Comparison of the milk composition of free-ranging blesbok, black wildebeest and blue wildebeest of the subfamily Alcelaphinae (family: Bovidae)

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Abstract

The proximate composition of milk from free ranging blesbok, black wildebeest and blue wildebeest is reported, with detailed analysis of fatty acid composition and protein identification by electrophoresis. The milk of the blesbok, black- and blue wildebeest contain respectively 5.6 ± 0.3, 4.3 ± 0.7 and 4.1 ± 0.9 g/100 g protein, 8.6 ± 1.1, 5.5 ± 1.5 and 7.5 ± 2.1 g/100 g fat, and 4.9 ± 0.4, 4.1 ± 0.6 and 5.3 ± 1.6 g/100 g lactose, and are comparable with ovine milk. The milk contains high levels of saturated fatty acids, respectively, 82.5 ± 1.7 g/100 g, 75.2 ± 1.5 g/100 g and 88.2 ± 1.8 g/100 g milk fat. The medium carbon chain length saturated fatty acids 8:0, 10:0 and 12:0 occur in the highest amounts recorded so far in ruminant milk, and the 14:0 content is the highest recorded in any milk. This suggests a genetic characteristic of the Alcelaphinae that reflects on the specificity and activity of the thioesterase involved in the fatty acid synthesis. By electrophoresis the κ- and γ-caseins are separated into multiple bands and the α-caseins of the wildebeest into two bands.

Introduction

Comparative studies of the milk of different species give insight into biochemical properties of milk synthesis and nutritional properties which would be difficult to investigate in a single species. The study of the composition of milk of ruminant species is mainly limited to the few commercially exploited animals such as the cow (Bos taurus), sheep (Ovis aries), goat (Capra hircus), camel (Camelus bactrianus), water buffalo (Bubalus bubalis) and yak (Bos grunniens) (Jennes and Patton, 1976, Oftedal, 1984, Casoli et al., 1989, Voutsinas et al., 1990). For other ruminant species, the information is limited to the content of the major nutrients (Landete-Castillejos et al., 2000, Gjøstein et al., 2004). Regarding the wild animals, more information is also known for the milk of the deer species than the antelope (Iverson and Oftedal, 1995, Landete-Castillejos et al., 2000, Gjøstein et al., 2004). Apart from the proximate composition of a few species, e.g. the black wildebeest (Connochaetus gnou), eland (Taurotragus oryx) (Van Zyl and Wehmeyer 1970), blue duiker (Cephalophus monticola) (Von Ketelhod 1976), and giraffe (Giraffa camelopardalis) (Hall-Martin et al. 1977) very little is known about the milk of African ruminants. Detailed studies on the nutrients have to date been carried out on springbok (Antidorcas marsupialis) (Osthoff et al., 2007a), sable antelope (Hippotragus niger) (Osthoff et al., 2007b) and African buffalo (Osthoff et al., in press). No information on the composition of milk of blesbok, or its close cousin bontebok (Damaliscus dorcas dorcas), or the blue wildebeest (Connochaetes taurinus taurinus) could be found in the literature.

Research on energy provision by milk nutrients receives great interest (Oftedal, 1984, Tilden and Oftedal, 1997, Power et al., 2002), as does the fatty acid content of, and deposition in, milk fat (Dils et al., 1977, Iverson and Oftedal, 1995, Milligan et al., 2007). This aspect is very important, because certain fatty acids are believed to play a direct role in the neurodevelopment of infants (Makrides et al., 1994, Kothapalli et al., 2007). The fatty acid composition in milk differs between species. In species with foregut fermentation, specifically the ruminants, the ingested fatty acids are changed by fermentation. Every species of single stomach digesters, such as the lion (De Waal et al., 2004), cat (Jacobsen et al. 2004), pig (Csapó et al., 1996), African elephant (Osthoff et al., 2005) and primates (Milligan et al., 2007) seems to have a unique need of certain fatty acids deemed essential, and the composition may be dictated by a preference for the incorporation of dietary fatty acids or de novo synthesized medium chain (8:0 –14:0) fatty acids.

In ruminants de novo synthesis of medium chain fatty acids is performed with lactate, acetate and 3-hydroxybutyrate, which are metabolites from the fermentation of carbohydrates by the rumen bacteria, as substrates. The length of de novo synthesized fatty acids depends on the specific properties of enzymes in the synthesis pathway. Fatty acids are synthesized by fatty acid synthase in an elongation process. In the liver and adipose tissues the fatty acids attain a chain length of 16 carbons or more. In the mammary gland the synthesis is terminated by a thioesterase before a chain length of 16 carbons is reached. Depending on the properties of the thioesterase, this termination may be effected after elongation of 8 to 14 carbons (Neville et al., 1983).

