Crossbreds prove best financially.
Barbara Mclean, of ADAS, said four different crossbred ewe types - all out of Welsh Mountain ewes - had been compared to pure bred Welsh Mountain ewes over a long-term study.
It found that the crossbred lambs performed better financially than pure Welsh lambs.
In the study, Welsh ewes were crossed with Texel, Cheviot, Dorset and Lleyn rams, and the resulting crossbreds were tupped with a Suffolk ram. The Dorset cross ewes had the best financial return, rearing the heaviest weight to weaning.
Using average market prices, Dorset crosses at weaning gave margins of pounds 41.96 compared to pounds 34.57 for a Welsh ewe.
Texel and Lleyn crosses ewes had average margins of pounds 40.87 and Cheviot crosses pounds 39.97.
The research was revealed at an open day at ADAS P wllpeiran.
Barbara Mclean said: "We evaulated a number of options - including changing to a bigger hill ewe, genetic improvement or using a crossbred ewe."