| Loach is widely distributed in China,but it is serious shortage of loach seedling supplybecause of overfish,environment pollution,abuse of pesticides and habitat destruction, soartificial propagation is an extremely urgent. The study included the selection of hormonetypes,hormone dosage and the best sex ratio of artificial propagation. The main results areas follows:1Comparison of morphological characteristics between Paramisguruns dabryanusand Misguruns anguillicaudatus.The data of BL/BH, CPL/CPH,HL/SL,MBL/HL were analyzed. The results showedthat CPL of P. dabryanus was1.07±0.10times, which is more than its CPH and CPL of M.anguillicaudatus was1.84±0.12times more than its CPH; MBL/HL of P. dabryanus and M.anguillicaudatus was1.05±0.11and0.54±0.11, relatively. CPL and MBL/HL betweentwo loaches were significantly different.(BL=body length,BH=body height,CPL=length ofcaudal peduncle,HL=head length, SL=snout length,MBL=length of mouth beard, HL=headlength)2The selection of loach parentsThe research on female fecundity of98loach parents indicated that the segment of thebody length in10～20cm accounted for72.4%of the total number of samples. Body lengthwas15cm or more, their absolute mean fecundity was15000, and the maximum fecunditywas up to more than25000. The result showed that selecting female loach with body lengthof10-20cm could possibly obtain the highest fecundity.3Several different hormones and their combinations on the effect of loach breedingBy injecting different volume of HCG, LRH-A3, HCG+LRH-A3andHCG+LRH-A3+DOM to female loach body length in15～20cm and12～15cm male loach,we separated them into five classes and three replicates and we had60experiments in total.Studying each set of experiments on the effect of loach breeding, the results showed that:(1)HCG can be used as a single oxytocin in loach artificial oxytocin, but needed a largeramount of oxytocin and its cost is high, it does not suit for the large-scale breeding.(2)Asingle injection of LRH-A3(1.6μg)can also lead to the loach estrus spawning, but it workedineffectively; when injected a small amount(≤0.4μg),the experimental groups hardlyspawned; contrarily(≥3.2μg), they would die, therefore, simple LRH-A3is not suitable forloach artificial breeding.(3)Composite hormones also had certain effect on oxytocin in thecase of low dose, the optimal concentration of HCG+LRH-A3is240IU+0.5μg.(4)The dose of HCG+LRH-A3+DOM in120IU+0.8μ g+0.5mg is the best group to induced spawning(the oxytocin rate was91.9%, each of the female ones spwaned7994.3eggs, fertilizationrate was88.1%).(5)Comparing the cost of spawning, the maximum was up to3761.9fen(the dosing of simple LRH-A3is3.2μg), the minimum is only69.0fen(the dosing ofHCG+LRH-A3+DOM is120IU+0.8μg+0.5mg), The study indicated that the best artificialoxytocin combinations and dose is HCG120IU+LRH-A30.8μg+DOM0.5mg.4Effects on the different sex ratio of loach breedingThe experimental groups were designed according to the sex ratio (4:1,3:1,2:1,1:1,1:2,1:3,1:4). Each female loach was injected with HCG120IU+LRH-A30.8μg+DOM0.5mg, while the male loach was injected with halved account. Each group had3replicates,and21experimental groups were needed. The results showed that oxytocin rate of thegroup in sexy radio of1:2was93.1%, and fertilization rate was90.5%, however, the dateof the sexy radio of1:2was90.3%and92.1%, between which the data were notsignificantly different (p＞0.05). In the producing process, the ratio of female to male in1:1could save the number of male loach, and reduce the production costs and labor intensity. |
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