Effects of Melamine and Urea formaldehyde contamination in Nile tilapia (Oreochromis niloticus) diets on growth performance, economic loss and toxicity appearance characteristic index

บทคัดย่อ

A study was performed to evaluate the effects of melamine (Me) and urea formaldehyde (UF) combinations  in diets on growth performance, and characterization of toxicity appearance. The combinations of three levels of Me and UF (0.5, 1.0 and 2.0%) were conducted with one control (no addition) in a completely randomized design (CRD). Four hundred and eighty mixed-sex fish with the initial weight of 9.67±0.03 g were assigned to 10 dietary treatments with 3 replications and fed for 6 weeks. No interaction was observed between Me and UF in this study. However, significant differences (P<0.05) in growth performance, feed efficiency and survival rate (SR) between the control and the fish fed with Me and UF combinations were observed. The body weight (BW) and body weight gain (BWG) linearly decreased while protein efficiency ratio (PER), feed conversion efficiency (FCE) and FCR were less efficient linearly (P<0.05) with the increasing levels of Me and UF combination, and were less efficient than the control (P<0.05). The SR and ELI as determined by PI showed significant linear decreases (P<0.05). A linear chronic pattern of appearance characteristic index of scale erosion, lesion and degeneration of viscera organs (liver, kidneys, spleen and ovary) was observed. Microscopic examinations of wet mount tissue and of histological changes of those tissue organs found them to be degenerated and damaged with numerous golden brown or transparent crystals. The crystals found provided evidence of strong correlation between the amounts and sizes of crystals, and the levels of Me and UF in diets. The results of this study indicated that the combinations of Me and UF in diets decreased growth performance, but increased economic loss index (ELI) and appearance characteristic of scale erosion and color change. The degeneration of tissue organs and crystals provided strong evidence in the prediction of Me and UF contamination in diets.