Effects of Different Feeding Patterns on the Growth of Micropterus salmoides

Yuzhang HAN, Zhourui WEN, Aiwu YI, Jun HUANG, Zhiqiang ZHU, Wenyu TONG, Hongping ZHENG

Abstract Three experimental groups with different feeding frequencies， different feeding rates and compensatory feeding were set up to study their effects on the growth of Micropterus salmoides. The results showed that different feeding rates of 2%， 3% and 4% had no significant effects on the growth of M. salmoides. Therefore， before the individual weight of 50 g， the fish could be fed with a feeding rate of 4%， which could be gradually decreased to 2% in the later period. Under the condition of relatively fixed feeding rate， different feeding frequencies had an impact on the growth of M. salmoides. Under the conditions of suitable water temperature， it is reasonable to feed twice daily. The experimental fish fed for 5 d and then deprived of feed for 1 d showed fully compensatory growth， and there were no significant differences in weight gain rate， daily weight gain and specific growth rate compared with the continuous feeding group （P>0.05）. Therefore， according to the feeding conditions of fish in the breeding process， stopping feeding for 1 d every 5 d could save feed and labor and improve breeding efficiency.

Key words Micropterus salmoides; Feeding rate; Feeding frequency; Compensatory feeding

Received： December 5， 2022  Accepted： February 6， 2023

Supported by Key R&D Program of Hubei Province （2022BBA0058）.

Yuzhang HAN （1967-）， male， P. R. China， senior engineer， devoted to research about pond engineering recirculating aquaculture and disease prevention.

*Corresponding author. E-mail： 2776266101@qq.com.

Micropterus salmoides， commonly known as Jiazhoulu and Heilu， belongs to Micropterus of the family Centrarchidae in the suborder Percoidei of Perciformes. M. salmoides is favored by breeders and consumers because of its fast growth， strong disease resistance， delicious and tender meat， high nutritional value and high economic value［1］. Driven by the economic benefits of aquaculture， the cultivation of M. salmoides has increased year by year throughout the country， and it has become one of the high-quality aquaculture species［2］. Because it can completely eat artificial formula feed after being domesticated， it is suitable for high-density aquaculture， and is also an excellent breeding object for facility fisheries. In this study， the effects of three different feeding patterns， namely， different feeding rates， different feeding frequencies and compensatory feeding， on the growth rate and feed conversion rate of M. salmoides were compared， and appropriate feeding methods and the possibility to optimize the feeding technology for M. salmoides based on the compensatory growth principle were explored， with a view to providing a theoretical basis for saving feed and labor during the breeding process of M. salmoides and improving the breeding efficiency.

Materials and Methods

Experimental materials

The experiment was carried out in the aquaculture base of Yuyatou Aquaculture Professional Cooperative in Zhijiang City， Yichang， Hubei Province. M. salmoides fingerlings used were purchased from a fingerling farm in Jingzhou. The test fish were raised in net cages （4.0 m×4.0 m×2.0 m） before the experiment temporarily， and the formal grouping test was started after 15 d. The fish were fed the test feed （largemouth bass Tonghua formula feed 8901， Tongwei brand） twice daily during the temporary feeding period. The nutrient composition of the feed is shown in Table 1.

Experimental design

The experiment was carried out in net cages （2.0 m×1.0 m×1.0 m）. Three different experimental groups of different feeding rates， different feeding frequencies and compensation feeding were set， and each group was set with three treatments in three repetitions， totaling 27 test cages. Group I was for different feeding rates （2%， 3%， 4%）. Group II was to test different feeding frequencies （feeding once， twice， thrice daily， with a feeding rate of 3%，）. Group III directed at compensatory feeding （feeding every day， feeding for 3 d and stopping feeding for 1 d， feeding for 5 d and stopping feeding for 1 d， with a feeding rate of 3%）. The experiment was carried out in two years. After 15 d of domestication， the purchased M. salmoides with strong physique and similar specifications was selected as the test fish. On July 26， 2019， 120 test fish with an initial average weight of 13.02 g were placed in each cage， and the experiment was ended on December 18， lasting for 146 d. During the experiment， the water temperature was 10.8-32.6 ℃. And on September 17， 2020， 100 test fish with an initial average weight of 14.16 g were placed in each cage， and the experiment was ended on November 22， lasting for 67 d. During the experiment， the water temperature was 18.2-28.4 ℃.

