In the dairy industry where margins are often tight, making the most out of home-grown forages is key. Grazed grass is the cheapest feed on the farm yet often it is not utilized to its full potential. Providing good grassland management is carried out it can have a positive impact on profitability, more milk from forage = improved margins.
Careful planning of your grazing platform early in the season before cows are even out is crucial for a successful grazing season. Set up a rotation and grass wedge from the beginning, but the length of rotation will all depend on grass growth rate. As the season goes on there can be a large variation in growth rates as seen in Table 1. Therefore, regularly monitor grass growth and adjusting the rotation length accordingly is important. Having a flexible approach is key to a successful rotation, with the heaviest covers grazed first.
To start with cows will need to be trained to graze. Turn cows out for around 2-3 hours a day for around 2 weeks before full turn out this allows for the rumen adaption and will help to set up a grass wedge as they will be eating a small amount around 5kg dry matter (DM) a day. As cows have their two largest meals at sunset and sunrise turn cows into new area post afternoon milking, the grass will be higher in sugars and have a higher dry matter therefore intakes will be greater.
Even though the optimum cover for grazing is 2800-3000kg DM, at the beginning of the season turn cows out when the cover is around 2,300kg dry matter. Grazing lower covers here compared to the rest of year allows cows to be off the pastures quicker which will reduce poaching. Poaching will lead to a reduced DM yield throughout the season, graze the dryer pastures first which are less susceptible. Aim to finish the first rotation by the third week of April. Grazing intervals will vary during the season. In April/May due to the rate of grass growth the interval will be the shortest and a higher stocking rate (Table 2) can be used to keep up with grass growth.
Make sure residuals are grazed down to the right height from the onset on season, residuals influence sward density, grass nutrient quality, DM yields and regrowth in the subsequent rotations. Target residuals at 5-6cm (1600- 1700kg/DM/ha). Grazing below 4cm will diminish the plant reserves so regrowth will be slower. To rectify pastures which haven’t been grazed low enough consider premowing in the next rotation or following with far off dry cow/ heifers, providing a high stocking rate for a short period of time before leaving the paddock to re grow for the milking herd.
During May- August when grass growth is at its maximum fields above 3300kg DM consider cutting for silage then putting them back into the grazing rotation. If the pastures are left too long/ grazed too late the tillers will continue to produce new leaves, however there will be no increase in grass mass due to the bottom tillers produced first will die off . If this occurs the dead material will build up in the base of sward which has very little feed value, decreasing grass utilisation.
By measuring pastures and assessing the grass supply for the next few weeks will allow any shortfall/excess to be addressed quickly. If there is a surplus of grass, the supply must be reduced. This can be done by either decreasing the total grazing area or rotation length by cutting a paddock for big bale silage, increasing the stock numbers on a grazing area e.g. introduce the dry stock onto pasture following milking cows. If a shortage has been identified, then increase the grass supply by either increasing the rotation length by buff er feeding or introducing silage ground into the rotation or decreasing the number of stock by housing dry cows etc.
In conclusion to have a successful grazing season grass monitoring is vital, by doing this it will enables several management decisions to be made. It allows excesses/ shortages to be planned for and better grass utilisation by grazing at correct covers and residuals.