ANIMAL PRODUCTION EVALUATION OF HERBAGE VARIETIES .2. COMPARISON OF ABERYSTWYTH S184, ABERENDURA AND GRASSLANDS HUIA WHITE CLOVERS

Perennial ryegrass/white clover (Lolium perennel Trifolium repens) pas tures of three white clover varieties were compared at UK lowland (Pla s Gogerddan, PG) and upland (Bronydd Mawr, BM) sites over three harves t years (1989-91) under continuous variable stocking (ewes and lambs u ntil weaning and lambs thereafter). Mean annual lamb output from small -leaved S184 (1179 kg ha(-1)) was 29% greater than that from prostrate small-leaved AberEndura at PG with medium-leaved Huia also giving 19% more output than AberEndura. At BM, output from 5184 (863 kg ha(-1)) was 19 and 14% greater than that from AberEndura and Huia respectively . The differences in lamb output between the small-leaved varieties ow ed to a combined effect of higher individual lamb growth rates and gre ater stock-carrying capacity, both of which were more pronounced in th e post-weaning period. The higher output from S184 relative to Huia at BM was attributed to higher stocking rate, particularly after weaning . Clover productivity and persistence were also studied under three cu tting-only managements at PG. Performance under a treatment cut at 2-3 cm every 10 d (T1), which is synonymous with assessment of persistenc e in UK National List testing, was poor with clover growing point numb er of only 498 m(-2) compared with 4906 m(-2) on the grazed sward in a utumn 1991. Although productivity and clover content under T3 (cut at 3-4 cm every 42 d - similar to National List yield regime) gave the sa me varietal ranking as lamb production, there was an under-estimation of the small-leaved varieties, particularly AberEndura, relative to Hu ia. An intermediate treatment (T2), cut at 3-4 cm every 21 d, also ove r-estimated the performance of the medium-leaved variety. Herbage data from ground level sampling every 21 d using exclosure cages on the gr azed swards were also poorly related to lamb performance. These result s highlight the effect of clover variety on lamb production, which app eared to be independent of leaf size, and also confirm the existing pr oblems associated with assessment of white clover varieties using a cu tting regime.