Partial fish meal replacement with fermented or enzymatically prepared soybean meal in weaned pig diets

Fish meal (FM) can be used as a protein source in weaned pig diets in South Korea due to the high digestibility of nutrients, favourable composition of amino acids (AA), and lack of anti-nutritional factors (ANF) that can reduce nutrient availability and negatively affect growth performance of young pigs (Kim et al. 2010). Soybean meal (SBM) is cheaper than FM and an important protein source fed to adult pigs because of its excellent balance of essential AA (Wang et al. 2011) and low fibre concentration. However, SBM contains ANF and therefore its high use in weaned pig diets is not recommended by nutritionists (Choct et al. 2010). On the other hand, fermented or enzymatically prepared SBM, which has a significant reduction in the amount of ANF (trypsin inhibitor <3.02 mg/g; raffinose <0.18%; stachyose <0.54% in this study), has been used to ameliorate the negative effects of the weaning lag (Min et al. 2009). The objective of this study was to determine the comparative efficacy of FM versus commercially available, solid state fermented SBM or enzymatically prepared SBM replaced at up to 50% of FM. Parameters of interest included growth performance, nutrient digestibility, and populations of some faecal bacteria. It was hypothesised that treated SBM may be a viable partial replacement for FM in weaned pig diets thereby reducing feed costs without compromising growth performance.

A total of 100 weaned pigs with a body weight (BW) of 6.6 ± 0.29 kg (mean ± SD) was used and were randomly allotted to five groups with four block replicates of five pigs per pen. Diets were formulated to meet or exceed the nutrient requirements by the NRC (2012), and diets were: 5% FM (FF-Skagen); 2.5% FM + 2.5% SoELAB (FEEDUP); 2.5% FM + 2.5% PepSoyGen (Nutraferma); 2.5% FM + 2.5% Soytide (CJ Cheiljedang Bio); and 2.5% FM + 2.5% HP 300 (Hamlet Protein) (as fed basis). Diets were fed for 3 weeks in mash form, and then each group was switched onto a common commercial diet as a crumble for 3 weeks. Growth performance in terms of average daily gain (ADG) and feed intake (FI), nutrient digestibility, and selected microbial population of faecal samples were measured in accordance with the methods described by Jeong and Kim (2015). All experimental data were analysed as a randomised complete block design, with one pen representing an experimental block unit. Data were analysed by GLM procedures (SAS 2001; USA) with Tukey’s test to indicate significant differences (P < 0.05) amongst means.

Although fermentation generates more free AA to improve nutrient availability, the amount of essential AA (SoELAB 23.7%; PepSoyGen 23.6%; Soytide 24.4%; HP 300 24.5%) was still lacking in comparison to FM (32.3%), which may have important implications. Concerning growth performance, SoELAB (ADG 487 g, FI 691 g) and HP 300 (ADG 494 g, FI 691 g) demonstrated no significant difference compared with FM (ADG 494 g, FI 701 g) after 6 weeks. With respect to nutrient digestibility, SoELAB and HP 300 treatments demonstrated no significant difference compared with FM treatment. Last, none of the SBM preparations demonstrated any significant differences in faecal score (P > 0.05), but differentially treated SBM (SoELAB, Soytide and HP 300) increased faecal Lactobacillus counts (P < 0.05) after 3 weeks while maintaining similar E. coli counts (P > 0.05) compared with FM treatment. Overall, the results from the present study indicated that treated fermented SBM has potential to serve as a replacement product for FM in diets fed to weaned pigs. The use of fermented SBM did not negatively impact any of the parameters examined. However, using fermented SBM as a complete alternative to FM may not be sufficiently adequate for providing essential AA in the diet. Henceforth, a fermented SBM and FM mixture in the diet is ideal, and can reduce feed costs without any side effects. Further studies should determine ideal mixture ratios in an attempt to maximise costs savings with growth performance.