Biology Dept. will feature Dr. Robert White speaking on weaning and lactation in caribou and muskoxen on April 30, 2010

by Kathleen McCoy  |   

Friday, April 30, 3-4 p.m.
CPISB, Room 120

Dr. Robert (Bob) White, vice provost of research and dean of the graduate school, will speak on "Weaning in Relation to Energy and Protein Costs of Lactation: Could the "Selfish Cow" be Expressing Maternal Investment?" Here are details on the talk:

Under conditions in which resources are variable, or of limiting availability, a female may appear "selfish" in that she produces less milk while maintaining her own body reserves, presumably to increase her propensity for future productivity. These findings appear antithetical to theory based on maternal investment (MI).  In order to maximize lifetime reproductive success such a female should invest her resources in offspring success at a proportional cost to her own productivity.

Observations that arctic caribou (Rangifer tarandus) undergo frequent breeding pauses in association with successful weaning of offspring in successive years, and that muskoxen (Ovibos moschatus) express alternate-year reproduction under poor environmental-resource conditions, support MI theory.  In order to maximize productivity, MI theory predicts that females also could extend lactation.

In both caribou and muskoxen, breeding pauses are associated with lactation that extends beyond normal weaning. Evidence for MI is that, depending on date of weaning (1.1-2.1 y in muskoxen), offspring from extended lactation are bigger than their cohorts at weaning. Recovery of body reserves strongly influences maternal body reserves at calving, which in turn influences both offspring birth weight and initial milk production. Thus, offspring growth and survival is influenced by maternal reserves.

Preservation of sufficient reserves for future productivity appears to have priority over investment in offspring in early lactation; hence, the "selfish cow" phenomenon. In extreme, arctic caribou may wean offspring within the first month. This post-natal weaning event is the first of five documented weaning strategies expressed by caribou. I will use data on energy and protein transactions in wild and captive caribou, reindeer and muskoxen to both support and question nutritional mechanisms that could be responsible for the expression of MI strategies.

Parking on the UAA campus is free on Fridays. No-host refreshments will be provided. For more information, please contact Elizabeth Winfree at (907) 786-4780.

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