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Nebraska Agriculture Experiment Station, Lincoln
Abstract
Data were collected on preweaning growth of rats transferred between sets of either three or two females. Each female raised two of her own pups and two from each other female in the set. The unit studied was either 9 or 4 depending upon whether a trio or pair of females was involved.
The data were analyzed so that the following held: (1) the way the litter was born measures all the factors, both pre-natal maternal as well as genetic differences littermates have in common; (2) the way the litter was raised measures differences in maternal ability; (3) the interaction born x raised measures any incompatibility between the young and the dam as well as the interactions between the different kinds of young raised together; and (4) the variance between full sibs born and reared alike contains the remaining portion of the genetic variance.
The analyses of both birth and weaning data showed that the portion of variance attributable to the several components of variance depended in large part on the degree of relationship between the dams involved in the sets. Where the dams were not closely related, the interaction term was, in general, responsible for a larger portion of the variance than when the dams were from the same line or were full sibs.
From the analysis of the data on gain from 21 to 42 days of age, it was found that the way the litter was born accounted for from 40 to 69% of the variance in gain. Both the way the litter was raised and the interaction term were of minor importance.
It was concluded that transferring pups from dam to dam should have little effect on the way the pups react to post-weaning regimes.
1 Published with the approval of the Director as Paper No.2412, Journal Series, Nebr. Agr. Exp. Sta.
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