Milk composition of Australian sea lions, Neophoca cinerea : variability in lipid content

Thirty-eight milk samples collected over three seasons from 23 individual Australian sea lions (Neophoca cinerea) were analyzed. Mean milk composition was 25.4% lipid (± 9.3% SD), 62.4% water (± 8.1%), 10.5% protein (± 2.2%), and 0.9% ash (± 0.2%). Milk composition appeared to vary considerably among females, and occasionally between successive samples from the same individual. Milk fat content was not correlated with pup age (stage of lactation), female mass, length of the preceding foraging trip, or time onshore prior to milk collection. The relatively low lipid content of Australian sea lion milk compared with that of some other otariid seals is consistent with the hypothesis that otariid females making relatively short trips to sea produce milk with lower fat content than those species which make foraging trips of longer duration.