Embryonal survival to 6 days in mice selected on different criteria for litter size.

Abstract

Embryonal survival was compared in mice resulting from four criteria of selection: LS = selection on number born; IX = selection on an index of ovulation rate and ova success; UT = selection on number born to unilaterally ovariectomized females; and LC = unselected control. Selection occurred for 21 generations with three replicates of the four criteria; thereafter, relaxed selection was practiced. The evaluation was performed using mice of two replicates at Generation 35 and one replicate at Generation 36. Data on a total of 289 female mice were recorded. Females, at an average age of 9 wk, were mated to males of the same line. Six days after mating, each female was killed, ovaries were excised, corpora lutea were counted and equated to number of ova shed, and the numbers of implantation sites in each uterine horn were recorded. Least squares means were .84, .91, .85, and .82 for left embryonal survival (left implantations/left ova) and .91, .90, .86, and .87 for right embryonal survival for LS, IX, UT, and LC, respectively. The right side had greater ovulation rate ( P < .001) and number of implantations ( P < .001). For embryonal survival, the criterion × side interaction was possibly important ( P < .09). Selection for litter size by different criteria increased ovulation rate ( P < .003) and embryonal survival ( P < .05) to 6 d. However, responses in embryonal survival were not greater after UT selection compared with LS or IX selection.

Components of litter size in mice after 110 generations of selection

“…The effect of selection for litter size in mice on ovulation rate and embryonic mortality during pregnancy has been reported previously (Joakimsen & Baker 1977, Bakker et al 1978, Durrant et al 1980, Pomp et al 1988, Clutter et al 1994, Ribeiro et al 1996, Johnson et al 1999. These studies revealed that selection for litter size lead to an increase in ovulation rate, and a subsequent reduction in embryonic mortality.…”

Divergent selection for uterine capacity in rabbits. II. Correlated response in litter size and its components estimated with a cryopreserved control population1

“…In studies of Rochambeau et al (1994; two selected lines) and García and Baselga (2002a; one selected line), selection for LS increased OR without any change in PS; however, García and Baselga (2002b) found that a correlated response in FS in another line selected for LS. In selection experiments for prolificacy in mice, increased LS has been essentially due to increased OR (Falconer, 1960;Joakimsen and Baker, 1977;Bakker et al, 1978;Ribeiro et al, 1996). Bakker et al (1978) and Ribeiro et al (1996) also observed an increase in PS.…”

“…In selection experiments for prolificacy in mice, increased LS has been essentially due to increased OR (Falconer, 1960;Joakimsen and Baker, 1977;Bakker et al, 1978;Ribeiro et al, 1996). Bakker et al (1978) and Ribeiro et al (1996) also observed an increase in PS. In pigs, it seems that an increase of LS in a line selected for this trait was due to an increase in OR maintaining the same PS (Bolet et al, 1989).…”

“…In the mice experiment, the line selected for high Table 4. Features of the marginal posterior distributions of the differences between high and control line (H -C), control and low line (C -L), and high and low line (H -L) in ovulation rate (OR) and number of implanted embryos (IE) UC showed a correlated response in LS caused by a greater OR (Al-Shorepy et al, 1992;Ribeiro et al, 1996), and a greater ES until d 6 after mating (Ribeiro et al, 1996). In rabbits, there are no other results relating to correlated response from lines selected to improve UC.…”

“…In rabbits, differences in the number of implanted embryos at 6 d of gestation between divergent lines selected by UC were found in intact females (Mocé et al, 2002). In the mice experiment, selection for higher UC increased ovulation rate (OR) (Al-Shorepy et al, 1992;Ribeiro et al, 1996), and embryo survival (ES) until d 6 after mating (Ribeiro et al, 1996) in intact females.…”