Assessing the Effectiveness of Providing Live Black Soldier Fly Larvae (Hermetia illucens) to Ease the Weaning Transition of Piglets

Abstract

Weaning is a stressful event for piglets, involving substantial changes to their nutritional and social environment. Providing edible enrichment around weaning may ease the weaning transition by increasing pre-weaning feed intake and improving post-weaning performance, health, behavior, and affective state. In this study, we investigated the effects of providing live black soldier fly larvae (BSFL) as edible enrichment pre- and/or post-weaning. Pre-weaning, piglets received either only creep feed (Pre-C, n = 14 litters) or creep feed and live BSFL (Pre-L, n = 15 litters) ad libitum, and post-weaning piglets either had no access to live BSFL (Post-C, n = 24 pens) or they could rotate tubes that released BSFL (Post-L, n = 24 pens) at levels up to 20% of their expected daily dry matter intake, resulting in treatments CC, CL, LC, and LL. No interaction between pre- and post-weaning treatment was found for any of the measured parameters. Before weaning, Pre-L piglets preferred to interact with larvae over creep feed, and Pre-C piglets interacted more with creep feed than Pre-L piglets. Total time spent on feed-directed behaviors did not differ. Continuous larvae provisioning increased caecum length and proximal stomach digesta pH, while it decreased the passage of glucose and fluorescein isothiocyanate through the colon wall on d3 post-weaning (CC vs. LL, n = 12 piglets/treatment). Post-weaning diarrhea and final body weight were not affected by treatment. After weaning, Pre-C piglets tended to eat more and grew marginally faster than Pre-L piglets. Post-C piglets spent more time eating and had a higher feed intake post-weaning than Post-L piglets. Based on home-pen behavioral observations, Post-L piglets actively explored and ate the larvae. Post-C piglets spent more time on exploring the environment and nosing pen mates, and they spent more time on manipulating pen mates on d8 and played more on d8 & 15 compared to Post-L piglets. Piglet responses to a novel environment and an attention bias test on d4 & 5 post-weaning were not influenced by larvae provisioning. In conclusion, pre-weaning larvae provisioning did not improve pre-weaning feed intake and post-weaning performance, however post-weaning larvae provisioning did benefit piglet behavior as less manipulation of pen mates was observed.

Keywords: affective state; behavior; black soldier fly larvae (BSFL); enrichment; health; performance; piglet; weaning.

Figure 1

Set-up of the pre- and post-weaning treatments. From d3 pre-weaning, piglets could access the feeding area that contained either two feeders with two feeding spaces containing creep feed (A), or two feeders with four feeding spaces, two containing creep feed and two containing larvae (B). Post-weaning, piglets either had access to an empty feeder (C), or access to a feeder to which two horizontally suspended tubes containing larvae were attached (D). A close-up of the tubes filled with larvae can be seen in (E).

Figure 2

The percentage of piglets per litter that ate creep feed (CF) or creep feed and/or larvae (Total) per day and individual eater types determined at the end of the pre-weaning period based on blue colored rectal swabs or pre-weaning home pen behavioral observations. Piglets had access to either only creep feed (Pre-C) or creep feed and live black soldier fly larvae (Pre-L). For the percentage of eaters (per day) and for the eater types (distribution of all types) the treatment effect is indicated as ^†(p < 0.1), ^*(p < 0.05), ^**(p < 0.01), ^***(p < 0.001) or ns (not significant). Data are presented as pen means ± SEM.

Figure 3

Time spent on feed-directed behaviors scored during the pre-weaning home pen observations of piglets having access to either only creep feed (Pre-C) or creep feed and live black soldier fly larvae (Pre-L). “Eating total” includes the time spent eating creep feed and eating larvae. Per day, treatment effects are indicated as ^†(p < 0.1), ^*(p < 0.05), ^**(p < 0.01), or ^***(p < 0.001). Data are presented as pen means ± SEM.

Figure 4

Time spent on all feed-directed behaviors (exploring feeder, exploring or playing with feed, and eating feed) toward creep feed (CF) and black soldier fly larvae (BSFL) as observed in the home pen of Pre-L piglets. Per day, effects of feed type are indicated as ^**(p < 0.01) or ^***(p < 0.001). Data are presented as pen means ± SEM.

Figure 5

Time spent on behaviors scored during the post-weaning home pen observations of piglets that had access to either only creep feed (Pre-C) or creep feed and live black soldier fly larvae (Pre-L) pre-weaning, and consequently had access to no larvae (Post-C) or had access to live black soldier fly larvae (Post-L) post-weaning, resulting in treatments CC, CL, LC, and LL. Any effects of pre-weaning treatment, post-weaning treatment, day, and their 2-way interactions are indicated as ^†(p < 0.1), ^*(p < 0.05), ^**(p < 0.01), or ^***(p < 0.001), and non-significant (p > 0.1) effects are not indicated. Data are presented as pen means ± SEM.