up while vulnerable soils are wet. The regrowth of a small area of pasture can be sacrificed to enhance the regrowth on the rest of the farm.

Some farmers use a sacrifice paddock when it is dry in autumn. By feeding supplements on a sacrifice paddock it allows future paddocks in the round to build up pasture covers.

Standing cows off pasture

The way cows eat (i.e. rate, bite size, chewing time, etc) affects the way nutrients are available and digested in the rumen. Strategically timed pasture restrictions may enable manipulation of nutrients supplied to cows, and change grazing behaviour to enable cows to be fed adequate pasture in short, intensive grazing sessions. This would enable the practice of restricting grazing times to reduce pasture damage and promote pasture re-growth not only to be used in winter for dry cows but also for milking cows particularly in late lactation

• Cows can consume their daily feed requirements very quickly, provided sufficient feed is offered to meet their needs.
• Standing cows off pasture makes them hungrier; therefore, they eat more efficiently by modifying their grazing behaviour when pasture is available. This is useful for minimising the duration cows need to be on pasture to meet their energy requirements.
• Standing cows off also reduces the number of urination and defecations on pasture and enables the capture and storage of nutrients during high-risk periods.
• Cows require an adjustment period for a change in their routine, and should be gradually introduced to restricted grazing
• The impact on milk production is affected by the additional walking distance to and from the stand-off area

Research: To gain a better understanding of cows eating strategies in response to standing-off, the intake and grazing behaviour of dairy cows in early lactation was investigated during the first and main grazing session of the day in a DairyNZ study. Cows were grazed according to three treatments

• 1x8, 8 hours of available grazing between am and pm milking in a 24 hour period;
• 2x4, 4 hours of available grazing after each milking in a 24 hour period.
• Control, representing the normal situation of 24 hours of available grazing excluding milking time.

Results showed daily pasture intake per cow did not differ between the three treatments. Cows in differing treatments managed their time available to eat differently. Cows in the 1x8 group had the highest bite size for the longest time and the steadiest bite rate, meaning they had the highest DM intake, especially in the first few hours. These cows also had the highest rate of hunger hormones, therefore how motivated cows are to eat, is determined by how hungry the cows are.

Impact on Milk Production: The impact on milk production is dependent on the resultant loss in pasture growth if the cows are not stood off, the stage of lactation, the timing of pasture allocation, the walking distance and farm topography and the quality of the standoff facilities.