Ovulation rate, embryo number and uterus length in purebred and crossbred Duroc, Landrace and Large White gilts

Abstract

Ovulation and embryo survival rate, number of live and degenerated embryos and uterus length were examined between 28–35 d of gestation in purebred Landrace (LD) and Large White (LW), and in crossbred LDLW, LWLD, Duroc (DR) LD and DRLW gilts. Purebred and crossbred gilts were mated to purebred DR, LD or LW boars. Ovulation rate and live embryo number differed between breed combinations (P<0.05) but differences in number of degenerated embryos, embryo survival rate and uterus length were not significant. Heterosis estimated from contrasts between crossbred LDLW and LWLD and purebred LD and LW gilts were 17.7% for ovulation rate and 13.3% for number of live embryos. Crossbred gilts from LD dams had higher ovulation rate (P<0.01) and live embryo number (P<0.10) than crossbred gilts from LW dams. Differences between white- and Duroccrossbreds were not significant. Live embryo number was highly correlated with embryo survival and uterus length. Correlation and regression coefficients between live embryo number and ovulation rate were significant in all breed combinations. Crossbred LWLD gilts had the highest ovulation rate and the largest number of live embryos. They had the largest potential to improve reproductive efficiency and were followed by crossbred DRLD and LDLW gilts.