Egyptian aquaculture suffers from increasing production costs; feed cost as high as ~50% of the total production cost. Therefore, increasing utilization of feed and improving its management can help reduce production costs. Feeding management one of tools which plays a great role in reducing feed costs by avoiding overfeeding, which reduces the amount of uneaten feed, thereby maintaining water quality for as long as possible. Feeding fish at the optimal time of the day and proper frequencies may optimize growth and feed efficiency and reduce waste . Additionally dietary acidifiers improve feed efficiency and nutrient availability in various aquatic species by lowering digestive pH in the stomach and foregut, Moreover it can reduce harmful microorganisms and promote beneficial microflora colonization of the gastrointestinal tract.
A 42-day trial 2 × 2 factorial study was conducted to investigate the importance of using lactic acid (LA) as a feed additive in different feeding regimes on the performance and feed efficiency of Nile tilapia fingerlings Oreochromis niloticus . This study was designed to evaluate two levels of feed additives 0% and 1% LA with two feeding systems—1) half of the daily meal was given in the morning and the other half in the afternoon and 2) 3/4 of the daily meal was given in the morning and the other 1/3 in the afternoon. The average initial weight of fingerlings was 15.33 g ± 3.5 (SE); fingerlings were stocked in 12 plastic aquaria (60 liters), with six fish in each aquaria . A commercial diet of 30 % crude protein was used with a feeding rate of 3% of the biomass; the water exchange rate was 20% of the volume of the water aquaria every day. Mean values of water physicochemical parameters during the experimental period were within the recommended values for aquaculture growth and tilapia culture. Results appeared, fishes that were fed a diet containing 1% LA showed better growth performance than those fed a basal diet without LA. Moreover, there were no significant differences in feeding systems regardless of the addition of LA. The interaction between the tested factors (dietary LA and feeding system) was significantly higher for all parameters in fishes that were fed a diet containing 1% LA and given 50% of their meal in the morning, followed by fishes that were fed a diet without LA and given 75% of their meal in the morning and fishes that were fed a diet containing LA with 75% of their meal in the morning. Fishes that were fed a diet without LA with 50% of their meal in the morning had the lowest growth rate and FCR. Additionally, blood parameters improved in the same manner of growth parameters. Finally this study recommends that using 1% of LA as feed additives in tilapia feed improves the fish performance regardless the used feeding system but In the case of using a diet without LA it is preferable to feeding the fish with 75 % of their daily meal in the morning.