In intensive shrimp farming, feed accounts for more than 50% of total production costs. Therefore, any mistake in feeding management directly affects the economic efficiency of the crop. One of the most common mistakes today is feeding shrimp according to human routines instead of following the shrimp’s biological rhythm and natural digestive capacity.
Identifying the right time windows when shrimp feed most actively and absorb nutrients best not only helps shrimp grow steadily but is also an important solution for reducing FCR, limiting feed waste, and minimizing pond environmental pollution.
THE BIOLOGICAL RHYTHM AND DIGESTIVE ENZYME SECRETION MECHANISM OF SHRIMP
Whiteleg shrimp are nocturnal. In their natural environment, shrimp often burrow into the pond bottom during the day to avoid predators and only truly forage after dark.
In high-density industrial farming conditions, this behavior may be partially altered through domestication. However, the gene code controlling shrimp’s biological rhythm does not change. The shrimp’s hepatopancreas does not secrete digestive enzymes continuously over 24 hours, but only becomes highly active at certain times.
Physiological studies show that the activity of important enzymes such as amylase and protease usually peaks during two main periods of the day and drops to low levels at other times.
If shrimp are fed heavily when enzyme activity is weak, the feed is not fully digested and absorbed, leading to nutrient loss, higher FCR, and poorer pond water quality.
WATER TEMPERATURE DETERMINES APPETITE AND METABOLIC RATE
The first key factor affecting shrimp appetite is water temperature, since shrimp are cold-blooded animals. Shrimp metabolism follows the Q10 rule, according to which the rate of energy metabolism doubles when temperature increases by 10°C (within the permissible range).
When water temperature exceeds 32°C (usually at midday), shrimp are easily stressed by heat. At this time, digestive enzymes are inhibited, and shrimp reduce feeding to prioritize thermoregulation.
Conversely, in the early morning when the temperature is below 26°C, the shrimp’s digestive system works slowly and nutrient absorption remains limited.
Therefore, forcing shrimp to eat heavily during hot midday hours or cold early mornings is not economically effective.
DIGESTION GREATLY INCREASES OXYGEN DEMAND
Another important factor that is often overlooked is the relationship between feeding and dissolved oxygen (DO) concentration. The digestion of feed, especially high-protein feed, consumes a very large amount of oxygen due to the thermic effect of food.
If shrimp are fed when dissolved oxygen is low, they do not have enough oxygen to operate the digestive system. Feed remaining in the gut for too long will ferment and produce toxic gases, increasing the risk of intestinal diseases.
This is why nighttime feeding, although consistent with the shrimp’s natural behavior, still carries significant risk if farmers cannot ensure that bottom-water oxygen remains abundant and stable.
THE BEST TIME WINDOWS FOR SHRIMP NUTRIENT ABSORPTION DURING THE DAY
By combining factors related to digestive enzymes, water temperature, and dissolved oxygen, two most effective feeding windows can be identified:
Morning window (9:00–10:00):
Water temperature has risen to a suitable level, and dissolved oxygen is high thanks to algae photosynthesis. The shrimp’s digestive system begins to function steadily, making this suitable for a light to moderate feeding.
Late afternoon/evening window (16:00–20:00):
This is the most important feeding window of the day. The water temperature is cool but still warm enough, while also matching the shrimp’s natural feeding behavior at dusk. The hepatopancreas secretes enzymes most strongly, helping shrimp absorb nutrients to the maximum, thereby improving growth rate and reducing FCR.
ADJUSTING FEED RATES TO OPTIMIZE COSTS
To optimize feed efficiency, farmers should:
Reduce feed amounts during hot midday hours
Allocate about 35–40% of the day’s total feed to the late afternoon/evening feeding
Proactively reduce or stop feeding when:
Shrimp molt synchronously
Dissolved oxygen is below 4 mg/L
Following the shrimp’s natural biological rhythm not only helps shrimp grow quickly and stay healthy, but also helps farmers significantly reduce feed costs, a decisive factor in the success of each crop.
Phuong Minh
Source: Tepbac.com
