The Investigation On Influencing Tactors About Egg-Laying Performance And Principal Diseases Of Chinese Alligator Breeding Population

Chinese alligator (Alligator sinensis) is an endemic and first-classed protected species in China. The breeding population enlarged greatly and it showed low ability of egg-laying and high disease ratio.We researched the influencing factors on the egg-laying performance and investigated on the main diseases existing in the population in the An hui Research Center of Chinese Alligator Reproduction. According to the statistical comparison between parental and offspring laying record over the years, we analyzed the main reason for the decline in laying performance of the Chinese Alligator offspring during incubation period from the point of captivity management. Based on the anatomic observation of the development of adult female follicles in different months from 2004 to 2012, combined with follow-up observation of laying changes of the breeding individual over the years, we studied the general rules for the follicle development and laying of the breeding population, and explored the improvement of the breeding system of Chinese alligators. In this paper, we also investigated the situation of disease occurrence of the breeding population in the areas of Xuancheng, Wuhu and Nanjing during 2010 to 2013, and summarized the etiology, symptoms, popular features, anatomical changes and prevention measures of common diseases of Chinese alligator breeding population, in order to provide some reference basis for artificial breeding of Chinese alligators. The main research results are as follows:1. The laying performance of parental populations which went through natural overwintering is superior to that of the offspring populations which went through artificial overwintering(p<0.01). In the offspring populations, the performance degradation phenomenon did not appear between the first filial generation and the second filial generation(p>0.05). The laying performance of the alligators between 7 to 8 years old was significantly higher than that of the ones which were 9 to 10 years old(p<0.01), provided that they all went through artificial overwintering. The main reason for the degradation of the Chinese alligator spawning performance is that the adult alligators which enter the breeding ground of crocodiles were all from high density artificial breeding and overwintering, and the incubation period of breeding and overwintering environment hindered the normal development of the gonad of the female Chinese alligators.2. The sexual maturity age of female Chinese alligator is 9 to 11 years old under artificial breeding conditions. Its laying period is about 28 years, with a rich period of 14 years.3. Follicular development of Chinese alligator has obvious periodicity. The adult alligator’s follicles begin to develop slowly in February every year. The follicular develop rapidly, the yolk sediment speed up and follicular volume increase obviously in April. June is the period of ovulation follicle and mature ovum turn into the Fallopian tube. The adult alligators begin to lay eggs after formed egg white and egg shell in late June to early July generally. Un mature follicles will be transferred to a resting state at the end of July. It would continue to develop in the next year, and form a continuous laying phenomenon. The follicles size of different individuals varies considerably in the same season. Chinese alligator’s follicles matured every two years instead of one year.4. The Chinese alligator laying clutch mass of captivity is positively correlated with age.The correlative coefficient is 0.9714. The related equation is y=137x0.7816.5. On the basis of further improving the pedigree management of Chinese alligator, we advanced the breeding age to 4 years old and established Chinese alligator breeding system. We proposed to improve the Chinese alligator reproduction and breeding system in the aspects of genetic management, nutrient management, adjusting micro-environment, etc.6. The common diseases of captivity Chinese alligator populations are gastroschisis inflammation, larval crocodile paralysis, rectal obstruction, deficiency disease, gastroenteritis, stomach worm disease, gout, pulmonary edema, trauma, skin mycosis, eye disease and frostbite, etc. The opportunistic pathogen generally existing in Chinese alligators’ living environment can easily cause disease when the alligators’ health begins to decline. Prevention combined with treatment is important for the prevention of diseases for Chinese alligators. Emphasis should be put on breeding management, active improvement of environmental and hygiene conditions actively, reduction of interference and enhancement of body immunity. Early treatment of the disease has better results.