Review: Drinking water for liquid-fed pigs.

Liquid feeding has the potential to provide pigs with sufficient water to remain hydrated and prevent prolonged thirst. However, lack of permanent access to fresh water prevents animals from drinking when they are thirsty. Moreover, individual differences between pigs in a pen may result in uneven distribution of the water provided by the liquid feed, leading to some pigs being unable to meet their water requirements. In this review, we look at the need for and provision of water for liquid-fed pigs in terms of their production performance, behaviour, health and welfare. We highlight factors which may lead to water ingestion above or below requirements. Increases in the need for water may be caused by numerous factors such as morbidity, ambient temperature or competition within the social group, emphasising the necessity of permanent access to water as also prescribed in EU legislation. The drinkers can be the target of redirected behaviour in response to feed restriction or in the absence of rooting materials, thereby generating water losses. The method of water provision and drinker design is critical to ensure easy access to water regardless of the pig's physiological state, and to limit the amount of water used, which does not benefit the pig.

High-fiber diets in pregnant sows: digestive utilization and effects on the behavior of the animals.

Twelve pregnant, multiparous sows were assigned during gestation to three dietary treatments in a 3 x 3 Latin square design to evaluate the effect of increasing levels of crude fiber (CF): a conventional diet low in CF (L, 15.8 MJ DE/kg of DM, 3.3% CF), a diet with a medium level of CF (M, 14.4 MJ DE/kg of DM, 10.6% CF), and a high-fiber diet (H, 12.9 MJ DE/kg of DM, 18.1% CF). The daily feed supply was adjusted to provide the same 33.4 MJ of daily digestible energy (2.4, 2.7, and 3.0 kg/d for diets L, M, and H, respectively). Over the day, a shorter time standing was spent when sows received the H diet (291 min/d) compared with the L (363 min/d) and M diets (324 min/d). Duration of feeding was longer with the high-fiber diet. Mastication represented the main part of the feeding activity in sows fed the H diet (56%) and was reduced with the M and L diets (40% and 25%, respectively). Feeding rate increased when fiber level decreased (67, 120, and 152 g/min for the H, M, and L diets, respectively). Feeding the fibrous diet reduced the incidence of nonfeeding oral behaviors. These results show that high-fiber diets can reduce apparent feeding motivation of pregnant sows and, thus, improve the welfare of sows subjected to feed restriction.

Feeding motivation and stereotypies in pregnant sows fed increasing levels of fibre and/or food.

Twenty-one multiparous sows were used in a Latin square design, from days 7 to 90 of gestation, to test the effect of fibre and food levels on feeding motivation and feeding-related stereotypies. Treatments were: VHF (very high-fibre, 29% ADF, 50% NDF, 4.5kg/day); HF (high-fibre, 23% ADF, 43% NDF, 3.5kg/day); C (control, 8% ADF, 20% NDF, 2.5kg/day); and control fed ad libitum (CAL). All diets except CAL provided a similar amount of major nutrients on a daily basis and were served in two meals. Each sow was subjected to each treatment for a 21-day period, at the end of which, behavioural observations were made. Two-hour observation periods starting at the afternoon food delivery revealed that sows spent more time eating on VHF and CAL (mean=21.2min) than on HF (13.2min) and C (7.6min) and more time on HF compared to C (p<0.01). When time spent eating was removed from total observation time, the percentage of remaining time spent in stereotypies was lower for VHF (median=17.9%) compared to C (median=49.8%), and lower for CAL (median=6.3%) compared to all other diets (p<0.01). During the period when lights were on (6.00-18.00h), 5min interval scans showed that VHF sows spent more time lying down and less time standing than C sows (p<0.05). Also, CAL sows spent more time lying down than sows on other treatments (p<0.01). During operant conditioning tests (OCT) performed before the afternoon meal and after the morning meal, less rewards were obtained by CAL sows (p<0.01), with no difference between other treatments. In conclusion, no reduction in feeding motivation of sows fed high-fibre diets could be measured by OCT, but very high levels of fibre were effective at reducing stereotypies and activity during the 2h post-feeding. However, these effects were not as marked as those observed with ad libitum feeding.

The effect of dietary fibre on energy utilisation and partitioning of heat production over pregnancy in sows.

A low (L) and high-fibre (H) diet were fed to six multiparous sows during gestation in a 2 x 2 repeated Latin square design. A single meal per day was given that provided 37.2 MJ digestible energy/d. The kinetics of heat production (HP) and its partitioning (fasting HP, activity HP, and thermic effect of feeding (TEF)) were determined. The TEF was partitioned between a dynamic component (TEFst) and a constant component (TEFlt). Digestibility of energy and nutrients was lower for the diet H. In spite of the lower metabolisable energy (ME) intake (33.9 v. 35.4 MJ/d for diets H and L respectively), HP was higher for diet H (30.5 v. 28.9 MJ/d) resulting in a lower energy retention. The estimated fasting HP was 270 kJ/kg body weight 0.75 per d at day 0 of gestation and increased with advancement of pregnancy. The TEFlt was not significantly different from zero for diet L, but represented 4.1% of ME intake for diet H. The TEFst was not affected by the diet but diet H delayed the postprandial peak of HP. Total TEF was higher for diet H than for diet L (11.7 v. 8.2% of ME intake). The longer duration of eating with diet H was compensated for by less physical activity between meals, so that activity HP was equivalent for both diets. The activity HP represented 20% of ME intake but was variable between sows. The ME requirements for maintenance averaged 440 kJ/kg body weight 0.75 per d. Feeding high-fibre diets increases HP, delays the postprandial peak of HP and maintains the basal HP at a higher level.

Changes in intragastric meal distribution are better predictors of gastric emptying rate in conscious pigs than are meal viscosity or dietary fibre concentration.

The effect of dietary fibre on the gastric emptying rate of solids is controversial. Similarly, the mechanisms by which it modulates food intake are partially unknown. Gastric emptying and proximal v. distal stomach filling were evaluated in triplicate on four conscious pigs using scintigraphic imaging. Each animal received in an isoenergetic manner a concentrate low-fibre diet enriched in starch (S) and two high-fibre diets based on sugar beet pulp (BP) or wheat bran (WB). All meals had the same viscosity before ingestion (100.0-100.5 Pa.s). Viscosity of the gastric contents was measured in four additional animals fitted with a gastric cannula. The gastric emptying rate of BP diet was significantly slower than S and WB diets (t1/2 78.4 (sem 5.68), 62.8 (sem 10.01) and 111.6 (sem 10.82) min for S, WB and BP diets respectively, P<0.05). For BP diet only, rate of distal stomach filling was steady during the first 120 min after the meal whereas that of S and WB diets decreased in an exponential manner. Numerous backflow episodes from the distal into the proximal stomach were observed for BP diet that generated the larger intragastric viscosity (0.26 (sem 0.03), 0.3 (sem 0.02) and 0.52 (sem 0.002) Pa.s for S, WB and BP respectively). In conclusion, viscosity of the meal or the percentage total fibre, unlike viscosity of the gastric contents, are poor predictors for emptying. The reduced emptying rate observed with BP is associated with major changes in intragastric distribution of the meal absent with WB and S diets.