Amino acid composition of pinniped milk

doi:10.1016/0305-0491(94)00162-N

Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology

Volume 110, Issue 3, March 1995, Pages 633-639

https://doi.org/10.1016/0305-0491(94)00162-N Get rights and content

Abstract

The total amino acid concentration and the amino acid pattern, i.e. the relative proportion of each amino acid (protein-bound plus free) to the total amino acids, in the milks of the Northern elephant seal, Antarctic fur seal, California sea lion, and Australian sea lion were determined. Total amino acid concentration was 10% (w/v) or greater and did not vary significantly among species. The most abundant amino acids in the milks of all species were glutamate, proline and leucine. Essential amino acids were 40%, branched-chain amino acids were 20%, and sulfur amino acids were 4% of the total milk amino acids in all species. There were differences among the pinnipeds in some of the individual amino acids; the milk of the Northern elephant seal was the most distinct among the pinnipeds with higher histidine, serine and cystine contents and a lower methionine content than that of other pinnipeds. There was little effect of stage of lactation on total amino acid concentration or amino acid pattern in pinniped milk. Comparison of milk from the four pinniped species with that of 14 other mammalian species suggests commonality in milk amino acid pattern despite the wide variation in total amino acid concentration among the species.

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Cited by (23)

Changes in total mercury, methylmercury, and selenium blood levels during different life history stages of the Baltic grey seal (Halichoerus grypus grypus)
2019, Science of the Total Environment
Citation Excerpt :
As the female has to preserve water reserves, water in milk is progressively substituted by fat during lactation (Baker, 1990; Riedman, 1990). The protein content in the milk of grey seals shows slight fluctuations and remains at a high level of around 10% (Baker, 1990; Davis et al., 1995). The composition of milk can significantly affect the levels of substances found in it.
Using the blood of grey seal pups, the blood and milk of female grey seals inhabiting the Hel Marine Station of Gdansk University's Institute of Oceanography (HMS), we monitored the transfer of total mercury (THg), methylmercury (MeHg), and selenium (Se) with blood during foetal life and nursing. Changes in the concentration of mercury and selenium were characterised in the pups' blood during their first three months of life when they transition from suckling, to a post-weaning fast, to eating fish.
In the blood of pregnant females, there was a significant decrease in THg and MeHg concentrations throughout the gestation, indicating the transfer of these toxins through the placenta into the foetus. At no other stage of the pup's development was there such a high level of THg and MeHg as on the day of birth, despite the incorporation of mercury into the lanugo during foetal growth. This suggests that the maternal transfer of mercury during gestation may be the time of greatest mercury exposure for a young seal pup. The consumption of milk caused a rapid increase in weight and a lowering of the mercury level in the blood in the subsequent days of the pups' life. The postweaning fast was the period of the lowest mercury concentration. The switch to a diet consisting of fish caused a systematic increase in the concentration of mercury in the blood of the pups.
Milk was the significant source of selenium for pups and the selenium concentration in females' blood was reduced during lactation.
The nursing period seemed to have the greatest impact on the mercury and selenium blood levels in examined seals. Natural development of the grey seal pup created an opportunity to decrease the levels of toxic substances obtained through the maternal transfer during foetal growth.
Changes in trace elements during lactation in a marine top predator, the grey seal
2013, Aquatic Toxicology
Citation Excerpt :
Overall, the mineral content in grey seal milk appears quite high in comparison with the one in terrestrial mammal milk. The high protein content in pinniped milk, being among the highest of any mammal (approximately 10%, Davis et al., 1995) may contribute to the high mineral content in milk since many metals are usually bound to proteins. Calcium level in milk was similar to that in other pinniped milk (around 700 mg/kg ww, Oftedal et al., 1987), higher than in human milk (252 mg/l, Dorea, 1999) and lower than in cow milk (1100 mg/l, USDA, 2007).
