Failure to achieve adequate mature live weight targets affects the heifer's lifetime performance, starting with low conception rates and leading to lower milk production in the first lactation, it says.
Yet a recent study, published in the Proceedings of the New Zealand Society of Animal Production 2013 concluded that between 86-92% of heifers were not achieving optimal weights.
DairyNZ data recommends that at the typical mating age of 15 months, dairy heifers should be at 60% of their mature live weight, with 42-47% attainment needed for the animal to reach puberty.
Ballance Agri-Nutrients product manager animal nutrition, Jackie Aveling, explains both under nutrition and deficiencies of specific nutrients can have a negative effect on the synthesis of hormones essential for reproduction.
"Nutrients specific to fertility include phosphorus, protein, selenium, copper, iodine, manganese and zinc. While some of these are adequate in New Zealand pastures others are deficient. Herbage testing can pick up the deficiencies and the results will form the basis of advice on what supplements are needed to balance those deficiencies in the heifer's diet."
As young animals need to gain an average of 600-800 g/day, depending on their breed, good nutrition helps achieve these consistent growth rates.
Aveling says regular weighing is recommended and it's important for all replacement heifers to reach their target weights.
"Group averages are not sufficiently accurate and you will still end up with underweight and potentially underperforming heifers. While weighing takes time, it is a lot more accurate than sizing up the heifer by eye and it ensures adjustments to feeding rates can also be monitored to ensure the right results are being achieved."
She says supplements such as the Crystalyx dehydrated molasses block balances pasture deficiencies by providing essential minerals and vitamins as well as protein and sugars on a little and often basis to the rumen to improve forage digestibility.
"Crystalyx trials both internationally and within New Zealand are returning very positive results on both dairy and beef animals. Extended trials to cover the full two year growing heifer are being conducted within New Zealand on farm so we will have good local information to support dairy farmers in getting the best results with their replacement heifers."
