Allometry of milk intake at peak lactation
Much attention has been given to the scaling of milk output and lactational strategies across species. However developed allometric equations for milk output in adult animals cannot be used for suckling young. Therefore, the purpose of the present study was to investigate milk intake and intake of milk nutrients in suckling mammalian young at peak lactation using phylogenetic independent contrasts in order to derive allometric relationships corrected for phylogeny. Milk intake and intake of milk nutrients (solid, fat, protein and sugar) at peak lactation for 40 mammalian species were evaluated for the present analysis to derive allometric relationships for suckling young. K*-values were calculated in order to detect phylogenetic signals across traits. Phylogenetic signals were high and significant for all traits examined, thus phylogenetically independent contrasts were calculated for log10 transformed milk intake and intake of milk nutrients, body mass and average daily gain to eliminate the potential lack of independence between species, because of their shared evolutionary history. The phylogeny for the species used in the present study was derived from a recently published mammalian Supertree with branch lengths derived from dated estimates of divergence times. Thirty allometric equations were calculated using phylogenetically independent contrasts. A strong (P < 0.001) positive relationship exists between neonate body mass and the response variables (milk intake, intake of milk nutrients), whether calculated for all mammals or separately for artiodactyls and carnivores, with the exception of sugar intake in carnivores. However, large deviations for some species and few outliers were found. The present equations could be used to predict values for species similar to those included in the present study that have not been studied, providing that the body mass falls inside the range of masses used to derive the equations. However, predicting values for missing species should be done with caution as they are not included in the phylogenetic tree that was used to derive the phylogenetically corrected equations.
KeywordsAllometry Lactation Milk intake Milk nutrients Phylogeny
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