No abstract

A 100 days experiment was conducted to determine the effect of feeding blood meal (BM) as a replacement of fish meal (FM), as the main source of animal protein, on growth rate and economic performance of Nile tilapia in fertilized pond. Three isonitrogenous diets (35% crude protein) were formulated using either FM as the main source of animal protein (Diet 1); 50% replacement of FM with blood meal (Diet 2); or 100% replacement of FM with BM (Diet 3). Three hundred Nile tilapia fingerlings (12±3 g) were randomly distributed into three groups of four replicates of 25 fingerlings per cage. The groups were randomly assigned the 3 diets which were fed at 2% of their biomass at 10 am and 4 pm every day. Percentage daily weight gain (DWG), relative growth rate (RGR), specific growth rate (SGR), survival rate and feed utilisation efficiency were measured. Fish fed diet 1 were larger (50.69 g) (P < 0.05) than those fed diet 2 (48.47 g) and 3 (40.37 g). Replacement of FM with 50% and 100% BM reduced the incidence cost (45.55, 37.83 and 31.88, respectively). The profit index was highest with 100% (9.42) replacement of FM, compared to 50% (7.95) and 0% (6.69). Although replacing FM with BM was associated with reduced growth, the economic return was better (P < 0.05). Based on the present results, it was economical to use BM as a major protein source instead of FM in formulating fish feed.

Considering price as the main limiting factor in the use of animal proteins, this study evaluated the protein quality of diets for Nile tilapia containing oilseed meals as replacements of fishmeal. A control diet (FMBD) (30% crude protein and 2900 Kcal DE/kg) was formulated using fishmeal (FM), soybean meal (SBM), canola meal (CM) and sunflower meal (SFM). The test diets SBBD, CMBD and SFBD were formulated by replacing 10% CP of FM by SBM, CM and SFM, respectively. The amino acid profile was determined by MPA FT-NIR spectrometer (Bruker, Germany). Fishmeal recorded higher levels (p &lt; 0.05) of lysine (7.81 mg/100 g), methionine (2.89 mg/100 g), arginine (5.87 mg/100 g), threonine (4.28 mg/100 g) and isoleucine (4.55 mg/100 g). The chemical score for all essential amino acid in fishmeal were higher than 100. Sunflower meal was a superior (p &lt; 0.05) protein source with an essential amino acid index (EAAI) of 1.14 compared to CM (0.80) and SBM (0.70). Substituting FM with SBM, CM or SFM, reduced (p &lt; 0.05) the levels of all amino acids apart from methionine which was increased (p &lt; 0.05) in the diet with SBM substitute. In all diets, methionine and isoleucine were the first and second limiting amino acids, respectively. Though the diet containing FM exhibited higher (p &lt; 0.05) EAAI (0.97), it was not satisfactory because it was limiting in methionine. The EAAI reduced (p &lt; 0.05) with replacement of fishmeal by SBM (0.78), CM (0.77) and SFM (0.76). The study showed that the control diet had good quality protein and substitution with SBM, CM and SFM gave useful protein diets.

This article reviews critical aspects of the aquafeed value chain in the Kenyan aquaculture sector. Aquaculture production in Kenya has grown steadily in recent years, to more than 18,000 tons in 2019. Due to the growing demand for fish and fish products, there has been a gradual shift from extensive to semi-intensive to moderately intensive aquaculture systems, leading to an increased demand for high quality commercial fish feeds. The current annual demand for fish feed in Kenya is estimated at 34,000 tons. It is the lack of sufficient and high-quality local fish feed production that has created a market for fish feed importers, which is currently estimated at 7,000 tons annually. However, the imported fish feed is expensive for most fish farmers, leading to low production. Local fish feed production through home-based formulation should be driven by fish farmers to contain the rising cost of feeds. Most cottage feed manufacturers produce mash, crumbles or sinking pellets because they lack extruder for making floating pellets, hence the need for quality control in the aqua-feed sector. Fish feed producers are weakly covered by financial services providers, hence the inability to compete effectively with other value chains. The paper outlines five key actors in the aqua-feed value chain from production to marketing. These include; raw material (ingredients) suppliers, feed manufacturers (feed formulators), distributors/wholesalers, retailers, and customers who are fish farmers. We recommend intensification of local aqua-feed production using locally available materials to reduce the importation. This will ensure the long term economic and ecological sustainability of the aquaculture sector. There is a need for favourable policies to lower importation rates for raw materials as a way of boosting the availability of additional feed resources and inputs.

Dietary composition of aquaculture feeds (aquafeeds) determines the quality of wastes from aquaculture production systems. These wastes, which are derived mainly from nitrogenous and phosphorus compounds subsequently affect water quality in the culture systems and the ambient environment. Depending on the type of culture systems and management practices employed, the aquafeed wastes can influence the water pH, algal turbidity, biological oxygen demand (BOD) and may cause fish mortality. The aquafeed wastes also can facilitate eutrophication leading into harmful algal blooms. Moreover, large quantities of aqua-waste are discharged as fish cannot retain all the food they consume which means a significant portion of the feed remains uneaten. In this paper, we review and discuss practical nutritional strategies and mitigation measures to reduce aquafeed wastes including controlled formulation using high-quality ingredients, enzyme-based aquafeed, processing, reduction of anti-nutrition factors and precision feeding. The paper further recommends strategies for enhancing the resilience of aquaculture production systems and mitigation measures to reduce the effects of aqua-wastes on ambient natural environments.