Evidence of Increased Methionine Dietary Requirement for Litopenaeus vannamei Genetically Selected High Growth Lines

摘要

Historically as late as the early 1980s, the best growth rates obtained for Litopenaeus vannamei were between 1.2 to 1.6 g per week (Smith et al. 1983, 1985). However, due to genetically selected high growth lines with improved feeds and production systems, the best growth rates obtained at the Texas AgriLife Research Mariculture Laboratory in clear water for the last two years are 2.5 to 3.2 g per week in the linear growth phase. With essentially a doubling of the growth rate for Litopenaeus vannamei, one would expect an increase in the dietary requirement for essential nutrients. Essential amino acids represent a group of very important essential dietary nutrients. Methionine is usually recognized as the most limiting of the essential amino acids.Fox et al. (2006, 2007) reported a methionine dietary requirement as low as 0.40% of diet (1.26% of protein) was adequate to support in excess of 760% weight gain of juvenile L. vannamei from an initial weight of 0.67 g to 5.78 g in five weeks. This represents a growth rate of approximate 1.2 g per week in the linear growth phase. More recently, Fox et al. (2010a, b) reported an estimated dietary methionine requirement of 0.45% (1.80% of crude protein) and 0.66% (3.28% of crude protein) using an enriched methionine soybean protein and crystalline DL methionine, respectively. The enriched soybean protein was achieved by covalent bonding of methionine to the protein via carbodiimide reaction. This paper reports the re-evaluation of the dietary methionine requirements using the genetically selected high growth lines (growth rates of 2.5 to 3.2 g per week in Clearwater) using improved diets. The impact on dietary nutrient requirements of the genetically selected high growth lines of L. vannamei is discussed.