FEED ▶▶▶
Maximise use of grazed grass
Dairy farmers now, more than ever, must ensure they maximise the use of every square inch of grazed grass to help produce milk at a lower cost.
BY CHRIS MCCULLOUGH W
Grass is a quar- ter of the cost of concentrates per kilogram of dry matter, there- fore it makes sense to in- crease intake of grazed grass for the dairy herd.
ith excellent summer grass-growing condi- tions being experienced on dairy farms the forage yields are high, but the utilisation of grazed grass is not as good as it could be.
Results from trials conducted on farm in Northern Ireland by Agri-Food and Biosciences Institute (AFBI) show that 12.2 tonnes of grass dry matter (DM) per hectare can be grown on average but only 7.5 tonnes is utilised. To help farmers maximise the use of grazed grass, AFBI has issued some guidelines to try to reduce the cost of milk production.
Assess grass growth and cover The ideal pre-grazing grass cover for dairy cows in a rotation- al grazing system (paddocks or strip-grazing) is 3,000kg DM/ hectare. This is equivalent to a grass height of 8–10cm and can sustain a high level of milk production with good compo- sitional quality. The sward recovery is also quicker than when heavier grass covers are grazed. Paddocks should be grazed down to around 1,600kg DM/hectare or 4cm. With grass growth and weather conditions changeable, it is essential for farmers to walk the grazing platform at least
once a week, either eyeballing or using a plate meter to as- sess the quality and quantity of grass in front of the herd. Surplus grass can be removed as silage, and it is important that this is cut at an early stage even though it is a light crop. This will ensure that leafy regrowth is available for grazing as soon as possible. During periods of grass shortage, cows may be fed additional concentrates or can be buffer fed silage until grass is in sufficient supply.
Consider batching cows In a spread calving pattern herd, AFBI urges farmers to con- sider batching cows using their milk yield as a parameter.
Groups could be: • Grazing full time – Moderate-yielding cows confirmed in calf and late lactation cows.
• Grazing by day and housed at night – Mid-lactation cows and those producing up to 30 litres.
• Housed full time, if practised by your particular system – Freshly calved and highest yielding cows.
For block calving cows, in either spring or autumn the herd can be managed as one block for ease of management either for fulltime grazing or grazed by day and housed at night.
Milk from grass Grass is a quarter of the cost of concentrates per kilogram of DM, therefore it makes sense to increase intake of grazed grass for the dairy herd. High-quality spring grazed grass, if managed correctly, is capable of supporting maintenance plus 20 litres of milk. To calculate the amount of milk produced from grazed grass for a dairy cow, establish the concentrates fed in kilo- grammes, divide by 0.45 to give the milk produced from con- centrates, then subtract from the total daily milk yield. For example, a cow producing 35 litres and fed 10kg of con- centrates is producing 22 litres from concentrates (10/0.45 = 22) and 13 litres from grazed grass (35 − 22 = 13). This high- lights that this cow is not producing enough from grazed grass and has a higher cost of milk production.
Energy and protein content of diet Energy, not protein or minerals, is the most limiting factor in the dairy cow. If cows are not milking as well as expected, or
50 ▶DAIRY GLOBAL | Volume 7, No. 3, 2020
PHOTO: PICASA
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