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The experiment consisted of a complete 2 x 2 x 2 factorial combination of two weaning ages (4 v. 6 week), two levels of dietary protein (H, 230 g CP/kg vs. L, 130 g CP/kg) and challenge with ETEC (+ v. -). An additional four treatments were added to test for the effects of protein source (dried skimmed milk powder vs. soybean meal) and AGP inclusion (yes vs. no) on challenged pigs of both weaning ages. At weaning (day 0), pigs were assigned to one of the experimental treatments for 2 weeks. On day 14 post-weaning, the same standard grower ration was fed to all of the animals until the 10th weeks of age. On day 3 post weaning, challenged pigs were inoculated with 109 cfu ETEC.
The ETEC challenge had a detrimental short-term effect on performance, decreasing average daily gain (ADG) (days 3 to 6; P<0.05) in both 4 and 6 week weaned animals. Compared with the non-infected counterparts, the challenged 4-week-weaned pigs fed the H diet showed a larger decrease in ADG immediately post infection than those fed the L diet, (42% and 25%, respectively; P=0.088). This effect was smaller in the 6-week-weaned pigs, 26% and 19% for the H and L diets, respectively. Pigs fed soybean meal had lower (P<0.001) daily intake and ADG (day 0 to 14) than those fed dried skimmed milk powder. Inclusion of AGP in the diet improved performance, particularly in the period immediately post infection, with infected pigs on the AGP diet gaining considerably more than those on the non-AGP diet.
In conclusion, the experimental enterotoxigenic E. coli challenge has a greater impact on the performance of pigs weaned at 4 weeks than those weaned at 6 weeks of age. The absence of AGP, increasing weaning age and decreasing dietary protein level may help to minimise the effects of PWC on performance, particularly in sub-optimal environments.
IJ Wellock, PD Fortomaris, JGM Houdijk and I Kyriazakis, 2008, Animal 2(6): 825-833.
