A study of the relationship between performance and dietary component digestibilities by swine fed different levels of dietary fiber.

A 49-d feeding trial, using 192 growing-finishing pigs (avg initial wt, 32 kg), was conducted to identify pigs of widely differing average daily gains (ADG) when fed 16% crude protein diets containing either 0, 7.5 or 15% corn cobs. There were linear decreases in both ADG (P less than .01) and gain/feed (P less than .001) with increasing levels of dietary corn cobs. Average daily feed intake increased linearly (P less than .001), but average daily digestible energy (DE) intake tended to decrease (P less than .08) with increasing dietary fiber level. Gain/DE was not apparently affected by dietary treatment. At the end of the feeding trial, 27 pigs, nine from each dietary treatment, were selected on the basis of ADG to represent pigs of above average, average and below average performance during the feeding trial. Previous ADG of the pigs selected for these were .93, .81 and .69 kg, respectively. In these pigs, plasma levels of glucose decreased (P less than .01) linearly, but urea N tended to increase (P less than .08) linearly with increasing level of dietary corn cobs. A digestion trial was conducted to determine if previous performance of the selected pigs could be related to the digestibilities of dietary components and the retention of N by these pigs. Nitrogen and dry matter (DM) digestibilities and dietary DE decreased linearly with increasing level of dietary corn cobs. The digestibilities of dietary neutral detergent fiber (NDF) and acid detergent fiber (ADF) decreased both linearly and quadratically with increasing level of corn cobs. Regardless of dietary treatment, no significant differences in any of these criteria were observed among pigs selected on the basis of widely differing ADG during the feeding trial.