Effects of dietary phosphorus and lipid levels on utilization and excretion of phosphorus and nitrogen by rainbow trout (Oncorhynchus mykiss ). 1. Laboratory-scale study

Abstract

Nutritional strategies to reduce both phosphorus (P) and nitrogen (N) excretion relative to growth of rainbow trout were tested in a 2 × 3 factorial experiment. The two factors were `dietary P level' and `dietary lipid level.' Reduction in dietary P from 14 to 8 g kg–1 dry diet was achieved by partial substitution of dietary fish meal with a combination of full‐fat soyabean meal, corn gluten and spray‐dried blood meal. Triplicate tanks of 35 rainbow trout per tank were fed experimental diets for 16 weeks and grew from approximately 40 to 250 g, in 15 °C spring water. All tanks were fed the same percent biomass per day. Diets were isonitrogenous, and dietary energy varied with dietary lipid. Diet digestibility data and results of the experiment were used to construct N and P budgets for the fish fed the various diets. A reduction in dietary fish meal from 500 to 200 g kg–1 dry diet, corresponding to a reduction in dietary P from 14 to 8 g kg–1 dry diet, resulted in >50% reductions in both solid and dissolved P waste, but did not affect growth, feed efficiency ratio (FER) or sensory characteristics of rainbow trout. Increasing dietary lipid from 170 to 310 g kg–1 dry diet led to higher growth rate and FER, and lower total N waste relative to weight gain, but did not change protein retention. Increasing dietary lipid level increased deposition of lipid in whole bodies of rainbow trout, and resulted in discernible differences in sensory characteristics of trout fillets.

Effects of dietary lipid and phosphorus levels on nitrogen and phosphorus excretion in young yellowtail Seriola quinqueradiata: A preliminary observation

“…Phosphorus supplementation in fish meal‐based practical diets for young yellowtail did not result in any difference in growth performance and N retention in the present study. Similar observations made earlier in rainbow trout also indicate that there are no significant changes in growth and apparent nutrient retention when fish are fed diets with different P levels 25 . A dietary P requirement for optimum growth, feed utilization and bone mineralization ranging from 5 to 8 g/kg has been reported for rainbow trout and other fish 11,26 , 27 .…”

Tracing dissolved organic matter (DOM) from land-based aquaculture systems in North Patagonian streams

“…Nitrogen and phosphorus from land-based aquaculture may directly contribute to eutrophication downstream of the outfall, and carbon inputs may alter stream metabolism (Rosa et al, 2013). It has been shown that after passing land-based aquaculture facilities, effluents show elevated levels of ammonium and phosphate, originating from direct excretion and nutrient leaching processes from organic matter and suspended solids (Green et al, 2002;Brinker et al, 2005;Sindilariu, 2007). Xenobiotics such as antibiotics, medical disinfectants and anesthetics are also widely used and are consequently present in the effluent from land-based aquaculture (Tello et al, 2010).…”

Impact of trout aquaculture on water quality and farm effluent treatment options

“…Part of the feed supplied remains uneaten and becomes feed wastes. From the ingested nutrients, the undigested part is excreted as particulate faeces (Bergheim and Asgard 1996;Cho and Bureau 1997;Green et al 2002), containing mainly organic carbon and phosphorus (Cripps 1994;Kelly et al 1997;Cripps and Bergheim 2000). The digested nutrients are partially retained in fish body mass (Schreckenbach et al 2001).…”

“…The digested nutrients are partially retained in fish body mass (Schreckenbach et al 2001). The rest is excreted as dissolved nutrients through the gills, mainly as ammonia, and via urine as phosphate and ammonium (Cho and Bureau 1997;Bureau and Cho 1999;Green et al 2002;Roy and Lall 2004).…”