|Articles||"Goat Milk Versus Cow Milk"||Article Index|
GOAT MILK VERSUS COW MILK
By: "Goat Handbook, United States, 1992"
The major breeds of US goats are:
b.. Toggenburg, brown with white facial, ear and leg stripes, another straight nosed, horned or hornless, mostly shorthaired, erect eared goat, as all Swiss are, has been very popular in the USA, comes from N.E. Switzerland, but is 4 inches shorter in height and 18 lb lighter in average than the Saanen. They have been bred pure for over 300 years, longer than many of our other domestic breeds of livestock. They are reliable milk producers summer and winter, in temperate and tropical zones. Mrs. Carl Sandburg, wife of the famous US poet had several world record Toggenburg does on official USDA tests.
c.. Alpine (including French, Rock and British), another Swiss breed (French Switzerland), horned or hornless, shorthaired, as tall and strong as the Saanen, with usually faded shades of white into black, with white facial stripes on black. They are second in milk production to Saanen and Toggenburg.
d.. LaMancha is a new, young breed developed in California from Spanish Murciana origin and Swiss and Nubian crossings. They are known for excellent adaptability and good winter production. They are also producing fleshier kids than the Swiss, but are not milking as much. They have straight noses, short hair, hornless or horns, and no external ear due to a dominant gene. They are more the size of Toggenburg. Their milk fat content is higher than that of the Swiss breeds.
e.. (Anglo)-Nubian is a breed developed in England from native goats and crossed with Indian and Nubian which have heavy arched ''Roman'' noses and long, drooping, pendulous ears, spiral horns and are shorthaired. They are leggy and as tall as Saanen, but produce less milk, though higher milk fat levels and are more fleshy. They are less tolerant of cold but do well in hot climates. They ''talk'' a lot, and are in numbers the most popular breed in USA and Canada. They have a tendency for triplets and quadruplets. They are horned or hornless and have many colors that may be ''Appaloosa''-like spotted.
f.. Oberhasli, a western Swiss breed, usually solid red or black, horned or hornless, erect ears, not as tall as Saanen, very well adapted for high altitude mountain grazing and long hours of marching; popular in Switzerland, but milk production is variable. They are also called Swiss Alpine, Chamoisie or Brienz.
g.. Angora originated in the Near East. The long upper coat (mohair) is the valuable product in the Angora in contrast to the Cashmere, where the fine underwool is the valuable product. Head has a straight or concave nose, thin, not very long; pendulous ears and twisted horns, in both sexes. It is a small breed, usually white. The haircoat is long with undulating locks and ringlets of fine, silky hair. The top quality fleece of purebreds may be 1-2 lbs, but slightly more in males and wethers. They are bearded. Spring moult is natural and shearing occurs just before. They are not very prolific and twinning is less frequent than in other breeds.
h.. Pygmy are dwarf, short legged goats from West and Central Africa and the Caribbean. Their growth rates and milk production are relatively respectable, although low, twinning is frequent and they are breeding all year usually. They are adaptable to humid tropics and resistant to trypanosoma.
i.. Others. There is little known about the so-called Spanish or bush goats that are kept on the open range in the Southwest mostly. Also, a few minor breeds exist in this country, e.g. the Sables, which are a colored variety of the Saanen. It would be profitable to know more about the other at least 60 goat breeds in the world and their comparative values under US conditions.
Adjustment Factors for Milk Records
A lactation length of 305 days has been defined as the standard for dairy cattle and also is used for goats. This standard assumes a 365-day interval between parturitions, which includes a 60-day dry period. However, many goats do not milk 305 days. A recent study shows that only one-third of all does with official records ending with a dry date milked 305 days. One reason for shorter records is that production of many does declines sharply with the onset of seasonal estrus and the does then are dried off. A standard lactation length of less than 305 days might be more useful for comparisons among does; however, the 305-day standard allows for reduced computing costs because doe and cow records can be computed the same way.
If a doe's lactation ends on or before 305 days because her production declined to the point at which continued milking was not worthwhile, then her record is considered complete. Such records are not projected to 305 days but are treated as complete 305-day records. If a lactation ends before 305 days for any reason other than going dry, such as the doe's being sold or the herd's discontinuing testing, the record is considered incomplete and is adjusted. If a doe is still milking and has fewer than 305 days in milk, the record is considered incomplete, adjusted, and referred to as a record in progress. If a doe milks for more than 305 days, the production for only the first 305 days is included in the 305-day record.
