Efeito da suplementação de ácido fólico sobre o desempenho reprodutivo de machos de jundiá (Rhamdia quelen)

Abstract

The reduction in the quality of gametes and offspring has been presented as a limiting factor for fish farming. Thus, the nutrition of breeders can be a strategy to solve these problems, due to its direct influence on the processes of gametogenesis and fertility of gametes. Vitamin B9 or folic acid, acts directly on the health, growth and reproduction of animals, participates in amino acid metabolism, nucleotide synthesis, DNA and RNA formation, in addition to antioxidant action, improving the seminal quality of animals. The objective of the present work was to evaluate the effects of folic acid supplementation on the growth and reproductive performance of silver catfish (Rhamdia quelen) males. A total of 720 silver catfish fingerlings (3.72±0.02g) were distributed in 24 multifilament net-tanks (4x2x1 m). The experiment lasted 300 days starting in autumn and ending in summer. In early spring, fish were classified into males (128.14 ± 1.83 g) and females (155.70 ± 1.97 g) and 15 animals of each sex were stocked per experimental unit. The animals were fed for 300 days with rations (34.75%PB; 3100 kcal ED kg-1) supplemented with 0.00; 0.75; 1.50; 2.25; 3.00 and 3.75 mg of folic acid kg-1 of feed. In the breeding season, males were submitted to semen collection. The fish were submitted to hormonal manipulation for synchronization of spermiation and the semen was collected after 10 hours (water at 24°C). The semen collected from the five males of each experimental unit, without contamination and good subjective motility, was analyzed for its motility, speed, concentration, membrane integrity and oxidative stress, in addition to pH and osmolarity. A semen sample was submitted to the technique of cryopreservation in liquid nitrogen. The same parameters were evaluated in cryopreserved and fresh semen. Thirty days after semen collection, the animals were anesthetized to obtain weight and length parameters, and blood was drawn for hematological and plasma analysis. Then, they were euthanized and dissected for evaluation of hepatosomatic, gonadosomatic and viscerosomatic indices, and collection of testicle and liver samples for analysis of oxidative stress. The data obtained were checked for assumptions, submitted to analysis of variance and Tukey's test, at 5% probability. For fresh semen, fish fed diets supplemented with 3.00 and 3.75 mg of folic acid.kg-1 showed the highest (p<0.05) motility (72.12 and 76.43%). In cryopreserved semen, males fed rations supplemented with 3.00 mg of folic acid kg-1 showed the highest (p<0.05) motility (55.54%), curvilinear velocity (69.57 µm s-1), average travel speed (49.53 µm s-1), straight-line speed (47.12 µm s-1) and sperm velocity (55.72±3.01 µm s-1). Oxidative stress in sperm cells decreased with increasing concentrations of folic acid, with better values at levels of 3.00 and 3.75mg of folic acid kg-1. The blood parameters of albumin, cholesterol and aspartate aminotransferase (AST) were affected, with a decrease in cholesterol and an increase in albumin and AST. Therefore, supplementation is recommended from 3.00 mg of folic acid kg-1 in rations intended for feeding male silver catfish (Rhamdia quelen) flocks.