Feeding management

（i） According to different feeding methods， corresponding weight of feed was weighed indoor every day， sub-packaged into different envelopes， and fed according to the experimental design. The feeding amount was adjusted every 20 d according to the sampling situation， and the actual feeding amount of each group was recorded in detail every day.

（ii） The test cages were aerated with bubble stone 24 h a day to ensure that the dissolved oxygen in the water was above 4 mg/L. Water temperature and dissolved oxygen were recorded every day.

Determination and analysis of growth performance

At the end of the experiment， the fish in each cage were caught， counted and weighed， and 30 fish were randomly selected from each cage for the measurement of the body weight， body length and total length， respectively.

Weight gain rate： WGR=100%×（W1-W0）/W0（1）

Daily gain： ADG=（W1 -W0）/t（2）

Specific growth rate： SGR=100%×（lnW1-lnW0）/t（3）

In the equations， W0 and W1 are the weights of fish at the beginning and end of the experiment （g）， and t is the test time （d）. The experimental data （average value） of each feeding pattern were taken as a sample value， and corresponding data of various experimental groups were subjected to analysis of variance forthe significance of differences， with P<0.05 as the level of a significant difference.

Results and Analysis

Effects of different feeding rates on growth performance of M. salmoides

Table 2 shows the effects of different feeding rates on the growth performance of M. salmoides. It can be seen from Table 2 that in 2019， after 146 d of experiment， the experimental group with a feeding rate of 2% had the largest body weight. Compared with the experimental group with a feeding rate of 3% and that with a feeding rate of 4%， there were no significant differences in weight gain rate， daily weight gain and specific growth rate （P>0.05）. In 2020， after 67 d of experiment， the daily weight gains of M. salmoides in the experimental groups with feeding rates of 2%， 3% and 4% increased in turn， but there were no significant differences in weight gain rate， daily weight gain and specific growth rate （P>0.05）.

Effects of different feeding frequencies on growth performance of M. salmoides

The effects of different feeding frequencies on the growth performance of M. salmoides are shown in Table 3. It can be seen from Table 3 that in 2019， the M. salmoides fed three times a day in group 3 grew the fastest， with an average weight of 111.14 g， followed by group 2. The M. salmoides fed once a day in group 1 grew the slowest， with an average weight of 107.83 g. The weight gain rates of experimental group 1， group 2 and group 3 were 728.19%， 731.49% and 753.61%， respectively， and there were no significant differences in weight gain rate and specific growth rate among the three experimental groups （P>0.05）. In 2020， the growth rate of M. salmoides fed twice a day in experimental group 2 was the fastest， followed by experimental group 3 and experimental group 1， and the weight gain rate， daily weight gain and specific growth rate in experimental group 2 were significantly higher than those in experimental group 1 and group 3 （P<0.05）.

Effects of compensation feeding methods on growth performance of M. salmoides

Table 4 shows the effects of compensation feeding methods on the growth performance of M. salmoides. It can be seen from Table 4 that the weight gains of M. salmoides in experimental group 1 （continuous feeding） and experimental group 3 （feeding for 5 d and stopping for 1 d） were higher than that in experimental group 2 （feeding for 3 d and stopping for 1 d）. There were no significant differences in weight gain rate， daily weight gain and specific growth rate between experimental group 1 and group 3 （P>0.05）， and the weight gain rate， daily weight gain and specific growth rate of the two experimental groups were significantly higher than those of experimental group 2 （P<0.05）.

Discussion

Effects of different feeding rates on growth performance of M. salmoides

The results of this study showed that different feeding rates of 2%， 3% and 4% had no significant effects on the growth of M. salmoides. The results in 2019 and 2020 showed that the weight gain rates with the feeding rates of 2% and 4% were the highest， and the 3% experimental group was relatively low， but there were no significant differences among the three， indicating that the 2% feeding rate could basically met the nutritional requirements of M. salmoides for feed under the experimental conditions. The results in 2020 were consistent with the research results of Zhao et al.［3］ and Lou et al.［4］. When the feeding rate reached a certain amount， the results were not better with the larger feeding rate， which can also be seen in the results of Lu et al.［5］ on juvenile Huso dauricus and Yang et al.［6］ on juvenile Takifugu obscurus.