Lactation in pinnipeds represents the most significant cost to mothers during the reproductive cycle. Dynamics of trace elements and their mobilization associated with energy reserves during such an intense physiological process remains poorly understood in marine mammals. The changes in tissue concentrations of 11 elements (Ca, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Se, V, and Zn) were investigated in a longitudinal study during the lactation period and during the post-weaning fast period. Blood, milk, blubber, and hair samples were collected sequentially from 21 mother–pup pairs of grey seals (Halichoerus grypus) from the Isle of May in Scotland. Maternal transfer through the milk was observed for all trace elements, except for Cd. As an indicator of the placental transfer, levels in pup lanugo (natal coat) revealed also the existence of maternal transfer and accumulation of all assayed trace elements during the foetal development. The placental and mammary barriers against non-essential metal transfer to offspring appear to be absent or weak in grey seals. Examining the contamination levels showed that this grey seal population seems more highly exposed to Pb than other phocid populations (2.2 mg/kg dw of grey seal hair). In contrast, blood and hair levels reflected a lower Hg exposure in grey seals from the Isle of May than in harbour seals from the southeastern North Sea. This study also showed that trace element concentrations in blood and blubber could change rapidly over the lactation period. Such physiological processes must be considered carefully during biomonitoring of trace elements, and potential impacts that rapid fluctuations in concentrations can exert on seal health should be further investigated.
Water-soluble vitamin homeostasis in fasting northern elephant seals (Mirounga angustirostris) measured by metabolomics analysis and standard methods
2012, Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Citation Excerpt :
For instance, in previous studies on northern elephant seals there was insufficient tryptophan present for detection in plasma (Houser and Crocker, 2004), and in milk analysis tryptophan is destroyed by acid hydrolysis (McKenzie, 1970). For this reason tryptophan was likely not measured in pinniped milk (Davis et al., 1995); however, it was detected in the present study and its relative changes were measured across the fast using metabolomics. There are potentially numerous compounds whose measurements are limited with standard techniques and the metabolomics method may be able to detect them using the small sample volumes obtainable from many wildlife systems.
Despite the importance of water-soluble vitamins to metabolism, there is limited knowledge of their serum availability in fasting wildlife. We evaluated changes in water-soluble vitamins in northern elephant seals, a species with an exceptional ability to withstand nutrient deprivation. We used a metabolomics approach to measure vitamins and associated metabolites under extended natural fasts for up to 7 weeks in free-ranging lactating or developing seals. Water-soluble vitamins were not detected with this metabolomics platform, but could be measured with standard assays. Concentrations of measured vitamins varied independently, but all were maintained at detectable levels over extended fasts, suggesting that defense of vitamin levels is a component of fasting adaptation in the seals. Metabolomics was not ideal for generating complete vitamin profiles in this species, but gave novel insights into vitamin metabolism by detecting key related metabolites. For example, niacin level reductions in lactating females were associated with significant reductions in precursors suggesting downregulation of the niacin synthetic pathway. The ability to detect individual vitamins using metabolomics may be impacted by the large number of novel compounds detected. Modifications to the analysis platforms and compound detection algorithms used in this study may be required for improving water-soluble vitamin detection in this and other novel wildlife systems.
Characterisation of proteins in the milk of fur seals
2005, Comparative Biochemistry and Physiology - B Biochemistry and Molecular Biology
Milk protein composition was investigated throughout the lactation periods of the Australian fur seal (Arctocephalus pusillus doriferus) and Antarctic fur seal (Arctocephalus gazella). The mean protein content of the milk was found to be 10.9% and 10.6% respectively. The concentration of total protein did not change during lactation, although a decline in casein content of the milk in late lactation was apparent. Milk protein concentration during a foraging/suckling cycle of the Antarctic fur seal analysed at the time of arrival on shore, and 24 h and 72 h after arrival was 12.8%, 11.4% and 12.5% respectively. Re-feeding animals at 72 h resulted in a significant increase in milk protein content to 14.9%. Characterisation of milk protein by SDS-PAGE analysis revealed 5 casein and 10 major whey protein bands. Amino-terminal sequencing indicated that the majority of the whey fraction of the milk is β-lactoglobulin (β-LG). The limited amino acid sequence indicated 3 different β-LGs were secreted in the milk. Subsequently, RT-PCR was used to extend the sequence of one of the β-LGs and translation of the 464 bp fragment indicated that it shared 79% sequence identity with feline β-LG II.
