Environmental considerations when grazing a winter crop

Soil loss risk increases significantly following the grazing of crop. This is due to the combined effect of having no vegetation to filter overland flow, and grazing related soil damage reducing the soils ability to absorb water.

Strategic grazing of high risk areas

Strategic grazing near waterways and careful management of Critical Source Areas (CSAs) can reduce losses of sediment and phosphorus from the paddock by 80-90%.

Buffer zones or grass strips in and around CSAs and next to waterways act as filters by slowing overland flow to trap suspended contaminants. Where possible, graze the paddock towards the CSA leaving an ungrazed buffer to filter runoff. If this is not possible, leave a buffer around the CSA and graze this buffer last in fine weather. The faster the water is flowing into a buffer zone (ie. The greater the slope of the paddock), the wider the buffer zone will need to be to provide time for effective filtering and infiltration.

P21 Project trial work at Telford Research Farm showed protection of CSAs and strategic management reduced soil and phosphorus losses by 80 -90 percent. This involved protecting CSAs in a winter crop paddock with an electric fence. These areas were grazed (quickly and lightly) in an on/off manner with cows under dry conditions to minimise any soil disturbance (and maintain their integrity to act as a buffer zones). If the soil is undamaged in a buffer zone this will allow the water to soak in (infiltrate) and therefore decrease the amount of water available for overland flow.See Critical source areas.

Back fences

Reduce soil damage by using a back fence. The back fence will reduce the herds walking therefore reducing the soil damage caused by treading the soil. Treading damage seals the soil surface, resulting in more water moving across the soil (runoff), which increases the loss of soil and nutrients. Move the back fence and portable trough at least weekly for the best results.

Portable water troughs

Cows must have access to fresh water everyday. The use and regular shifting of portable water troughs in conjunction with back fencing will reduce soil treading damage. If it is not possible to use a portable trough, it is recommended to put up a back fence at the permanent trough.

Farmer tip:

"Making everything easier for the cows fell into place when I started using a portable water trough. The troughs were a bit of a pain for the first couple of years – but after I saw a neighbour roll hers out through the crop (so she didn’t have to roll it up in mud) it made it much easier. I also saw she had bent the ball cock, so the trough only half filled – made it easier to tip out and move."

Tips for portable troughs:

• Plan how you will move your portable trough so that you don’t move it across grazed crop area. Consider putting the trough under the side fence.
• Secure the portable water trough to a fence post so that cows can’t tip the trough over when they rub it. If you don’t have suitable fence posts, consider using a waratah.
• Bend the ball cock arm or shorten the ball cock string so that the trough only half fills. This reduces the chances of overflowing and reduces the effort required to tip the trough over.
• Put a non return valve and camlock setup where the water pipe meets the water trough to make the join stronger and easier to shift.

Cow considerations when grazing a winter crop

The performance of your herd in the coming season relies on them calving in good health and being at the target body condition score.

Transitioning onto crop

Cows must be transitioned onto winter crops to allow the gut bacteria to adjust to a new feed source. Transitioning onto brassicas (kale, swedes, turnips and rape) can be completed over a shorter time frame than fodder beet. Poorly managed transition can result in sick or dead cows. For more information around transitioning and common animal health conditions on crop, check out the feeding and transitioning on to brassicas guide, or Transition on to fodder beet.

Cow condition

Cows in good body condition are better able to withstand cold as the fat layer beneath the skin acts as an insulating layer.

Cow condition must be planned for prior to winter. See Body condition scoring for advice on how to do this. 

Cows that are in poor condition going into winter will require higher feeding levels than cows that in are in good condition.

Cow allocation and feed utilisation

It is important that cows are allocated enough feed to achieve their body condition score targets. Feed utilisation rates on crop based diets are often lower than grazed pasture diets and must be taken into account when determining appropriate allocations. To determine the appropriate feed allocation for your cows, use the Winter crop allocation calculator.

Feed utilisation rate can be influenced by grazing management. Reduce trampling wastage by moving the fence once or twice a day rather than offering a few days feed at a time.

Crop is utilised more efficiently when long, narrow breaks, rather than wide breaks, are offered, as less of the crop is trampled. To ensure that all cows have access to the crop, there should be 0.7 metres of feed face per cow. If the paddock has a short feeding face, consider splitting the herd by condition score, and feeding both ends at the same time, rather than running the animals in one larger herd.

Downhill grazing interrupts a cow’s natural grazing stance, which decreases crop utilisation. More crop or supplement may need to be allocated to ensure they do not lose condition.

Cold stress

If a cow is clean and dry and there is little wind or rain, cold stress is rare until ambient temperatures fall below -10°C. The factors that increase the risk of cold stress are:

• low temperatures
• wind, rain, and mud
• low condition scores
• low feeding levels.

In poor weather, allow for decreased utilisation and increased demand. A combination of strong wind and rain is the trigger to provide shelter and/or increase feed allowance.

Depending on the BCS of the herd, and the weather situation, wet and windy conditions require an additional 0.5 – 3 kg DM/cow/day. The tables below provide a guide for how much extra feed is required in certain weather situations. Note that the information in these tables is extra feed intake, not extra feed offered.

Farmer tip:

"I am always watching the weather forecast – two or three times a winter we will have rough weather come through for about three days. Before the rough weather hits I will feed the cows extra (especially supplement). That means when the weather hits they have full stomachs and are more settled. I find that after the weather calms down I also need to feed them extra."

 Cows at BCS 4

	0-3 degrees C	4-7 degrees C	8-10 degrees C
	1kg DM	0kg DM	0kg DM
	2kg DM	1kg DM	0kg DM
	3kg DM	2kg DM	1kg DM

Cows at BCS 5

	0-3 degrees C	4-7 degrees C	8-10 degrees C
	1kg DM	0kg DM	0kg DM
	1-2kg DM	1kg DM	0kg DM
	2-3kg DM	1-2kg DM	1kg DM

Sudden increases of fodder beet as a percentage of the diet can lead to animal health risks, especially during the transition period. Additional feed required should be allocated through other sources.

The map (right) shows the number of days in an average winter that cows require additional feed allocation (minimum of an additional 0.5kg/DM/day).  

Make sure staff understand the contingency feeding plans for different weather situations.

Cow health

When checking cows on crops it's important to look out for:

• lameness, injury, loss of BCS, mastitis
• health issues caused by consumption of the crop (red water, bloating, wobbly or down cows)
• slipped or early calved cows
• frozen troughs/pipes and empty troughs.

Some of the signs of health issues that can occur on crops are:

Younger stock should also be checked for pink eye, ringworm, and scours.

Find out more about illness that can occur on brassica crops here.

Cow lying time

The welfare code requires a minimum of eight hours lying time per day. Correct lying times reduce the risk of lameness and stress, which leads to better animal health and condition.

Weather has a major influence on cow lying behaviour. Studies show lying times are reduced shortly after wet weather events, as cows find wet soils uncomfortable to lie on. If wet weather continues for a prolonged period, lying times can be too low for too long.

If possible, have a plan B for periods of wet weather when the crop paddocks become very muddy. Options include:

• drier paddocks elsewhere on farm
• a stand-off facility will reduce treading damage, however, hard surfaces for lying are no more preferable than wet mud.