Balancing rations to complement high protein spring grass not only makes economic sense, but can also help the environment, according to calculations carried out by Mole Valley Farmers.
Mole Valley Farmers recently added nitrogen output to its Precision Nutrition rationing programme and this has enabled the nitrogen impact of different diets to be assessed. It is presented as estimated nitrogen output in grams per day and grams per litre.
Cows will naturally excrete some dietary protein as waste nitrogen. Some of this represents unnecessary waste and can also act as an environmental contaminant.
Therefore, Mole Valley Farmers’ new assessment for nitrogen is now used to establish the impact of feeding different levels of protein, alongside spring grass. In the example, grass was supplemented with a combination of buffer feed and parlour concentrates balanced to deliver two different protein levels; 18.9% CP in the dry matter (DM) or 16.7%. 
Both diets were made up of different ingredients, but designed to deliver 38 litres of milk. The results showed that offering higher protein feeds, along with spring grass had no benefit on production. 
It also resulted in 11% more nitrogen being lost to the environment, compared to the lower protein ration. This equated to a predicted 520g/cow/day of nitrogen excreted on the higher protein ration, versus 461g/cow/day on the lower protein diet.
Mole Valley’s technical manager, Dr Matt Witt, said the fact spring grass can be anywhere between 20-30% CP (DM) – depending on the season – made it easy to over-supply protein, especially when also buffer feeding and feeding through the parlour.
“All of these sources can quickly take total dietary protein levels well above nutritional targets,” he explained. “That’s why it’s important to reduce dietary protein levels in complementary feeds like buffer mixes and parlour cakes to complement grazed grass at turnout.”
Dr Witt stressed that with careful consideration, it is possible to tweak diets so production aims are maintained, whilst also benefitting the environment.
“With protein feeds having some of the highest feed costs, such a strategy is unlikely to increase costs, and could in fact lower them,” he adds. “Our results show that there is scope to put rations together that deliver on production and margin over purchase feed, whilst also having a positive impact on the environment, simply by thinking about the feeds you choose.”
Although there are currently no penalties, or rewards for nitrogen excretion, growing pressure to reduce farming’s environmental footprint means the industry needs to be prepared for change.
That’s why we have decided to take the lead, said Dr Witt. “We want to understand nitrogen excretion from dairy cows and how that’s influenced by diet. We’re trying to find out what normal looks like in terms of nitrogen excretion, equip ourselves for the future and help our farmer customers be on the front foot.”
The addition of nitrogen output parameters to the rationing program follows the launch of methane excretion calculations at February’s Dairy-Tech.