What is feed efficiency?
Feed efficiency is a metric commonly used by the dairy industry to describe how well a cow is able to convert feed and forage into milk – the more efficient she is, the less feed she needs to produce a litre of milk. As an example, very efficient cows in early lactation have the potential to produce up to 2kg of energy corrected milk (ECM) for every 1kg dry matter intake (DMI), with top herds achieving 1.7L per kg of feed throughout lactation.
There is a wide variation amongst individual cows regarding efficiency, with several factors playing into this including genetics, animal health, stage of lactation and nutrition. At the heart of this is the rumen, with its trillions of microbes, or “bugs”, that digest feed and forage, which means that nutrition and management have a significant role to play in driving feed efficiency.
It may be tempting to reduce levels of concentrate feeding to lower expenses. However, when you reduce feeding levels alone, this can negatively impact yields and constituents.
An essential fact to remember is that a cow in early lactation will always prioritise milk production over the maintenance of her own body reserves. When the diet does not provide enough to cover demands for milk, she will mobilise energy from body reserves to make up this deficit. This results in excessive body condition score (BCS) loss which leads to poor health, fertility and higher rates of lameness later in lactation, meaning additional costs and inputs. Minimising BCS loss in early lactation is critical to preparing cows for a successful breeding period.
To avoid this happening, it is critical that we focus on DMI, especially during early lactation as cows come to peak yield and intakes gradually rise. As mid- and late lactation performance are both influenced by peak yield, cows should be sufficiently supported during this period with a diet that is balanced to meet their requirements, reach their genetic potential and minimise excessive weight loss.
A high-quality silage given ad lib can alone provide an average fully housed cow enough to cover maintenance plus 13-14L milk. Additional concentrate should be provided through the parlour or diet feeder to complement existing forage and ensure nutritional needs are met. As a rule of thumb, cows yielding 25L/day and fed high quality silage (73 D-value) will require around 5-6kg of concentrate feed. Lower DMD silage will require higher levels of feeding to achieve a given yield.
In a typical Holstein/British Friesian cow, the first 6kg of concentrate fed will result in a conversion of 2.0kg milk per kg of feed consumed. After this, higher rates of feeding (6kg+) will typically give around 1-1.5kg milk/kg feed. (Cross-bred herds may not respond as well, and higher merit cows may continue to respond at higher levels of feeding.)
Spring grass considerations
For herds where grazing makes up a larger proportion of the diet, there are a several key considerations for optimising grass utilisation in the rumen.
Spring grass can be high in sugars and and low in structural fibre, which can lead to poor rumen function. Additionally. high levels of protein in the form of RDP can cause excess ammonia breakdown, which drains energy from the cow and can cause unfavourable conditions for embryo implantation if this is not balanced nutritionally. Both can be detrimental to cow performance and lead to yield and condition loss, fertility issues and illnesses such as ketosis. Varying levels of moisture can also wreak havoc on intakes.
For higher yielding herds, buffer feeding can provide an effective tool to help counteract low dry matter, declining quality and availability of grass to ensure that nutrient requirements are met. A nutritionist or feed advisor can help you to work out how much supplementary or buffer feeding your herd requires depending on your circumstances.
Feed the rumen, feed the cow
The cornerstone of every dairy diet is forage, including silage and grazed grass. Its quality, consistency and digestibility are all key considerations for how easily the cow – and the microbes in her rumen – can make use of it to ultimately produce milk.
The rumen and the microbes within it act as the engine of the cow, providing up to 80% of the energy and 60% of protein requirements through the digestion of feed. This fact alone makes the rumen a significant opportunity for driving feed efficiency, as well as profitability, in our herds.
The rumen microbes work similarly to an anaerobic digester, breaking down forage and feed in a sealed environment. Research has found that this microbiome is responsible for more than 60% of variability in feed efficiency. Some of this variability is due to differences in the microbial make-up or profile of individual cows, which can significantly affect how much DMI is required to produce a litre of milk. This difference can be up to 2.5kg less DMI required for more feed efficient cows which equates to approximately 8-10kg FW of a typical grass silage, saving 1 tonne FW of silage per day in a herd of 100 dairy cows with no loss in yield.
Support the rumen microbes with Actisaf live yeast
Actisaf live yeast supports growth of specific species of rumen microbes that are highly correlated with fibre digestion and feed efficiency.
By optimising the rumen environment to allow microbes to thrive and extract more nutrients from the diet, Actisaf also buffers the rumen and has been proven to do this more effectively than sodium bicarbonate. The risk of acidosis or sick stomachs in herds is also significantly reduced, along with any potential loss in yield.
A recent study from the University of Nottingham found that supplementing Actisaf to a high performing herd in the first four months of lactation increased feed efficiency by 5.5%. This was achieved primarily through increased digestion of fibre in the rumen, which yielded an extra 5.9% (or 2.8kg) of energy corrected milk with no change in feed intakes or body condition loss – providing an 8:1 return on the cost of Actisaf.
Effectively, the cows reached higher peak yield, which can translate to up to 580L of extra milk per 305-day lactation - lowering cost of production by more than 1 ppl. For a farm supplying one million litres a year this equates to £10,000 per year, presenting a significant opportunity for dairy farmers this spring.