Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 1996
Publication Date: N/A
The objective was to implement a simulation model integrating ovulation rate, potential embryonic viability, and uterine capacity to explain litter size in mice. A secondary objective was to simulate responses in uterine capacity of mice selected on alternative criteria to increase litter size. Simulated responses were compared to observed results from a mouse selection experiment conducted at University of Nebraska-Lincoln. The fou criteria of selection were: LS=selection on number born; IX=selection on an index of ovulation rate and ova success; UT=selection on number born to unilaterally ovariectomized females; and LC=unselected control. Comparisons were made between observed and simulated data statistics of the base population and observed and simulated responses after 13 generations of selection. Phenotypic and genetic parameters for uterine capacity were generated taking into consideration observed means, standard deviations, and correlations between left and right litter size, as well as observed responses in number born. Simulated means in the base population were 13.22 for ovulation rate and 16.30 for uterine capacity with heritabilities of .25 and .065, respectively. Observed and simulated responses per generation in litter size through 13 generations of selection were .15 and .16 for LS; .17 and .18 for IX; and .10 and .11 for UT, respectively. Simulated responses in uterine capacity and ovulation rate were 2.19 and 2.37 for LS; 1.60 and 3.21 for IX; and 3.40 and .71 for UT, respectively. Uterine capacity was an important component of the variability in litter size; however, ovulation rate was the more limiting component. The model was able to generate statistics for litter size and its components that were similar to those observed in the experimental work.