RESUMO
Twelve experiments on intraspecific crossbreeding of channel catfish, Ictalurus punctatus, for improvement of body weight are compared and reviewed. Crossbred fingerlings resulting from matings of unrelated F1 crossbred populations did not show heterotic growth. Crossbreds resulting from pure strain P1 showed an average increase of 10.3 percent in growth above the fastest growing parent strain. Marion female X Kansas male, a crossbred from two rapidly growing domestic strains, was the fastest growing to fingerling size. Average increase in body weight (fingerling to harvest size) by crossbreds was 1.5 percent greater than the fastest growing parent strain. Marion X Kansas, Auburn X Kansas, and Auburn X Uvalde were the fastest growing crossbreds to harvest size (8-13 percent increase in growth rate). Six of nine crossbreds made from Pi generations expressed heterosis above both parent strains for body weight. Eight of nine crossbreds grew better than at least one of their parents. Reciprocal crossbreds did not grow at the same rate. Males and females of a specific strain had different combining abilities with other strains. There was a maternal effect for combining ability. All crossbreds made with Auburn females exhibited heterosis.
Assuntos
Peso Corporal , Cruzamento , Cruzamentos Genéticos , Peixes/fisiologia , Animais , Feminino , Peixes/genética , MasculinoRESUMO
Tilapia aurea showed a specific immune response to Salmonella typhimurium. S. typhimurium was introduced into the gut of T. aurea by force-feeding. S. typhimurium was isolated from the fish viscera after 15 days, but at 30 days viable cells were not detected. T. aurea had an antibody titer to S. typhimurium after 30 days which was fivefold greater than the natural background antibody titer. An elevated antibody titer was not indicative of active bacterial infection.
Assuntos
Anticorpos Antibacterianos/análise , Doenças dos Peixes/diagnóstico , Peixes/imunologia , Salmonelose Animal/diagnóstico , Salmonella typhimurium/imunologia , Testes de Aglutinação , Animais , Fatores de TempoRESUMO
Salmonella typhimurium declined rapidly when inoculated into Tilapia aurea culture pools fertilized with fresh swine waste. Within the water column, a 95% decline of viable cells occurred during the first 6 h. Isolation of viable salmonellae was possible at 16 days post-inoculation, but not at 32 days. Similarly, salmonellae could be detected in the viscera and epithelium of T. aurea at 16 days, although not at 32 days. Salmonellae were not isolated from the fish flesh, nor was there evidence of septicemic infection.