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Zero-grazing dairy cows delivered a higher margin per hectare than both a silage-based diet and grazing in paddocks, according to a new study published by AgriSearch and released at the RUAS Winter Fair.
Research conducted at AFBI Hillsborough found that the total cost of zero-grazed grass was £123/t of dry matter (DM), compared with £148/tDM for silage and £99/tDM for grazed grass.
Both zero-grazing and silage brought extra costs associated with grass harvesting and slurry application, and equated to £268/ha and £787/ha respectively.
However, the gap between costs narrowed on a per tonne of feed basis, as silage had the highest total utilisable yield of 11.5tDM/ha, compared with 9.84tDM/ha for zero-grazing and 7.95tDM/ha for grazing.
In terms of profitability, data collected from studies at AFBI Hillsborough and Scotland’s Rural College found that silage delivered the lowest margin on both a per head and per hectare basis.
Cows on all treatments were fed concentrates at 7.5kg/day, and zero-grazed cows had the highest forage intake and milk yields at 12.1kg DM/day and 29.5l respectively. This compares with 11.2kg DM/ha and 27.9l for grazing, and 11.6kg DM/day and 25.7l for silage respectively.
Margin over feed and forage subsequently stood at £5.15/cow/day for grazing, £4.87/cow/day for zero-grazing and £3.08/cow/day for silage.
However, grazing supported a stocking rate of 3.57 cows/ha, while zero-grazing could support 4.45 cows/ha and silage 5.1 cows/ha. This meant zero-grazing delivered the highest margin over feed and forage per hectare at £21.66/ha/day, compared with £18.37/ha/day for grazing and £15.7/ha/day for silage.
The publication from AgriSearch also provides a guide in best practice for zero-grazing. It highlights that good grassland management is essential for zero-grazing, and costs for any system can vary widely on an individual farm basis.
The booklet states that zero-grazing can deliver benefits such as better grass utilisation, increased stocking rate and suitability for fragmented farms. However, disadvantages include variability in dry matter of feed, daily labour requirements and machinery costs.
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