Feed conversion ratio (FCR) is the ratio or rate measuring of total used feed and total weight of shrimp harvested per unit area. For each species, each feed had different feed conversion ratios. FCR depends on basic factors such as: species and quality of seed, feed quality and feeding, water quality.
Each species will have a different FCR. For example, the white leg shrimp has a FCR of 1.1 - 1.3 and the black tiger shrimp’ is 1.6. Seed quality also influences the feed conversion ratio because of poor quality shrimp seed as the slow-growing shrimps will result the poor output, thus the total shrimp weight harvested on 1 unit area will decrease. In order to increase efficiency and improve FCR, it is necessary to select breeding stock on the basis of prestige and to test shrimp quality before stocking. Some of the following methods also help reduce FCR in shrimp culture:
1. Preparing the pond thoroughly
Before the start of the crop, it is necessary to thoroughly remove the trash fish, crab cuffs, etc. in the pond to reduce the FCR caused by the consumption of food from these unwanted species. For shrimp ponds that cannot be completely eliminated trash fish, farmers have to use manual methods to remove trash fish in the pond.
2. Water quality management.
Water is the habitat of aquatic animals. Poor water quality has a direct impact on their physiological function. It will directly affect the appetite of the shrimp, resulting in reduced digestive function of the intestines and reduced digestion of nutrients in the intestine thereby increasing the FCR, especially the dissolved oxygen factor. A good pond management can reduce the amount of food left over, thus, FCR is low, farmer then can save 10-30% of food intake and improve water quality.
3. Should not feed the shrimp too late.
Experienced farmers know that feeding should not be too late, because digesting food is a process of consuming oxygen, feeding too late can easily lead to hypoxia. At night, in many ponds, dissolved oxygen is less than 3 mg. When feeding shrimp in low dissolved oxygen (at 3 mg/l), the FCR is at least 1 times greater than that at the area with high dissolved oxygen (at 6 mg/l).
It is therefore necessary to design ponds that can collect waste and remove it by siphon tubes periodically. It will also reduce the oxygen consumption of pond bottom waste. Use aeration equipment in the feeding area to provide continuous and stable dissolved oxygen to help maintain the shrimp's appetite thereby improving digestibility.
4. Adjust the food properly
Research results from Carter Ullman 2018 have shown that daily feed intake can be increased without significantly affecting water quality or FCR by increasing the number of feeds from 2 to 6.
In practice, the amount of food used should be divided into several times a day (6 or 7 times a day) or households should install the feeding system. Although using a feeder, the farmer also needs to adjust the feed quantity according to the feeding conditions of the shrimp.
5. Use feed appropriate to the model
Shrimp farming in 2 or 3 stages or using Biofloc method will help to save considerable amount of food. Each farming system will use a different kind of food including characteristics such as protein content, lipid, fiber ... and moisture.
6. Maintain intestinal tract in the culture process.
Intestinal tract is the most important organ for digestion and absorption of nutrients. Therefore, the health of the gut has a direct influence on the feed ratio. During shrimp culture, the addition of intestinal bacteria such as B. subtilis, yeast extract and other additives can protect the intestines of the shrimp, helping to maintain digestive function and uptake of intestinal food. Previous studies have shown that nucleotide supplementation of 30-50 g / kg of yeast helps stimulate growth, immune function and increase intestinal wall thickness of white shrimp.