HOT AND FAT

Currently there are two hypotheses, which are considered in context with lactation, when females raise their young. The first one deals with the heat produced as a side effect of the females metabolism operating at peak rates. The heat dissipation limitation hypothesis predicts that milk synthesis works best when i) ambient temperatures are lower or ii) when the females are given opportunity to dissipate heat to the environment. The second hypothesis centres on the role of endogenous adipose tissue fat reserves, which, through serving as important fuel, may enable the female to reach metabolic rates as high as 8times resting metabolic rate during lactation without significant losses of body mass. The ready mobilisation of body fat may cap peak food intake and heat production during lactation while at the same time fuelling milk synthesis. We suggest testing the above concepts in four significant mouse models while providing experimental evidence for an innovative extension of the heat dissipation limitation. While the main focus of the studies related to heat dissipation limitation was on comparing total quantitative milk production, we would like to draw attention on the milk quality, specifically on milk fatty acid composition assessed with a lipidomic approach using a combination of gas chromatography and mass spectrometry. We predict that already established effective experimental manipulations of the female heat load may lead to clear differences in the milk lipidomic profiles of the animals. Specifically, we expect that the heat load experienced by the female may lower the proportion of n-3 fatty acids, which are key to the development of neuronal membranes in the offspring. Our project may contribute to improve maintenance/breeding conditions of lactating females. In addition, we suggest considering milk lipidomic fatty acid profiles in lactation studies addressing heat dissipation limitation as well as the role of body fat reserves. Apart from the phylogenetically even more important role of mothers milk for the transfer of immunoglobulins on top of the nutritive aspect, we assume a putative biomarker role of specific milk fatty acids for the optimal development of juvenile mammals.