New system illustrates environmental impact of feeding too much protein at turnout

Mole Valley Farmers has found that balancing rations to complement high protein spring grass makes both economic and environmental sense.
calendar icon 11 April 2020
clock icon 3 minute read

Mole Valley Farmers has recently added nitrogen output to its Precision Nutrition rationing programme, which enables the nitrogen impact of different diets to be assessed. This 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 nitrogen represents unnecessary waste, and can also act as an environmental contaminant.

Mole Valley Farmers’ new assessment for nitrogen was 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 percent CP in the dry matter (DM) or 16.7 percent. 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 percent 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 Feed Solutions Technical Manager, Dr Matt Witt says the fact spring grass can be anywhere between 20-30 percent CP (DM) - depending on the season - makes 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 explains. “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 stresses that with careful consideration, it is possible to tweak diets so production aims are maintained, whilst also benefiting 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 Mole Valley Farmers has decided to take the lead, explains Dr Witt.

“We want to understand nitrogen excretion from dairy cows and how that’s influenced by diet,” he explains. “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 Mole Valley Farmers’ Precision Nutrition rationing program follows the launch of methane excretion calculations at February’s Dairy-Tech.

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