Liver function key to maximising yields on robotic milking systems
Rationing of robotic milking herds needs to ensure liver metabolism, and specifically glucose production, are prioritised to ensure cows can reach their full genetic potential.
According to recent research carried out by Josef J Gross of the University of Bern in Switzerland, the availability of glucose is a major limiter of milk production. Indeed, with greater attention on its provision, whilst maximising cow health, there’s the potential for high yielders to achieve more than 100kg of milk per day, he says.
Such figures may appear extreme, but global milk production has increased steadily for decades. In the US, the average annual milk production per cow has doubled within the last 40 years and is now about six times greater than 100 years ago.
The 100kg cow
Senior Nutritionist for Mole Valley Feed Solutions, Dr Robin Hawkey believes 100kg a cow a day is achievable on high-yielding robotic systems. That’s as long as the four cornerstones to maximising yields are adhered to genetics, management, environment and nutrition.
“On robotic systems, many farmers have invested in genetics and putting robots in a cow-friendly environment with top-notch management, but has nutrition kept pace?” he asks. “It’s about looking at elite nutrition for elite genetics. Without it, you’ll never hit the true yield potential of your herd.”
With reducing milk prices and increasing costs, adding 10-20% more litres could bring big benefits. Thinking about how the diet is balanced to promote glucose production will help drive this uplift in production. Glucose is essential for milk production, immunity and the central nervous system.
The fact that rumen cannot produce glucose itself and relies on the liver to do so, means this stems around managing liver function. In fact, Dr Hawkey says nutritional excellence comes down to managing the liver, rumen, udder and feet (see “The wheel of success for robotic herds” graphic).
“The rumen is the engine and the liver is the gearbox,” Dr Hawkey says. “The rumen and post rumen digestion produces the nutrients and the liver decides what to do with them.”
When rumen nutrients are digested, volatile fatty acids are produced, such as propionate, acetate and butyrate. They enter the blood and go to the liver, where they are converted into glucose through gluconeogenesis.
Energy demand
This glucose is in particular demand post-calving when a cow’s energy demand suddenly increases. In fact, a cow producing 60kg of milk per day can have an energy demand five times greater in peak lactation compared to a dry cow, according to Josef Gross.
Around calving, the cow’s dry matter intake naturally drops creating an energy gap which is even greater in high yielders. Research carried out by the University of Illinois and Cornell University says because dry matter intakes lag the increased nutrient demands for milk production after calving, increased substrate delivery can account for only a small proportion of the increased metabolic activity. As a result, key metabolic pathways, such as overall liver function, must be up-regulated.
Dr Hawkey adds: “When the ruminant digests the TMR, volatile fatty acids are produced. The rumen can support a 30-40 litre cow, but above that, the rest of digestion and metabolism needs to kick in. That includes post ruminal digestion and absorption of by-pass proteins."
The majority of glucose produced by the liver comes from propionate produced in the rumen. This is driven by high-starch diets. However, if too much starch is provided, rumen acidosis can be an issue. As a result, other sources or “glucogenic substrates” are needed. These include:
1. By-pass starch
By-pass starch, such as that delivered by maize grain or maize silage, is digested after the rumen. The products of that digestion (mainly propionate) are used by the liver to produce glucose.
2. Propylene glycol
Propylene glycol can be fed pre-calving to create a “glycogen reservoir” in the liver. This is like “carb loading” before a big race. It can also continue to be fed post-calving through the robot for 60-90 days.
3. Silage fermentation acids.
This is a small source of glucogenic substrates. When cows eat silage, they digest fermentation acids, such as lactic acid and acetic acid. This liberates carbon skeletons which end up in the liver and are used to create glucose.
Glucogenic substrates need to be balanced in the TMR and compound fed through the robot. This will be largely influenced by the amount of maize fed, Dr Hawkey says.
For advice on rationing on robotic milking systems, please call the Mole Valley Farmers Feed Line on 01566 780261 or contact your local nutritionist.
