The current practice of pregnant sow housing uses individual housing in stalls. However, producers are under a great deal of pressure to return sows to group housing due to various reasons. There are several advantages and disadvantages of individual and group housing. The most striking and important advantage of individual housing is that it reduces physical aggression in group housed sows. Aggression has a big impact on sow welfare and productivity. This study proposed to modify diet by increasing fiber and fermentable carbohydrate in the diet to increase satiety in pregnant sows. These two methods increase satiety by two different methods. One mechanism increases gut fill, which reduces hunger to some extent, but does not eliminate it. The second method increases nutrient provisions in the blood further away in time from the meal, and triggers the feeling of satiety in the brain.
This method too does not eliminate hunger entirely but is helpful in maintaining satiety for a longer duration. In this study, we combined these two separate methods of increasing satiety. We hypothesized that they would be additive in effect and more useful than each separately. Our experiment was to determine the effects of the different diets independently. Then our second experiment made combinations of the diets to determine if there was any additive effect.
In Experiment 1 sows were fed 1 of 5 diets: 1) control (corn/soybean standard diet), 2) resistant starch at 10.8% inclusion rate, 3) beet pulp at 27.2% inclusion rate, 4) soyhulls at 19.1% inclusion rate, or 5) soyhulls at a 14.05% inclusion rate but the amount of feed per sow was increased by .44 pounds over the 4.4 pounds fed in the other 4 treatments. Sows were maintained on these diets for 3 weeks after which they were mixed into groups of 5 and data were recorded to determine if sows fought less based on diet. Sows on soyhulls rested more during the 3 weeks on diets while sows on beet pulp stood more. Sham chewing increased for sows on all diets during the duration of the study but was lowest for sows on soyhulls. When the sows were mixed, sows on the control diet bit at each other the most while sows on the resistant starch diet bit at each other the least. Heart rate was lowest for sows on both the diets with soyhulls. Thus this study found that dietary inclusion of either resistant starch or soyhulls helped to improve welfare by reducing aggression and increasing satiety, without effecting production.
In Experiment 2 sows were fed 1 of 4 diets: control, ad libitum, 1.5 x the amount of resistant starch as fed in Experiment 1 (16.2% inclusion rate), and a 50:50 combination of resistant starch and soyhulls as fed in Experiment 1. The same procedures and measures were obtained as in Experiment 1. In this experiment, very few differences if any were detected for behavior, physiology or productivity, with sows on all treatments performing similarly. It is noted that in this experiment aggression of control sows was very low as compared to Experiment 2. This likely prevented treatment differences from being realized. It is not clear why aggression was low in this experiment.
In conclusion, resistant starch and soyhull diets similar to those as fed in Experiment 1 can be useful to decrease aggression and abnormal behaviors.