Effect of stocking density and dietary supplements (Ractopamine and L-Carnitine) on growth, reproduction, and body composition of all-female, Macrobrachium rosenbergii (De Man, 1879) | |
| Author | Rahman, Md. Moshiur |
| Call Number | AIT Diss no.AQ-22-02 |
| Subject(s) | Macrobrachium rosenbergii Shrimps culture Carnitine |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Aquaculture and Aquatic Resources Management |
| Publisher | Asian Institute of Technology |
| Abstract | The giant freshwater prawn (GFP), Macrobrachium rosenbergii (de Man, 1879), is a commercially farmed freshwater crustacean with a wide geographic distribution. This prawn is extensively cultured because of its high demand and growing local consumption in most of its native ranges. Differential growth among male, female, and mixed-sex populations is a major bottleneck in its aquaculture. Therefore, all-male and all-female farming are feasible solutions in giant freshwater prawn production. All male prawn stocks grow quicker than all-female or mixed-sex populations in a culture environment, but their size variability and territorial behavior still pose challenges in all-male prawn culture. All-female prawn farming is more feasible for intensive prawn rearing owing to their more uniform growth and high survival rates in ponds and tanks. However, slower growth rates and early sexual maturity may be a limitation in all female prawn farming. Hence the present study aimed to standardize all-female prawn farming practices in tanks, particularly in an intensive rearing system. The effect of stocking density and two potential feed additives, viz. ractopamine and L carnitine, on the growth, biochemical composition, and gonadal maturity of all-female giant freshwater prawn, Macrobrachium rosenbergii were investigated in this study. Three experiments were conducted as part of this research. In the first study to evaluate the optimum stocking density for intensive rearing, all-female prawns were reared in 1,000 L indoor tanks for 60-days at stocking densities of 4 (T1), 8 (T2), 16 (T3), 24 (T4), and 32 (T5) prawns/m2 in triplicates. The survival rate, mean final weight, daily weight gain, and specific growth rate (SGR) were the highest in T1, and feed conversion ratio (FCR) was the lowest and most efficient in T2. The stocking density of 8 prawns/m2 (T2) was found to be feasible for good growth performance, while the estimated density for optimum yield was 23.5 prawns/m2 , indicating that all-female prawns are amenable to intensive farming. The distribution of ovarian stages was not significantly different across the densities tested. The results indicated that while the stocking density significantly affected growth parameters, it did not significantly affect the all-female prawn's gonadal maturation. In the second experiment, prawn juveniles were stocked at 10 prawns/m2 in 15 indoor tanks (1000 L) for 60 days with five treatments in triplicates. A beta-agonist feed additive, ractopamine hydrochloride (RAC), supplemented at increasing levels of 0 (T1, control), 5 (T2), 10 (T3), 15 (T4), and 20 mg/kg (T5) in the prawn feed, was used to test its effect on growth, body composition, and gonadal development of all-female prawns. The 10 mg/kg RAC (T3) diet showed significant weight gain, daily weight gain, and SGR over other treatments. Improved protein and lowered lipid contents were also observed in RAC-treated prawns. All the treatments had significantly greater stage 1 (non-reproducing, virgin) females than control, indicating effective suppression of gonadal maturity. Residue analysis of whole prawn samples at the end of the experiment revealed no traces of ractopamine in prawns. The quadratic regression analysis of weight gain, SGR, FCR, and yield revealed that the optimum dietary ractopamine level for all-female prawn culture should be between 10 and 15 mg/kg. These findings imply that adding RAC to all-female prawn diets improves growth performance while suppressing gonadal maturation. In the third trial, a 60-day feeding study on all-female prawn M. rosenbergii was conducted in fifteen 1000 L tanks, with five treatment groups viz. 0 (T1; control), 0.25 (T2), 0.50 (T3), 0.75 (T4) and 1.00 g/kg (T5) in triplicate using a functional feed additive L-carnitine, testing its effect on prawn growth, body composition, and gonadal maturity. Daily weight gain (0.46 ± 0.06 g/day) and specific growth rate (3.48 ± 0.12) were considerably enhanced (p < 0.05) in the T3 group with 0.5 g/kg L-carnitine feed. The crude protein content of prawns fed L-carnitine supplemented diets increased, whereas the fat content reduced. On the other hand, dietary supplementation enhanced growth but did not influence gonadal maturity in all-female prawns. The present study indicates that 0.5 g/kg L-carnitine feed can potentially be used as a functional additive for better growth performance in the practical diets of all-female giant freshwater prawns. In conclusion, stocking density influenced growth but not gonadal maturation in all female prawns. Stocking densities up to 24 prawns/m2 yielded the maximum biomass, survival, and feed efficiency, suggesting the intensive farming potential of all-female prawns. This is the first study to evaluate the effect of two potential feed additives, ractopamine and L-carnitine, on improving the growth of prawns. Ractopamine slows gonadal development but accelerates growth in all-female prawns. L-carnitine enhances growth and whole-body biochemical composition but not gonadal maturation in prawns. Researchers in Israel and Thailand are working to establish large-scale all female prawn populations without needing to manually segregate male and female prawns and ensure a steady supply from commercial hatcheries. The current study is expected to speed up the efforts to make giant freshwater prawns more a |
| Year | 2022 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Aquaculture and Aquatic Resources Management (AQ) |
| Chairperson(s) | Krishna R., Salin |
| Examination Committee(s) | Anal, Anil Kumar;Tsusaka, Takuji W.;Amararatne Yakupitiyage |
| Scholarship Donor(s) | National Agricultural Technology Program Phase II project (NATP-2), Bangladesh Agricultural Research Council (BARC), Bangladesh |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2022 |