Deficiency diseases
Under intensive rearing conditions, nutritional deficiencies may result from incomplete feed formulations or poor manufacturing processes and storage. Under extensive conditions, deficiencies are less likely to occur if the standing biomass is in accordance with recommended stocking and fertilization rates.
EAA deficiencies usually lead to reduced growth, poor feed utilization efficiency and high mortalities (Table 15). It has also been reported that excessive dietary tyrosine can cause kidney malfunction (Boonyaratpalin, 1997), and high mortalities were observed with fish fed elevated L-arginine levels (Murillo-Gurrea et al., 2001).
EFA deficiencies, particularly for 20:5n-3 (EPA), have been well studied and most often occur during larval rearing (Table 15). Larvae become pale and, when stressed, swim erratically and "faint", after which they either recover or die (Dhert et al., 1990; Rimmer et al., 1994). Wanakowat et al. (1993) also reported a reddening of the fins, abnormal appearance of eyes, and swollen and pale livers. Artemia enrichment is therefore necessary to avoid deficiencies that could occur at 18–20 DPH (Rimmer et al., 1994).
There is very little knowledge of the mineral requirements and associated deficiency symptoms (Glencross, 2006). Vitamin requirements are better understood and deficiency symptoms are presented in Table 16. Under fertilized pond culture conditions, vitamin supplementation in the feed may be reduced as many are at least partially provided by the natural food.
