Milk and Energy Intakes of Suckling California Sea Lion Zalophus californianus Pups in Relation to Sex, Growth, and Predicted Maintenance Requirements

Oftedal, Olav T.; Iverson, Sara J.; Boness, Daryl J.

doi:10.1086/physzool.60.5.30156130

Cited by 103 publications

(69 citation statements)

References 32 publications

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“…The percentage of energy supplied by protein is quite low (12-21) by comparison with carnivores that do not fast during lactation (27-50; Gittleman & Oftedal, 1987). This low level is believed to reflect the slow rates of growth and relatively high energy expenditure rates of sucking pups (Oftedal et al 1987b;Thompson et al 1987). The composition of the milk thus conforms to expectations for a fasting animal.…”

Section: Sea Lions and Fur Seals (Carnivora: Otariidae)supporting

confidence: 61%

Use of maternal reserves as a lactation strategy in large mammals

2000

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The substrate demands of lactation must be met by increased dietary intake or by mobilization of nutrients from tissues. The capacity of animals to rely on stored nutrients depends to a large extent on body size; large animals have greater stores, relative to the demands of lactation, than do small animals. The substrate demands of lactation depend on the composition and amount of milk produced. Animals that fast or feed little during lactation are expected to produce milks low in sugar but high in fat, in order to minimize needs for gluconeogenesis while sustaining energy transfers to the young. The patterns of nutrient transfer are reviewed for four taxonomic groups that fast during part of or throughout lactation: sea lions and fur seals (Carnivora: Otariidae), bears (Carnivora: Ursidae), true seals (Carnivora: Phocidae) and baleen whales (Cetacea: Mysticeti). All these groups produce low-sugar high-fat milks, although the length of lactation, rate of milk production and growth of the young are variable. Milk protein concentrations also tend to be low, if considered in relation to milk energy content. Maternal reserves are heavily exploited for milk production in these taxa. The amounts of lipid transferred to the young represent about one-fifth to one-third of maternal lipid stores; the relative amount of the gross energy of the body transferred in the milk is similar. Some seals and bears also transfer up to 16-18 % of the maternal body protein via milk. Reliance on maternal reserves has allowed some large mammals to give birth and lactate at sites and times far removed from food resources. Lactation involves the mobilization and export of substantial quantities of nutrients in milk, placing large nutrient demands on the mother. If she is unable to meet these added demands by dietary intake, she must reduce milk output, mobilize nutrients from maternal tissues or employ some combination thereof. However, reduction in milk output may compromise survival of the young. In nature, lactation is often timed to periods of food abundance so that the mother can match dietary intake to lactational needs, and does not have to choose between her own future and that of her offspring.An alternative approach is to disengage lactation from maternal food intake by storing nutrients in tissues during periods of abundance and then mobilizing these nutrients into milk at a later date. Such an approach is only possible if the types and amounts of nutrients stored in tissues are sufficient to cover the demands of lactation. The sufficiency of nutrient storage is largely governed by the allometry of energy expenditure (Oftedal, 1993): since small animals expend energy at a much higher rate (relative to body mass) than large animals, small animals are physically unable to store sufficient energy to cover expenditures for any length of time.A simple calculation for 4 g shrews illustrates this point. If a shrew deposits body fat equivalent to 250 mg/g body mass (M), the energy content of the fat stores will be about 39 kJ, while lea...

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Section: Sea Lions and Fur Seals (Carnivora: Otariidae)supporting

confidence: 61%

Use of maternal reserves as a lactation strategy in large mammals

2000

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“…One group of eutherian mammals, the fur seals and sea lions (Pinnipedia: Otariidae), have secondarily lost the ability to synthesize a-lactalbumin because of gene mutations and changes in transcription rates (Sharp et al, 2005;Reich and Arnould, 2007;Sharp et al, 2008); therefore the milk is devoid of lactose or lactose-based oligosaccharides (Oftedal et al, 1987a and. These taxa manage to produce large volumes of high-fat milk (Oftedal et al, 1987b;Arnould and Boyd, 1995;Arnould et al, 1996), but the secretory processes by which the aqueous phase is secreted have not been studied. In mice, knockout of the gene for a-lactalbumin results in a very low level of secretion of high-fat milk, and the offspring do not survive (Stinnakre et al, 1994;Stacey et al, 1995).…”

