milk protein is low or cows are losing excessive condition, energy is the first thing to check. Farmers should check the total DM intake of the animal as well as the quality (i.e. energy content) of the concentrates used. Spring grass has a higher protein content at 20% than aver- age quality silage at 12%, consequently cows should be fed a lower protein concentrate at grass: 15–18% protein on a fresh weight basis. High protein in the diet can result in excessive body weight loss as the cow metabolises the extra protein. Avoid feeding high protein diets during the breeding season to reduce the risk of embryonic loss and poor fertility performance. Dietary protein levels can be monitored through milk urea testing; the optimal is 20–35 mg/100ml.
Lower milk butterfat In early season, grass is leafy and has a low fibre content and milk butterfat may fall. Cows should be fed a fibre-based (sugar beet, soya hulls, citrus pulp) concentrate. This is to re- duce the risk of digestive upsets and will help to maintain milk butterfat percentage. In certain situations it may be necessary to include an acid buff in the diet to reduce the risk of rumen upsets. As the grazing season progresses, grass quality deteriorates and feeding a cereal-based concentrate may be more beneficial.
Managing high grass cover Even the best grassland managers can have grazing swards that become too long for quality grazing, over 3,000kg DM/ha, therefore farmers need to consider improving grass utilisation.
These options can be used: • Pre-mowing – weather permitting, cut the grass a day prior to grazing and let the cows pick up the wilted forage from the swathe. Best results are achieved when the grass is cut by a disc mower without a conditioner. This will ensure
better grass utilisation and also high-quality regrowth.
• Leader/follower – this enables higher yielding cows to achieve higher grass intakes and milk yields by allowing the cows to eat the leafy portion of the sward. The stem residue can then be grazed down quickly by other stock such as heifers or dry cows.
• Topping – After the second grazing rotation, paddocks should be topped if there is an accumulation of stemmy material and poor quality grass around dung pats. This will improve the quality of the regrowth and subsequent graz- ings. Set the topper to cut grass at 5–6cm height. Topping should be carried out immedi- ately after cows are removed from a grazing area as a later topping will check the re- growth. Research has shown that topped swards will im- prove yield by 1.2 litres/cow/ day in mid to late season, compared to swards that were not topped.
• Alternate grazing and cutting – Cutting all grazing paddocks at least once during the season leaves a clean sward with an even regrowth and may im- prove grass utilisation and cow performance later in the season.
With excellent summer grass-growing conditions the forage yields are high, but the utilisation of grazed grass is not as good as it could be.
Grass is a quarter of the cost of
concentrates per kilogram of dry
matter, therefore it makes sense to increase intake of
grazed grass for the dairy herd.
Flexible grazing management During periods of wet weather, adopt a flexible approach. This may involve on/off grazing, allowing cows to graze for a few hours after milking and feeding them silage when housed. The aim is to keep up grass intake, manage swards and avoid damage to grassland.
▶DAIRY GLOBAL | Volume 7, No. 3, 2020 51
PHOTO: CHRIS MCCULLOUGH
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