Managing Your Grazing System
A key grassland efficiency target is to have your core grazing area grazed by mid to late April. This is necessary to prepare the grazing area for the second rotation, as it is critical to setup the area in a wedge to avoid having too much of the area at the optimal stage for grazing all at the same time. To achieve this target, the area required for the cows from now until first cut aftermaths become available for grazing in June must be calculated. The optimum grazing stocking rate for this period is influenced by a number of factors including stage of lactation, meal feeding and the grass growth potential of your farm. However 5 cows per ha
(2 cows per acre) is a good target, and will suit many farm situations. This means that a 100 cow herd requires 20 ha or 50 acres during this period. If your cows are not yet turned out, then achieving the first grazing rotation by the mid/late April target will be difficult. Selecting fields with lower grass covers to graze can help, as this will allow a much larger area to be grazed quickly, or alternatively dry stock should be used to enable the first rotation to finish on target.
After establishing the target size of the grazing area in early season, this needs to be allocated on a daily basis. The key principle is to maintain a rotation length of 18-21 days, as this is essential if grass quality is to be maximised. When grass growth is at its peak, an 18 day rotation will help maintain sward quality. Using the 100 cow example above, the cows should be grazing 1 ha (2.5 acres) per day. If the cows are grazing a smaller area daily, then this will slow the rotation, and it is likely that there will be a surplus of grass. Once a surplus or shortage is identified, corrective action should be taken immediately to maintain the rotation length on target.
Flexible system or fixed paddocks
To achieve this 18-21 day rotation length, fresh grass can be offered using a flexible strip grazing system or using fixed paddocks. Essentially both systems managed correctly can achieve similar results. A potential advantage of the fixed paddock setup is that surpluses and shortages become apparent very quickly. However, when strip grazing there can be a tendency for the rotation to simply get longer as a progressively smaller area is offered daily and more grass accumulates ahead of the cows. This accumulation of grass will be of poorer quality, and will have a negative effect on animal and sward performance at subsequent grazings. In addition, a back fence should be used when strip grazing large fields to prevent the cows grazing the re-growth.
Fresh grass can be offered once or twice daily, with the preference in the 24 hour setup to provide the fresh grass after the evening milking. There are no clear advantages in providing fresh grass after every milking in good grazing conditions. In wet conditions however fresh grass must be provided after each milking to minimise pasture damage. A complication in providing 24 hour allocations of fresh grass is that many farms have separate ‘night’ and ‘day’ blocks in order to have cows close to the parlour in the morning, and also not wanting to cross roads etc twice daily. A grazing platform with well surfaced and wide laneways will speed up the time taken to move cows and increase the options for grazing management, particularly in difficult weather conditions.
Aim to have all of the core grazing area grazed by mid to late April
Maintain a rotation length of 18 – 21 days
Identify and remove surpluses as soon as possible
Strip grazing and paddock systems need the same discipline to ensure surpluses and shortages of grass are correctly managed
by Andrew Dale, AFBI, and Mark Scott, CAFRE