It is important to keep a constant supply of high-quality grass in front of a dairy herd, according to advice by College of Agriculture, Food and Rural Enterprise (CAFRE) dairying development advisor, Dr. Jane Sayers.
“The key is to focus on maximising the cow’s daily grass intake,” according to Dr. Jane Sayers.
Grass is a “cost-effective feed” that can be used all year-round.
Dr. Sayers said that with good grazing management, dry matter (DM) intake of 15kg DM/head/day is achievable, and with excellent grazing management, an intake of up to 17 to 18kg DM/head/day can be achieved.
She added: “Successful management of high yielding cows at grass requires excellent grassland management and targeted concentrate supplementation to allow the cow to meet her nutritional requirements.”
CAFRE
Cows need to be fed dense, leafy, high digestibility sward with a pre-grazing cover 3000-3200kg DM/ha, grazing the sward down to a post grazing cover of 1700 to 1800kg DM/ha.
Ideally, the swards should be at the three-leaf stage, which is the optimum for intake, sugars, leaf to stem ratio, minerals, regrowth and responsiveness to fertiliser.
Sayers stated that it is critical that cows are allocated the correct grazing area to support intakes, e.g., a 100-cow herd requires 1.0ha/day (2.5ac/day) to support intakes of 15kg grass DM/cow/day.
Additionally, fresh grass should be offered after milking and the farmers should maximise the time a cow spends grazing at pastures to support high grass intakes.
The M+ figures quoted below are “only achievable” under ideal grazing conditions and will be reduced due to wet weather, as this reduces grass intake.
Reduction in grass DMI
Reduce M+ setting in parlour by:
Continuous light rain
1 kg/DM/day
2.0 – 2.5 litres
Continuous heavy rain
2 kg/DM/day
4.0 – 4.5 litres
Where cows are yielding above the M+ production figures for grass, supplementation with concentrate is necessary, cows should be fed at a rate of 0.45kg concentrate for each additional litre milk produced.
Failure to feed cows for their level of production will result in reduced milk yield, poor quality milk composition, low body condition score and poor fertility throughout the season.
Cows should be fed a low protein concentrate at grass, preferably 16%. Swards that are well managed and fertilised can have crude protein greater than 21%.
Much of this protein in grass is rumen degradable, leading to excess levels of ammonia in the rumen and high blood and milk urea levels, which can have negative effects on cow fertility and reduce milk yields.
According to Sayers, energy is the “greatest limiting nutrient” in the dairy cow diet. Milk yield should only drop on average by 2.5%/week (10%/month) from peak yield.
Where grass availability may be limited due to restricted grazing ground, poor grass growth, mixed weather or management, the farmer might consider buffer feeding or partially housing cows at night.
The aim is to balance the estimated grass availability with silage and concentrates to help maintain the cow’s level of milk production, health and fertility status.
Dr. Sayers advised:
“Fibre increases and sugar declines as the grazing season progresses, this suggests that higher fibre concentrates may be more appropriate in the early season, while higher starch supplements would best balance late-season grass.”
In early grazing season, the use of quality digestible fibre and sugar sources is encouraged to reduce the risk of digestive upsets.
The adviser added that during periods of grass shortage, the farmer should offer cows 2kg to 4kg DM of high quality silage at milking time. This will allow a build-up of grass and extend the grazing rotation.
