The protein content of grass silage on Irish farms has dropped over the past 10 years, according to Teagasc’s Padraig O’Kiely.

And, he said, if protein levels of silage are low, cattle simply won’t thrive.

“Low protein silage will have a negative impact on animal performance through reduced feed conversion efficiency.

“In some cases, silage can have a low protein content while being highly digestible and this may occur as a result of lower nitrogen input into grass crops prior to harvest,” he said.

He also said that farmers should aim to have a 12-14% protein content in their silage.

When the protein content of grass silage drops below this level (12-14%), cattle will require an additional source of protein in their diets, he said.

“Cattle fed on highly digestible silage, with low protein levels, will require an additional source of protein to address this deficit. How much should be added will depend on the protein content of the supplement.

“In many cases, concentrates have surplus levels of protein to address this issue, but when both the silage and concentrate level is low, an additional protein source must be added to the diet,” he said.

Teagasc research suggests that, weanlings will require a 16% crude protein ration if they are being fed a low protein silage.

And, freshly calved cows, where silage is the sole source of forage will need a ration with a crude protein content of 20%.

O’Kiely also advised farmers to carry out silage testing, to be fully aware of both the protein and energy content of their silage, as there is wide variation from farm-to-farm.

A recent Glanbia silage analysis report, shows that the protein content of silage is low this year, with the bottom 25% of samples having an average protein content of 10.1%.

The report also says that the average crude protein content is lower than it should be at 11.9%.