With the liver having a vital role in supplying energy to the cow, paying close attention to liver function is crucial. Hannah Park reports.
Meeting high yielding dairy cows changing nutritional requirements is a constant challenge, and the main focus is often on the rumen. Cargill ruminant technology specialist Dr Philip Ingram, says the mantra feed the rumen not the cow has gone a long way to improving dairy cow diets.
But, he adds many herds are failing to perform, even on the most carefully formulated rations. He says: We are often finding that this is because liver function is sub-optimal. As advisers and nutritionists, we often need to think more about the vital role played by the liver in supplying energy to the cow.
The process of extracting energy from feed starts in the rumen, but key to its success is the cows liver which has many functions, Dr Ingram explains, including energy management and detoxification of the blood.
The liver should be viewed as the cows energy-control centre.
This organ, which turns the volatile fatty acid propionate produced in the rumen into glucose, or energy, and makes it available to the cow, is the engine room.
It has to be working efficiently, or be primed, to allow the cow to perform in terms of milk yield, health and fertility, to its full potential.
About 85% of ruminal propionate is built into glucose by the liver, and fat mobilised from body reserves must be processed there before it can be used for energy.
And cows do require a huge amount of energy, for body maintenance and for producing large volumes of milk, particularly in peak lactation. Average daily yields of 45kg are not unusual.
During transition and early lactation, cows will use body condition to support milk yield.
This can reduce the livers ability to manage energy which is a major cause of reduced performance, and production diseases, in early lactation says Dr Ingram.
Propionate produced in the rumen is key when it comes to energy to support maintenance, milk production and fertility.
About 85% of the propionate is transformed into glucose by the liver so good liver function is vital.
If it is sub-optimal, the potential energy available from the feed consumed by the cow, and converted into propionate by the rumen, will be limited. Ensuring good liver function allows the cow to maximise the production of the energy she needs from her ration.
Good rumen function and feeding a balanced ration, which provides the correct ratios of protein and energy, as well as a stable rumen pH, are all important, along with good feed consistency, presentation and management protocols, he says.
But even when focusing on and removing these potential bottle necks, poor liver health can still be a barrier to feed efficiency. Cows need good liver health in order to manufacture glucose efficiently. The liver can be a major bottle neck if it is not operating efficiently and this can cause knock-on production and health issues.
Management, such as maintaining a steady and optimal body condition score throughout the cows production cycle and ensuring good feed intakes during the close-up dry period can help here.
There are also products that can improve liver function, he says, including Cargills LiFT.
Reducing cow stress and keeping immune activation to a minimum will also support a smooth transition period.
The aim is to avoid immune activation caused by stress that might be linked to factors like poor diet, poor hygiene or gut irritation.
This starts at drying off period, by paying close attention to protocols, such as hygiene and health routines in the parlour and housing to avoid sources of infections. And at calving, making sure pens and equipment are clean.
Dry cow housing should be well ventilated and dry, and cow moves should be minimised, he says.
Every time a cow moves to unfamiliar surroundings her intake drops for a few days which disrupts her energy supply just when she needs stability.
A well-balanced diet with good feed access is essential in transition cow care.
