Silver carp (Hypophthalmichthys molitrix) is a well-known viable aquaculture commodity in Pakistan that is well adapted to confinement, has fast growth rates, high feed conversion ratios, and can withstand a wide range of temperatures. silver carp can attain a maximum length of 140 cm and weight up to 50 kg. Furthermore, it has distinctive feeding behavior, including rapid zooplankton gulping, fine particle filtration, and a non-intrusive snapping attitude toward swimming zooplankton in front of other tank companion fishes.

 Silver carp has a high market value due to its higher lean mass, high-quality protein, and long shelf life. The production efficiency of many aquaculture fish species has recently been improved worldwide through the growing trend of intensive aquaculture.  Intensive aquaculture is an organized fish farming system to achieve maximum fish production. However, temperature fluctuations, overcrowding, water quality deterioration, and infectious agents’ invasion are the major limitations of such systems. These factors can impose oxidative stress, disrupt various physiological processes, histopathological changes, and ultimately immunological deficiencies. 

The practical solution to preventing these negative effects is to add certain supplements to the fish feed. Feeding a balanced diet according to fish requirements under a controlled environment is the main objective of the modern intensive aquaculture production system. Research is established that overdosage and deficiency of dietary Se, vitamin E, and vitamin C has detrimental effects on the health and growth of different animal species.  

Selenium (selenocysteine (Se-Cys), a well-known cofactor form, contains 21 amino acids and has 25 forms in the animal body. It is a component of the active center of glutathione peroxidase (GPx), which protects cells and membranes from oxidative damage by catalyzing hydrogen peroxide and lipid peroxide reduction. Se deficiency can cause growth depression, loss of appetite, and other symptoms. Vitamin C another name for ascorbic acid has scavenging free radicals’ effects and participates as a cofactor in several metabolic recycling processes (Smirnoff 2018). Dietary vitamin C requirements are varied according to fish type, stage of growth, body size, and changes in environments. Vitamin E supply disrupts systemic lipid peroxidation through neutralization of the peroxide radicals and resulting minimize the oxidation of pool fatty acids. 

It is well established that dietary vitamin E has a positive impact on growth, immunity burst, and produces stronger as well as healthy fish. However, dietary supply of Se, vitamins E, and C and their synergistic impact on performance silver carp is still not clear. For this, a series of experiments were carried out at the Training and Research Demonstration Fish Hatchery, Ravi Campus, UVAS, Pakistan. This research was conducted under the supervision of HEC-recognized Assistant Professor Dr Mahroze Fatima.

In experiment one, a total of 420 fingerlings silver carp were fed on five diets: 1) basal diet as a control (C), 2) with 0.5 (N-0.5), 3) and 1 mg/kg sodium selenite (N-1), 4) with 0.5 (M-0.5), 5) and 1 mg/kg Se methionine (M-1), and with 5) 0.5 and 6) 1 mg/kg Se yeast (Y-1). The 0.5 mg/kg dietary supply of methionine-based Se. In experiment two, a total of n=300 juvenile silver carp were fed on five dietary Se methionine levels @ 0.0 mg/kg, 0.3 mg/kg, 0.6 mg/kg, 0.9 mg/kg, and 1.2 mg/kg of the basal diet. In experiment 3, a total of 480 juvenile silver carp were stocked in 24 aquaria (20 fish/100L aquaria), and distributed to eight pelleted diets: D1 (basal diet without any supplementation), D2 (basal diet supplemented with 0.9 mg/kg Se), D3 (basal diet supplemented with 300 mg/kg vitamin C), D4 (basal diet supplemented with 100 mg/kg vitamin E), D5 (basal diet supplemented with 0.9 mg/kg Se, and 300 mg/kg vitamin C), D6 (basal diet supplemented with 0.9 mg/kg Se, and 100 mg/kg vitamin E), D7 (basal diet supplemented with 300 mg/kg vitamin C, and 100 mg/kg vitamin E) and D8 (basal diet supplemented with 0.9 mg/kg, 300 mg/kg vitamin C, and 100 mg/kg vitamin E). Based on the results of these experiments, the conclusion is that selenium methionine is the best source and has a dosage @ 0.9 mg/kg in the diet. Dietary supplementation of Se methionine, vitamins E and C improved growth performance, Se deposition in tissues, and antioxidant status of silver carp without affecting the meat quality.

Written by Maida Mushtaq and Mahroze Fatima (PhD scholar, University of Veterinary and Animal Sciences, Lahore)