With soya predicted to be well over £450/t this winter, a new approach based on increased precision could be the way to tackle costs while also improving efficiency.

“If you want to make cows more efficient, the protein and amino acid requirements of the dairy cow have to satisfied first to reduce costs per litre," said Sion Richards from Adisseo.

He says protein systems used in ration formulation have evolved over the last 40 years to better reflect what happens in the rumen, moving from crude protein to digestible protein and most recently to metabolisable protein systems.

“Quite simply, cows don’t need protein per se in the diet. What they need is a supply of amino acids which they then synthesise into the specific proteins such as milk protein or body protein.”

He added that all proteins are made up of a combination of 20 amino acids. When protein is fed to the cow, a significant proportion of the protein is broken down to nitrogen and amino acids. These are reconstituted in the rumen into microbial protein, a good source of amino acids. This microbial protein then passes into the hindgut to supply amino acids for the cow to use.

“This is the microbial protein which is the cheapest way to provide protein to the cow, so we want to optimise this by supplying a synchronised balance of energy and protein to the rumen to achieve maximum microbial protein production."

In the hindgut, microbial protein is joined by bypass protein which is protein which avoided fermentation in the rumen. Together these are used to meet the cow’s metabolisable protein and amino acids requirements.

“To be effective, a diet must provide the supply of amino acids the cow requires. As soon as an amino acid becomes limiting, the performance of the cow is affected. In most UK dairy diets, methionine is the first limiting amino acid with an estimated 95% of diets being deficient, with lysine being the second limiting amino acid.

“The usual approach when formulating diets is to formulate to metabolisable protein and usually to over feed such protein to try and ensure that the cow is supplied with all the amino acids required. The problem is pushing up protein use increases costs, nitrogen excretion and environmental pollution as any nitrogen not utilised and absorbed is excreted, driving down the overall efficiency of nitrogen utilisation (NUE)."

Dr Richards said that a more precise way to meet amino acid requirements is to supplement the diet with rumen protected amino acids, meaning the cow gets what she needs in the most effective form.

In turn, less total protein is needed to supply her needs, reducing costs, reducing excretion and increasing NUE. While the average NUE is about 26% in the UK, some herds have been able to achieve 35% by formulating to amino acid requirement. This change in NUE is the equivalent of feeding around 1kg less protein per cow per day or the equivalent of 2kg less soyabean meal which shows the size of the potential opportunity.

“A typical UK dairy diet is 17-18% crude protein which oversupplies metabolisable protein (MP) by 8-10% while often failing to supply sufficient essential amino acids. A typical diet formulated to balance amino acids will be 14-16% crude protein with a MP oversupply of less than 5% while delivering more closely to what the cow requires.”

He pointed out that the average dairy diet in the EU is already 16% crude protein while diets in the US are closer to 15%. The reason is that there is a bigger uptake in these countries of feeding for specific amino acid balance. Currently fewer than 5% of the UK dairy herds are fed this way.

“Products are available to allow diets to be formulated to lower total crude protein but with specific amino acid supplements to meet requirements more precisely. For example, MetaSmart is a rumen-protected source of methionine.

“Adding 35g/cow of MetaSmart would improve methionine supply and allow a reduction of 1kg/day of soya in the diet. This would make around 0.9kgDMI available which could be used to increase total energy content which in turn would stimulate increased microbial protein production.

“With soya predicted to be well over £450/t this winter, saving 1kg would reduce diet costs by 45p/cow/day. Adding 35g MetaSmart will typically cost less than 20p/day, allowing a reduction in feed costs while feeding the cow better and helping boost milk price through superior milk quality," concluded Dr Richards.