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Submitted to: Open Journal of Animal Sciences
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/10/2014 Publication Date: 1/13/2015 Publication URL: http://handle.nal.usda.gov/10113/60175 Citation: Kulkarni, G., Zhang, H. 2015. Evaluation of reproductive characteristics of 21 highly inbred lines of White Leghorns divergently selected for or segregating in tumor resistance. Open Journal of Animal Sciences. 5:59-70. doi: 10.4236/ojas.2015.51008. Interpretive Summary: Inbred lines of chickens are costly and technically hard to develop yet they are invaluable genetic resources for both research and diagnostic tests to say the least. The USDA, Agriculture Research Service laboratory at East Lansing, Michigan, has developed and maintained a good number of specialized experimental lines including inbred lines through enormous efforts by many scientists served in the laboratory during the past decades. A total of 21 inbred lines were evaluated for important reproduction performance characteristics, including fertility, embryonic mortality, and hatchability of fertile eggs using reproduction records during an 8 year period (2005-2012). The data clearly showed significant differences in all the three characteristics from year to year, and among the genetic lines, which strongly suggest both environmental and genetic factors played roles influencing the reproduction characteristics of the inbred lines. The findings would help researchers to better understand and take action to improve the reproduction performance of the inbred lines, which would then reduce the costs for maintaining the lines and improve the availability of chicks from the lines for research and diagnostic needs. Technical Abstract: Reproduction performance of 21 inbred experimental lines of White Leghorns were evaluated based on samples of reproduction records over a period of eight consecutive years. Two lines (63 and 72) have been extensively used in studies, especially in research seeking for genetic and epigenetic factors underlying resistance to avian tumor virus-induced diseases in chickens. The other 19 lines are recombinant congenic strains (RCS), which were generated by crossing lines 63 and 72 followed by two consecutive backcrosses to the line 63 and then full-sib mating. In theory, each RCS processes 7/8 of progenitor background line 63 genome and a random sample (1/8) of the progenitor donor line 72 genome. All 21 inbred lines share a common major histocompatibility complex haplotype, B*2. The estimated average fertility of the 21 inbred lines ranged from 72.9% (RCS-J) up to 96.8% (RCS-P). Both progenitor lines 63 and 72 were observed with lower average fertility (82.4% and 81.6%, respectively) in comparison with the RCS except the RCS-J, suggesting a substantial polygenic component underlying the fertility phenotype. The average embryo mortality rate ranged from 14.5% (RCS-P) up to 47.0% (RCS-M). The background line 63 fell at about the middle of the range (28.3%) significantly higher than the donor line 72 (15.7%), which was among the group with the lowest embryo mortality. By definition, hatchability of fertile eggs is reversely correlated with embryo mortality. The average hatchability ranged from 26.5% (RCS-M) up to 66.8% (line 72) while the background line 63 remained (46.6%) at about the middle of the range. The variability of the average embryo mortality and hatchability observed among the 21 inbred lines indicated the two correlated traits also follow polygenic models of inheritance. Findings from this study paves the way for further investigation on genetic and environmental influence over reproductive performance of inbred lines of chickens, and particularly in understanding and improving the reproduction fitness of invaluable genetic resources like these inbred lines. |
