Biological response of piglets challenged with Escherichia coli F4 (K88) when fed diets containing intestinal alkaline phosphatase

The aim of the study was to investigate the effect of intestinal alkaline phosphatase (IAP) added to diets on growth performance, diarrhoea incidence (DI), blood metabolites, relative organ weight, and intestinal morphometry of weaned piglets challenged with enterotoxigenic Escherichia coli F4 (K88). A total of 64 crossbred entire male piglets (25-day-old and 7.16 ± 0.28 kg body weight) were allocated into four treatments: control diet (CD-), CD- + antimicrobial growth promoter (AGP), CD- + 15 mg IAP/kg of diet and CD- + 30 mg IAP/kg of diet, with eight replications. At 15 days, all piglets were orally challenged with 6 ml of a solution containing K88 (106 colony forming units/ml). Microencapsulated IAP in acid solution showed 14.43% solubility and pH values of 1.69, 1.72, 1.51, and 1.52 at the different times measured (0.5 h, 1.0 h, 17.0 h, and 24 h); differently, IAP in basic solution had 4.10% solubility and pH values increased (5.95, 6.10, 6.32 and 6.63) according to the different times, respectively. On days 25-35, piglets that received 30 mg IAP and CD- showed a better feed conversion ratio (P = 0.075) compared to those fed 15 mg IAP. Piglets that consumed 30 mg IAP or CD- had higher (P = 0.004) average daily gain on days 35-44. On days 35-44, the piglet average daily feed intake was lower (P = 0.033) with 15 mg IAP compared to AGP. In the entire period, piglets fed 15 mg IAP showed a reduction in average daily gain (P = 0.040) and average daily feed intake (P = 0.092). Piglets on 30 mg IAP showed an improvement (P ≤ 0.05) in DI in the pre-and post-challenge periods. The relative spleen weight of the piglet increased (P = 0.043) in response to 30 mg IAP. Overall, the addition of 30 mg IAP to diets improves the growth performance, attenuates DI, and promotes an increase in spleen relative weight to maintain the healthy state of piglets.