Enrichment with Hermetia illucens live larvae in a cage-free system: effects on welfare and egg production and quality in laying hens of two genotypes.

The effect of the enrichment (10% ad libitum daily feed intake) with live larvae of Hermetia illucens (HI) was evaluated on behavior, egg production and quality from 36 to 40 weeks of age in 1800 laying hens of two genotypes (brown and white) randomly allocated in 8 pens of an aviary system. The larvae enrichment significantly affected space use and behavior, increasing the number of birds on the floor (P < 0.001), the proportion of clean eggs and that of eggs laid in the nest (P = 0.001), while reducing inactivity, floor pecking and the distance hen-operator at the avoidance test in enriched compared to non-enriched pens. As for differences between genotypes, the rate of inactive hens was higher (P = 0.001) in brown compared to white hens, while the rate of hens pecking the floor and showing preening was lower (P < 0.001). The number of piling events was markedly lower in brown compared to white hens (P < 0.001) and brown hens were also more likely to approach a novel object (P = 0.044). Then, brown hens showed higher rates of broken eggs (P = 0.008), fewer eggs laid in nests and more eggs laid on aviary tiers (P < 0.001). Egg quality differences were limited with more blood and meat spots (P < 0.001), lower yolk proportion (P < 0.001) and thicker shells (P < 0.001) in brown compared to white hens. In conclusion, the enrichment with HI live larvae increased species-specific behaviors in both genotypes without substantially affecting egg production and/or quality. On the other hand, the enrichment improved the space use as eggs laid in the nests increased at the expenses of floor eggs, which finally resulted in an improvement of production.