Close monitoring and tailoring heifer grazing management nutrition is key to meeting growth and reproductive targets at grass. We spoke to a nutritionist to find out more.
TEXT MELISSA WOOD
Heifer rearing accounts for 20% of total herd expenditure, making it a significant factor in the sustainability and efficiency of dairy businesses. And, according to Advanced Ruminant Nutrition’s Julia Wadeson, grazed grass is a cost-effective option to feed youngstock during the spring and summer months. But producers must carefully consider the transition to turnout to ensure heifers hit key growth targets.
“Producers must have a strategy to ensure they achieve target heifer growth rates, including grazing-management protocols,” says Miss Wadeson, adding that poor heifer performance during the grazing season can be an issue on many units.
“Too often heifers are grazed on grassland away from the main unit, or turned out to pastures furthest from the yard where they are out of sight and out of mind. Many are bolused pre-turnout and then there’s little further management or intervention until housing.”
She says that this lack of monitoring can lead to suboptimal heifer growth and a deterioration in health. “As a result, heifers may return to the unit in poorer condition than expected, below between 55% and 60% of mature bodyweight, and past the ideal age of between 13 and 14 months for breeding. This can significantly impact average age at first calving.
“Heifers will begin cycling when they reach 50% of their mature bodyweight, and this should be achieved by 12 months old to support optimal fertility in bulling heifers, and egg quality at service,” explains Miss Wadeson. Producers should also closely monitor heifer stature because 50% of skeletal growth occurs within the first six months. Bulling heifers should ideally be grown to 90% of their mature stature by between 13 and 14 months old, for optimal reproductive performance and calving ease. This underlines the importance of encouraging skeletal growth, as well as increasing bodyweight.
Crucial details
“Failure to monitor heifers can lead to avoidable problems,” says Miss Wadeson. “Producers often overlook crucial details, such as the age of returning heifers. If these heifers have passed the optimal age for first service, the knock-on effect is that producers will try to get them in calf quickly and ‘miss’ younger heifers that are actually at the suitable age for mating. Missing these heifers has a significant impact not only on their future health and productivity, but also a major impact on profitability.”
Close monitoring: regularly check the weight and stature of growing heifers
Producers must identify smaller heifers pre-turnout and monitor body condition scores regularly to prevent performance losses and health issues. “We need to ensure that heifers are growing in stature, as well as weight. Holsteins should, on average, achieve growth rates of between 0.85 and 1kg per day, while Jerseys should gain between 0.55 and 0.7kg per day.”
Miss Wadeson adds that a proactive approach to feeding is key to heifer development. “Before turning heifers out to pasture, fresh grass samples should be taken for analysis of macro and micronutrients. This allows turnout diets to be tailored to each unit to help meet heifer requirements.
“Spring grass typically provides sufficient protein and energy for heifer growth and development, but nutritional quality deteriorates as the season progresses. This is why producers may see declining performance in their heifers towards the end of summer. So subsequent samples should be regularly taken to allow ration adjustments to keep heifer growth rates on track.”
Supplementation is important too. Fresh spring grass is often lacking in essential vitamins and minerals that are crucial to heifer development, such as vitamins A, D and E, and cobalt, iodine, selenium and copper.
Levels vary from farm to farm, depending on mineral availability of the soil and pH, so it is important to analyse pastures to ensure heifers are correctly supplemented. Minerals and vitamins should be balanced to support optimal fertility, health and growth, and hoof formation, and this can be achieved through feeding compounds, offering mineral blocks, or administering boluses. “Whatever method is used, it’s key to ensure that heifers are covered for the entire grazing season,” says Miss Wadeson.
Access to clean water is also vital, and sources should ideally be situated within a short walking distance – fewer than 250 metres from grazing areas. Testing water to check for contamination or high amounts of antagonists, such as molybdenum, sulphur, zinc and iron, is also important. All can reduce intakes and impair the absorption of copper, which can show up as brown coats in grazing heifers. “Looking at minerals from all sources is essential because some deficiencies are slow to materialise. Relying on visual signs of deficiency and poor performance is not recommended.”
Whole-herd approach
A grazing plan for the whole herd is also important because heifers have different requirements to the milking herd. “Producers should aim for a daily dry matter intake equivalent to 3% of heifer body weight for sustained growth and favour rotational grazing over set-stocking.
“Young heifers should be offered grass with a pre-grazing cover of between 2,500kgDM/ha and 3,000kgDM/ha, or between 8cm and 10cm in height, and moved onto new pasture once they reach between 1,800kgDM/ha and 2,000kgDM/ha.
“During their first grazing season heifers will struggle to meet low residuals, so older cattle can be moved onto these fields afterwards to graze grass down further,” adds Miss Wadeson.
Management and feeding should be tailored to heifer age and stage of development. “For example, first-grazing calves should be introduced to grass gradually, as they will need to learn how to graze.
“Supplementing the youngest heifers with straw and concentrates will ensure nutritional requirements are met while grazed-grass intakes are still low. Continued concentrate feeding will also support further rumen development, which will improve digestion and utilisation of fresh grass,” she adds.
“In-calf heifers can thrive at grass, provided there is adequate nutrition, supervision and care. And heifers coming up to breeding age benefit from close proximity to the farm, for regular monitoring and serving, or from being housed until confirmed in-calf. “Proactive management strategies will lay the foundations for a productive future in the milking herd.”