For aquatic animals, vitamin C is not an "icing on the cake" nutrient, but a crucial substance that determines their survival. Fish and shrimp cannot synthesize vitamin C by themselves and rely entirely on feed to obtain it. Once lacking, the consequences are more serious than you can imagine.
What are the manifestations of vitamin C deficiency in fish?
1. Surface lesions
Surface rot: Fish lacking vitamin C have fragile skin and mucous membranes that are prone to bacterial invasion, leading to local ulcers. In severe cases, scales may fall off and muscles may be exposed.
Bleeding symptoms: Bleeding around the eyes, mouth, at the base of the fins and in the abdominal cavity, similar to scurvy in mammals. For instance, when grass carp lack vitamin C, their eye sockets become congested and their gill covers bleed, while salmon show muscle bleeding and abnormal fin cartilage.
2. Skeletal deformity
lVC is involved in collagen synthesis. When it is deficient, cartilage development is hindered, leading to spinal deformities (such as scoliosis and lortosis), skull softening, and even inability to swim normally. When salmon and trout lack vitamin C, the supporting cartilage of the gill covers and fins becomes abnormal, internal organs bleed, and ascites accumulates.
3. Growth stagnation
Fish lacking vitamin C have poor appetite, slow growth and reduced feed efficiency. When there is a deficiency of vitamin C in the spotted forked tail ð« , weight gain stops, the vertical stripes on the sides of the body fade, the gill filaments and cartilage bend, and the mortality rate occurs
Ii. What are the manifestations of vitamin C deficiency in shrimp?
1. Shell crisis
Soft shell disease: Insufficient calcification of shrimp shells makes their texture soft and they are prone to being eaten by their own kind or mechanically damaged.
Black spots and ulcers: Black stripes appear on the abdomen and legs, black spots form in the stomach or intestines, and the subshell tissue ulcers, eventually leading to mass deaths (typical "Black Death").
Molting disorder: Reduced molting frequency and prolonged molting cycle, with new shells being parasitized by bacteria before hardening, leading to a sharp increase in mortality during the molting period.
2. Immune breakdown
Decreased disease resistance: Shrimp lacking vitamin C have increased susceptibility to pathogens such as Vibrio and leukoplakia virus, and recover slowly after getting sick.
Stress response intensifies: During typhoons, sudden changes in water quality or transportation, shrimp are prone to stress behaviors such as swimming in the pond, turning red, and climbing grass. A deficiency of vitamin C will further amplify these symptoms.
Iii. What are the deep-seated causes of VC deficiency?
VC is prone to oxidation and is lost in large quantities during feed processing, storage and dissolution in water. For instance, the 24-hour loss rate of common crystal VC in water exceeds 50%, while the stability of coated VC is more than four times that.
The demand varies from fish to shrimp
Prawns: Chinese prawns require 4000mg/kg of ascorbic acid polyphosphate. After supplementing with phosphate-esterified VC, the weight gain rate of grouper prawns increased by 30%.
Fish: After supplementing with vitamin C, the growth rate of tilapia increased by 20%, and Atlantic salmon fry supplemented with VC-2-phosphate can promote bone development.
Four. Scientific Supplementation of Vitamin C: Both internal administration and external application, using a dual approach
1. Select highly stable coated VC or phosphate-esterified VC and add it to the feed. Adjust the dosage according to the farmed species and growth stage.
2. In case of typhoons or sudden changes in water quality, apply vitamin C at a concentration of 0.5 to 1ppm throughout the pond to alleviate the stress response of fish and shrimp.
3. Regularly observe the body surface, feeding and activity of fish and shrimp, and supplement vitamin C regularly in combination with water quality testing.