Maintenance and growth requirements for nitrogen, lysine and methionine and their utilisation efficiencies in juvenile black tiger shrimp, Penaeus monodon, using a factorial approach

摘要

We used a factorial approach to distinguish maintenance from growth requirements for protein, lysine and methionine in the black tiger shrimp, Penaeus monodon. Juvenile P. monodon (initial weight 2p"4 g) were fed during 6 weeks one of ten semi-purified diets based on casein and purified amino acids (AA) as N source. The diets contained four levels of crude protein (CP, from 5 to 54 % DM diet) with two levels (% CP) of lysine or methionine (normal or 30 % deficient). Requirements were determined using linear and non-linear regression models. We could thus obtain the first ever data on maintenance (N equilibrium) requirements for CP and AA in P. monodon. CP requirements for maintenance (4p"5 g/kg body weight (BW) per d) represented approximately 19 % of the CP requirement for maximal N gain (23p"9 g/kg BW per d). The marginal efficiency of utilisation reached a maximum of 38 % for N, 0p"77 for lysine and 1p"62 for methionine using N gain as response. Lysine requirements were 0p"20 g/kg BW per d for N maintenance and 1p"40 g/kg BW per d for maximal N gain. Methionine requirements were 0p"11 g/kg BW per d for N maintenance and 0p"70 g/kg BW per d for maximal N gain. The lysine (5p"8 %) and methionine (2p"9 %) requirements for maximal N gain, expressed as percentage of protein requirement, agree with literature data using a doseresponse technique with smaller P. monodon. The observed interaction between dietary CP and methionine for N gain demonstrates that requirements for indispensable AA (expressed as % CP) cannot be evaluated separately from CP requirements.