Characterization of milk composition in narrow‐ridged finless porpoises (Neophocaena asiaeorientalis) at different lactation stages

Abstract

Lactation plays a vital role in reproductive success, evolving with ecological adaptations of mammalian life histories. Knowledge of the lactation process in odontocetes is scarce and limited to a handful of species. We investigated the changes in milk composition across different lactation stages, including prepartum mammary secretion and early, mid‐ and late lactation of narrow‐ridged finless porpoises. Prepartum mammary secretion was greenish and characterized by high protein, low sugar, and negligible fat contents. In contrast, milk fat became predominant over protein and sugar contents throughout all lactation stages. At the early lactation stage, the contents of all milk constituents except water varied greatly. At the mid‐late lactation stage, the gross milk composition was relatively stable and was composed of, on average, 67.34% ± 4.13% water, 9.96% ± 0.75% protein, 21.40% ± 3.24% fat, and 1.72% ± 0.73% sugar. Our findings provide new insight into milk composition at different lactation stages in the narrow‐ridged finless porpoise.

Characterization of milk protein composition of the Yangtze finless porpoise

“…Milk protein composition likely varies between lactation stages in the finless porpoise (Zeng et al . ). Zeng et al .…”

“…The milk sampling procedure was described in detail by Zeng et al . (). The milk samples were immediately frozen in a liquid‐nitrogen dewar and then stored at −80 ºC in a laboratory freezer until analysis.…”

“…The total sugar concentration was significantly lower in the prepartum milk (0.62% ± SD 0.02%) than that in the mature milk (1.72% ± SD 0.73%) (Zeng et al . ). In the present study, the α‐lact concentration significantly increased from the premature to mature milk (R α‐lact = 4.19, two‐sample t ‐test, t = −62.11, df = 5, P < 0.05).…”

“…), similar to the premature milk of the finless porpoise, which also has low α‐lact and sugar concentrations (Zeng et al . ). These examples do not contradict the above inferences that lactose is predominant in the mature milk.…”

“…The increased sugar content found by Zeng et al . () was likely due to increased lactose synthesis activity. Lactose may thus become the dominant sugar in the mature milk of the finless porpoise, which is frequently the case in many cetacean species (Pilson and Waller ; Jenness and Odell ; Pervaiz and Brew ; Urashima et al .…”