Composition of Milk

Carbohydrates.  Both lactose as a simple sugar, but also more complex oligiosaccharides that may be digested through microbial intestinal cellulases are reported as primary carbohydrates in elephant milks of both species (Kunz et al., 1999)  (Osthoff et al., 2008) (Uemura et al., 2006) although theoligosaccharide community appears to be more complex in African compared to Asian elephant milks (Osthoff et al., 2008). Asian elephant milk has also been reported to contain high levels of glucosamine an abundant monosaccharide important in cartilage development (Takatsu et al., 2017). 

While peaking at 5% in early milk, lactose drops to ~2% (Kobeni et al., 2020); Asian elephant milks showed a similar pattern of decrease in lactose, but at an even lower concentration (~1%; (Abbondanza et al., 2013). Total carbohydrates (lactose plus oligosaccharides plus mono-, other di- and trisaccharides) in elephant colostrum comprise between 3-5% of milk composition (Kobeni et al., 2020),  rapidly increasing (by day 3) to 11-12%, then decreasing throughout lactation (8% by 12 mo, 6% by 24 mo), with the oligosaccharides becoming the major fraction - a pattern opposite that seen in human milks. Lactose and isoglobotriose reached equal levels at mid-lactation (Kobeni et al., 2020), and the latter was the main oligosaccharide also identified in Asian elephant milks (Kunz et al., 1999;  Uemura et al., 2006). Although not found in human or other primate milks, this compound is seen in the milks of various wildlife and livestock species. Regarding total oligosaccharides plus lactose content, elephant milks appear more similar to human than many other livestock mil. Nonetheless the unique profiles and concentration of specific carbohydrate fractions may be important for optimal immune system and brain development  (Kunz et al., 1999;  Uemura et al., 2006) so must be considered in appropriate milk replacers. While lactose may be an important early energy source, levels are typically low in elephant milks and lactose-containing replacers should likely be treated with lactase enzyme. 

Early publications of elephant milk composition did not differentiate carbohydrate fractions, and techniques used may have only measured total sugar content in the past. As interest, methods and understanding have developed, it is becoming clearer that lactose represents the dominant carbohydrate in elephant milk early in lactation, decreasing over time, whereas oligosaccharide levels peak in mid-lactation (Osthoff et al., 2005) (Osthoff et al., 2007), thus suggesting possible different functions (energy vs immune support?) at different stages of life. The specific role of milk oligosaccharides to the applied nutrition of elephants has not yet been investigated in detail but should be considered in interpreting some of the stage of lactation differences noted for these pachyderms (see Table 4.5).

Proteins. African elephant colostrum contained almost 5% protein, which declined to 2.5-3% after one month, then steadily increased for the rest of lactation to ~4 to 7% (Kobeni et al., 2020). Similarly in Asian elephants, milk protein increased from ~4% at 3 mo to just over 5% in late lactation (Abbondanza et al., 2013) (Dierenfeld et al., 2020). Expressed on a per energy basis, protein remains rather constant in Asian elephant milk. Casein is the predominant protein in African elephant milk, followed by whey; this pattern is similar to equine milks, but not other mongastic or human milks which contain higher concentrations of whey.   

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Fats. Elephant milks have a rather unique fatty acid profile, with up to ½ to 2/3 comprising capric (C10:0) and lauric (C12:0) acids; capric acid comprised 60-70% of glyceride fatty acids, and increased with stage of lactation, in African elephant milk  (McCallaugh and Widdowson, 1970). These are both medium-chain saturated fats, with the former found in small amounts in goat and cattle milks, but both found in high concentrations in coconut oil. African elephant milks contain high concentrations of medium-chain length fatty acids, and low amounts of both long-chain and unsaturated fatty acids (Kobeni et al., 2020). Unpublished data sampled from Asian elephants (Takatsu, Z, Morinaga Milk, Kangawa, Japan) supports extrapolation of this general pattern to Asian elephant milks as well (Osthoff, personal communication 2022).  

Ash/minerals.  Ash content of colostrum was 0.3% and changed to 0.2% after four days (Kobeni et al., 2020). By the 12th month of lactation, ash content reached approximately 0.5% in African elephant milk, which is similar to an average value reported for a zoo-based Asian elephant (Mainka et al., 1994)(Mainka et al., 1994) but considerably below that reported in milks from 6 Asian elephants in late lactation in Myanmar (0.9%; (Dierenfeld et al., 2020). Little information is available on specific minerals in elephant milks; high K and Na concentrations in colostrum decreased initially (after 3 days), then gradually increased and remained stable after about 12 mo.  Stable values of 0.2% K, 0.03% Na, and 0.01% Mg were reported for African elephant milks (Kobeni et al., 2020). Ca and P occurred at low levels in African elephant colostrum (0.03 and 0.02%, respectively) then increased to 0.12 and 0.05%; these values were lower than Ca and P recorded for Asian elephant milks (0.1-0.2% for Ca, 0.06-0.12% for P, Abbondanza et al. 2013). Ash increases reflected increases of all major macrominerals (Ca, P, Mg, Na and K) over lactation (Kobeni et al., 2020) and may suggest a higher mineral need for growing calves during this rapid growth period (up to 1 year). Microminerals were found at low yet constant amounts in African elephant milk (Fe <0.06%, and Cu, Mn, and Zn at <0.001%; Kobeni et al., 2020), but have not been quantified in Asian elephant milks. 

