By Sarah Clack,
Agriculture Victoria dairy extension officer
There has been a good start to the season in many areas of northern Victoria.
To make the most of it, grazing management of pastures can be used to maximise pasture growth and utilisation helping us to get the most out of the resources invested.
The aim of good grazing management is to balance the requirements of the pasture and the herd.
Grazing rye-grass pastures between the two- to three-leaf stage allows the pasture to reach maximum production.
When the tiller reaches the two-leaf stage it has restored its energy reserves used to regrow after the last grazing and the pasture is nutritionally balanced for the herd.
Allowing the tiller to reach the three-leaf stage before grazing is a bonus, as the third leaf is an extra 30 to 40 per cent larger than the second leaf.
If the pasture grows beyond the three-leaf stage, the first leaf begins to die, losing quality and increasing wastage.
The grazing rotation length is determined by the leaf appearance rate. As the temperature declines and day length shortens going into winter, the leaf appearance rate slows.
This means the grazing rotation needs to be lengthened to allow the pasture to continue to reach the two to three-leaf stage target.
If our leaf appearance rate is 15 days, the rotation length would need to be 45 days to reach the three-leaf stage. This would make the pasture area on offer per day 1/45th of the total milking area.
Leave a post grazing residual of four to six centimetres between clumps.
This is where the tiller stores its energy or ’fuel’ to re-grow.
Grazing below 4 cm will reduce the energy reserves available for regrowth resulting in smaller tillers and less pasture available at the next grazing.
Grazing above 6 cm has no benefit to growth and increases pasture wastage.
Do not allow stock to have access to the pasture for longer than two to three days as this will result in new shoots being grazed and a reduction in growth.
Increasing the rotation length decreases the area of pasture available and often the amount of pasture available, leading to lower post-grazing residuals.
Supplements — for example, grain, silage and hay — are used to manage the residual height.
If post-grazing residuals are below 4 cm more supplements should be offered to the herd to increase the residual.
If residuals are above 6 cm less supplement should offered to the herd to minimise pasture and supplement wastage.
Remember, keep an eye on the leaf stage of the pasture you are offering to the herd and the post-grazing residual as the cows leave the paddock each day to see if you are reaching your target leaf stage and post-grazing residuals.
Lengthening or shortening the grazing rotation is about reaching the desired leaf stage, ideally two- to three-leaf stage.
The post grazing residual, a measure of feeding level including supplementary feeding, is used to maintain a residual height of 4cm to 6 cm.
For information on managing dry conditions, visit: http://agriculture.vic.gov.au/home
For more information on winter grazing management, phone Sarah Clack at Agriculture Victoria, Tatura on 5824 5502 or email: firstname.lastname@example.org