Modification of foraging behaviour and pasture damage by dietary manipulation in outdoor sows

Food restricted sows under extensive conditions forage for considerable periods of time, and this can give rise to serious pasture damage. The objective of this experiment was to study the effects of feeding a fibrous diet (containing 600 g/kg sugarbeet pulp), either at a restricted or ad libitum level, on foraging behaviour and the consequences of this for pasture damage. Twenty-four multiparous outdoor sows, without nose rings, were selected in two consecutive batches of six pairs of sows. The pairs were allocated to one of three feeding regimes in a replicated 3 x 3 Latin square design: a control diet (C) fed at a restricted level (2.5 kg) once daily, a fibrous diet fed at a restricted level once daily (RF) to supply the same energy as treatment C, and a regime with ad libitum fibrous diet (AF). RF sows took longer to consume their ration than control sows (RF = 42, C = 18, SEM 2.7 min, p < 0.001). Liveweight gain over a two week period was highest for sows on the AF regime (AF = 13.0, RF = 3.3, C = 1.0, SEM 2.75, p < 0.01), but there was no significant difference in backfat change. Time sampling of behaviour during 6 h/day showed that sows fed the fibrous diet spent more time lying than C sows (C = 219, RF = 249, AF = 259, SEM 5.1 min, p < 0.001) and less time engaging in foraging behaviours (C = 103, RF = 58, AF = 41, SEM 5.8 min, p < 0.001). Absolute values for pasture damage were highest in C paddocks, but no differences were statistically significant (e.g., C = 12.7, RF = 7.4, AF = 5.0, SEM 3.39 change in % overturned earth per 2-week period). Feeding a high-fibre diet to outdoor sows, at either a restricted level or ad libitum, reduced foraging behaviour but did not reduce pasture damage to commercially acceptable levels. (C) 1998 Elsevier Science B.V.