Heritability of Litter Size in Swine

Heritability of litter size was studied in three inbred lines of swine. An intra-group regression of the record of the daughter on the record of her dam was made to estimate heritability. A total of 1970 daughter-dam comparisons were made. Only data of the number born alive in the first litter were used. A heritability estimate for litter size for the Minnesota No. 1 was 0.05±0.13, for the Minnesota No. 2 it was −.04±0.10 and for the Minnesota No. 3 it was 0.17±0.14. An overall heritability estimate for all animals studied was found to be 0.03±0.07. None of the heritability estimates obtained were found to be significantly different from zero or significantly different from each other (P>.05). The values found in this study fall within the range of those reported elsewhere, but are considerably less than a major portion of those reported. From this study it was concluded that heritability for litter size is low and the response to mass selection for increased performance within a line or breed will be negligible.