A method to adjust incomplete records and records in progress uses the USDA projection factors in Table 1. Different categories of factors are required to adjust records because of variations in the lactation curve, particularly in the rate of decline of production after the peak and the number of days milked. To select the appropriate factor, the following information is necessary: breed, herd average production, month of kidding, days in milk, and age of doe at kidding. An adjusted or projected record is the incomplete record plus an estimate of production for the rest of the lactation. That estimate is the projection factor times the last sample-day production times the number of days from the end of the incomplete record through 305 days.
Suppose a Nubian doe freshens in March at 25 months of age. She has an incomplete record at 130 days of 800 lb milk and 27 lb fat. Her last sampleday production is 5 lb milk with 3.4 The herd average is 1,725 lb. Then, her projected record would be 800+0.69(5) (305-130) =1,404 lb milk and 27+0.76(5) (0.034) (305-130) =50 lb fat.
Age-Season Lactation production increases with age until maturity and then declines. Month or season of kidding also influences lactation production. For example, does kidding in the early spring produce more milk than those kidding later in the year. Lactation records can be adjusted to a common age and season of kidding to standardize the effects of age and season. The factors in Table 2 standardize production to that expected from a doe kidding from January through March at 36 months of age.
The adjustment factors vary by breed, age, and season of kidding. Records are adjusted for age and season by multiplying production by the appropriate factor from Table 2. To illustrate, consider the Nubian doe from the previous example: Adjusted milk=1.07(1,404)=1,502 lb Adjusted fat=1.08(50)=54 lb.
The factors in Table 2 were computed by assuming a smooth change by age and by ignoring lactation number. Recent results, however, suggest that lactation number should be considered, particularly for does kidding about 24 months of age. Equations recently developed at the University of California in Davis provide factors that vary by parity. These factors may be more accurate; however, the factors reported here should contribute to improved comparisons among does.
AI has some key advantages over natural breeding.
b.. AI can increase the rate of genetic improvement in an herd, as long as superior bucks are consistently selected. In natural service, the prospective breeder has only the buck's pedigree to rely on, whereas AI bucks should be progeny tested for their transmitting ability of milk and fat percentage, weight gain, type conformation, etc.
c.. AI allows breeding of different portions of the herd to different bucks. Young does may be bred to not yet proven but high potential bucks, while the majority of the herd can be bred to proven high quality bucks.
d.. AI permits breeding of many does on one day when synchronization is practiced. No long drives to top bucks are involved.
e.. The danger of transmission of diseases or parasites is greatly reduced. (The transmission of diseases through frozen semen needs further study.)
f.. The time of breeding can be more carefully regulated, and the owner knows exactly when the doe was bred, as opposed to pasture servicing by a buck that is allowed to run with the herd.
g.. AI induces good recordkeeping of dates of heat, breeding, pedigrees, etc. This will aid in herd improvements and enable the owner to make better culling decisions.
AI technicians of the cattle industry may not necessarily be of much help when it comes to inseminating goats, for the modern method of inseminating cattle (rectal palpation) differs from that of breeding goats (speculum method) considerably. The speculum was used on cattle early in AI history, and some cattle inseminators may be capable of teaching goat insemination.
The cost of getting started in AI, not including semen purchases, will generally run around $500, of which $400 to $450 is tied up in the liquid nitrogen tank, which is necessary for storing semen any length of time. Temperatures must be kept at -320F (-196C) for sperm survival to be maximized at breeding time. It may be possible to share the cost of the tank with neighboring goat owners or dairy farmers, thus alleviating some initial costs of an AI program.
If AI is to be used with any hope of achieving a good level of success, much must be known and well understood by the prospective inseminator.
b.. understanding of storage and handling of semen
c.. ability to use, in a proper and sanitary manner, the equipment required for inseminating goats
d.. ability to accurately detect heat at an early stage
e.. necessity of keeping accurate, up to date records of heat cycles, breeding, kidding, reproductive problems, treatments, and any other pertinent information that may reflect on the goat's reproductive patterns.
