Milk is the sole food for newborn mammals. The composition of each species is complex and unlikely to be duplicated. To understand milk as a food, a holistic approach is required. Milks of non-dairy animals have to be studied for this purpose. The research is focused on the composition of milk from African mammals. The results contributed to information on species in specific, as well as milk chemistry in general, on the following 4 aspects:

Milk fat

The fatty acid composition of milk triacylglycerols differs from body adipose fat and plant fats regarding length and degree of unsaturation. The major fatty acids are the long chain palmitic, oleic and linoleic acid, and ruminant milks contain butyric acid. Some species, eg. blesbok and elephant, contain a high content of medium length fatty acids such as capric, lauric and myristic acids. This affects the physical melting and setting properties as well as digestibility. The fatty acid synthesis by the milk glands of these species must be different, but the reasons of this specialization are not clear.

Milk proteins

Whey proteins consist of functional proteins that play a role in milk synthesis and infant protection. The major protein fraction is the caseins, with sole role being nutrition. Caseins occur as a randomized structure, bind calcium and phosphate and are combined, in a certain ratio, in casein micelles. The micelles occur as suspension, so that more proteins are found in milk than can occur in dissolved form. Most mammals have 4 casein types, some 3, while the African elephant is the only species known to have only 2.

Milk sugars

Lactose is the major sugar in most mammalian milks. Longer chain oligosaccharides occur in small amounts. They play an important role as prebiotics to the intestinal bacteria, while protecting  against pathogenic organisms. The chemical structures of oligosaccharides may differ between species, which in turn determine specialized intestinal bacteria populations.

Milk evolution

Comparison of the milk nutrients of 26 African mammal species, representing 5 Orders and 16 different taxa by statistical methods showed that milk composition is determined phylogenetically. As examples, the milk of carnivores and herbivores differ, and amongst ruminants, Alcelaphinae (blesbok, hartebeest and wildebeest) differs from Bovinae (cow, eland, kudu).

Milk structure
Overlay of structure models of lactose synthase complex from bovine and elephant milk.

Prof Osthoff collecting milk from a darted white rhinoceros cow
Prof Osthoff collecting milk from a darted white rhinoceros cow.

Recent Publications

Madende M and Osthoff G (2019) Comparative genomics of casein genes. Journal of Dairy Research, 86: 323-330 (IF 1.17)

Madende M, Osthoff G, Kemp G and Stoychev S (2018) Characterization of African elephant beta casein and its relevance to the chemistry of caseins and casein micelles. International Dairy Journal, 85, 112-120. (IF 2.201)

Osthoff G, Hugo A, Madende M, Deacon F and Nel PJ (2017) Milk composition of free-ranging red hartebeest, giraffe, reedbuck and warthog and a phylogenetic comparison of the milk of African Artiodactyla. Comparative Biochemistry and Physiology. A. 204, 93-103 (Imp. 1.56)

Madende M, Osthoff G, Patterton HG, Patterton HE, Martin P and Oppermann D (2015). Characterization of casein and alpha lactalbumin of African elephant (Loxodonta africana) milk. Journal of Dairy Science, 98, 8308-8318 (IF 2.45)

Smith E-A, Myburgh J, Osthoff G and de Wit M (2014). Acceleration of yoghurt fermentation time by yeast extract and partial characterization of the active components. Journal of Dairy Research, 81, 417–423. (IF 3.08)

Osthoff G, Hugo A and de Wit M (2012). Comparison of the milk composition of free-ranging eland and kudu (subfamily Bovinae, tribe Tragelaphini), and gemsbok and scimitar oryx (subfamily Hippotraginae) with observations on lechwe, okapi and Southern kudu. SA Journal of Wildlife Research, 42. 23–34.


FACULTY CONTACT

Faculty Manager: Velaphi Makgwahla
T: + 27 51 401 3199
E: makgwahlamvt@ufs.ac.za

Marketing Manager: Elfrieda Lötter
T: +27 51 401 2531
E: lottere@ufs.ac.za

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