DAIRY farmers have been urged to keep a close eye on the energy intakes and sources of their cows this winter.

North Yorkshire farmer and 2009 Gold Cup winner Geoff Spence includes a balanced C16/C18 rumen protected fat in the diet of his high yielding cows.

However, he recently attempted to cut back on the levels in the ration to reduce costs and rely more on the energy provided in his forage.

Mr Spence, of Lowfields Farm, Brompton, near Northallerton, said: "In our high yielding group, we’ve always included Golden Flake, a rumen protected fat with a high level of C18fatty acids, to help push yield while maintaining body condition.

“This autumn, because of the high ME value of our first-cut grass silage, we halved the feed rate of Golden Flake from 300g/head/day to 150g/head/day.

"To our surprise, this decision resulted in an immediate drop in 1.5l/cow/day, which equated to a loss of 30.86p/cow/day, which across the group of 170 cows was a loss of £15,720 for the month.

"In addition, bulling activity also reduced, and for this reason we quickly reinstated the higher feed rate to get the yield and fertility back on track."

The loss was calculated based on a milk price of 30.44ppl. The net loss of 45.55p/cow/day, took into account 14.8p for the cost of 150g of Golden Flake.

Bethany May, ruminant nutritionist at Trident Feeds, said the herd's dramatic drop in yield was due to the removal of the additional energy in the form of C18 fatty acids.

She said: "C18 fatty acids have a glucose sparing effect which can cause the cow to mobilise less body reserves, which can cause appetite depression, meaning additional energy intake. The C16 fatty acids can be used to lift milk yield and milk fat percentage, increasing the value per litre. If removed, the cow may no longer be able to sustain the high levels of production, which was seen in Geoff’s herd.

"It’s also important to note that rumen protected fats such as Golden Flake, can also help to maintain or increase body condition through offsetting negative energy balance (NEB), providing essential energy for the cow, which is linked to improved fertility."

Miss May said this seasons forages are feeding well, with high ME values, resulting in some producers pulling back on supplementary energy sources and relying heavily on forages.

"However, this reduction in other key energy sources, such as fats and carbohydrates, means in some cases, early lactation energy requirements aren’t being met, and productivity is therefore negatively impacted," she said.

"Traditionally the use of supplementary fats in fresh cow rations has been questioned, especially when forages are high in energy. However, new research supports the use of protected fats, highlighting the importance of choosing the right types of fat to avoid depressed intakes.

"Producers should therefore look to include rumen protected fats, that are high in C16 and C18 fatty acids alongside good quality forages to boost energy density and minimise NEB."