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|Title:||A Study of Effects of Blood Types, Sires, Litter Size and Other Factors on Sex Ratios in Pigs|
|Department / Program:||Animal Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
Agriculture, Animal Culture and Nutrition
|Abstract:||Sex distributions were studied in association with 11 pig blood group systems, (A, B, C, D, E, F,G, H, J, K and L) in matings segregating for blood types and analyzed by using segregation ratios as well as by the least-squares method. Effects of sire, litter size and selection for high whole-body potassium per unit weight of boars on sex ratios were all considered. A total of 1,328 litters of pigs over seven generations in five breed classes (Duroc, Duroc selected, Yorkshire, Yorkshire selected and Duroc x Yorkshire crossbred selected classes) were studied.
The segregation study agreed well with Mendelian expectation, indicating in general that differences in segregation ratios within males and within females among blood types were not significant. However in the H system the ratio of heterozygotes to homozygotes was higher in both male and female offspring.
Results from least-squares analysis suggest that the effects of blood types on sex ratios were less consistent and most likely due to chance. The A system, serologically similar to the human ABO system, did not show a significant effect on the sex ratios.
Selection for high whole-body ('40)K might affect sperm motility through a possible increase in potassium ion level in semen and a resultant decrease in the proportion of male piglets in the selected groups compared to the unselected ones.
Significant sire effects on sex ratios were indicated in the Duroc unselected and Yorkshire selected classes. The influence of sires on sex ratios may be due to a particular XY chromosome combination in the boars as male differentiation is triggered by the H-Y antigen whose synthesis requires genes on both the X and Y chromosomes.
The heritability estimate of sex ratios was not more than 6.5% suggesting very little genetic variation available for altering sex ratios in swine.
The correlation (r = -0.05) and regression analysis for litter size and sex ratios revealed that larger litters tended to have fewer males and that there was no difference between males and females in preweaning mortality.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
|Date Available in IDEALS:||2014-12-15|