Introduction:
Why goat milk? This is a critical question for all who are trying to establish a dairy goat business and industry. The value of goat milk in human nutrition has so far received very little factual and academic attention (Haenlein, 1984, 1988, 1992; Park, 1991). However, if facts of the role (and superiority in certain instances)of goat milk in human nutrition can not be identified and promoted, it will be difficult justifying growth of the goat business as an industry next to the dairy cattle business. Since the milk supply from cows is more plentiful and cheaper, the challenge is to demonstrate why there are good reasons to produce goat milk; if not, dairy goats will be relegated to being only a pet business.
Despite a widespread absence of infrastructural organization for goat milk in the United States, more commercial successes with goat milk marketing are becoming known in recent years (Loewenstein et al., 1980; Kapture, 1982; Haenlein, 1985; Pinkerton, 1991; Hankin, 1992; Jackson, 1992). Also, significant new research station efforts in Texas, California, Oklahoma, Georgia, Alabama, Florida, Pennsylvania, Louisiana have been advancing new knowledge of goat milk production on the farm, and of the physiology, biochemistry and veterinary aspects of the animal in recent years. In addition to that, a new scientific journal--Small Ruminant Research--has become established by the International Goat Association initially quarterly but now on a monthly basis and with broad international support, published since 1988 by Elsevier Science Publishers at Amsterdam, The Netherlands. Volumes of new scientific data presented at five major, quintannual, international goat conferences have become widely circulated. Thus, it is high time to include in these developments the sanitarians, for establishing quality standards, and the medical profession, for evidence on the medical benefits and values in human nutrition of goat milk.
Medical Research Evidence for Goat Milk
Powerful justification for goat milk can come from medical needs (not just desires) of people, especially infants afflicted with various ailments, including cow milk protein sensitivities. Swedish studies have shown that cow milk was a major cause of colic, sometimes fatal, in 12 to 30 percent formula-fed, less than 3-month-old infants (Lothe et al., 1982). In breast-fed infants, colic was related to the mother's consumption of cow milk (Baldo, 1984; Cant et al., 1985; Host et al., 1988). In older infants, the incidence of cow milk protein intolerance was approximately 20 percent (Nestle, 1987).
A popular therapy among pediatricians is the change to vegetable protein soy-based formula; however, an estimated 20 to 50 percent of all infants with cow's milk protein intolerance will also react adversely to soy proteins (Lothe et al., 1982). Approximately 40 percent of all patients sensitive to cow milk proteins tolerate goat milk proteins (Brenneman, 1978; Zeman, 1982), possibly because lactalbumin is immunospecific between species (Hill, 1939), but beta-lactoglobulin appears to be the major allergen in cow's milk.
Biochemical Differences Between Goat Milk and Cow Milk
Goat milk proteins have many significant differences in their amino acid compositions from the milk of other mammalian species, especially in relative proportions of the various milk proteins and in their genetic polymorphisms (Jenness, 1980; Boulanger et al., 1984; Addeo et al., 1988; Ambrosoli et al., 1988). The major protein in cow milk is alpha-s-1-casein, but goat milk may differ genetically by having either none ("Null" type) or much ("High" type). Null types have shorter rennet coagulation time, less resistance to heat treatment, curd firmness is weaker, pH is higher, protein and mineral contents in milk are lower, and cheese yields are less than in high types. This in turn indicates and may explain significant differences to cow milk in digestion by infants and patients (Mack, 1953), which traditionally have been explained by the "homogenized" nature of goat milk fat.
Actually, the composition of goat milk fat may be much more important than the prevalence of large numbers of small fat globules, because it too differs significantly from the composition of cow milk fat under average feeding conditions (Haenlein, 1992). The various components of milk fat, fatty acids, differ in carbon chain length and saturation, which has nutritional and medical significance. Goat milk fat normally has 35 percent of medium chain fatty acids (C6-C14) compared to cow milk fat 17 percent, and three are named after goats: Caproic (C6), caprylic (C8), capric (C10), totaling 15 percent in goat milk fat vs. only 5 percent in cow milk fat (Table 1). Besides their unique flavor, which has serious consequences in improper handling of goat milk, these medium chain fatty acids (MCT) have become of considerable interest to the medical profession, because of their unique benefits in many metabolic diseases of humans (Babayan, 1981).
Capric, caprylic and other MCT have been used for treatment of malabsorption syndrome, intestinal disorders, coronary diseases, pre-mature infant nutrition, cystic fibrosis, gallstone problems, because of their unique metabolic abilities of providing energy and at the same time lowering, inhibiting and dissolving cholesterol deposits (Schwabe et al., 1964; Greenberger and Skillman, 1969; Kalser, 1971; Tantibhedhyangkul and Hashim, 1975, 1978). It seems apparent that in this lipid area is great potential for identifying a unique importance and role for goat milk, specifically goat milk fat and probably goat milk butter, which has not received much attention at all. And all this adds even more importance to the establishment of acceptable practices and standards for quality goat milk production, which so far has been lagging behind those for dairy cows, but which require separate establishment because of the many unique physiological and metabolic characteristics of goats compared to cows (Haenlein, 1980, 1987a, 1991; Hinckley, 1991; Kalogridou-Vassiliadou et al., 1992).
Table 1. Comparison of Milk Fat Compositions in Goat, Cow and Human Milk (weight%)
Principal fatty acids in milk fat Goat milk fat Cow milk fat Human milk fat Melting point o F
C4:0-Butyric 3 3 trace 18
C6:0-Caproic 2 1 trace 25
C8:0-Caprylic 3 1 trace 16
C10:0-Capric 10 3 2 31
C12:0- Lauric 7 2 6 44
C14:0- Myristic 13 10 9 54
Total Medium Chain Acids (C6-C14) 35 17
C14:1- Myristoleic 1 1 trace -
C16:0- Palmitic 28 26 23 63
C16:1- Palmitoleic 3 3 3 33
C18:0- Stearic 6 13 7 70
C18:1- Oleic 21 32 37 16
C18:2- Linoleic 4 3 8 23
C18:3- Linolenic and others 1 2 4 7
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