Physiology of Finfish and Shellfish (2+1)

4.4.11. Faeces

The non-digestible fraction of the dies along with sloughed intestinal epithelial cells, mucous, catobolised digestive enzymes and bacterial constitute the main components of the faeces. The composition of this varies with respect to the composition of food.

Carnivores – 100C = 29G + 44M + 7E + 20F

Herbivores – 100C = 20G + 37M + 2E + 41F

Chanos chanos : Faecal loss 50-65%

Protein are easily being digested in fish and assimilation above 90% is recorded. But if the protein is in excess of the requirement of the fish deamination occurs with excretion of nitrogen, mainly at ammonia and urea across the gill. Unlike mammals (under normal conditions) which tend to use a large protein of carbohydrate and lipid for energy, fish normally exploit a portion of their protein (upto 14-15%) stone as an energy source. The fish can utilize fat and carbohydrate under stressed conditions.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O 10.1

2C₃H₅ (C₁₅H₃, COO)₃ + 145O₂ → 102CO₂ + 98H₂O 0.703

Study of energy utilization substance through energy with the following detail.

Oxygen consumption ml O₂/hr = 388.3 ml O₂/kg/fish

Carbondioxide output = 660.4ml/hr/kg fish

Total nitrogen excretion = 33.12 mg/kg/hr

Oxygen consumption for 1hr = 388.3ml/kg fish

or = 554.7 mg/kg fish

Carbon-di-oxide output for 1 hr = 660.4 ml/kg fish

Respiratory quotient = 660.4 / 388.3 = 1.701

CO₂ relased from anaerobic metabolism = 660.4 x 0.701 / 1.701

Since maximum aerobic RQ is 1

= 272.2 ml /kg/ fish

Aerobic CO₂ output for 1 hr = 660.4-272.2 = 388.2 ml/kg/fish

Oxygen required to degrade protein to produce 33.12mg of nitrogen = 33.12/0.148 = 223.8 mg/kg

Carbor-di-oxide equivalen to 15.6ml of O₂ in the prot in break down (Since, the protein RQ is assumed to be unity for fish system = 156.6ml/kg/fish.

Non protein oxygen = 388.3 – 156.6 = 237.7 ml/kg fish.

Non protein CO₂ = 388.2 – 156.6 = 231.6

Non protein RQ = 231.6 / 231.7 = 0.9996.

Lactate product for releasing 6.19 milli moles of CO₂ in 1 hr = 6.19 millimoles/kg fish

Glycogen (Glucose) utilized for 6.19 millimoles of lactate production = 6.19/2 = 3.1 millimole.

The energy released from 1 mole of glucose thro glycolysis is 52kcal or 52cal per millimole, from this it can be estimated that the total yield from anaerobic source is 161.2cal (3.1x52cal) per kg fish. Thus the total energy utilization by fish is computed as 2045.74 cal (Protein 715.66; carbohydrate:lauobic 1061.33; carbohydrate and fats in fish are 34.98; 51.88 and 5.26 respectively and the remaining percentage of 7.88% derived from available source.

Carnivores = 100c = 29G + 44M + 7E + 20F

Herbivores = 100c = 20G + 37M + 2E + 41 F

Assimilation efficiency of fish is comparatively less in herbivores than carnivores.

In carnivores W₂ loss is more.