Costs and benefits of maternally derived immunity in a game bird system
Ellis, Matthew B.
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This thesis examines the costs and benefits of maternal allocation to both mother and offspring in gamebirds, specifically ring necked pheasants (Phasianus colchicus) and the Chinese painted quail (Coturnix chinensis). Maternal allocation of compounds from the mother to the young during early development can potentially have both positive and negative effects. For example the transfer of nutrients to the offspring can help to increase post-partum survival and subsequent life time reproductive success. In contrast, the transfer of stress hormones can potentially have long term negative effects on the offspring’s development. The first part of this thesis investigates the effects of the transfer of immune components from mother to offspring, which are known to have positive short term effects (protection against pathogens in early development). There is therefore considerable interest in whether this response can be induced by maternal vaccination to confer protection to young birds in commercial situations. However, it is unclear how this affects life-history trade offs in the mother and the development of the offspring post-hatching. These effects are especially important in the gamebird industry where birds are commercially reared on a large scale before being released into the wild. Chapter 2 therefore examines the costs and benefits to the mother of producing a maternally transmitted immune response to the CoxAbic vaccine, such as the impact of vaccination on egg laying characteristics and body condition. Chapter 3 looks at these costs and benefits to the chicks by examining growth rates and survival after a challenge of live coccidia in offspring from vaccinated and unvaccinated mothers. Chapter 4 examines the immune response to vaccination in adult pheasants. Finally, chapter 5 considers other factors that have been shown to affect the allocation decisions of females, specifically the effect of male characteristics on female reproductive effort.