Section: Evolution Of Milk Secretionmentioning

confidence: 99%

The evolution of milk secretion and its ancient origins

Oftedal

2012

Animal

196

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Lactation represents an important element of the life history strategies of all mammals, whether monotreme, marsupial, or eutherian. Milk originated as a glandular skin secretion in synapsids (the lineage ancestral to mammals), perhaps as early as the Pennsylvanian period, that is, approximately 310 million years ago (mya). Early synapsids laid eggs with parchment-like shells intolerant of desiccation and apparently dependent on glandular skin secretions for moisture. Mammary glands probably evolved from apocrine-like glands that combined multiple modes of secretion and developed in association with hair follicles. Comparative analyses of the evolutionary origin of milk constituents support a scenario in which these secretions evolved into a nutrient-rich milk long before mammals arose. A variety of antimicrobial and secretory constituents were co-opted into novel roles related to nutrition of the young. Secretory calcium-binding phosphoproteins may originally have had a role in calcium delivery to eggs; however, by evolving into large, complex casein micelles, they took on an important role in transport of amino acids, calcium and phosphorus. Several proteins involved in immunity, including an ancestral butyrophilin and xanthine oxidoreductase, were incorporated into a novel membrane-bound lipid droplet (the milk fat globule) that became a primary mode of energy transfer. An ancestral c-lysozyme lost its lytic functions in favor of a role as a-lactalbumin, which modifies a galactosyltransferase to recognize glucose as an acceptor, leading to the synthesis of novel milk sugars, of which free oligosaccharides may have predated free lactose. An ancestral lipocalin and an ancestral whey acidic protein four-disulphide core protein apparently lost their original transport and antimicrobial functions when they became the whey proteins b-lactoglobulin and whey acidic protein, which with a-lactalbumin provide limiting sulfur amino acids to the young. By the late Triassic period (ca 210 mya), mammaliaforms (mammalian ancestors) were endothermic (requiring fluid to replace incubatory water losses of eggs), very small in size (making large eggs impossible), and had rapid growth and limited tooth replacement (indicating delayed onset of feeding and reliance on milk). Thus, milk had already supplanted egg yolk as the primary nutrient source, and by the Jurassic period (ca 170 mya) vitellogenin genes were being lost. All primary milk constituents evolved before the appearance of mammals, and some constituents may have origins that predate the split of the synapsids from sauropsids (the lineage leading to 'reptiles' and birds). Thus, the modern dairy industry is built upon a very old foundation, the cornerstones of which were laid even before dinosaurs ruled the earth in the Jurassic and Cretaceous periods.Keywords: evolution, lactation, milk composition, casein, milk fat globule ImplicationsLactation has an evolutionary origin and biological context within which its secretory processes and milk constituents evolved. This revi...

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“…Milk lipids of seals and sea lions furnish 85-95% of the total caloric intake of neonates and are characterized primarily by long-chain and unsaturated fatty acids, including a very large percentage (10-30%) of n-3 PUFA derived from their marine diets (28,29). Suckling pups consume phenomenal quantities of lipid daily at 600 g to 5 kg (30,31), or up to 10-to 20-fold higher on a body weight basis than neonates of the human or dog. Rapid blubber deposition suggests rapid and efficient absorption of milk lipid (28,32,33), but the mechanisms of hydrolysis and digestion are unknown.…”

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confidence: 99%

Positional specificity of gastric hydrolysis of long‐chain n−3 polyunsaturated fatty acids of seal milk triglycerides

Iverson

Sampugna

Oftedal

1992

Lipids

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Long-chain n-3 polyunsaturated fatty acids (n-3 PUFA) of marine oils are important dietary components for both infants and adults, and are incorporated into mlUo~ following maternal dietary intake. However, little is known about the hydrolysis of these PUFA from milk triglycerides (TG) by lipases in suckling young. Seals, like human~, possess gastric lipase; however, the milk lipids of seals and sea lions are almost devoid of the readily hydrolyzable medium,chain fatty acids, and are characterized by a large percentage (10-30%) of n-3 PUFA. Gastric hydrolysis of milk lipids was studied in vivo in suckling pups of three species (the California sea lion, the harp seal and the hooded seal) in order to elucidate the actions and specifit~ ity of gastric lipases on milk TG in relation to fatty acid composition and TG structure. Regardless of milk fat content (31-61% fat) or extent of gastric hydrolysis (10-56%), the same fatty acids were preferentially released in all three species, as determined by their relative enrichment in the free fatty acid (FFA) fraction. In addition to 16:1 and 18:0, these were the PUFA of 18 carbons and longer, except for 22:6n-3. Levels of 20:5n-3 were most notably enriched in FFA, at up to five times that found in the TG. Although 22:6n-3 was apparently also released from the TG (reduced in the diglyceride), it was also notably re~ duced in FFA. Positional analysis of milk TG based on the products of Grignard hydrolysis revealed that these PUFA, including 22:6n-3, were preferentially esterified at the a-position of the TG, and that the fatty acids not released during gastric hydrolysis were located at the sn-2 position. The extreme reduction of 22:6n~ and enrichment of 20:5n-3 in FFA is discussed. Results from this study are consistent with reports that gastric lipase acts stere~ specifically to release fatty acids at the a-positions (sn-3, sn-1). We conclude that the n-3 PUFA in milk are efficiently hydrolyzed by gastric lipase and that this has important implications for digestion of milks enriched in PUFA by neonates in general. Lipids 27, 870-878 (1992).Long-chain n-3 polyunsaturated fatty acids (n-3 PUFA), characteristic of marine otis, have become a major focus of research due to their potent

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Milk and Energy Intakes of Suckling California Sea Lion Zalophus californianus Pups in Relation to Sex, Growth, and Predicted Maintenance Requirements

Cited by 103 publications

References 32 publications

Use of maternal reserves as a lactation strategy in large mammals

Use of maternal reserves as a lactation strategy in large mammals

The evolution of milk secretion and its ancient origins

Positional specificity of gastric hydrolysis of long‐chain n−3 polyunsaturated fatty acids of seal milk triglycerides

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