DIET SELECTION BY CATTLE OFFERED A CHOICE BETWEEN SWARDS TREATED OR UNTREATED WITH SLURRY - EFFECTS OF APPLICATION METHOD AND TIME SINCE APPLICATION

Reduced contamination of herbage following shallow injection rather th an surface spreading of slurry may affect the acceptability to cattle of swards that recently received slurry. A short-term, indoor test was used to assess selection by cattle between untreated swards, and swar ds treated with slurry. Grass turves (0.25 m(2)) were placed on a 20 c m deep soil base in a sward box. Dairy cow slurry, applied at a rate o f 36 m(3) ha(-1), was either spread evenly on the surface (S), or pour ed into two slots cut into the sward 10 cm apart and 5 cm deep, to sim ulate shallow injection (I). Control swards (C) received no slurry. In dividual Limousin x Friesian steers were offered paired combinations S vs C or I vs C at 10 min, 2 h, 24 h, 4 days, 7 days, 14 days or 21 da ys after slurry application (six steers per treatment on each occasion ), and allowed to take 50 bites (Phase 1) after which grazing was term inated. Three animals per treatment were then allowed to resume grazin g until no further grazing occurred (Phase 2). A greater time was spen t examining and eating C, a greater proportion of bites was taken on C and sward surface height (SSH) was reduced more on C compared with th e treated sward S or I in both S vs C and I vs C, in both Phase 1 and Phase 2. More time was spent eating on I, a greater proportion of bite s was taken on I and SSH was reduced more on I in I vs C than on S in S vs C, in both Phase I and Phase 2. The effect of method of slurry ap plication to the treated sward was to modify grazing on the adjacent c ontrol sward. Thus, SSH reduction was greater on C for I vs C than for S vs C in Phase 1, although fewer bites were taken. The addition of w ater immediately after surface application of slurry (SW) gave a signi ficant increase in the time spent grazing and the proportion of bites taken on SW when offered with a control sward with water applied (CW) compared with S for S vs C.