The feeding rate of M. salmoides is closely related to the weather and water temperature. In the study， it was found that when the weather or water temperature suddenly changed， there would be residual feed in the test cages with high feeding rates. The experimental period in 2019 was relatively long， and the maximum and minimum air temperatures in the experimental period were beyond the range of the optimum temperature for the growth of M. salmoides［7］. Some studies have shown that when the water temperature exceeds the optimum temperature for growth， the feeding rate of fish will continue to increase， but at this time， the part of energy consumed for fish growth has begun to decrease， while the part of energy used to maintain basic metabolism has increased， resulting in a reduction in feed conversion rate［8］.

Generally， when the weight of fish is small， the feeding rate is higher than that of fish with large weight. The appropriate feeding rate for M. salmoides fingerlings in a small size is greater than that for fingerlings in a large size. The feeding rate is 4% for individuals lower than 50 g， and gradually decreases to 2% in the later stage， which can ensure feed utilization rate while reducing feed input cost.

Effects of different feeding frequencies on growth performance of M. salmoides

The results showed that under the condition of relatively fixed feeding rate， different feeding frequencies affected the growth of M. salmoides. The weight gain rate with feeding once daily was lower than those of feeding twice daily and feeding thrice daily.

The weight gain rate with feeding once daily was lower than those with feeding twice daily and thrice daily. The results showed that under the condition of relatively fixed feeding rate， different feeding frequencies had an impact on the growth of M. salmoides. The weight gain rate with feeding once daily was lower than those with feeding twice daily and feeding thrice daily. At present， there are several different views on the effect of feeding frequency on fish growth.  Wang et al.［9］ believed that the specific growth rate of Pelteobagrus vachelli increased with the increase of feeding frequency from 21 to 60 d， while Wang et al.［10］ believed that there was no significant difference between the weight gain of M. salmoides fed twice daily and once daily in winter. Xie et al.［11］ believed that the feeding frequency of 2 times/d could meet the nutrition and energy requirements for the growth and development of M. salmoides， when studying the effect of feeding frequency on the growth of M. salmoides in pond engineering recirculating aquaculture. The effect of feeding frequency on fish growth may vary due to different fish species and specifications， feeding rate， breeding environment， seasons and other conditions. In this study， the water temperature in the experimental period of 2020 was in a relatively suitable range for M. salmoides， and the weight gain rate， daily weight gain and specific growth rate of the experimental group fed twice daily were significantly higher than those of the experimental groups fed once and thrice daily. M. salmoides likes feeding in the daytime， and its feeding rate is significantly affected by the environment. Under the conditions of ponds and other facilities， the change of dissolved oxygen in the water body during the day is relatively small， so it is reasonable to feed twice daily under the conditions of suitable water temperature.

Effects of compensatory feeding methods on growth performance of M. salmoides

Compensatory growth refers to the abnormal growth phenomenon or ability of animals after a period of growth stagnation or weightlessness under adverse environmental conditions when the environmental conditions return to normal［12-13］. With regard to the effects of compensatory feeding methods on fish growth， studies at abroad believe that some fish species can show over-compensatory or fully compensatory growth after nutrition restriction［14］. Some studies show that fish can only achieve partial compensatory growth［15］ or do not show compensatory growth［16］ after nutrition restriction. The results of this study showed that the weight gains of the test fish in the groups of continuous feeding and feeding for 5 d and stopping for 1 d were significantly higher than that of the experimental group fed for 3 d and stopped for 1 d. The test fish in the group of feeding for 5 d and stopping for 1 d showed complete compensatory growth， which is similar to the study of Zhou et al.［17］ showing that one day of starvation per week could achieve compensatory growth of M. salmoides. Starvation time is the key factor to compensate for the growth effect in the feeding process of M. salmoides after starvation. According to weather conditions and fish feeding conditions during the breeding process， feeding can be stopped for about 1 d every 5 d to achieve the purpose of saving feed and manpower and improving the breeding efficiency.

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