Producing Quality Goat Milk
Mounting evidence indicates several basic differences in goat and cow physiology, biochemistry, microbiology and in the composition of their milk. Standards based on research with dairy cows are discriminatory to dairy goats in many aspects and must be replaced by suitable goat milk standards. Practices which assure safe and wholesome quality of goat milk are based on dairy cow experiences but must be confirmed for applicability to goat husbandry, not only for microbiological safety, but also for acceptability of taste and odor, which so far has been a widespread major deterrent to public acceptance of goat milk, and therefore impedes its use in human nutrition where medical reasons indicate its value.
Why goat milk? This is a critical question to be asked and answered by all who are trying help 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 we can not and do not identify and promote facts of the role, and superiority in certain instances, of goat milk in human nutrition, we will have a hard time justifying growth of the goat business as an industry next to the dairy cattle business. As the milk supply from cows is more plentiful and cheaper, we have the challenge to demonstrate why there are good reasons to produce goat milk; if not, we are strictly only in the pet business.
Despite a widespread absence of infrastructural organization for goat milk in the USA, 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, and Pennsylvania 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. Besides that, a new scientific journal Small Ruminant Research has become established by the International Goat Association on a monthly basis and with broad international support since 1988. And the volumes of new scientific data presented at four 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 and nutritional benefits of goat milk.
MEDICAL RESEARCH EVIDENCE FOR GOAT MILK
Powerful justification for goat milk can come from medical needs, especially for 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 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).
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 (Table 1), and three are named after goats: Caproic (C6), caprylic (C8), capric (C10), totaling 15 percent in goat milk fat versus only 5percent in cow milk fat. 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 syndromes, 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 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, 1990; Kalogridou-Vassiliadou et al., 1992).
MONITORS OF QUALITY MILK STANDARDS
This discussion is limited to the effects the farm producer can and will have on the quality of milk, which is a most perishable and most fragile product, easily affected negatively by improper feeding of the animals, improper handling of them prior and during milking, improper handling of the milk during and after milking including improper equipment handling, cooling and transportation (Haenlein, 1987b). To safeguard quality milk production, at least 5 major parameters are routinely monitored by various agencies which have jurisdiction over the production of milk through commercial channels:
These five parameters need to be at optimum or it will cost the farmer money, directly or indirectly. If milk composition is below minimum market standards, if somatic cell counts and bacteria levels indicate mastitis or unclean and improper handling, if milk is off in appearance, flavor, taste and temperature, if milk contains water or veterinary or sanitary treatment or pesticide residues or traces of toxic molds from feeds, then entire loads of milk shipment or tanks can be unsalable, can be condemned and a big financial loss to the farmer, jeopardizing even future milk sales.
Technology has come to the farmers' aid and enabled great progress in sanitary milking and milk house facilities in recent years. It is in the farmers' direct financial interest to take advantage of this technology, which can deliver milk from the mammary gland of goats to the cooling tank and processing plant without ever coming in contact with barn air, with other animals or the workers. This can eliminate a whole host of environmental odors, microbes, contaminations and assure a truly quality milk. However, technology requires its own proper care and sanitary management, otherwise it will lead to oxidation, contamination, bacteria invasion, and loss of the quality of milk it was meant to assure.
What then can the goat milk producer do to assure the best quality and best possible income from the sale of his milk, especially when instead of modern technology the traditional hand-milking is still practiced? Information from dairy cow production and cow milk research can help in advising goat milk producers, while research with goat milk production and handling is just starting in the United States, more found in foreign languages or non-existing. This has led to the unfortunate application of cow milk standards by regulatory sanitary officials to goat milk in commerce, in the absence of established separate goat milk standards, and to the detriment of goat milk producers.
GOAT MILK FLAVOR
Acceptable, attractive milk odor and taste is probably the single most important quality standard of goat milk, because of a long history of widespread negative popular perception of goat milk being "goaty." In fact, the national U.S. dairy products judging procedures list "goaty" as one of the four odor characteristics of bad versus good milk, cheese, yoghurt, cream and butter. Goaty odor does not need to happen, because well produced and well handled goat milk is indistinguishable in taste and odor from quality cow milk. Although goat milk has a higher content of the strong smelling caproic, caprylic and capric acids in its milk fat, with good milking practices they are enclosed within the fat globule membrane. This membrane is, however, more fragile in goat milkfat than in cow milkfat, is easily broken during improper handling, insufficient cooling and repeated rewarming, and then enzymes are liberated that can produce odors.
