The low feeding level for pregnant sows, common in commercial practice, has been linked to the occurrence of stereotypies and, in group-feeding systems, with aggressive competition for feed. Whilst the high intake capacity of dry sows limits any attempts to feed a conventional diet at a higher level without concomitant problems of excessive growth and obesity of the sow, it might be possible to control intake by the use of high fibre diets. The suitability of several fibrous ingredients in diets to be offered ad libitum was investigated in the first experiment. Six diets with a high inclusion level of either ulmolassed sugar-beet pulp (SBP), barley straw (BS), oat husks (OH), malt culms (MC), rice bran (RE) or wheat bran (WB) were formulated. A total of 36 sows received one of the diets during a 3-week period. Voluntary feed intake of the SEP diet was significantly lower than that of the other five diets (2.3 kg, 6.4 kg, 7.7 kg, 6.8 kg, 7.6 kg and 7.1 kg day(-1) for diet SEP, BS, OH, MC, RE, and WE respectively, SED 0.65, P < 0.001). Apparent neutral detergent fibre and acid detergent fibre digestibilities were highest with diet SEP (0.84 and 0.80 respectively for SEP vs. 0.33-0.51 and 0.13-0.37 for other diets). Sows receiving diet SEP gained only 2.2 kg in weight, while the sows receiving other diets gained between 39.2 and 47.7 kg (SED 6.3, P < 0.001). In the second experiment, four diets with increasing inclusion level of SEP were formulated. A fifth diet was formulated with both a high SEP inclusion level and high energy density. Each diet was offered ad libitum to eight pregnant sows during a 3-week period. Voluntary feed intake decreased from 5.0 to 3.0 kg day(-1) (SED 0.30, P < 0.001) when the inclusion level of SEP increased from 400 to 650 g kg(-1) . The intake of the SEP fraction was 2.0 kg day(-1) for all diets (SED 0.20, not significant). Apparent nutrient digestibility increased with increasing inclusion level of SEP. It is concluded that a diet containing a high inclusion level of SEP could give an acceptable level of energy intake if used in an ad libitum feeding system for dry sows.
