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Full-Text Articles in Life Sciences
Alternative Methods Of Selection For Litter Size In Mice: I. Characterization Of Base Population And Development Of Methods, A. C. Clutter, Merlyn K. Nielsen, R. K. Johnson
Alternative Methods Of Selection For Litter Size In Mice: I. Characterization Of Base Population And Development Of Methods, A. C. Clutter, Merlyn K. Nielsen, R. K. Johnson
Department of Animal Science: Faculty Publications
Studies on a base population of mice were used to establish an index of components of litter size and a physiological model for measuring uterine capacity to be used subsequently in a selection experiment evaluating alternative methods for practicing selection to increase litter size. Heritability estimates of litter size, ovulation rate and ova success (fraction of ova resulting in fully formed pups) were .18, .33 and .15, respectively. No significant genetic or phenotypic correlation was found between overall ovulation rate and ova success. Phenotypic means and genetic variances were higher for characteristics measured on the right than on the left …
Twinning In Cattle: Ii. Genetic And Environmental Effects On Ovulation Rate In Puberal Heifers And Postpartum Cows And The Effects Of Ovulation Rate On Embryonic Survival, S.E. Echternkamp, K. E. Gregory, G. E. Dickerson, Larry V. Cundiff, R. M. Koch, L. Dale Van Vleck
Twinning In Cattle: Ii. Genetic And Environmental Effects On Ovulation Rate In Puberal Heifers And Postpartum Cows And The Effects Of Ovulation Rate On Embryonic Survival, S.E. Echternkamp, K. E. Gregory, G. E. Dickerson, Larry V. Cundiff, R. M. Koch, L. Dale Van Vleck
Department of Animal Science: Faculty Publications
The potential of ovulation rate before 18 to 21 mo of age in puberal heifers as an indirect selection criterion for twinning rate was considered. Heritability (h2) was .07 ± .03 for single observations and .34 ± .18 for the mean of 7.9 estrous cycles per heifer. Estimated repeatability (r) of ovulation rate was ≤h2, indicating negligible permanent environmental effects. Expected h2 for mean ovulation rate (assuming h2 = r = .07 for single observations) for increasing numbers of estrous cycles would be as follows: 4, .23; 6, .31; 8, .38; and 10, .43. …
Twinning In Cattle: 1. Foundation Animals And Genetic And Environmental Effects On Winning Rate, K. E. Gregory, S. E. Echternkamp, G. E. Dickerson, Larry V. Cundiff, R. M. Koch, L. Dale Van Vleck
Twinning In Cattle: 1. Foundation Animals And Genetic And Environmental Effects On Winning Rate, K. E. Gregory, S. E. Echternkamp, G. E. Dickerson, Larry V. Cundiff, R. M. Koch, L. Dale Van Vleck
Department of Animal Science: Faculty Publications
Foundation cows were selected using prior records from one of two sources, private herds or other projects at the Research Center. Comparing twinning rates before and after selection, the repeatability was lower for those from the fist (.08) than for those from the second (.16) source with a combined value of .12. Realized heritability of single-parity twinning rate estimated from selection of parents and response in daughters of foundation females was .06. Paternal half-sib estimate of heritability of twinning rate was .02 ± .07. Estimates of repeatability computed from calving records of females born in the project indicate that permanent …