The functional evaluation of Pichia pastoris hydrolysate as a protein source partial replacement of soybean meal in diets of growing-finishing pigs

As the most important plant-based protein ingredient in animal husbandry, soybean meal has become key focu in the feed industrym highlighting the need to reduce its inclusion rate and identify alternative protein sources. Pichia pastoris hydrolysate (PPH) has regarded as an ideal single-cell protein (SCP) due to its efficient and low-cost protein biosynthesis. This study aimed to evaluate the effects of PPH partial substitution of soybean on the growth performance, immune status, gut microbe and meat quality of growing-finishing pigs. A total of 180 pigs with similar weight (31.48 ± 0.91 kg) were divided into 5 groups, including the control group (fed with basal diet) and treatment groups with PPH levels of 1.25%, 2.5%, 3.75% and 5%, respectively. Every group had 6 replicates, and each replicate consisted of 6 pigs. After 76 days on feed, all pigs were weighted, then one pig/replicate was slaughtered to collect blood samples and fresh fecal samples for further analysis, as well as evaluating the carcass traits and meat quality of pigs. PPH supplement improved the growth performance and carcass traits of pigs, especially the 2.5% PPH replacing 14.18% soybean meal, although there was no obvious difference in meat quality between control group and 2.5% PPH group. Results of serum immune-related factors showed that PPH supplement markedly elevated antioxidant status, increased serum anti-inflammatory factors and immunoglobulin levels, and strengthened the intestinal barrier of pigs. Fecal microbiome sequencing indicated that PPH could modulate fecal microbiome diversity, and promoted the probiotics proportion in the gut of pigs to varying degrees. Above findings revealed that partial replacement of soybean with PPH, not only significantly improved the growth performance and carcass traits of growing-finishing pigs, but also immunity performance and intestinal microecology, which provide insights into the application possibility of the PPH serving as an alternative feed ingredient in swine production system to offer excellent protein sources.