RESUMO
Ovine production is one of the most important activities in animal production in tropical regions. The Barbados Blackbelly, a very interesting genetic resource, particularly well adapted to a harsh home environment in the humid tropics of the Caribbean. This review concerns this breed. It comprises aspects related to the breed history and standards and most importantly its reproductive and productive performances and gastrointestinal parasite tolerance in the Caribbean, North America and Central America and their introduction and use in crossbred trials in other regions of the tropics.
Assuntos
Cruzamento/história , Carneiro Doméstico , Animais , Barbados , Região do Caribe , História do Século XV , História do Século XVI , História do Século XVII , História do Século XX , Reprodução , Ovinos , Doenças dos OvinosRESUMO
A common evolutionary response to predation pressure is increased investment in reproduction, ultimately resulting in a fast life history. Theory and comparative studies suggest that short-lived organisms invest less in defence against parasites than those that are longer lived (the pace of life hypothesis). Combining these tenets of evolutionary theory leads to the specific, untested prediction that within species, populations experiencing higher predation pressure invest less in defence against parasites. The Trinidadian guppy, Poecilia reticulata, presents an excellent opportunity to test this prediction: guppy populations in lower courses of rivers experience higher predation pressure, and as a consequence have evolved faster life histories, than those in upper courses. Data from a large-scale field survey showed that fish infected with Gyrodactylus parasites were of a lower body condition (quantified using the scaled mass index) than uninfected fish, but only in lower course populations. Although the evidence we present is correlational, it suggests that upper course guppies sustain lower fitness costs of infection, i.e. are more tolerant, than lower course guppies. The data are therefore consistent with the pace of life hypothesis of parasite defence allocation, and suggest that life-history traits mediate the indirect effect of predators on the parasites of their prey.