8 March 2002

Best substitute for pasture in sheep systems found

High feed costs are

motivating many producers

to experiment with

home-grown feeds, with

variable results.

This special, edited by

Hannah Velten, kicks off

by looking at trials which

show their potential, but

raise agronomy concerns

LOTUS (trefoil) has the potential for substituting grass in sheep systems because of its nutritive quality. But there are problems with crop establishment and persistence.

Mariecia Fraser, of the Institute of Grassland and Envir-onmental Research (IGER) has studied the effect of lotus when fed as a grazed crop to finishing lambs.

Suffolk x Mule lambs from a late lambing flock were grazed between September and Novem-ber on plots of Leo variety lotus at IGER Aberystwyth. They were finished at fat class 3L.

Performance comparison was made between lambs on red clover, lucerne and ryegrass (see table). "Compared with lambs on grass, the group on lotus showed higher growth rates and took fewer days to finish, without putting on condition," says Dr Fraser.

The increase in dry matter intakes of lotus over grass were not found to be statistically significant in explaining increased performance, but rather the amount of nitrogen retained in the animal.

"Much of the 23% crude protein content of lotus remained in sheep, rather than being lost as faecal nitrogen," she adds.

Lotus contains high levels of condensed tannins, says IGERs Mark Robbins. "These bind protein and smuggle it through the rumen, decreasing N emissions into the environment. This is an important quality in animal feed."

However, despite its nutritive quality, lotus is not renowned for establishing well or persisting. In fact, IGER trials of lotus have been badly hampered because of crop failure over winter and its lack of competitiveness against weeds and grasses, says Dr Fraser.

In an attempt to find a variety suited to the site, IGER research-ers have traced 14 lotus varieties. Early indications show German and Czech varieties may be successfully grown in the UK. &#42

Performance effect of forage legume grazed

Red clover Lucerne Lotus Ryegrass

Growth rate (g/day) 229 200 277 182

Days to finish 40 38 35 49

Eye muscle depth (mm) 27.1 25.7 26.4 25.9

Subcutaneous fat depth (mm) 4.1 3.6 3.8 3.9

Intake (kg of dry matter/day) 1.66 1.81 1.41 0.98