Many sources can be identified for off-flavors in cow milk and the same applies to goat milk: feeds (molasses, citrus pulp), forages (rape, rapeseed meal), weeds (onions, garlic), environmental odors (oil, gasoline, moldy rags, lime, cement, active bucks); normal physiology (early lactation colostrum, late lactation high salt contents, estrus, mastitis, sickness); improper handmilking procedures; improper equipment and handling (oxidation due to risers in milking pipelines, vacuum slips and searches, sun exposure, filthy clogged strainers and pipeline connections, unclean milking equipment, wash water not hot); slow air cooling instead of water cooling or refrigeration; variable temperature during storage, addition of warm milk to cold storage milk, transport in unrefrigerated containers, etc.
Good procedures exist about how to best achieve acceptable milk flavor and with it production of quality milk:
To monitor the concerns for quality milk production, a number of gauges and tests can be routinely used on dairy
goat farms. Often it is difficult to overcome seasonal breeding and the then common late stage of lactation in
all goats, which means that at some time of the year most members of a goat herd are in late lactation with naturally
high levels of salt, solids and somatic cell counts in their milk. CMT (California Mastitis Test) checking of udder
halves should be routine and can make a difference in quality control of goat milk.
The National Mastitis Council has promoted effective mastitis control programs, the so called 5-point program
for reduction in somatic cell counts states:
1. Use only functionally adequate milking machines, or hand-milking in the correct manner.
2. Dip teats after each milking with an effective, approved product.
3. Administer promptly a full series of recommended treatments to all clinical cases of mastitis.
4. Treat udder halves at drying-off of goats with an approved antibiotic preparation for drying-off.
5. Cull animals with chronic infections when they do not respond to treatments.
I add to this list: Don't use milk for sale from udders with very high somatic cell counts or high CMT. Feed
that milk to chickens, pigs or a calf.
And I also add: Don't let goats rest on concrete floors during the cold season, provide wooden slatted, false
floors or warm clean bedding, or natural pasture, to keep udders from getting cold chills and infections.
Goat milk must be cooled like it is officially prescribed down to the holding temperature range of 36 to 42o
F within a short time after milking. This is not possible by air cooling, only by water cooling, agitated
exposure to refrigerated tank walls, and in counter-current heat exchange coolers. Once cool, quality goat milk
must be held in the 36 to 42o F range without interruption nor variation to maintain its quality and
A quality bonus payment helps efforts in achieving and maintaining high-quality milk. Milk composition and yield
changes with mastitis, even subclinical mastitis, which has visibly normal milk but high somatic cell counts. Some
components in milk, such as whey proteins, lactose, lipase, sodium, chloride increase with mastitis, while milk
fat, solids, casein, calcium, phosphorus, potassium and cheese yield decrease. Thus, taste quality of goat milk
is directly affected by the status of udder health.
INSPECTION AND LAB REPORTS
Dairy lab reports provide several milk quality criteria required by local, state and federal health inspectors:
1. Standard plate counts (SPC) of bacteria should be less than 10,000 per milliliter.
2. Pre-incubation count (PIC) of specific bacteria should be less than 20,000.
3. Direct microscopic somatic cell count (DMSCC) should be less than 300,000.
4. Direct microscopic count (DMC) should be less than 30,000.
5. Temperature resistant bacteria count (THC) should be less than 1,000.
6. Freezing point temperature decrease or cryoscopy (CRY) in degrees C below zero must be between -0.530 and
-0.550, which indicates absence of water in milk.
7. Antibiotics or growth inhibitors (ABI) in milk must be negative.
8. Holding temperature (TEM) of the milk should be between 34 and 39 degrees F always.
These tests monitor trouble due to animals, equipment and people. The California Mastitis Test (CMT), obtainable
from any feed or supply dealer is an excellent farm-side monitor, even for goats, and should be used often and
regularly on each goat and each udder half. Even better yet is the monthly somatic cell count (SCC) testing of
each goat in the herd under the DHIA program, if the somatic cell counting is not by the Coulter counter.
MILK SECRETION IS DIFFERENT IN GOATS
The most obvious difference in anatomy is that there are only two teats on the goat udder vs. four on cow udders.
Less obvious is the relatively larger inside volume of the teat and gland cysterns. That is why good goat udders
look much more collapsed and empty after milking than cow udders. The smaller, tighter diameter of the teat sphincter
and meatus of goat udders makes milking and milking-out somewhat different. Also, the milk let-down effect in goats
takes only a few seconds compared to one minute in cows. Goat manure should always be pellets and drier than cow
manure, which is much higher in water content or normally sloppy and easily soiling the flanks and udders of cows,
while goats stay normally dry and have clean flanks and udders. This difference makes milking preparation procedures
for goats potentially much easier to be sanitary. It is not risky to only dry clean goat teats and udders for the
milking of low-bacteria-count goat milk. Also, prevalent bacteria and pathogens in goat udders are often of different
species than in cow udders.
