This study consisted of a series of experiments which investigated the water use of growing/finishing pigs (25-90 kg), newly weaned pigs (5- 12 kg) and gestating sows. Drinker type was found to affect water use in growing pigs. For example significantly more water (28 %) was used from Mono-flo nipple drinkers than Arato bite drinkers (P<0.01). For all classes of pigs studied water use was significantly increased by increasing the water delivery rate. The percent increase in water use over the extremes of water delivery rate tested in individual trials were respectively: ration fed growing pigs, 105 % (300-900 cm³ /min P<0.001); ad libitum fed growing pigs, 52% (200-1100 cm³/min P<0.01); gestating sows, 25% (500-2500 cm³/min P<0:01); and newly weaned pigs 109% (175-700 cm³ /min P<0.001). In newly weaned piglets, increasing the water delivery rate from 175 to 700 cm³/min resulted in a significant increase in feed intake (44 g/piglet/day, P<0.001) and growth rate (37 g/piglet/day, P<0.01). For growing pigs (27-55 kg), a relationship was established between water intake, feed intake and liveweight, from which it could be hypothesised that the pig had a limit to daily volumetric intake. This was found to be 12.0 ±1.2 % of liveweight. When feed intake was restricted, water intake increased to maintain the 12% volumetric limit. This hypothesis was validated from other published work extending the weight range to 105 kg. Evidence was produced indicating that newly weaned pigs also have a constant volumetric daily limit. It is suggested that in cases where feed intake needs to be restricted, water intake could be manipulated in order to limit feed intake. This would permit the wider use of ad lib feeding systems and the welfare benefits these allow. The water use of a grower/finisher unit was modelled according to a 12 % volumetric limit and the factors affecting water intake and wastage. The water intake of grower/finisher pigs was predicted using this model. This enabled the percentage of water wasted by different drinker types and delivery rates to be estimated. For wet fed pigs, increasing the water to feed ratio from 1.63:1 to 3. 25: 1 significantly increased feed digestibility (P<0. 05). As many experiments conducted to evaluate the digestible energy of feeds may have used low feed to water ratios (generally around 2:1) it is suggested that many of these studies have attributed incorrect nutritional values to raw materials used in diets for pigs.

A programme of study was undertaken to assess the welfare status of multiparous gestating sows housed in dynamic groups in a straw yard and fed by electronic sow feeders (ESF). Comparison of production figures from the Seale-Hayne herd with those nationally confirmed its status as a typical commercial unit. In an initial series of investigations, detailed ethograms were compiled to describe the animals' repertoire of activities and interactions. Lying and straw manipulation were found to be the predominant behaviours and attacks directed towards the head were the most commonly performed type of interaction. Although there was little evidence of aggressive behaviour, most interactions were found to occur in areas where there was an obvious source of competition, namely the feeding and lying areas. A recording scale was devised to assess the level of skin damage arising from aggressive interactions. Whilst data revealed a relationship between parity and the extent of injury, both the frequency and intensity of injury were found to be low for all animals and there was very little evidence of vulva biting, commonly cited as a major criticism of group-housing systems. Animals were observed to rest predominantly in the lying area. There was an association between parity and resting location, with older animals occupying those areas perceived to be more favourable. Recently introduced gilts and sows were observed to integrate gradually with the main group. An argument is put forward for the existence of sub-groups based upon parity within the main group, although it was concluded that it was difficult to prove such a theory. A series of voluntary feed intake (VFI) trials revealed that the animals' feeding motivation was not satisfied by the allowance fed in gestation. Results from a trial when animals were offered a high fibre, low energy diet in comparison with their conventional feed suggested that the animals had a requirement for a certain level of energy and were not motivated simply by a desire for gut-fill. However, a subsequent investigation into the animals feeding behaviour did not reveal any evidence of a frustrated feeding motivation; there was little evidence of non-feeding visits and few animals were recorded in the feed queue throughout the day. It is concluded that sows can be group-housed in a dynamic system on a restricted feed intake without detriment to their welfare or productivity status. A number of factors were found to be critical to the success of such a system including the freedom for animals to behave as individuals, the regular provision of fresh straw and adequate space for newly introduced animals to integrate gradually with the herd.

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