6 December 1996

Silages falling short of paper performance…

By Jessica Buss

DAIRY producers are being warned that some of this years high quality grass silages are not feeding as the analysis suggests – reducing milk yields and increasing the risk of infertility or acidosis.

Yet nutritionists are baffled by whats causing poor performance.

"Some silages just arent as good as it suggests on paper," says Midlands Genus consultant Ian Browne, who recommends producers re-analyse their silage.

He reports that cows have been struggling to do 25 litres on 30-litre rations, despite sufficient dry matter intakes and adequate protein and energy supply.

Differences between the silage and its analysis may be due to aerobic spoilage, or because energy is being used to mop up free nitrogen in high protein silages, says Mr Browne.

Neil Adams, his colleague in Wiltshire, has also seen more variation in silage quality within clamps. "Rations need fine tuning all the time and silage samples should be sent for analysis frequently," he says.

ADAS nutritionist Bruce Cotrill suggests the instability of the silages, some of which were analysed some time ago, could be one reason why cows arent performing as predicted from the silage analysis or their own intakes.

Poor aerobic stability is also the cause of clamp face slip that allows extra air into the silage, says Mark Harrison, consultant to Farmlab.

"A silage with a core sample analysis of 11 ME could drop to 9.5 ME at the face after four days through poor stability." He advises analysing what cows are eating from the exposed face.

In other situations he attributes poor performance to high lactic acid silages. These are well preserved but not good for animal performance, especially when fed in diets that are designed to reduce butterfats, he says.

Dr Tony Andrews of the Royal Vet College suggests early lactation cows losing bodyweight are likely to be in energy deficit, so it is important to check body condition score.

He advises weekly scoring the same sample of six cows from each 100 and comparing scores with milk yields and diets.

Ensuring animals take plenty of exercise would improve their efficiency in dealing with energy from feed, he says.

"Animals often dont get enough exercise in winter – and taking more would imGom prove the efficiency of dealing with energy from feed," he says.


ENERGY DEFICIT


How to avoid it:

&#8226 Re-analyse silage frequently.

&#8226 Ensure cows get exercise in winter.

&#8226 Condition score regularly.