Spring grazing management has a large influence on the overall annual productivity of grass-based production systems like we have in Ireland.
According to Teagasc, spring grazing must strike a balance between feeding the herd well and setting up the sward for the next rotation. It says there are four main objectives to be met i) grazing the correct amount of area each week; ii) grazing out swards to the correct height (3.5-4cm); iii) ensuring cows are on a rising plane of energy intake; and, iv) including enough forage fibre in the diet.
Teagasc advises farmers to graze one third of the milking platform area by early March, or about 1 per cent per day, rising to 1.5 pre cent each week through February. It says another one third should be completed by 17 March.
Teagasc notes that these area targets hold for spring and winter calving herds alike. It advises farmers to start with lower covers (8- 900kg DM/ha) for a few days to settle cows into grazing.
It cites that daily grass allowance will depend on herd demand. Spring calving herds at lower stocking rates may be able to offer up to 13kg DM of grass per day from mid-February.
It also says forage supplementation may be needed for herds with higher daily demand. Aim for at least 12kg DM total forage intake (grass and silage combined). Minimum grass allowance per grazing bout is 5kg DM.
Teagasc states on a high grass diets, 2-4kg of concentrate is adequate for spring calving herds. It says increase by 1kg where silage is fed. High energy rations work best – high crude protein rations are not necessary.
The Teagasc Spring Rotation Planner (SRP) is a management tool to remove guesswork from decision making during this period. The SRP allocates an increasing proportion of the farm each day to the herd from turnout to grass in spring up to magic day (where growth rate equals demand),there by rationing grass supply in spring until growth exceeds demand.
Teagasc notes there are a couple of key rules to remember with the SRP.
1. Stick to the plan. Skipping ahead of the area plan per day will result in a short first rotation and may also compromise subsequent growth rates.
2. Manage according to postgrazing residuals. Postgrazing residual height should be maintained at 3.5 to 4 cm. If postgrazing height exceeds 4cm on the daily grazing allocation, then demand per day must be increased (reduce supplementation, increase stocking rate); where postgrazing residual height falls below 3.5 cm, feed supply must be increased (increased supplementation/reduce stocking rate)