Influence of Enzymatically Hydrolyzed Whole Blood Formulated Diet on Nutrient Digestibility, Fecal Bacterial Count, and Immune Responses of Weaned Piglets Challenged with Escherichia coli Lipopolysaccharides

Weaning stress and immune challenges can negatively affect the health and performance of young pigs by inducing inflammatory responses. Functional protein sources, such as enzymatically hydrolyzed whole blood (EHB), may help alleviate inflammation and improve immune status during stressful conditions. A total of 20 late-weaned pigs [Landrace × Yorkshire × Duroc], 42 days of age, with an initial body weight of 15.34 ± 1.17 kg, were used in a 2-week experiment. Pigs were allotted to a 2 × 2 factorial arrangement with two dietary protein sources [plasma protein (PP) and/or EHB] and two immune challenges (saline or LPS). The four experimental groups were as follows: (1) Plasma-Sal, PP diet + saline injection; (2) Plasma-LPS, PP diet + LPS injection (100 μg/kg BW); (3) EHB-Sal, EHB diet + saline injection; and (4) EHB-LPS, EHB diet + LPS injection (100 μg/kg BW). Each treatment consisted of five replicate pens with one pig/pen. Pigs fed either protein diet with and without LPS showed no (p > 0.05) difference in their nutrient digestibility and microbial population. However, pigs challenged with LPS exhibited a higher (p < 0.05) rectal temperature, with significant differences observed at 6 h and 12 h post-injection (p < 0.001). Dietary effects (p < 0.05) were observed for IL-6 and TNF-α concentrations, with pigs fed EHB exhibiting lower values compared with those fed the PP diet following LPS challenge. Consistent with an inflammatory response, pigs challenged with LPS showed elevated (p < 0.05) IL-6 and TNF-α concentrations, together with increased white blood cell and lymphocyte counts, at 12 h post-challenge. Moreover, significant (p < 0.05) diet × LPS interactions were detected for IL-6 and TNF-α concentrations at 6 h post-challenge, indicating that dietary EHB attenuated the inflammatory response induced by LPS. In summary, a diet formulated with EHB showed a reduced effect of LPS challenge in pigs, making it promising as a functional dietary protein source for improving immune resilience in weaned piglets.