Dietary ingredient composition affects faecal waste production and characteristics in yellowtail kingfish (Seriola lalandi)

Abstract

This study investigated the effect of different animal-based ingredients on faecal waste production and characteristics in yellowtail kingfish (Seriola lalandi). Seven ingredients of animal origin were tested: KM – krill meal; SHM – shrimp head meal; NIM – natural ingredient meal consisting of freeze dried krill (Euphausia superba), sand eel (Ammodytes marinus), smelt (Atherina boyeri) and squid (Loligo patagonica) (all included at 25% on dry matter basis); PHA – poultry meal with high ash content; PLA – poultry meal with low ash content; HFM – hydrolysed feather meal and POM – pork meal. Ingredients were incorporated at 30% (HFM – 15% inclusion) in a basal diet, which was predominantly marine-based. Yellowtail kingfish (mean initial weight 41 g) were fed the experimental diets restrictively, in triplicate groups. Fish performance, nutrient digestibility and faecal waste production were investigated over a 35 day experimental period. In addition, faecal characteristics were visually evaluated, and faeces removal efficiency and particle size distribution (PSD) were measured. Organic matter digestibility (OM) differed between diets, hereby altering the amount of faecal waste produced (g OM/kg DM FI). Test ingredients affected faeces removal efficiency by settling (%) and the amount of non-removed faeces (g OM/kg DM FI). Effects of ingredients on faeces removal efficiency were small compared to effects on faecal waste production. SHM, inclusion resulted in an improved faeces removal efficiency, while other animal-based ingredients did not improve faeces removal efficiency. Overall, this study highlights the importance of ingredient digestibility (and thus faecal waste production) for solid waste management in yellowtail kingfish.