Can black soldier fly larvae meal be used as a main protein in nursery pig diets?
What's the impact on growth performance and fecal scores?
By Brenda Christensen and Lee-Anne Huber
Nursery pig diets are typically expensive due to the inclusion of various highly digestible protein ingredients to support growth after weaning. With greater restriction of antimicrobials as growth promoters, nursery diet formulations must now provide easily digestible nutrients and also deliver gut modulating properties to minimize gastrointestinal dysfunction (e.g., diarrhea) post-weaning.
One issue with acquiring protein ingredients for pig diets is the direct competition with the human food market. In this context, the exploration of insect protein ingredients can be beneficial for swine production. Full-fat black soldier fly larvae meal (BSFLM) is highly digestible and contains medium chain fatty acids and chitin, which are functional components that can reduce inflammation and assist in reducing pathogenic bacteria in the gut.
The objective of the study was to determine the effect of partially replacing soybean meal (SBM) with BSFLM in nursery pig diets on growth performance and fecal scores. At weaning (21 days of age), pigs were placed in nursery pens (five pigs per pen) and were randomly assigned to one of four dietary treatments (n=5): a high-complexity (contained highly digestible animal proteins and 10.8% SBM) with and without 3,000 ppm ZnO (HC + and HC−, respectively; representative of commercial diets), low-complexity (corn- and SBM-based; 31.8% SBM; LC), or LC with 30% inclusion of full-fat black soldier fly larvae meal (BSFLM) to partially replace SBM (LCFL; 8.0% SBM, 30% BSFLM; Table 1).
These diets (phase 1) were fed for two weeks, followed by four weeks of a common corn-SBM diet (phase 2) to determine if there were lasting effects of the experimental diets. During the study, individual pig body weights and per-pen feed disappearance were recorded weekly, fecal consistency scores (0-firm and dry feces, 1-soft and pasty feces, 2-yellowish fluid feces, 3-clear, water-like feces) were recorded every other day for the first week after weaning, and fecal E. coli colony forming units was determined seven days after weaning.
In this study, pigs fed HC- and HC+ had greater bodyweight and average daily gain during phase 1 compared to pigs provided LC and LCFL diets (Table 2). In phase 1, pigs fed HC+ had the greatest average daily feed intake followed by pigs given HC-, with LC and LCFL pigs having the lowest average daily feed intake.
The gain-to-feed ratio of HC- pigs was greater than LCFL pigs in phase 1, however in phase 2, LC and LCFL pigs had greater gain-to-feed ratios than HC-. Therefore, during phase 1 the pigs given diets containing highly digestible animal protein sources, with our without pharmacological ZnO grew better than those provided low-complexity diets, even when BSFLM was used as a digestible protein source.
Due to the functional components of BSFLM, it was expected that pigs would have improved fecal scores and lower E. coli colony forming units after weaning, however this was not the case. On day three, pigs fed LCFL had softer feces than HC+, with HC- and LC fed pigs intermediate (Figure 1).
By day 7 after weaning, only HC+ fed-pigs had a reduction in E. coli colony forming units (Figure 2). Therefore, the full-fat BSFLM did not protect pigs from post-weaning proliferation of E. coli, but this study reinforced the efficacy of ZnO against E. coli.
Previous studies have shown BSFLM to be effective in improving growth performance and gastrointestinal attributes when included at 7.4% of the diet. Whereas this study demonstrates that at a 30% inclusion, BSFLM had a negative effect on growth. Additionally, since BSFLM is an emerging feed ingredient it is still cost prohibitive, particularly at high inclusion levels. Therefore, for newly weaned pigs, high dietary inclusion levels of BSFLM are not recommended.
This work was funded by the Ontario Ministry of Food, Agriculture and Rural Affairs
Dive into the full study here.
Christensen is a postdoc student and Huber is an associate professor in swine nutrition, both in the Department of Animal Biosciences, University of Guelph.
