Buffer feeding dairy cows at grass is required to bridge any shortfall that may exist between nutrient supply and animal requirements for milk production. These shortfalls may exist for a number of reasons, such as a low grass supply caused by stocking rate restrictions, lace of adequate grass regrowth due to poor weather conditions or low grass quality (poor digestibility). Also, high yielding cows who require dry matter intakes (DMI) well in excess of that which may be achieved on grass alone.

It is well known that grass DMI is closely correlated with digestibility, a 1% fall in dry matter digestibility (DMD) results in a fall in DMI of 0.6 kg per day. Significant falls in DMD are not common in early season but are frequently associated with low intakes on summer grazing. Early season grazing management also has a major impact on grass quality later in the grazing season.

Grazing management strategies in recent times have focused on grass DMI allowance per day, with 20 kg DMI per head, being the norm. It has been suggested that if the allowance is raised above this level, increased grass DMI will result and higher milk production will be sustained.

Energy intake is the most limiting factor for milk production, although all cows will mobilise body energy reserves to augment a low dietary energy supply. Higher yielding cows demonstrate a much greater willingness to do this than lower yielding cows, much to their own detriment, as low body condition scores are frequently associated with reproductive failure.

Grass dry matter intakes have been measured in many experiments all over the world involving various combinations of grass allowance, grass quality, season, cow merit, daily milk yield, stage of lactation and concentrate feeding. Results have shown:

• Grass intake is highly variable over the grazing seasons
• Dairy herd intakes are between 12-18 kg DM. In practice this can be a lot less due to inclement weather conditions etc.
• Dairy herd grass intakes of >20KG DM per day have not been achieved
• Mature cows have higher intakes than heifers

KEY FACTORS FOR SUCCESSFUL BUFFER FEEDING

If the wrong feeds are used e.g. grass silage, finely ground cereals, poor quality proteins etc., the outcome of buffer feeding will be disappointing, with reduced grass intakes and a zero or negative response in terms of milk yield, composition and body condition.

Well-constructed buffer feeds supplement grass intakes – they do not replace grass. They result in good responses in terms of yield, composition and body condition. The quality ingredients to be used are;

Maize silage, whole-crop wheat, molasses, brewers grains, course cereal grains, sodagrain, sugar beet pulp, citrus pulp, soybean meal and straw.

WHEN TO BUFFER FEED?

Are you considering whether or not to buffer feed the herd? Here are some problems to consider:

• Any sudden drop in milk yield
• Grass allowance < 20 kg DM
• Grass quality is low
• During inclement weather
• If milk protein is falling
• A significant proportion of cows are yielding > 25 kg/day
• Dung is very loose
• There are a high proportion of heifers in the herd

Remember to introduce supplements immediately when a problem emerges – waiting will extend the period that cows are underfed.

Author: Denis Dreux