Coming into peak lactation, a cow has an increased demand for calcium, magnesium and phosphorous. For high production milking cows, the diet does not supply adequate amounts of these macrominerals to meet a cow’s requirements, therefore, supplementation is required.
Macrominerals play an important role in achieving peak milk. After calving, the emphasis shifts from transition, where the cow is battling with a negative nutrient balance (where energy is often that first limiting nutrient), to striving for a high milk yield, termed peak milk.
Calcium is very important for milk production in cows. Not only are pasture calcium levels often below requirements, other feeds commonly given in early lactation, such as barley, wheat and maize silage, are also low in calcium. In early lactation, the ideal levels of calcium supplementation needed to reach peak milk are really high. As a guide, it’s not uncommon to be feeding 150g of limeflour for the first 100 days of lactation. This requirement could be even higher depending on liveweight, breed and level of production, so consult with your nutritionist to check that the level you are feeding is adequate.
Magnesium is important throughout lactation and has a role of stimulating the production of hormones that help to regulate calcium levels. These hormones improve the ability of a cow to absorb calcium from the diet and to mobilise calcium from the bones. So, as we approach peak milk, don’t be tempted to reduce magnesium supplementation.
Phosphorous (P) is a mineral that is often forgotten when it comes to lactating dairy cattle. It is important in the integrity and development of the skeletal system, milk production, reproduction, and energy metabolism. Signs of P deficiency are non-specific and include ill-thrift, poor appetite, poor growth and lactational performance and unsatisfactory reproduction. In severe deficiency, bone mineral mass is lost. Feeds such as maize silage, fodder beet and soya hulls are low in P and can increase the risk of a P deficient diet. Another contributing factor may be the reduction of Palm Kernel Expeller (PKE) in the diet. PKE is relatively high in P and may have previously masked other dietary shortfalls. Even pasture can be deficient in phosphorus, so feed testing is something that is useful to be part of your normal farm practice.
Offering supplementary feeds and doing extended feed tests of your pasture allows the diet to be assessed for any shortfalls in mineral supplementation.
PGG Wrightson offers a range of solutions to assist with supplementing your dairy herd with calcium, magnesium and phosphorous. If you would like to complete an extended feed test, contact your local PGG Wrightson Technical Field Representative, who can assist you.
