Straw bedding provides a number of functions which affect the behaviour and welfare of pigs including comfort, recreation and diet. It has been suggested that the importance of these different functions will vary depending on the life/production stage of the pig. The available literature indicates that all of the above functions are relevant to all the different stages except newly born piglets. The occupational value of straw appears to be highly important. The actual mechanisms by which straw affects the pig's motivation systems are still poorly understood. It is therefore uncertain whether suitable alternatives to bedding exist or even if straw bedding in itself is completely satisfactory. Until satisfactory alternatives are available straw bedding should continue to be recommended in terms of pig behaviour and welfare.

A welfare assessment method was built, based on criteria related to behaviour, lesion scores and human/animal interactions, and tested thereafter in two main types of farms differing by their type of floor: either concrete, fully or partially slatted (C; n = 42) or straw bedding (S; n = 40). Observations were carried out on 40 to 60 pigs per room for three periods (90, 130 and 162 days of age, respectively, for P1, P2 and P3). Behaviour was assessed through five scans with a two-minute interval between two successive observations. Each behaviour was expressed in relation to the total amount of active behaviours. Injuries were scored on a three-level scale (none, mild, severe). Social behaviour was significantly more important at P1 whereas behaviours related to disturbance were more frequently observed at P3. Bursitis did not differ significantly between periods in S farms but did so in C over time. Small differences were seen between periods for injuries: severe lesions (scratches) and lameness were rare on the different flooring systems and severe wounds and tail lesions were less frequent in S than in C farms. Investigation of the environment was more pronounced on S floors, whereas positive social behaviour was more prevalent in C. All criteria studied were characterised by a noticeable variability in both floor types, showing room for improvement in terms of animal welfare in some farms.

Both dietary fermentable carbohydrates and the availability of straw bedding potentially affect activity patterns and energy utilisation in pigs. The present study aimed to investigate the combined effects of straw bedding and fermentable carbohydrates (native potato starch) on energy partitioning in growing pigs. In a 2 × 2 factorial arrangement, 16 groups of 12 pigs (approximately 25 kg) were assigned to either barren housing or housing on straw bedding, and to native or pregelatinised potato starch included in the diet. Pigs were fed at approximately 2.5 times maintenance. Nitrogen and energy balances were measured per group during a 7-day experimental period, which was preceded by a 30-day adaptation period. Heat production and physical activity were measured during 9-min intervals. The availability of straw bedding increased both metabolisable energy (ME) intake and total heat production (P < 0.001). Housing conditions did not affect total energy retention, but pigs on straw bedding retained more energy as protein (P < 0.01) and less as fat (P < 0.05) than barren-housed pigs. Average daily gain (P < 0.001), ME intake (P < 0.001) and energy retention (P < 0.01) were lower in pigs on the native potato starch diet compared to those on the pregelatinised potato starch diet. Pigs on the pregelatinised potato starch diet showed larger fluctuations in heat production and respiration quotient over the 24-h cycle than pigs on the native potato starch diet, and a higher activity-related energy expenditure. The effect of dietary starch type on activity-related heat production depended, however, on housing type (P < 0.05). In barren housing, activity-related heat production was less affected by starch type (16.1% and 13.7% of total heat production on the pregelatinised and native potato starch diet, respectively) than in straw-enriched housing (21.1% and 15.0% of the total heat production on the pregelatinised and native potato starch diet, respectively). In conclusion, the present study shows that the availability both of straw bedding and of dietary starch type, fermentable or digestible, affects energy utilisation and physical activity of pigs. The effects of housing condition on protein and fat deposition suggest that environmental enrichment with long straw may result in leaner pigs. The lower energy expenditure on the physical activity of pigs on the native potato starch diet, which was the most obvious in straw-housed pigs, likely reflects a decrease in foraging behaviour related to a more gradual supply of energy from fermentation processes.

At the Iowa State University Armstrong Research and Demonstration Farm in southwestern Iowa, a Swedish feeder pig production system was studied and demonstrated for 2-1/2 years. The system is based mainly on straw bedding, simple buildings, and intensive management. The system was designed to minimize pig stress and use of subtherapeutic antibiotics in the feed. Gestating and breeding sows were group-housed in a hooped structure with individual feeding stalls. Large round bales of cornstalks were used for bedding. Farrowing, lactation, and nursery phases were housed in a remodeled hog house. Cubicles with rollers and oat straw bedding were used for farrowing. Two groups of Yorkshire × Landrace sows bred to Hampshire boars produced feeder pigs in the system. Conception rates averaged 95%, and litter size averaged 11.3 live pigs/litter. Sows were allowed to select their own bedded farrowing cubicle. Prewean pig mortality, mostly from crushing, was high (29%), occurring primarily in the first 3 days. At 2 weeks of age the cubicles were removed and group lactation occurred. After group lactation the average pig weaning weight was 10.4 kg at 33.9 days of age. At weaning the sows were removed, and the pigs remained in the bedded farrowing/lactation room for 24 additional days. The pigs weighed 24.8 kg at 60 days of age, and overall nursery phase average daily weight gain was 549 g/day. Overall pig health was excellent with no major clinical diseases confirmed. The demonstration exceeded reproductive performance measures of typical small- and mid-sized Iowa farms.