Influence of Hormone D on the Thymus and Zootechnical Aspects of Nile Tilapia (Oreochromis niloticus) Larvae
Author: Pedro Anderson de Paiva dos Santos (Currículo Lattes)
Advisor: Dr. Luís Alberto Romano
Abstract
The Nile tilapia, Oreochromis niloticus, is one of the most commercially traded fish species in the world. Due to its ease of handling and ability to consume inert feed from first feeding, it becomes an excellent species in aquaculture. Recently, scientists have determined that vitamin D should be considered a hormone. More recent studies point to the physiological role of hormone D in regulating both innate and adaptive immunity. Despite efforts to expand current knowledge about the fish immune system, it remains limited compared to what is known for mammals. Therefore, the present study aimed to evaluate different levels of hormone D inclusion in Nile tilapia (Oreochromis niloticus), analyzing the thymus and zootechnical aspects. The experiment was carried out at the Aquaculture Station of UFC over a period of 56 days, in 250 L tanks with constant aeration. Nile tilapia larvae aged 2–3 days post-hatching were used in order to assess the influence that the addition of hormone D may have on the thymus and zootechnical parameters. The physical-chemical parameters of the water and its nitrogen compounds were monitored throughout the experiment. The zootechnical aspects were measured at the end of the trial to evaluate the effect of hormone D. Histological sections were analyzed using Zen Lite software to measure thymus size. The results showed that hormone D has an influence on zootechnical traits, with all treatments that included the hormone showing improvements in weight and size parameters. Regarding thymus area, the addition of the hormone to the feed led to an increase compared to the control. Thus, it was concluded that the concentration of 135,000 IU/kg was the most suitable for Nile tilapia larvae fed over the 56-day period.