Pre and Post Calving Diets
Pre-Calving Diet
Ideally the diet should consist of restricted pasture (up to 2kg dry matter per day) with low potassium grass hay or straw fed to appetite. Feed a specialist dry cow supplement such as Barastoc Lead Up Pellets at 2-3kg per day for a minimum of 14 days prior to calving. In addition, unrestricted access to clean water is essential to help maintain the high intake of dry feeds required in a pre-calving diet.
Generally, hay is low in nutrients and fairly large amounts are needed to meet the cow’s energy requirements. This keeps the rumen distended, maintaining capacity to permit higher intakes after calving, whilst reducing the risk of a displaced abomasum. Pasture should be limited at this time as it contains relatively high levels of potassium (a cationic element) and rumen degradable protein.
These nutrients work against the desired anionic state for the springing cow. Pasture also requires less chewing and is less filling than hay.
When concentrate feeds are fermented in the rumen they produce volatile fatty acids. These acids, particularly propionic acid, stimulate the rumen papillae to grow. This increases the surface area of the rumen and promotes the absorption of the higher concentration of nutrients in the post calving diet. In addition, the rumen microbes become adapted to concentrate feed, reducing the risk of acidosis and improving feed utilisation in early lactation.
Many herds suffer some sub-clinical milk fever (hypocalcaemia), even if no cows actually show clinical signs. Low blood calcium levels reduce muscle control leading to difficult calvings, retained afterbirth, displaced abomasum, and mastitis. The muscles of the digestive tract are also affected. This may lead to reduced food intake and subsequent acidosis, ketosis and a weakened immune system.
To stimulate calcium release from bone, the pre-calving diet should have a slightly acidifying effect, or a negative dietary cation-anion balance (DCAB). DCAB is the sum of the alkaline cations (sodium, potassium, calcium and magnesium) minus the sum of the acidic anions (chloride, sulpher and phosphorus) in the feed. A good indicator that the diet is sufficiently anionic is urine pH. The average urine pH of Holsteins should drop to between 6 and 6.5 and the average urine pH of Jerseys should drop to between 5.8 and 6.2. However, if pH drops below this, the diet is too acidic and feed intake will be reduced. Anionic salts increase the mobilisation of calcium from bone, helping to reduce the risk of milk fever and the associated depression of appetite.
Finally, ensure the feeding area is large enough for all the cows – if all cows cannot get access to feed, timid cows and heifers will not eat to appetite, leading to reduced intakes and metabolic problems after calving.
Post-Calving Diet
Do not lose the advantages gained through good pre-calving nutrition by under-feeding after calving.
High quality forage should be available to appetite and if insufficient pasture is available, high quality silage or hay should be provided. In addition, high-energy concentrate feed, balanced for protein, minerals, trace elements and vitamins is essential With feed available to appetite, a steady increase in intake is stimulated. But, if feed is limited, more body tissue is mobilised, reducing appetite and leading to a vicious cycle of increasing weight loss and falling intakes. Even with pasture available to appetite, high yielding cows will not be able to meet their energy requirements and a high-energy supplement should be fed at the rate needed to meet energy requirements for peak production. This will minimise weight loss and improve fertility. Cows that lose less than half a body condition score after calving have the highest conception rates. In addition, as milk production drives appetite, every extra litre at peak can result in an extra 200 litres over the lactation.
Finally, low intakes early in lactation can limit the amount of minerals, trace elements and vitamins consumed. Adding minerals through the supplementary feed should rectify this. Other additives such as buffers may also be required to achieve maximum efficiency of feed utilisation.
In summary, good feed management throughout the dry and transition periods can give big benefits in milk production, health and reproductive performance in the next lactation.