Effect of Miscellaneous Meal Replacements for Soybean Meal on Growth Performance, Serum Biochemical Parameters, and Gut Microbiota of 50–75 kg Growing Pigs

SIMPLE SUMMARY: Given the escalating production of livestock and poultry coupled with the surging cost of soybean meal, the quest for alternative raw materials capable of replacing soybean meal is gaining increasing significance. Rapeseed meal, cottonseed meal, and sunflower seed meal, which are common by-products of agricultural production, offer viable plant-based protein substitutes for soybean meal in pig production. This study reveals that the incorporation of miscellaneous meal (rapeseed meal, cottonseed meal, and sunflower seed meal) as a substitute for soybean meal in the diet did not significantly influence the growth performance, apparent nutrient digestibility, serum amino acid content, or fecal microbiota diversity of growing pigs weighing between 50 and 75 kg. These results suggest that miscellaneous meal (rapeseed meal, cottonseed meal, and sunflower seed meal) could potentially serve as a partial or complete replacement for soybean meal in the diet of growing pigs. ABSTRACT: This study was carried out to investigate the effects of miscellaneous meal (rapeseed meal, cottonseed meal, and sunflower seed meal) as a replacement for soybean meal on growth performance, apparent nutrient digestibility, serum biochemical parameters, serum free amino acid contents, and gut microbiota of 50–75 kg growing pigs. A total of 54 healthy growing pigs (Duroc × Landrace × Yorkshire) with initial body weights (BWs) of 50.64 ± 2.09 kg were randomly divided into three treatment groups, which included the corn–soybean meal group (CON), corn–soybean–miscellaneous meal group (CSM), and corn–miscellaneous meal group (CM). Each treatment included six replicates with three pigs in each replicate. Dietary protein levels were maintained at 15% in all three treatment groups. Additional rapeseed meals, cottonseed meals, and sunflower seed meals were added to the CSM group’s meals to partially replace the 10.99% soybean meal in the CON group in a 1:1:1 ratio. Pigs in the CM group were fed a diet with a mixture of miscellaneous meals (7.69% rapeseed meal, 7.69% cottonseed meal, and 7.68% sunflower seed meal) to totally replace soybean meal. Our findings revealed that there was no significant impact of replacing soybean meal with miscellaneous meal on the ADG (average daily gain), ADFI (average daily feed intake), or F/G (feed-to-gain ratio) (p > 0.05) of growing pigs weighing 50–75 kg, nor on the crude protein, crude fat, or gross energy (p > 0.05) of the diet. On the other hand, compared to the CON group, the CM group exhibited significantly elevated serum alanine aminotransferase (ALT) and triglyceride (TG) levels (p < 0.05), while urea levels were significantly reduced (p < 0.05). No significant effect was observed on the serum free amino acid contents (p > 0.05) following the substitution of soybean meal with miscellaneous meal. A t-test analysis indicated that compared with the CON group, the CM group exhibited a significantly diminished abundance of Euryachaeota at the phylum level and augmented abundance of Desulfobacterota at the genus level. This study demonstrated that the miscellaneous meals (rapeseed meal, cottonseed meal, and sunflower seed meal) as a substitute for soybean meal in the diet had no significant negative effects on the growth performance, apparent nutrient digestibility, serum amino acid content, or diversity of fecal microbiota in 50–75 kg growing pigs. These results can be helpful in developing further miscellaneous meals (rapeseed meal, cottonseed meal, and sunflower seed meal) as functional alternative feed ingredients to soybean meal in pig diets.