Performance and carcass characteristics of boars, barrows, and gilts with ultrasonic estimates of muscle development and fat deposition

Efforts to improve performance and carcass character-istics in swine by genetic means have been hampered by a lack of accurate methods of evaluation of prospective breed-ing animals. However, swine testing stations have gained prominence in supplying data for swine selection programs within the past several years. Testing stations are used primarily to obtain data for these purposes: (1) to progeny test the parents of animals in the test station; (2) to use as a guide in selecting full or half sibs of animals being tested; and (3) to use as an indicator of the tested pig\u27s merit as a potential breeding animal provided that slaughter is not a requirement of the testing procedure. Accumulation of more fundamental knowledge of growth and development in swine is needed before effective control of the pig as a meat producing animal can be achieved by the breeder and feeder. Consumer preference has motivated the producer to place more emphasis on the lean cuts with less “rind” fat, but with sufficient finish to enhance eating quality. It is fitting that the swine producer encourage development of methods of live animal evaluation which will result in an acceptable muscle to fat ratio. With respect to economically important traits, purebred livestock producers need to apply practices to improve precision in breeding animals of increased genetic merit so that commercial hog producers can rely on their transmitting ability to a greater degree. Distinctive advantages are recognized for testing specific animals which subsequently are to be used in the breeding herd. Since many testing stations permit any barrow or gilt combination to be tested alongside boar littermates, it is questionable whether the effect of sex on performance and carcass traits has received adequate consid-eration. Although there is evidence that sex differences exist, few adjustments are currently being made. The objectives of this experiment were to expand existing knowledge on growth and development, to determine the effect of sex on performance and carcass characteris-tics, and to measure the reliability of the somascope for improving accuracy in selection for superior performance and carcass traits in swine