| Although the hatching rate of fertilized eggs under natural incubation conditions is high,the hatching efficiency is low,and it is difficult to meet the needs of large-scale goose breeding industry.Simply using chicken hatchers to incubate goose eggs often results in fewer goslings hatching from already limited goose eggs.Therefore,how to hatch the limited goose eggs into more goslings and more robust goslings has become an urgent problem to be solved in today’s goose raising industry.Experiment 1: We observed the difference between natural hatching and chicken hatching machine,and put forward the incubation strategy of large Angle egg turning,and found that the strategy of large Angle egg turning significantly improved the hatching rate of fertilized goose eggs.Further study found that the death rate of embryos in the 60° group was two percentage points lower than that in the 70° group during the 19-28 days of incubation,so we designed the experiment of "variable Angle" egg turning strategy,that is,set the Angle of egg turning forward and backward as 70°(the Angle of egg turning is 140°)during the 0-18 days of incubation.After 19-28 days of incubation,adjust the forward and backward egg turning Angle to 60°(egg turning Angle to 120°).It was found that although there was no statistically significant difference in the variable Angle egg-turning strategy,the fertilized egg hatching rate of the two kinds of goose eggs in incubation was the highest,and the Huoza goose eggs reached the highest of 91.76%,which was much higher than that of the fertilized egg hatching rate of 85% in the conventional hatching Angle(45°-50°).In addition,it was found that the optimum egg turning Angle of Sanhua and Huoza geese(Holdobaghi geese and Taizhou geese cross)was different.The optimum forward and backward turning Angle of Sanhua goose eggs was 60°,and the hatching rate of fertilized eggs was 86.31%.The optimum forward and backward turning Angle of Huoza goose eggs was 70°,and the hatching rate of fertilized eggs was up to 90.56%.It was further found that high Angle egg flipping affected 18-29 days of mortality.In the incubation of Sanhua goose eggs,the mortality rate of 18 to 29 days in the large Angle group(70° group)was 2.18% lower than that in the small Angle group(50° group).During hatching of Huoza goose eggs,the mortality rate of 18 to 29 days in the large Angle group(70° group)was 2.19% lower than that in the small Angle group(50° group).The weight of the goslings was also related to the Angle of egg turning.The greater the Angle,the greater the birth weight of the goslings.The 50° group was 108.26 ± 9.77g;The 60° group was 109.37 ± 9.89g;The 70° group was 111.38 ± 8.29 g;In 70° to 60° group,110.63 ± 10.48 g.The key growth-related hormones of 27E(27 embryo age)embryos and 1D(1 day old)goslings were detected.The key growth-related hormones T3,GH and IGF1 in the large Angle group were significantly higher than those in the small Angle group.Experiment 2: Based on the large Angle group of experiment 1,the birth weight of goslings increased and the blood growth-related hormones increased,and the experiment was designed to verify the effect of large Angle egg turning on the secretion of growth-related hormones in goslings by influencing the secretion of T3.By intraperitoneal injection of T3 at different concentrations,GH in blood was significantly increased at the dosage of 32.5-130 μg/kg at 12 h compared with the control group.Further observation of GH concentration at different time after injection showed that GH in blood increased significantly compared with the control group at intraperitoneal injection of 65 μg/kg T3 after 8 h.It is also suggested that high Angle egg turning may regulate the later growth of goose embryo and goslings by affecting the concentration of thyroid hormone in embryo.In addition,quantitative analysis of key growth-related genes in the hypothalamus showed that the expressions of GHRH,RARB and RXRA were not increased after intraperitoneal injection of T3,while THRB and Raldh1 were significantly increased in the hypothalamus.These data suggest that T3 may not regulate the body weight growth of goose embryos through the GHRH pathway in hypothalamus and affect the growth of goslings.Experiment 3: In order to further clarify the specific regulatory mechanism of T3 regulating GH signaling pathway,transcriptome sequencing was performed on hypothalamic tissues of goslings at 2 h and 8 h T3 injection after based on the data of GH concentration changes after T3 injection in experiment 2.The results showed that the expression of TTR gene was the highest after T3 injection,suggesting that high concentration of T3 down-regulates the expression of TTR in hypothalamic cells,regulates the physiological homeostatin of T3,and affects the concentration of retinol in blood and cerebrospinal fluid.After T3 injection,the differential genes that existed only at 8 h were enriched,and the results showed that the differential genes were significantly enriched in the retinol-RA metabolic pathway,which also suggested that the retinol-Ra metabolic pathway responded to the changes of T3,which also indicated that the retinol-RA metabolic pathway was an intermediate pathway in the regulation of growth by T3. |
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