Negative energy balance (NEB) is a problem that affects cows in early lactation, when feed intake is not meeting the energy demands of milk production.
Almost all cows will have some degree of NEB in early lactation, but excessive or prolonged NEB can lead to conditions such as ketosis, fatty liver, displaced abomasum and reduced milk yields.
Although early spring turnout has many benefits, it is difficult to get enough dry matter into cows to protect rumen function.
Dr. Richard Kirkland, ruminant nutritionist for Volac Wilmar Feed Ingredients, said: “As dairy herds are turned out for spring grazing, producers must balance rumen function and energy demands to avoid butterfat depression and fertility issues.
“Rumen function is put under a lot of pressure at turnout as cows go from having a controlled ration that is balanced in fibre and starch, to a more variable forage base of grazed grass.”
Negative energy balance
Weather is nearly always the biggest challenge for grazing spring grass, making it harder for energy supply to be maximised, with a drop in fertility as a consequence.
In perfect grazing conditions, dry matter and energy intakes are usually not an issue – but they can be significantly reduced in wet, overcast conditions.
During early lactation, cows cannot eat enough to meet the high energy demands of milk production and enter a state of NEB.
This is where a cow uses energy from body fat stores to support the genetic drive for milk production, which leads to a loss in condition.
According to Dr. Kirkland, research indicates a fall-off in conception rates of around 10% for every 0.5 body condition score (BCS) loss in this period.
To minimise this effect, the composition of buffer feed needs to be carefully considered.
Dr. Kirkland said: “High-fibre supplements such as citrus pulp and soya hulls will provide a better balance in the rumen and in conjunction with a rumen-protected fat supplement, can provide the greatest response in milk fat as observed in research studies at the University of Nottingham.
“While it may work out on paper, supplementation with rapidly-fermentable carbohydrates such as wheat or barley as energy sources, offers greater challenges and increased risk of acidosis and making the fall in milk fat worse.”
Fat supplementation
Individual fatty acids impact cow performance and influence partitioning of nutrients between milk and body fat stores (cow condition).
Dr. Kirkland recommends that fat supplements are selected based on the blend of fatty acids depending on the stage of lactation, with individual farm challenges and requirements to maximise returns from specific milk contracts considered.
To support both fertility and milk production, Kirkland advises feeding a rumen-protected fat supplement with a research-proven ratio of C16:0 (palmitic acid) and C18:1 (oleic acid), to strategically influence the partitioning of nutrients between milk and body condition.
He added that fatty acids are the building blocks of fat supplements and influence the partitioning of nutrients to specific areas of cow performance.
“During the early lactation period, C18:1 is a key fatty acid, increasing partitioning of energy and nutrients to improve body condition as well as improved development of fertilised eggs.
“However, given the challenges of early spring grass, products containing higher levels of C16:0 can be considered as effective ingredients to increase milk fat production.
“Careful choice of supplements is essential at grazing to provide those vital megajoules of energy in a form that stimulates the rumen and milk fat production,” he added.
“Selecting a rumen-protected fat supplement, farmers can support both fertility and milk production performance while helping ensure energy demands are being met in a safe way.”