Reproductive Organs and Functions
b.. Estrus - As estrogen levels peak, the doe will come into heat. This can be observed by changes in behavior (increased bleating and restlessness), willingness to be bred, and the swelling of the external genital area. The period of ''standing heat'' (acceptance of the buck) will generally last for 24 to 36 hours.
c.. Ovulation, or the release of the egg, is accomplished by the rupturing of the follicle, expelling the egg from the ovary, and receiving it into the oviduct via the fimbria funnel. This occurs very near, or soon after, the end of standing heat (6 hours before to 12 hours after). Egg life is 12 to 24 hours, while the sperm lasts 24 to 48 hours.
d.. Metaestrus - in this stage, the ruptured follicle is undergoing cellular differentation to form a functionally important tissue mass, the corpus luteum (yellow body). This structure is responsible for the secretion of progesterone, a hormone which prevents the development of another follicle and prepares the uterus to receive a fertilized egg.
e.. Diestrus - is the longest period of the estrous cycle in does. During this period of corpus luteum influence, two events may happen. If fertilization of the egg occurred, the corpus luteum will persist for the entire gestation period, preventing follicular development and keeping estrogen levels low. If no fertilization took place, the progesterone secretions of the corpus luteum gradually lessen, allowing a new cycle of follicular development to begin, with a corresponding increase in estrogen levels. The length of time required for one estrous cycle without fertilization, ranges from 17 to 24 days in goats, with the majority taking 21 days. Shorter cycles are not uncommon (5-10 days).
f.. The egg, after being expelled from the ovary, passes into the oviduct via the infundibulum, and toward the cornua (horns) of the uterus. This movement is produced by wave-like motions of the ciliated (hair-like projections) cells of the oviduct. Sperm and eggs meet in the oviduct and fertilization occurs in the middle to upper one third of the duct.
g.. The egg continues into the horn of the uterus, where, if it has been fertilized and undergone several cellular divisions, it will become attached to the uterine wall. If no fertilization has occurred, the egg will degenerate and the cycle goes on.
h.. The cervix of the uterus plays a key role in artificial insemination, as it is the external entrance to the uterus which must be located and penetrated with the inseminating instrument. The cervix is normally tightly closed, except during periods of heat or kidding. Semen is deposited on the vaginal side of the cervix in natural services, but AI requires the deposition of semen in the uterine side of the cervix. This is because of the greatly reduced volume of semen that is used in AI. If the 0.5 to 1 cc of semen in AI were deposited on the vaginal side of the cervix, there is a good chance that none of the sperm would reach the egg.
i.. The vagina serves as the connecting tube between the uterus and the outside opening, the vulva. It is part of the birth canal, and also contains the urethral opening, from which urine will pass during emptying of the bladder.
In most cases, the inseminator will acquire the semen needed by direct purchase from a commercial operation, in which case it will be shipped to the inseminator. It is of the greatest importance that the semen be transferred to permanent storage (the liquid nitrogen tank) without exposing it to anything approaching air temperature. Generally, this means transferring the container element which houses the semen directly to the liquid nitrogen tank. Here it can be safely stored for long periods of time, since biological activity practically stops at liquid nitrogen temperatures (-320F). Semen is generally to be used within 6 months, but conceptions have resulted from semen stored for several years, although sperm survival is decreased, resulting in lower conception rates.
Semen Collection Bucks are handled basically the same way as bulls for semen collection. Three basic methods may be employed, but all three require an artificial vagina, a double walled device with an opening at one end and collection tube at the other. The inner lining holding warm water should be coated with a light application of water soluble lubricating jelly.
The three methods of semen collection are:
b.. A buck is trained to mount a dummy instead of a live doe. The same procedures are followed for sample collection. Mounting may be facilitated by applying vaginal mucus scrapings of a doe that is in heat to the dummy, at least during the training process.
c.. Use of electro-ejaculation. The buck is not required to mount an object, although an artificial vagina should still be used for semen collection. An electrode unit, which has a number of contact rings, is inserted into the buck's rectum. Slight electric stimulation brings on ejaculation. This technique generally results in good samples in quantity and quality. However, the sperm concentration of the sample will be lower. This method does not require extensive training, and will allow collections from bucks that may refuse or are unable to mount and serve an artificial vagina.
b.. Semen may be stored 24 to 48 hours by placing the collection tube in a container of water and putting this unit in a refrigerator. No diluter is needed, although plain egg yolk can serve as simple extender to double the number of does that can be served.
c.. Semen that is to be stored for longer periods of time must be mixed with a diluter and very carefully frozen. A commercially prepared diluter extender, such as Ortho Semen Diluter is desirable, although plain milk can be used successfully also.
