• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Cystophora cristata
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.653.9954; http://fatlab.biology.dal.ca/wp-content/uploads/2013/06/MellishIversonBldMetab_CJZ2001.pdf

Blood metabolites as indicators of nutrient utilization in fasting, lactating phocid seals: does depletion of nutrient reserves terminate lactation? J.E. Mellish and S.J. Iverson Abstract: Metabolites of lipid (free fatty acids (FFA) and β-hydroxybutyrate (βHBA)) and protein (blood urea nitrogen (BUN)) oxidation were measured during lactation in 18 female grey seals (Halichoerus grypus) and 6 female hooded seals (Cystophora cristata) as indicators of nutrient depletion and possible cues for pup weaning. FFA levels were high during lactation in both grey seals (51.2 ± 2.3 mg·dL–1) and hooded seals (67.0 ± 8.1 mg·dL–1), and levels were primarily related to the rapid lipid mobilization required for their high respective milk-fat outputs (P = 0.002). βHBA concentrations were negligible throughout lactation in both species (0.30 ± 0.14 and 0.03 ± 0.01 mg·dL–1, respectively). Grey seals exhibited a decrease in BUN levels over the course of lactation (i.e., days 0–15, 39.3 ± 1.8 – 23.5 ± 3.3 mg·dL–1, P < 0.001), which suggests protein sparing despite the added energetic cost of milk production over the 16-d lactation period. In contrast, hooded seals showed higher levels and no change in BUN levels (i.e., days 0–3, 43.2 ± 2.1 – 45.8 ± 2.1 mg·dL–1, P> 0.3), suggesting that there is less need to spare protein in a species which lactates for only 3.6 d. Females of both species weaned their pups before entering stage III fasting, therefore metabo-