Study Of The Adaptability To Dietary Protein Level In Chinese Soft-Shelled Turtle (Pelodiscus Sinensis)

In this study the adaptability to protein level and compensatory growth of Chinese soft-shelled turtle were investigated. Chinese soft-shelled turtle just incubated (inintail body weight 3.0g)were divided into two groups and fed with two diets analyzed to contain 42.69%(diet 1) and 32.54% (diet 2) of crude protein, respectively, untill the body weight was about 90g, then the trial began, in the first period the two groups were continue fed with the two diets for 40 days, at the end of the first period experiment, the two groups were then divided into two treatments, respectively, so there are four treatments in all: treatment 1 (diet 1-diet l,T₁), treatment 2 (diet 1 -diet 2, T₂), treatment 3 (diet 2-diet 1, T3), treatment 4 (diet 2-diet 2, T₄) in the second period which last for 28 days. The main results were as follows:1. During the first period experiment, weight gain (WG) and special growth rate (SGR) of the turtle fed with diet 2 containing 32.54% crude protein was significantly lower than those fed diet 1 containing 42.69% crude protein, and in the second period experiment the T3 has the biggest WG and SGR significant higher than the others, while the T₂ showed the worst WG and SGR significant lower than the others, and no significant difference was found between the T₁ and T4. The results indicate a compensatory growth in the T₃ and an adaptability to dietary protein level in the T4.2. In the first period the feed intake rate (FR) of the turtle fed the diet 1 was significant lower than those fed diet 2, while feed conversion ratio (FCR) was significant higher than diet 2, protein efficiency ratio (PER) of the turtle fed the diet 1 was lower than those fed diet 2, but there was no significant difference.In the second period no significant difference was found in FR within the four treatments, the FCR and PER in T₂ and T₄ were significantly lower and higher than others, respectively, and no significant differences were found within the others.3. The apparent digestibility coefficients (ADCs) of dry matter, protein and energy were significant higher in turtle fed diet 1 than that of fed diet 2. There was no significant difference in the ADCs of other nutrition ingredients.4. No significant difference (P > 0.05) was found in body composition among turtles fed with different diets. In the first period body composition of turtle fed with diet 2 seems to contain more fat and energy.5. Dietary protein level has significant effect on the nitrogen budget. The nitrogen budgets of the first period were shown as follows:Diet 1: 100C = 45.75G + 8.26F + 45.99UDiet 2: 100C = 53.83G + 9.75F + 36.42U The ratio of urine nitrogen was lower in turtle fed with diet 2. The nitrogen growthefficiency was increased in turtle fed with diet 2, significantly different with turtle fed dietl.The nitrogen intake and assimilation efficiency of nitrogen in turtle fed with diet 1 weresignificantly higher than turtle fed with diet 2. The result indicated that reducing dietaryprotein level can inhance the protein utilization rate.The nitrogen budgets of the second period were shown as follows:Ti: 100C = 39.59G + 7. 15F + 53.26U T2! !00C = 37.77G + 9.58F + 52.65U T3: 100C = 43.96G + 7.38F + 48.66UT4: 100C = 51.45G + 10.28F + 38.27UIn the second period, feed was changed into diet 1 in the treatment 3, but the nitrogen budgets was maintained, so although fed with diet 1, the urine nitrogen was still lower than that of Ti and the nitrogen growth efficiency was higher, it was the main mechanism of turtle's compensatory growth.The urine nitrogen in T4 was significant lower than the other treatments, while assimilation efficiency of nitrogen was significant higher than the other treatments, so although it's nitrogen intake was lower than Ti but it showed similar growth performance, these results indicated that there was an adaptability to dietary protein level in Chinese soft-shell turtle and inhance the protein utilization rate was the main mechanism.6. Dietary protein level has significantly effect on the energy budget. The energy budgets of the first period were shown as follows:Diet 1: 100C = 40.09G + 9. OIF + 4.30U + 46.59RDiet 2: 100C = 35.78G + 11. 12F + 2.70U + 50.40R In the present study the energy intake in the turtle fed with diet 2 was higher but for a lower digestibility so the assimilation efficiency of energy was lower than that of turtle fed with diet 1, also the high metabolize energy contribute to a lower energy growth efficiency than that of diet 1, despite a significant lower urine energy.The energy budgets of the second period were shown as follows:Ti: 100C = 27.80G + 8.55F + 6.51U + 57.15R T2: 100C = 25.21G + 10.03F + 3.89U + 60.87R T3: 100C = 36.62G + 8.68F + 4.48U + 50.22RT4: 100C = 29.89G + 10.95F + 2.83U + 56.33R In the second period, the diet of T3 was changed into diet 1, the assimilation efficiency of energy was improved and metabolize energy was reduced and the most important was the lower urine energy was maintained, that was the reason of the rapid growth of T3, and the main mechanism of compensatory growth in Chinese soft-shelled turtle.In the second T4 get a much lower ratio of urine energy, significantly different with the other three and the metabolize energy decreased so more energy was used in growth, this is the reason for a similar growth performance to Ti and turtle' adaptability to protein level.T2 and T4 were fed with same diet but the urine energy and the metabolize energy in T2 is significant higher than T4, while the energy growth efficiency is significant lower than T4, it indicate that the pre-domestication has an obviously influence on turtle adaptability to protein level.7. In this study the length, width and weight of digestive tract were measured to investigate the relationship between morphological characteristics of turtle digestive tracts with its food quality and energy requirement. The length and width of digestive tract organs of turtle fed diet 2 were increased compared with that of diet 1, but the weight was reduced. The length, width and weight of digestive tract were increased in female turtle compared with male.