Comparison of dietary essential amino acid requirements determined from group-housed versus individually-housed juvenile bluegill, Lepomis macrochirus

Abstract

Two 60‐day experiments were conducted sequentially to determine (i) lysine requirement of juvenile bluegill, Lepomis macrochirus based on the dose–response method, (ii) requirements for other essential amino acids (EAAs) using whole‐body amino acid profile and (iii) whether differences in growth rates of group‐housed versus individually‐housed bluegills lead to different lysine requirement levels because of the presence and absence, respectively, of social hierarchies. Seven, semi‐purified, experimental diets (isonitrogenous, isocaloric) were prepared to contain graded levels of digestible lysine (10–31 g kg−1). Experiment‐1 involved group‐housed bluegills (approximately 27 g, n = 10 fish/chamber, 4 chambers/diet) whereas experiment‐2 involved individually‐housed bluegills (approximately 30 g, n = 1 fish/chamber, 14 chambers/diet). Fish were fed twice daily to apparent satiation. Bluegill growth responses in both experiments generally improved (P < 0.05, anova) with increasing dietary lysine levels from 10 to 16 g kg−1, and then levelled off with further increase in lysine level (P > 0.05). Optimal dietary lysine level (digestible basis) was estimated to be 15 g kg−1 based on broken‐line regression analyses of relative growth rate and feed conversion ratio with no differences being observed between the two rearing methods. Determined dietary requirement levels for other EAAs ranged from 2.4 g kg−1 (tryptophan) to 15.3 g kg−1 (leucine).

Replacing fish meal with increasing levels of meat and bone meal, soybean meal and corn gluten meal, in diets of juvenile bluegill,Lepomis macrochirus

“…Similarly, digestible energy values determined in our previous studies were used for all ingredients except for fish oil and lecithin, for which energy levels were assumed to be 90% digestible (Masagounder et al . ). Costs for the major ingredients (FM, MBM, BM, SBM, CGM corn and wheat) were based on prices (average values as used by Masagounder ) published in Feed Magazine for 2008 and 2009, whereas those for other minor ingredients were based on commercial supplies (Table ).…”

“…Digestibility coefficients of the protein sources, corn and wheat determined in our previous studies (Masagounder et al . , ) were used to obtain digestible protein and amino acid levels for the experimental diets. Similarly, digestible energy values determined in our previous studies were used for all ingredients except for fish oil and lecithin, for which energy levels were assumed to be 90% digestible (Masagounder et al .…”

“…soybean meal, a safety margin of 10% was added to the previous reported values (Masagounder et al . ) and provided as minima. For lipid, a range of 80–100 g Kg −1 was allowed to be included in the diet formulations, following the level (80 g Kg −1 ) recommended for 6‐g bluegill (Hoagland, Davis, Tuan & McGraw ).…”

“…The dry weight of the unconsumed feed was corrected for leaching as described by Masagounder et al . () and then subtracted from the total feed weight provided, to determine total feed consumption by the bluegill in each chamber. Water temperatures and dissolved oxygen levels (recorded daily) were maintained at 23.4 ± 0.8°C and 7.2 ± 0.2 mg L −1 , (mean ± SD), respectively, whereas NH 3 ‐N and NO 2 ‐N levels (recorded weekly) were maintained at <0.1 mg L −1 and <0.2 mg L −1 respectively.…”

“…In the recent past, Allan, Parkinson, Frances, Stone, Booth, Rowland and Warner‐Smith () developed a least‐cost diet formulation for Australian silver perch Bidyanus bidyanus after conducting sequential studies on digestibility (Allan, Rowland, Mifsud, Glendenning, Stone & Ford ) nutrient requirements (Allan & Rowland ; Allan, Johnson, Booth & Stone ) and feedstuff inclusion limits (Stone, Allan, Parkinson & Rowland ). A similar approach was used to develop a cost‐effective diet formulation for juvenile bluegill, based on the digestibility of common feedstuffs (Masagounder, Firman, Hayward, Sun & Brown ), and the dietary requirements for essential amino acids (EAAs) (Masagounder, Hayward & Firman ), as well as protein and energy (Masagounder ). Information concerning palatability of feedstuffs was not readily available; however, our recent study of bluegill's digestibility (Masagounder et al .…”