Seasonal reproduction, usual in this country, is another important difference in milking goats. Cows are bred
in every month of the year, therefore their milk is always a composite of early, middle and late stage lactation.
Goats, unless specially treated, breed only in early fall and are fresh only in early spring, normally. Thus, at
various times of the year, dairy goats are all in early, or middle, or late stage of lactation, accentuating normal
seasonal milk composition changes, that are related to stages of lactation, to estrus and low amounts of milk.
For example, fat, protein and somatic cells in milk normally are high in early and late lactation in cows and in
goats, while lactose is usually the opposite.
All these differences might give already doubts about the validity of using the same standards for evaluating milk of the two species. Not surprisingly, the compositional differences are also part of physiological differences in the secretion process of milk from inside the udder from the alveolar cells. Cow milk secretion has been termed "merocrine," which is defined as "the act of secretion leaves the cell intact." Goat milk secretion, on the other hand, has been termed by researchers "apocrine," which is defined as "the secretion-filled free end of a gland cell is pinched off, leaving the nucleus and most of the cytoplasm to recover and repeat the process."
SOMATIC CELL COUNTS
Equipment for monitoring somatic cell count (SCC) levels in cow milk includes the CMT applied in the barn, and electronic automated machines in labs, the so-called Coulter Counter, or the Fossomatic, which use different chemical principals to achieve supposedly the same SCC evaluations.
The important question of whether these three worldwide adopted methods and the legal threshold set by Public Health officials of 1 million SCC/ml milk apply to cow and goat milk equally accurately and validly, despite the many mentioned differences in the physiology and composition of milk of the two species has only recently begun to be studied (Haenlein, 1987a, b; Hinckley, 1991; Kalogridou-Vassiliadou et al., 1992). Research has established that the SCC in cow milk is indicative of, although less than equal, the number of leukocytes in milk, which of course indicates subclinical or clinical mastitis. In contrast, goat milk contains from the apocrine secretion process many non-leucocytic cell particles, that do not have DNA or a nucleus as leukocytes do. Thus, only SCC methods which specifically identify DNA, give valid counts of leukocytes in goat milk. Socalled "total somatic cell count" is not only unreliable, but useless and wrong for inspectors monitoring legal thresholds of quality of goat milk.
It was determined that visibly normal goat milk had less numbers of pathogenic bacteria than cow milk under similar conditions. Relationships between SCC from CMT and Fossomatic were similar for goat or cow milk. However, absolute SCC numbers rose much higher in normal goat milk than expected from cow milk, which suggests that the goat udder responds to pathogens much more actively than cow udders do.
It was also concluded that if CMT scores were used for legal thresholds, at CMT-1, a misclassification of 52percent of normal goat milk would occur. A legal threshold of 1 million SCC/ml would misidentify 25percent and 35percent of bacteriologically negative, i.e. normal goat milk by the Coulter Counter and Fossomatic methods, respectively.
Not included in these studies were additional normal SCC increases due to advancing lactation, since only the first 6 months of lactation were tested. This will then be expected to further increase the absolute levels of SCC in normal goat milk above those reported in the studies so far. Finally, these tests used only fore-milking samples, while it is known that the last strippings are higher in SCC. Thus, absolute levels of SCC in bulk tank goat milk containing all milk portions, fore, middle and last, would be expected to be higher yet than in the studies, regardless of season of year or stage of lactation, influencing the setting of the legal threshold.
Valuable research information on goat milk mastitis and somatic cell counts has been published by Caruolo, Dulin, Hinckley, Lerondelle, Maisi, Nesbakken, Park, Poutrel; and Judy Kapture (Portage, WI), ADGA member on the National Conference on Interstate Milk Shipments has very actively pursued the problem of somatic cell count legal thresholds. Their conclusions are that:
Recently, the National Milk Producers Federation joined forces with the American Veterinary Medical Association to develop a "quality assurance protocol" plan and campaign, that should ensure freedom from drug residues in milk such as sulfamethazine, other sulfonamides, antibiotics gentamicin, erythromycin, oxytetracycline, other pesticides and even toxic mold residues, etc. The public does not want safe, low-level residues in milk, but demands zero-tolerance, totally residue-free milk. Thus, quality production and handling of milk is a real challenge for the goat farmer as it is for the cow farmer. It can be done and is being done more and more.
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