Vitamins. Reported vitamin levels in elephant milk are low; <0.1 mg/kg for vitamin A, <0.3 mg/kg vitamin E, and <1 µg/kg for vitamins D3 and K, particularly during the first month of lactation in African elephants (Kobeni et al., 2020). In a zoo setting, vitamin A measured in African elephant milk (from a supplemented animal) ranged from 28-171 IU/100 g, vitamin D 22-70 IU/100 g, and vitamin E, 0.33-0.88 µg/ml (mg/kg) (Parrot, 1996). Milk from a zoo-sampled Asian elephant averaged 0.33 µg/ml vitamin E, with vitamin A, 0.46 µg/ml (Mainka et al., 1994), whereas semi-free-range Asian elephant milk samples contained vitamin E levels of 0.18 µg/ml (Dierenfeld et al., 2020). 

Energy. Gross energy measured in Asian elephant milk samples ranged from 1000 (birth) to 2000 (2 years of age) kcal/1000 g, steadily increasing energy density through lactation (Abbondanza et al., 2013). Values measured from African elephant samples remained at ~250 kcal/1000 g to approximately 9 mo of lactation, then increased to ~800 kcal/1000 g with the increase in milk fat and protein (Kobeni et al., 2020).  

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Milk Composition Changes During Stages of Lactation

For African but not Asian elephants, changes in milk composition are strong up to about 12 mo of lactation with little or no change thereafter. Conversely, Asian elephant milk constituents (particularly fat increases at the expense of sugars) continued through 30 months of lactation, with protein and mineral constant remaining rather constant. These changes need to be considered in feeding programs. The unique properties of elephant milks, including high oligosaccharide content – which may comprise up to half of the total sugar, and a unique fatty acid profile rich in medium-chain saturated fatty acids may be difficult to duplicate using typically available human- or livestock-based milk replacers. Furthermore, Asian elephant milk has been shown to contain a high level of glucosamine with levels >100X greater than found in cow’s milk, and >10X the levels found in human milk (Takatsu et al., 2017). Potential developmental, health, and growth consequences of possibly not duplicating these specific compounds or nutrient profiles through current hand-rearing practices with elephant calves have not been assessed.

Few published values of elephant colostrum are available, and recent observations with African elephants are extrapolated to Asian elephant colostrum. As in other species, colostrum can have an extremely different composition compared with mature milk. Kobeni et al. (2020), working with a human-accustomed African cow was able to examine detailed changes in colostrum to milk from the day of the calf’s birth. They measured total carbohydrate levels from 3 to 5% over the first 2 days, that rose to >11% for the first few months, then gradually leveled at 6%. Lactose was the dominant carbohydrate, with colostrum containing 1.9%, rising to 5% after 3 days, then a constant decrease to 2%. Simultaneously, oligosaccharides were 2.1% at day zero, rising to 4.3% the first month then declining and stabilizing at 3.3%. Isoglobotriose became the major carbohydrate fraction by the fourth month, increasing from 0.8 to 2.2% at 12 months of lactation and to 1.5% at 19 months of lactation. 

Protein (primarily casein) was also higher in colostrum than milk after 1 month (4.7 vs. ~3%), then gradually increased over lactation to between 4 and ~7%; this pattern has also been described in Asian elephants (Abbondanza et al., 2013).  Milk fat was low in colostrum (~2%), rising to above 12% after 13 months, then fluctuating between 8 and 16% - again, similar to values and patterns reported in Asian elephants. 

Specific fatty acid patterns in African elephant milks over lactation were recently summarized (Kobeni et al. 2020): colostrum was high in C10:0 (capric acid, 31%), C12:0 (lauric acid, 17%), C16:0 (palmitic acid, 15%), and C18:1 (oleic acid, 18%). These proportional values changed by mid-lactation at 9 months, with capric reaching ~60%, lauric 27%, and both palmitic and oleic acids decreasing below 5% contribution. Fatty acids containing 10 carbons or less decreased over lactation, while those with >16 carbons decreased. Saturated fatty acids comprised ~73% of milk fat in colostrum, and up to 95-96% of milk fat by mid- to late lactation. Energy originally derived from lactose is likely replaced by lipid utilization later in lactation, but specific fatty acids may also have relevance to overall health and development. 

Minerals (ash) content was found to be higher in colostrum than milk (0.3 vs 0.2%), declining within 4 days, with an increase up to about 0.5% by 12 months. This pattern of increase throughout lactation has been seen in both African and Asian elephant milks (see Table 4.5). Colostrum was higher in Na and K (0.12 and 0.11%, respectively) compared with milk after 3 days (0.02 and 0.07%). Both minerals increased after about 11-12 months to 0.186 and 0.025%, respectively. K values are similar to those of cow’s milk; elephant Na values are lower. Mg showed a similar trend to Na, starting at 0.007% and stabilizing at 0.014%. Both Ca and P were low in colostrum (0.034 and 0.019%), then increased to 0.12 and 0.05% in African elephant milk; values for Ca and P were about about double those values when measured in Asian elephant milks (0.1% and 0.06% vs 0.22% and 0.12% for P at 2 and 28 months, respectively; Abbondanza et al. 2013).  Mineral needs increase with growth/lactation. 

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