Maternal Heterosis in Swine: Reproductive Performance and Dam Productivity

Abstract

SummaryThe objectives of this study were to estimate the heterosis of crossbred gilts for ovulation rate and the maternal heterosis of crossbred gilts for dam productivity. A total of 470 gilts were saved for breeding of which 72 were considered reproductive failures. Estimates of heterosis were made from 193 pregnant gilts slaughtered 30 days postbreeding (106 crossbred and 87 purebred)and 192 litters farrowed (98 three-breed and 94 two-breed cross).The reproductive failure rate for all gilts was 15.3% with there being very little difference~ between purebred and crossbred gilts. Estimates of heterosis for ovulation rate were not significantly different from zero, although crossbred gilts of all breed groups consistently had fewer corpora lutea per gilt than purebreds (13.48 vs 13.03). The embryo survival rate for embryos from crossbred gilts was 9.52 + 3.23% higher than for embryos from purebred gilts. No other estimate of maternal heterosis for traits measured on gilts slaughtered 30 days postbreeding was significantlY different from zero, although crossbred gilts consistently had more embryos per litter 30 days postbreeding (10.77 vs 9.95). Three-breed cross embryos were also .46 + .36 mm longer than two-breed cross embryos.Crossbred gilts consistently had larger and heavier litters at all ages and raised a larger percentage of their pigs from birth to weaning

Individual and maternal heterosis estimated from single crosses and backcrosses of swine

“…Estimates presented in table 23 were 3.2 (P<.01), 3.2 (P<.01), 13.0 (P<.01), 29 (P<.05) and 77 pounds for litter weight born, born alive and at 21, 56 and 154 days, respectively. These estimates agreed with those of Johnson and Omtvedt (1975) but are somewhat higher than those of Smith and King (1964). Deviations witliin a group with a common letter do not differ significantly (P<.05).…”

“…(Johnson and Omtvedt, 1975;Johnson et al, 1974) has indicated that maternal heterosis was of little importance for similar traits.…”

“…Deviations due to specific combin ing ability appeared to be a reflection of differences in litter size with little effect from the differences in pig weight. Johnson and Omtvedt (1975) (table 22). Largest litters farrowed came from third-parity dams but later differences indicated a possible but non-significant advantage to second-parity dams.…”

Systems of crossbreeding in swine

“…For example, JOHNSON et al (1978) reported that crossbred gilts weaned 1.24 more pigs than purebred gilts. Also, JOHNSON and OMTVEDT (1975) found that crossbred gilts consistently had larger litters at all ages. Increases in number weaned of 5,10 to 19, and 20% were reported for crossbred sows by SMITH and KING (1964), MCLAREN and SMITH (1972) and DILLARD and ROBISON (1968), respectively.…”

Individual and maternal heterosis estimated from single crosses and backcrosses of swine

“…These estimates agreed with those of Willham (1950), Smith and McLaren (1967), and Bereskin e^ al. (1974) but are somewhat higher than those of Young e^ (1976aYoung e^ ( , 1976b (Johnson and Omtvedt, 1975;Johnson et al, 1974) has indicated that maternal heterosis was of little importance for similar traits.…”