Selection for Ovulation Rate in Swine: Correlated Response in Litter Size and Weight

Selection for ovulation rate in rabbits: Direct and correlated responses estimated with a cryopreserved control population1

“…In rabbits selected for OR, the genetic correlation between OR and LS was estimated with low precision, as in the experiments of selection for OR in other polytocous species [see Cunningham et al (1979) and Rosendo et al (2007) for pigs and Bradford (1969) and Land and Falconer (1969) for mice]. Therefore, conclusions about its value should be taken with caution.…”

“…Selection for ovulation rate has been unsuccessful as a means of indirectly improving litter size in pigs (Cunningham et al, 1979;Rosendo et al, 2007;Leymaster and Christenson, 2000) and mice (Land and Falconer, 1969;Bradford, 1969), despite the increase in ovulation rate. The lack of correlated response in litter size has been associated with an increase in the postimplantation mortality [see Bradford (1969) for mice and Freking et al (2007) for pigs].…”

Genetic variability of age and weight at puberty, ovulation rate and embryo survival in gilts and relations with production traits

“…Litter size at birth is the main contributor to variation in sow reproductive efficiency (Tess et al, 1983), but is poorly heritable and consequently rather difficult to improve through selection (Bolet et al, 1989 (Cunningham et al, 1979). Subsequent selection for litter size produced a significant increase in litter size (Lamberson et al, 1991 (Tess et al, 1983;Rydhmer, 1993).…”

Selection on testis size as an indicator of maturity in growing animals II Correlated responses in reproductive rate

“…Selection for ovulation rate in pigs has changed ovulation rate substantially, but not litter size (Cunningham et al, 1979;Johnson and Neal, 1988).…”

“…In a previous experiment with mice (Islam et (Cunningham et al, 1979;Johnson and Neal, 1988 (Land et al, 1980;Haley et al, 1989). Other workers have found some evidence of a correlation between testis size and litter size or ovulation rate in sheep (Ricordeau et al, 1979(Ricordeau et al, , 1986Purvis et al, 1988), cattle (Toelle and Robison, 1985a) and pigs (Schinckel et al, 1983;Toelle and Robison, 1985b;see Haley et al (1989) for review).…”