Amongst the non-ruminants, such as bats (Hood et al., 2001) and primates (Milligan et al., 2007, Osthoff et al., 2009a), there is evidence that ecological (diet) as well as phylogenic (genetic) factors may contribute to differences in fatty acid composition of milk fat. To date such observations amongst ruminants are still unclear, although it is known that members of at least the Caprinae sub-family, specifically the sheep (Ovis aries)(Haenlein and Wendorff, 2006) and goat (Capra hircus)(Park, 2006), may contain 10–19% medium chain fatty (8:0–12:0) acids in milk fat compared to the less than 10% in other ruminant milk. The single sample of okapi milk analyzed may suggest that amounts higher than 10% are also found in milk of the Giraffidae (Glass and Jenness, 1971). Amongst the Bovini tribe of the Bovinae subfamily, the proximate and fatty acid composition of the domesticated cow (Jennes and Patton, 1976), yak (Lkhagvajav, 1978), buffalo (Jensen, 1995) and African buffalo (Osthoff et al., in press) differ. Regarding the fatty acids, the greatest differences were shown to occur in 16:0, 18:0 and 18:1 (Pandya and Khan, 2006, Osthoff et al., in press).

It was mentioned above that medium chain length fatty acids are formed due to the termination of elongation after 8 to 14 carbons by a thioesterase (Neville et al., 1983). Very little emphasis is placed on the composition of myristic acid (14:0) in the comparisons of milk amongst species. The reason might be that the greatest differences in medium chain fatty acid composition in milk are observed in the 8:0 to 12:0 acids (Iverson and Oftedal, 1995). The 14:0 content is very constant at below 10%. Only in a few species have amounts above 10% been detected, such as the brown lemur (Eulemur fulvus), slow loris (Nycticebus coucang) (Myher et al., 1994) and Norway rat (Rattus norwegicus) (Mills et al., 1990). In general, only ruminant milk contains above 10% of 14:0, which is an indication of the chain length specificity of their thioesterase, but contents as high as 16% have only been found in blackbuck antelope (Antilope cervicapra) (Dill et al., 1972) and gazelle (Gazella granti) (Glass and Jenness, 1971).

In the current study we were able to investigate the milk composition of three antelopes, blesbok (Damaliscus dorcas phillipsi), black- (Connochaetes gnou) and blue wildebeest (Connochaetes taurinus taurinus), and explain phylogenetic (genetic) and nutritional effects on the composition of milk nutrients and fatty acids. We compare three animals of one subfamily, the Alcelaphinae, of which two are related at genus level. With 29 protein incoding loci Grobler and Van der Bank (1995) have shown that the genetic distance between the two wildebeest species is only 0.02 ± 0.014, and between these and the blesbok 0.121 ± 0.066. The milk composition of the three antelopes has not yet been described in detail, and to our knowledge no comparative study between the milk of closely related ruminants has so far been conducted.

Section snippets

Materials and methods

Milk was obtained from four blesbok and three black wildebeest on a game farm 30 km west of Bloemfontein, Free State Province, and five blue wildebeest on a game farm 50 km west of Bloemhof, Northwest Province, South Africa during culling operations for meat production in July 2007. In both areas the animals roamed on vegetation of Dry Cymbopogon-Themeda Veld (Acocks 1988). Milk was drawn immediately after death by palpation of the teats while simultaneously sustained pressure was exerted on

Results

The proximate analysis of the milk of the blesbok, black wildebeest and blue wildebeest is shown in Table 1 and the fatty acid composition of the fat fraction of these milk samples in Table 2. The analysis compared the known animals' milk with bovine (Jennes and Patton, 1976, Smit et al., 2000), ovine (Pirisi et al., 1999) and caprine milk (Simos et al., 1991). The nutrient composition of the milk of six domestic cows was in the same order of magnitude as that reported by Jennes and Patton

Discussion

The standard deviation of the values for nutrient composition in the studied milk are quite high, but might be an indication of variation between individuals, because variation due to the ewes being at different stages of lactation can be ruled out. All the calves that were with the mother animals were approximately of the same age. A more likely explanation would be that some ewes were suckled prior to milk sampling. The high standard deviation of the fat content in the milk might be an

Acknowledgements

The authors acknowledge the contribution of Mrs. Eileen Roodt for the lipid extractions and Mr Johan du Toit of Raakvat Jagklub, Bultfontein, for allowing our presence during culling operations to collect milk.

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