SELECTION FOR 12-DAY LITTER WEIGHT IN MICE

Effect of selection for litter size and body weight on hormone-induced ovulation rate in mice.

Genetic differences in natural vs hormone-induced ovulation rates were compared in immature female mice from five lines that had undergone long-term single-trait and antagonistic index selection for litter size and(or) 6-wk BW. Lines used were control (K); high litter size (L+); high BW (W+); low litter size and high BW (L-W+); and high litter size and low BW (L+W-). Natural ovulation rate at a...

Single-trait and antagonistic index selection for litter size and body weight in mice.

INDIVIDUAL SELECTION BASED ON FEMALE PERFORMANCE ONLY WAS CONDUCTED IN FOUR LINES OF MICE: L(+) for increased litter size, W(+) for increased 6-week body weight, L(-)W(+) for a selection index aimed at decreasing litter size and increasing 6-week body weight and L(+)W(-) for a selection index aimed at increasing litter size and decreasing 6-week body weight. A fifth line (K) served as an unsele...

Adjustment of 21-day Litter Weight for Number of Pigs Nursed for Purebred and Crossbred Dams

Alternative methods of selection for litter size in mice: III. Response to 21 generations of selection.

Alternative methods of selection to increase litter size in mice have been practiced for 21 generations followed by six generations of relaxed selection. Three replicates were used with four selection criteria: index of components (IX:I = 1.21 x total ovulation rate + 9.05 x ova success), uterine capacity (UT), litter size (LS), and an unselected control (LC). In IX, ovulation rate and ova succ...

Reciprocal recurrent selection for 21-day litter weight of crossbred gilts. I. Selection applied and genetic change in reproduction of crossbred gilts.

Six cycles of reciprocal recurrent selection (RRS) between Line 8 (Duroc) and Line 9 (Beltsville No. 1) were completed at the Fort Reno Livestock Research Center, El Reno, Oklahoma. A randomly mated control line was maintained. Each cycle of selection required three seasons. Selection of purebred pigs (born in the second season) was based on the mean 21-d litter weight of their maternal and pat...