ferent breed makeups. It is widely used in commercial beef production because of the benefits it has to offer cow-calf producers. Improvements in efficiency can be dramatic if appropriate breed combinations are used. Crossbreeding does not eliminate the need for outstanding purebred cattle since efficient systems require well characterized, superior purebred cattle. Crossbreeding in beef cattle...

Three strains of brook trout Salvelinus fontinalis (domestic [D], Laval [L], and Rupert [R]) and their reciprocal hybrids were reared from 7 to 21 months of age in three different environments (indoor, constant temperature conditions; indoor, seasonal temperature variations; and outdoor, seasonal temperature variations) to test for the occurrence of heterosis in important life history traits of...

If in the sexual Penna ageing model conditions are applied leading to complementary bit-strings, then marriages between brothers and sisters, or between close cousins, may lead to more offspring than for unrelated couples. Inbreeding is usually a bad thing for humans and many animals; the Egyp-tian pharaos liked marriages between brothers and sisters which led to the city named Philadelphia but...

Extensive mark-recapture data from banner-tailed kangaroo rats, Dipodomys spectabilis, have shown that both males and females are highly philopatric and suggest the possibility of close inbreeding. However, indirect analyses based on genetic structure appear to contradict direct observations, suggesting longer dispersal distances. Using microsatellite genotypes from most members of a banner-tai...