Abstract
Live black soldier fly larvae (BSFL) could function as environmental enrichment for pigs as they are edible, odorous, manipulable, and destructible, though the interest of pigs in live BSFL is unestablished. In this study, three trials were performed to assess this interest in order to verify the suitability of live BSFL as enrichment. Eight (Trial 1 & 2) and 16 (Trial 3) pairs of weaned pigs were included. In Trial 1, the relative motivation of pigs to consume live BSFL compared to corn, raisins and feed pellets was evaluated in no-choice and subsequent two-choice preference tests including all (combinations of) feed items. In Trial 2, the feed items in the no-choice and two-choice tests were provided in tubes that had to be rooted or pushed to access the feed items. In this trial BSFL, corn, feed pellets, and empty tubes were compared. In Trial 1 & 2 each day had two 15 min tests occurring six hours apart. In Trial 3 the long-term interest in live BSFL provided in the tubes for a 5-day period was compared to feed pellets provided in tubes, to jute sacks, and to rubber balls attached to chains. Tubes with live BSFL or pellets were refilled every morning. The relative interest was determined through intake of feed items and/or time spent interacting with the items, as measured by 1.5- or 1 min scan sampling. In Trial 3, the time spent on oral manipulation of pen mates was also scored through scan sampling. In all trials the interaction with and consumption of live BSFL was significantly higher compared to the other items, indicating a clear preference for live BSFL, and pigs remained engaged with BSFL as long as they were accessible. In Trial 3, interest in live BSFL decreased on day 5 compared to day 1, interest in jute sacks and feed pellets decreased on day 3 compared to day 1, and interest in rubber balls attached to chains was continuously low. Pigs also spent less time on oral manipulation of pen mates when having access to live BSFL, pellets, or jute sacks, compared to rubber balls attached to chains. Overall, pigs showed high and extended interest in live BSFL, confirming their suitability as edible environmental enrichment. Pigs were willing to work for access to live BSFL by rooting and pushing tubes, which can be employed when providing live BSFL as enrichment commercially.
Highlights
The consequences of incorporating insects into the diet of pigs have been of recent interest, yet their potential effectiveness as environmental enrichment has received little attention
In Trial 3 (T3), the pigs’ long-term interest in live black soldier fly larvae (BSFL) provided in tubes was compared to interest in pellets provided in tubes, two jute sacks hanging from the pen wall, and two rubber balls attached to chains hanging from the pen wall (Fig. 1)
The behavioural interaction with the feed items was influenced by feed type (F(3,21) = 23.5, p < 0.0001), where pigs interacted more with live BSFL than with all other feed items, and no other differences occurred
Summary
The consequences of incorporating insects into the diet of pigs have been of recent interest, yet their potential effectiveness as environmental enrichment has received little attention. BSFL meal (full-fat or partially or fully defatted) has been included in pig diets without interfering with normal growth, feed intake, nutrient di gestibility or intestinal morphology (Biasato et al, 2019; Chia et al., 2019; Crosbie et al, 2020; Spranghers et al, 2018; Yu et al, 2020), or in some cases with beneficial effects on growth and feed/gain ratio (Yu et al, 2020, 2019) and on caecal microbiota composition (Biasato et al, 2020). Providing BSFL as whole, live larvae could serve an additional function as environmental enrichment and, as such, benefit pig welfare, as was found in broilers (Ipema et al, 2020a, 2020b). In barren environments without enrichment, pigs have limited possibilities to perform explor atory behaviour, which often causes them to redirect these behaviours towards pen fixtures and pen mates
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