Fur Seal Adaptations to Lactation: Insights into Mammary Gland Function
2005, Current Topics in Developmental Biology
Citation Excerpt :
This makes the fur seal an ideal model for the study of milk protein synthesis. The protein concentration of fur seal milk ranges from 10 to 22% and is among the highest of any mammal (Arnould and Boyd, 1995b; Arnould and Hindell, 1999; Davis et al., 1995; Georges et al., 2001; Goldsworthy and Crowley, 1999; Trillmich and Lechner, 1986). The proportions of casein to whey protein vary considerably between species (Anderson et al., 1985), including the pinnipeds (Ashworth et al., 1966; Trillmich et al., 1988), and may reflect differences in diet between species.
The fur seal (Arctocephalus spp. and Callorhinus spp., members of the pinniped family) is a mammal with the unusual capability to modulate its lactation cycle by turning milk production on and off without the typical mammalian regression and involution of the mammary gland. Lactation has evolved from constraints arising from the spatial and temporal separation of infant nursing and maternal foraging as the mother gives birth and feeds the pup on land while acquisition of nutrients for milk production occurs at sea. The lactation cycle begins with the female fur seal undergoing a perinatal fast of approximately 1 wk, after which time she departs the breeding colony to forage at sea. For the remainder of the long lactation period (116–540 days), the mother alternates between short periods ashore suckling the young with longer periods of up to 4 wk of foraging at sea. Milk production continues while foraging at sea, but at less than 20% the rate of production on land. Fur seals produce one of the richest milk reported, with a very high lipid content contributing up to 85% of total energy. This feature serves as an adaptation to the young's need to produce an insulating blubber layer against heat loss and to serve as an energy store when the mother is away foraging at sea. This atypical pattern of lactation means mothers have long periods with no suckling stimulus and can transfer high‐energy milk rapidly while on land to minimize time away from foraging grounds. The absence of suckling stimulus and milk removal during foraging does not result in the onset of involution with associated apoptosis of mammary secretory cells and a subsequent progressive breakdown of the cellular structure of the mammary gland. The mechanisms controlling lactation in the fur seal mammary gland have been investigated using molecular and cellular techniques. These findings have shed light on the processes by which the unique features of lactation in the fur seal are regulated.
Nutrient, fatty acid, amino acid and mineral analysis of natural prey of the Hawaiian monk seal, Monachus schauinslandi
1999, Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Proximate nutrients, gross energy content, mineral, amino acid and fatty acid composition were determined for teleost, cephalopod and crustacean prey of the Hawaiian monk seal. Crude protein was highest in the octopus, Octopus cyanea (80.0%), crude fat was highest in the Muraenid teleost, Gymnothorax eurostus (14.1%), whereas crude ash was highest in the lobster, Panulirus marginatus (11.6%). Gross energies ranged from 4.0±0.01 kcal g⁻¹ in the Labrid teleost Bodianus bilulunatus to 6.0±0.12 kcal g⁻¹ in the moray eel, Gymnothorax undulatus. Essential amino acids occurred in lower concentrations as a percentage of the total amino acids (35.8±2.6%) than non-essential amino acids (64.2±2.6%), but the ratio of individual amino acids to total amino acid concentrations were similar to those required by some monogastric terrestrial species and fingerling salmon. The fatty acid concentrations varied widely among species (range=1.2–16.5 mg 100 mg⁻¹); however, the teleosts had higher total fatty acids than the non-teleosts. This study indicates that, from a nutritional standpoint, some prey may be more beneficial to the Hawaiian monk seal; however, these prey are not necessarily the most abundant or available to some populations of the monk seal.

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General paperAmino acid composition of pinniped milk

Abstract

J. Dairy Sci.

J. Nutr.

J. Nutr.

J. Dairy Sci.

J. Nutr.

J. Dairy Sci.

Lactation strategies in pinnipeds: problems for a marine mammalian group

General paper
Amino acid composition of pinniped milk