The effects of L-lysine in the diet of silver catfish (Rhamdia voulezi) female broodstocks
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The objective of this study was to assess the L-lysine effect in silver catfish, Rhamdia voulezi female reproduction. Four hundred fish were used distributed in a random in 16 net cages (25 fish each × 4 replicates = 100 fish per treatment). The treatments consisted in four diets, isoproteic and isoenergetic (30% crude protein and 3,500 kcal kg-1 digestible energy) with different L-lysine levels: T1: 1.30; T2: 1.40; T3: 1.60 and T4: 1.95%. After 185 days of experiment 18 females per treatment were weighed, measured, and submitted to hormonal induction (0.5 and 5.0 mg kg-1 Carp Pituitary Extract). The females were then sacrificed and had their ovaries, liver and fat removed and the respective organosomatic indices were estimated. With regard to the reproductive parameters, the released oocytes, absolute fecundity and remaining ovaries were influenced (P < 0.05) by the diet, and the highest mean values were observed in the treatment with 1.95% L-lysine. Among the organosomatic indices, only the visceral fat was influenced (P < 0.05). The estradiol levels and the composition of essential amino acid in oocytes were not affected (P > 0.05). We can conclude that L-lysine affects the reproductive parameters and accumulation of visceral fat in R. voulezi.