Mid season management in a challenging grass year
Olwen B Gormley, CAFRE Senior Dairying Development Adviser.
The 2015 grass year to date has proved to be really challenging. The prevailing low milk prices and poor margins meant dairy farmers were seeking to make maximum use of grass to reduce the costs of production. However variable weather, leading to difficult grazing conditions meant cows had to be re-housed with no settled grazing pattern established. While good levels of grass production were achieved on a number of farms, efficient utilisation of the grass has been the challenge and farmers now find themselves with stemmy, poor quality swards. The aim on farm should be to improve both the quantity and quality of grass grown the rest the year and this article will outline some steps which will help to achieve better grazing management.
The recommended pre-grazing grass cover for dairy cows in a rotational grazing system (paddocks or strip-grazing) is 3,000 - 3,300kg DM/hectare. This is equivalent to a grass height of 12-14cm. Not only have these swards the potential of sustaining a higher level of milk production of good quality but their recovery is much quicker than where heavier grass covers are grazed. It is also important to graze out swards to a post grazing cover of 1600kg DM/ha that is, 4-5cm. This leaves a clean base to the sward and is more responsive to fertilizer leading to a quicker re-growth. The figures below highlight the potential of good quality grass for milk production.
Potential daily milk yields per cow produced from high quality swards which are well managed ( litres ):
Monitor grass growth
When grass growth and weather conditions are so changeable, it is essential to walk the available cow grazing area at least once a week. While this practice is time consuming it will pay dividends, as it is the only sure way to assess the quantity of grass in front of the herd. The weekly GrassCheck information provided by AFBI and CAFRE should be used to match predicted grass growth to herd demand. Farmers using GrassCheck are in a better position to manage grass mid-season to reduce feed costs. As a guideline when there is more than one week’s supply of grass with covers suitable for grazing ahead of the cows there is a risk of building up a grass surplus. Provided conditions are suitable some of this excess grass can be removed as silage, normally as round bales. It is important that surplus grass is cut at an early stage even though it is a light crop. This will ensure the regrowth is available for grazing as soon as possible and minimise the risk of a grass shortage if grass growth is reduced.
Grazing high grass covers
When grazing swards with high grass covers utilisation can be improved provided the weather is dry and sunny by pre-cutting the grass the day prior to grazing and letting the cows eat the wilted forage from the swathe. Best results are achieved when the grass is cut by a mower without conditioner. Not only does this practice improve grass utilisation but it ensures a high quality regrowth.
The alternative is to graze laxly allowing the cows to eat the leafy portion of the sward. The stemmy residue then requires topping or grazing down quickly with other stock, for example, heifers or dry cows.
After the second grazing rotation paddocks should be topped when there is an accumulation of stemmy material and poor quality grass around dung pats. This will improve the quality of the regrowth and subsequent grazings. It is important that the topper is set to cut grass at 5-6cm height, about the same level achieved when swards are well grazed down. Skimming over the surface of the sward and removing only seed heads is not effective in improving sward quality. Topping should be carried out immediately after cows are removed from a grazing area as a later topping will check the regrowth.
A flexible approach to grazing management is a key factor in achieving maximum milk production from grazed grass. With changing weather conditions affecting both grass growth and ground conditions sometimes it is necessary to make changes to grazing management on a daily basis. In wet weather it is valid to graze paddocks out of rotation or house cows at night in order to minimise poaching until conditions improve again.
Repairing poached swards
Dig a few inspection pits to assess the degree of compaction and damage caused by poaching. If only the top few centimetres are affected some farmers have noted improved “carrying capacity” from spike aeration. If the poaching has caused damage down to 6cm then you need to consider stitching in and rolling short term with a full reseed later in the season. Review your fertilizer policy. Damaged swards will benefit from lime application and assessing whether other plant nutrients including potash and sulphur are required.
The grass challenge
Lower milk prices have refocused attention on making the maximum use of grazed grass, it is the cheapest feed for dairy cows provided it is well managed. The challenge for all dairy farmers is to maximise the potential of grass in this difficult period. Discuss the grazing options for your farm with your local CAFRE Adviser.