Adaptations to seasonality - a comparative view of energy expenditure during lactation in two ruminant species: European roe deer (Capreolus capreolus) and mouflon (Ovis orientalis musimon)

Abstract

Energy expenditure depends on resource availability (e.g. food, body reserves). Reproduction is a major energetic challenge for mammals living under highly variable seasonal conditions. Lactation represents the most energy demanding time in a female's annual cycle. To understand how important adaptations facilitating lactation are, we studied its energetic costs.Two ruminant species of similar size (about 25 kg body mass) were used in an investigation to learn more about their adaptations to seasonality: The European roe deer (Capreolus cupreolus Linnaeus, 1758) and the European mouflon (Ovis orientalis musimon Schreber, 1782). Energy investment into lactation was estimated using stable isotope techniques with two different approaches. The D20 dilution technique for estimating milk intake described for sheep lambs by Coward et al. (1982) and the doubly labelled water method for measuring energy expenditure (Speakman 1997).Milk intake was estimated by the D20 dilution technique in 2-week-old roe deer fawns and mouflon lambs. Estimated milk intake rates were then transferred into the respective energetic investment into lactation. It was calculated as well from energy expenditure data in growing fawns during their first two weeks post partum using results of the doubly labelled water technique.Results for roe deer showed an energy investment into lactation of 5.6MJ/d metabolizable energy (ME) per fawn. In mouflon this value was approximately 5.7 MJ/d per lamb. Twins are extremely rare in mouflon, they routinely get only one offspring per year. Keeping in mind that roe deer often give birth to twins, or sometimes even triplets we measured more than twice the energy investment into lactation than predicted from theoretical calculations (Lechner-Doll et al. 2000).

Origination of antlerogenesis

“…In such regions, the antler cycle and other life events (such as birth times, rutting season, etc.) are optimally timed and synchronized between individuals and populations (Lason et al, ). By contrast, in areas without seasonal changes such as the tropics there is no synchronization between individuals/populations and the antler cycle sometimes lasts longer than a year.…”