Effect Of Social Rank On Reproductive Behavior And Parental Efficiency In Competitive Mating Flocks Of Geese

Animals determine their social rank(SR)in the group through agonistic behavioral interactions(ABI).The SR of an animal in the group has an important impact on the size of its living environment,the intake of nutrients,and its reproductive activities.Reproductive behaviors(including courtship,mounting,and mating(MA))are important factors affecting reproductive efficiency(RE)in geese.Improving RE and breeding gander with high RE is always one of the important breeding goals.Under natural mating conditions,SR has an important impact on the RE of geese.In order to accurately evaluate the genetic contribution rate(GCR)of gander in different SR of a population,this study used parental efficiency(PE)to measure the GCR of different ganders.The experiment was divided into two parts.Experiment 1 measured the effect of ganders’ SR on courtship behavior,mating behaviors and PE through a single-factor experimental design.Experiment 2 measured the effects of SR and sperm motility(SM)on PE using a two-factor nested experimental design.The ganders in each flock were of the same age,the same breed,and the similar weight.The semen volume and sperm concentration of the goose were preliminarily selected before the experiment.Trial 1 consisted of three replicates,where group I included 9♂×45♀(male-female ratio1:5),group II included 11♂×55♀(male-female ratio 1:5),and group III included 15♂× 90♀(male to female ratio 1:6).Before the test,the ganders were raised in a single cage to determine the body weight.The necks of ganders were marked with different colors.Cameras were set up around the experimental house.Behavioral and mating behaviors totaled 12 days,and the SR of the geese within the flock was determined based on ABI.Eggs were collected during the observation period,and DNA of offspring was extracted after hatching.Molecular genetic markers were used to identify the genetic relationship between parents and offspring.After the test,the blood of gander was collected and the concentrations of T,LH and FSH hormones were measured.Experiment 2 explored the effects of SR and SM on RE.The ganders were housed in a single cage and their body weights were measured.Semen was collected 3 times within 12 days,and SM was analyzed.According to the level of SM,the ganders were divided into three groups:high,medium,and low,and three SR of high,medium and low were nested within each group.Each SM group included two replicate test groups,for a total of 6 experimental groups.Each sperm motility group contained two replicate experiments,for a total of 6 experimental groups.Each experimental group included 3 gander and 18 female geese(male-female ratio 1:6).The entire experiment consisted of 18 gander and 108 female geese.Blood of goose was collected and the concentrations of T,LH and FSH hormones were measured.The gander and female geese were reared in mixed groups,and cameras were set up around the experimental goose house.After the male and female geese were mixed together,the ABI and breeding behavior of each gander were observed for a total of 15 days and hatch.The PE of each gander was analyzed by paternity testing technology,and the influence of the SR and SM of the goose on the PE was analyzed.The results of experiment 1 showed that the distribution of gander in the three flocks was2:2:5,3:4:4 and 5:5:5 in high,medium and low SR,respectively.SR had no significant effect on the frequency of courtship and mounting behavior(P > 0.05),but had a significant effect on the frequency of MA(P < 0.05).PE of gander presents a skewed distribution,and the PE of gander with high SR,which account for the minority of gander flocks,accounts for 47-58 % of the total PE of the whole goose flock.The results of experiment 2 showed that both SR and SM of gander had significant effects on PE(P < 0.05).The PE of gander in the high SM group was significantly higher than that in the middle and low SM groups,and the difference was significant(P < 0.05).The individual PE of the goose flock is characterized by skewed distribution,and the PE of gander with a high SR,which is a minority of the gander flock,accounts for 47 %-54 % of the total PE of the whole goose flock.There was no direct correlation between SM and reproductive behavior(courtship,straddling,mating)(P > 0.05).Taking ABI and SM traits as breeding selection criteria can improve the ganders’ PE,breeding for traits of high SR and high SM can improve PE of gander.The RE of a goose flock depends on the uniformity of gander SM traits.