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Adequate nutrition of growing heifers can be a challenge over summer months when ample quality pasture is not available. Frequently low protein diets through this period can limit frame and muscle growth rates. Well grown heifers that conceive on time can go on to be highly productive dairy cows; but if they do not meet these criteria it is a lost lifetime opportunity. There is no such thing as a ‘catch-up phase’.
Around puberty between eight to ten months of age heifers should reach hip height of 1.2 meters. For joining at thirteen months, they should weigh 360+ kgs and achieve a hip height of 1.30 to 1.35 meters. A target of 85% of heifers pregnant within three cycles requires an average of 1.7 services per conception.
So where do we lose it, especially over summer? As above, inadequate protein certainly is a handicap to growth. For the goal of lifetime production, it is critical that heifers achieve the above growth goals.
Achieving timely pregnancy, especially in seasonal or group calving patterns, is very dependent on vitamin and mineral nutrition. It’s a real gamble relying on forages to supply necessary vitamins and minerals due to both content and bioavailability of both in forages. Supplementation is essential to meet growing heifers’ needs. Where a grain supplement containing a sound vitamin/mineral mix is not feed through the two years from birth to calving, supplementing with a ‘self-feed’ vitamin/mineral mix is essential. Dairytech Nutrition manufactures an all-weather loose lick product for this purpose and has excellent feedback on heifer development and fertility.
Supplementation of Vitamins A, D3 & E , trace minerals of zinc, manganese, cobalt, iodine, and selenium are well documented (NRC 2001) to improve ovarian function and embryo quality. Research shows eight fewer days open and 0.5 fewer services per conception with higher pregnancy rates. Macro elements of magnesium, phosphorous, sulphur, calcium and salt tend to be more involved with growth and skeletal development, but not limited to this. Our ryegrass pastures are very low in calcium especially, a strong argument apart from soil health, to reinstate clovers in our pastures.
Any production animal’s value will rest on a balanced diet. However, it needs to be noted, that, a pregnant animal with an unbalanced or deficient diet will provide the same to the developing foetus. Too often, heifers are left to their own resources on out-blocks or agistment, not just compromising their growth and development, but also, another generation in the unborn calf. Nutrition during pregnancy becomes even more important to meet both heifer and developing calf’s needs for macro and micronutrients.
As a generalisation, pasture is a reasonably well balanced diet for energy, fibre and protein. However, the variations in pasture can be wide as we see in lactating cow diets throughout the year, and even between farms at any given time; no more so than through spring when diets frequently become grass and grain.
Summer pastures generally require supplementation, not just for quality, but more so quantity. Silage certainly can meet this void, but as above, supplementation with self-feed vitamin/mineral loose licks is essential to meet their deficiencies/availabilities in forages. Our heifers, to enjoy longevity as lactating cows, require these nutrients, but so too the developing calf. With sound nutrition, calves are more likely to have healthy birthweights and a strong start to life.
Managing body condition through the heifers first two years has lifelong production and fertility consequences. Adequate energy and protein are essential for a balanced diet. Over conditioned heifers are generally deficient in protein and lack growth of muscle tissue and frame, assuming minerals nutrition is not inadequate. During the months prior to first calving it is essential body condition be well managed. Like dry cows, any over-conditioning or under-conditioning will precipitate energy related disorders of ketosis and displaced abomasum.
Both over-conditioned and under-conditioned heifers will not perform well due to prolonged negative energy balance. Calves from under-conditioned heifers are typically less vigorous.
Well-grown heifers become high performing cows with high dry matter intakes post-calving that persist well into lactation. Fertility and health are serendipitous outcomes of high performance induced in the previous two years of growth and development.
We have the genetics in our herds for far superior performance than Dairy Australia data reveals. Studies at Purina Animal Nutrition Centre (USA) highlighted that high performance can be achieved with longevity and no ‘burnout’. Managing our heifer’s development has significant long-term benefits to the viability of individual farm businesses, but also our industry.