Dietary flavor in corn and soybean meal-based diet reduced post-weaning diarrhea by attenuating weaning stress and systemic inflammation of pigs

Weaning period is a critical phase in swine production, and is characterized by reduced feed intake, growth retardation, and increased incidence of diarrhea. Supplemental dietary flavor has been used as a nutritional strategy to improve feed palatability and support early post-weaning growth. However, information on the effects on nutrient digestibility and systemic immune responses is still lacking. Therefore, this study evaluated the effects of dietary flavor on growth performance, frequency of diarrhea, nutrient digestibility, and systemic immune responses of weaned pigs. A total of 72 weaned pigs ([Landrace × Yorkshire] × Duroc; 28 d of age; average initial body weight = 6.51 ± 0.21 kg; equal sex ratio) were randomly assigned with two dietary treatments (four pigs per pen; nine replicates per treatment) for 42 d. Dietary treatments were a basal weaner diet based on corn and soybean meal (CON; one-phase mash diet formulated to meet or exceed basal nutrient requirements) and the CON supplemented with 0.05% dietary flavor additive containing a milky scent (FLA; Luctarom; Lucta Guangzhou Flavors Co. Ltd, Guangdong, China). Pigs in the FLA group had greater (P < 0.05) average daily gain between days 1 and 14 and tended to have greater (P = 0.087) average daily gain between days 1 and 42 compared to CON. Average daily feed intake (P = 0.092) and feed efficiency (P = 0.065) tended to be greater in the FLA group than CON group between days 1 and 14. Pigs fed FLA tended to reduce (P = 0.087) frequency of diarrhea between days 1 and 14 and have greater (P = 0.092) the apparent total tract of digestibility of gross energy than those fed CON. In systemic immune responses, the FLA group tended to have greater serum TGF-β1 (P = 0.089) and tended to reduce packed cell volume (P = 0.074), white blood cell counts (P = 0.081), serum IL-6 (P = 0.059), and serum cortisol (P = 0.070) on day 14 compared with the CON group. Our findings suggest that dietary flavor supplementation may improve growth performance and modulate systemic immunity in weaned pigs, potentially through enhanced nutrient digestibility and regulation of inflammatory responses.