Does body growth impair immune function in a large herbivore

According to the principle of allocation, trade-offs are inevitable when resources allocated to one biological function are no longer available for other functions. Growth, and to a lesser extent, immunityare energetically costly functions that may compete with allocation to reproductive success and survival. However, whether high allocation to growth impairs immunesystem development during the growing period or immunesystem performance during adulthood is currently unknown in wild mammals. Using three roe deer( Capreolus capreolus) populations experiencing contrasting environmental conditions, we tested for potential costs of growth on immunephenotype over both the short-term (during growth), and the long-term (during adulthood) over the course of an individuals’ life. We investigated potential costs on a set of 12 immunetraits that reflect both innate and adaptive responses, and compared them between sexes and populations. Although fast growth tended to be associated with low levels of some humoral traits (globulins) during the growing period and some cellular immunetraits (i.e. eosinophil and neutrophil counts) during adulthood, evidence for a trade-off between growth and other immunecomponents was limited. Unexpectedly, no detectable growth costs on immunitywere found in females from the population experiencing the least favourable environment. We discuss our findings in the light of the complex interplay between resource allocation strategies among reproduction, maintenance and immunity, in relation to local environmental conditions experienced by roe deer.