5 May 1995

Top silage ups lamb

birth weights

Researchers north and south of the Irish border provide the latest tips on livestock production and silage-making. Rebecca Austin reports

EARLY-cut, precision-chopped and well-fermented silage increases intake as well as ewe performance, has reflected in lamb and ewe weights at birth, according to trials at Hillsborough Aricultural Research Institute in Co Down, Northern Ireland.

Wilting the crop before ensiling also improves intake levels, but has little effect on ewe performance.

In the Hillsborough trials, cutting the crop in mid May, rather than early June, saved 12kg of concentrate a ewe over the last six weeks of pregnancy.

Ewes fed leafy early cut silage consumed more forage than others offered a late cut stemmy silage. The former group also produced heavier lambs than those fed an inferior silage at a higher concentrate level.

Cutting silage early increases the energy value of ensiled grass, but fermentation is likely to be poorer than from a later cut. The report therefore recommends producers pay close attention to achieving a good fermentation when making early cut silage.

Work at Hillsborough proves that sheep are very sensitive to the length of silage offered to them (see table). More than 80% of grass ensiled with a precision-chop harvester is in lengths of less than 5cm, while flail harvesters only achieve 20% in the same bracket.

The higher intake of precision chop silage by sheep at Hillsborough was reflected in higher birth weights and heavier ewes. Subsequent trials have consistently found intakes of precision-chop silage 30% better than flail harvested material.

As with cattle, higher dry matter also encourages higher intakes. An increase of about 5% in dry matter content at the time of ensiling improved silage intake by the same percentage. But in this case there was no marked change in ewe performance, when compared with unwilted silage intakes.

Ewes are more likely to produce weak lambs and to lack sufficient milk at lambing if they are fed untreated grass which has been ensiled at a very high moisture level.

Such practice generally produces a silage with a pH around 4.4 and a high ammonia content.

With a good quality, well fermented silage, consumption is usually about 1kg dry matter (DM), or 5kg fresh material a day during the last six weeks of pregnancy.


Effect of harvester type and concentrate level on ewe performance

Precision chopFlail

Silage DM intake in1.391.05

mid pregnancy (kg a day)

Concentrate given in last186186

six weeks pregnancy (kg)

Silage DM intake in1.061.090.840.66

late pregnancy (kg a day)

Ewe weight change from+1.80-2.40-2.90-8.00

housing to lambed (kg)

Lamb birth weight (kg)5.405.105.204.80