| Exogenous recombinant mouse leptin was injected into hyline grey laying hens to research effectsof leptin on blood biochemical parameters, development and reproduction, feeding behavior andexpression of leptin receptor gene, to research the effects of leptin on energy metabolism, developmentand reproduction and behavioral parameters of laying hens.25hyline grey laying hens at30weeks oldwith similar weight (1560g±114g) were divided into5treatments:(I) free feeding group;(II) fastinggroup;(III) fasting+50μg/kg BW/d leptin;(IV) fasting+200μg/kg BW/d leptin;(V) fasting+400μg/kgBW/d leptin. Record the egg weight, food intake and water intake of laying hens every day.(1) Effects of Exogenous leptin on energy metabolism and behavior changes in laying hensAfter fasting in two days showed fasting led to body weight decreased significantly, body weightof test II~V were92.24%,99.18%,98.53%,95.30%of free feeding group. Compared to free feedinggroup, fasting groupdecreased very significantly (P<0.01), test III and IV, decreased significantly(P<0.05). No significant difference was showed in remianing tests (P>0.05); proportion of abdominalfat weight, proportion of abdominal fat weight of test I, II, IV was obviously lower than that in test V,only58.98%、45.85%、58.71%, the differences were significant (P<0.05), no significant differenceswere found in other tests (P>0.05).Intestinal villus length, crypt depth, V/C: duodenal, compared to free feeding group, villus lengthin free feeding group was shorted by16.24%, decreased significantly (P<0.05), crypt depth increased by22.60%significantly (P<0.05), the mean value of V/C decreased by35.40%significantly (P <0.05).Villus length of test III~V, V/C was lower than group I, crypt depth was higher than that of free feedinggroup, the difference was not significant (P>0.05). The jejunum, compared to free feeding group, theaverage villus length of fasting groupwas shorted by14.75%, differences were significant (P<0.05),crypt depth increased by21.83%significantly (P<0.05), Villus length of test III~V were lower than freefeeding group, while crypt depth was higher (P>0.05), V/C values of test II~V were lower than that offree feeding group, the difference was not significant (P>0.05). The ileum, villus length and V/C valuesof test I, III, IV and V were higher than test II, the differences was not significant (P>0.05), crypt depthof test I, III, IV and V were lower than test II, the difference was not significant (P>0.05).Feed intake, feeding frequency, water intake and drinking frequency: with the increase of Injectionamount of exogenous recombinant mouse leptin, feed intake, feeding frequency, water intake anddrinking frequency of four fasting groups of laying hens decreased gradually. Feed intake, test III，IVand V were92.86%,89.89%and75.46%of test II. Test V decreased significantly (P<0.05). No significant differences were showed between Test II~V and free feeding group (P>0.05); Feedingfrequency, test III~V were87.09%,65.52%,63.00%of test II. Compared to fasting group, Test III~Vdecreased very significantly (P<0.01), to free feeding group,test IV and V decreased very significantly(P<0.01); test III~V drinking water weight were82.83%,71.20%,57.65%of fasting group(P<0.05);Drinking frequency, test III~V were84.24%,74.03%,28.53%of test II. Test II~V group decreased, thedifferences in every two groups were very significant (P<0.01). Compared to free feeding group, test IVand V showed a significant decrease (P<0.01).Glucose, triglyceride: with the increase of injection amount of leptin, the glucose, triglyceridecontents showed a downward trend in overall. The glucose contents of test III and IV were61.15%,59.59%of fasting group (P<0.05), while no significant differences were showed between test II~V andfree feeding group (P>0.05). Triglyceride, TG content in each group had no significant changes; thedifference was not significant in other groups (P>0.05).Time of food intake: Time of feed intake and water intake of laying hens firstly increased and thendecreased with the injection amount of leptin increase. The feeding time and drinking time in test IIIreached the peak then decreased substantially. Compared to test IV, test V decreased significantly(P<0.05). Time of feed intake and water intake of four fasting tests were not lower than test I mainly.Changes of other behaviors: the occurrence times of feather combing, stretching, turn-back in alltests showed no significant variation, the difference was not significant (P>0.05). The fights occurrenceof test II~V decreased significantly (P<0.01).(2) Effects of Exogenous leptin on ovarian reproductive function in laying hensOvary weight proportion, stroma weight proportion, oviduct weight proportion and oviduct length:Ovary weigh proportion of fasting groupwas only42.86%of free feeding group, the difference wassignificant (P<0.01)，oviduct weight proportion of fasting groupwas only65.02%of free feeding group,the difference was significant (P<0.05). Ovarian weight proportion, oviduct weight proportion, oviductlength of fasting groupwere lower than those of test I, III, IV and V, differences were not significant(P>0.05).Follicle weight and follicle number: the number and weight of large yellow follicle in fasting group(follicle diameter>22-30mm) and were25%,12.60%of free feeding group, the differences weresignificant (P<0.05). White follicle, yellowish follicle, small yellow follicles, medium yellow folliclesof Test I~V had no significant differences in the number and weight (P>0.05), increased by21.83%significantly (P<0.05), Villus length of test III~V were lower than free feeding group. V/C values of testII~V were lower than that of free feeding group, the difference was not significant (P>0.05). The ileum,villus length and V/C values of free feeding group, test III~V were higher than test II, the differenceswas not significant (P>0.05), crypt depth of free feeding group, III~V were lower than test II, thedifference was not significant (P>0.05). Estradiol, progesterone, estradiol, compared with free feedinggroup, E2content of test II~V decreased significantly in the third day (P<0.05), refed after two days offasting, E2content of test II~V increased significantly (P<0.05). The E2content of test III, IV werehigher than test I, II and V (P<0.05). Progesterone, compared with free feeding group, after two days of fasting progesterone content of test II~V decreased significantly (P<0.05). After fourth days of recoveryby ad libitum, progesterone content of test III, IV gradually increased, and then decreased. No obviouschange was showed in fasting groupand V.(3) Effects of exogenous leptin on expression of OB-R gene in liverQuantitative expression of OB-R gene of liver in test I, III, IV and V were35.19%,6.17%,7.41%,3.09%of test II, the difference was not significant between all tests (P>0.05). |
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