Growth performance and hemobiochemical parameters in South African dusky kob (Argyrosomus japonicus, Sciaenidae) offered brewer's yeast (Saccharomyces cerevisiae) as a feed additive

Abstract

There is some evidence that single‐cell proteins such as yeast have the potential to improve feed utilization in aquaculture fish, but this has not been investigated in the economically important dusky kob, Argyrosomus japonicus. This study was, therefore, designed to determine the effect of graded levels of dietary inactivated brewer's yeast, Saccharomyces cerevisiae, on the growth performance and hemobiochemical parameters of dusky kob in a 6‐week feeding period. Five isonitrogenous and isoenergetic diets—consisting of three brewer's yeast‐containing diets at rates of 50,150, and 300 g/kg dry matter (BY5P0, BY15P0, and BY30P0, respectively); a commercial dusky kob diet containing 10% probiotic mix but no brewer's yeast (BY0P1, positive control); and a commercial dusky kob diet with neither the probiotic mix nor the yeast (BY0P0, negative control)—were formulated. A total of 65 fish, weighing an average of 7.02 ± 0.10 g, were randomly distributed to each of 20 replicate tanks. Each dietary treatment was randomly allocated to four tanks and offered to fish at a rate of 2.8% fish body weight per day. A total of 10 fish from each tank were randomly sampled once a week for length and weight measurements. Blood was drawn from five fish per tank (20 fish per treatment) for hematology and serum biochemical analyses at the end of the 6 weeks. Fish on the BY0P0 diet achieved the highest weight gain of 18.53 ± 0.69 g after 6 weeks. Growth rate was significantly reduced in the groups fed BY15P0 and BY30P0 diets compared to the BY0P0, BY0P1, and BY5P0 groups. Fish fed the BY0P0 diet recorded the highest average feed conversion efficiency (FCE) of 0.22, while the BY30P0‐fed group recorded the lowest FCE of 0.15. Hematocrit and alanine transaminase levels declined with increasing levels of yeast. It can be concluded that the maximum inclusion level of brewer's yeast that does not impair growth performance and health of dusky kob is 50 g/kg.

Black Soldier Fly Larvae Meal as a Fishmeal Substitute in Juvenile Dusky Kob Diets: Effect on Feed Utilization, Growth Performance, and Blood Parameters

“…Haematological parameters of experimental fish are an effective index to monitor physiological and pathological aberrations that may arise when novel dietary components are evaluated [21,45]. All haematological and serum biochemistry parameters from the current study were within the normal range for dusky kob [21,46]. These results suggest that feeding BSFM-containing diets did not compromise the physiological status of the dusky kob.…”

Bioprocessing post‐consumer food waste for use as a fish feed ingredient

“…Intracellular nutrients are not as readily available from intact yeast cells as from disrupted cells. Thus, not all yeast‐derived nutrients were bioavailable to the fish and slower growth was observed (Oliva‐Teles and Gonçalves, 2001; Madibana & Mlambo, 2019). A similar decrease in fish growth rate was also observed after substituting more than 40% of FM with yeast‐fermented poultry by‐product in the diets of Nile tilapia (Dawood, Magouz, Mansour, et al, 2020).…”

Yeast as major protein‐rich ingredient in aquafeeds: a review of the implications for aquaculture production

“…In general, these studies showed positive responses even at high replacement level of fishmeal protein, except few where high inclusion of S. cerevisiae linearly depressed growth and nutrient utilisation in fish. Examples of these are in rainbow trout (Hauptman et al 2014), Atlantic salmon (Øverland et al 2013), Nile tilapia (Ozório et al 2012), Southern African dusky kob (Madibana & Mlambo 2019) and Mirror carp (Omar et al 2012). Fermentation media, yeast strain and post‐fermentation processing, as well as fish species and diet formulation are factors that may be responsible for the decreased growth and nutrient utilisation with increasing levels of S. cerevisiae in some fish species (Øverland & Skrede 2017).…”

“…In general, these studies showed positive responses even at high replacement level of fishmeal protein, except few where high inclusion of S. cerevisiae linearly depressed growth and nutrient utilisation in fish. Examples of these are in rainbow trout(Hauptman et al 2014), Atlantic salmon(Øverland et al 2013), Nile tilapia(Ozório et al 2012), Southern African dusky kob(Madibana & Mlambo 2019) and Mirror carp…”