2.. For a homemade milk diluter, it is best to use fresh 3.5 pasteurized, homogenized whole milk. It must be heated and held at 210F for 10 minutes in a glass boiler, keep the lid in place so that no moisture is lost. Next, the milk is cooled in a water bath with the lid on. When the milk is in equilibrium temperature with the water bath, the water condensation on the inside of the lid is shaken back into the milk. To every 400 cc of milk, add 100,000 units of potassium G crystalline penicillin and 500 mg crystallin di-hydrostreptomycin sulfate, mixing well. Warm this diluter to about body temperature before adding the fresh semen at 19:1 ratio. Place the diluted semen in a water bath at body temperature of 101F and allow to cool slowly. Semen may be frozen, if the extender contains an antifreeze compound, slowly, stepwise for storage on dry ice or in liquid nitrogen.
3.. A microscope, capable of 900x magnification is an essential tool when doing your own semen collection in order to determine semen quantity and quality. First, place a semen sample on a clean slide and cover with a coverslip or another slide. Set the magnification to 400x and observe the appearance of dark patches or spots thru the scope; four dark areas or more per microscope field represent high concentrations of sperm, a really good sample. Three dark areas is somewhat chancy for use at a diluted service, but is good enough for natural service. Two dark areas should be used only for natural services and one dark area means that the concentration of sperm is too low for even natural service. Switching to 900x, the sperm cells can be individually observed for normal structures. Diluting in warm saline is helpful. Coiled tails, broken tails, absence of tails and abnormal shapes all constitute deficient sperm cells. Sixty to 70% good motility before freezing should be observed in a good sample, with a minimum of 30% motility after freezing and thawing.
The concentration of a buck semen ejaculate can be determined accurately by using a red blood cell diluting pipette and standard hemocytometer techniques. Typical results during the breeding season are 3 to 5 billion sperm per cc. Optical density can also be used to estimate sperm concentration if the photometer has been calibrated for buck semen. A simpler technique involves the determination of a spermatocrit using microhematocrit pipettes. The aliquot of semen is centrifuged for 10 minutes; for each percentage point of packed sperm, approximately 200 million sperm cells per cc are present. Correction is made for the percent motile sperm, after which the ejaculate can be diluted appropriately to supply a minimum of 125 million motile sperm in each breeding dose. It is often difficult to introduce more than 0.2 ml of semen into the cervix, so dilution to a final concentration of 600 million to 1.2 billion live sperm per cc has been recommended. When no laboratory support is available, fresh semen for immediate use may be diluted up to 5 times in extender if it is yellowish and 10 times if the ejaculate is white. A straw holding 0.5 cc of this diluted semen will provide adequate sperm if excessive reflux does not occur.
Storage and Removal of Semen from the Liquid Nitrogen Tank
When working with semen in the liquid nitrogen tank, it is important to keep the racks below the frost line in the neck of the tank. Removal of semen from the tank for periods as brief as 10 seconds, such as for identification, before replacing it to the tank will often result in lowered fertility levels. If the right rack can't be located in 5 seconds, lower the canister back to the bottom of the tank for at least 30 seconds before trying again. Also, when handling semen, try to stay out of any direct sunlight, as ultraviolet light has a spermicidial effect.
The semen comes in two basic types of packaging: ampules (1 ml) and straws (0.5 or 0.25 ml). The ampule is the most common type of packaging for buck sperm. Both ampules and straws are stored in racks (canes), which are aluminum pieces that hold a vertical row of ampules, usually six.
A few key reminders concerning semen storage:
b.. Never lift a canister above the frost line of the tank.
c.. When the semen is removed with a forceps from the tank it should be placed immediately in the thaw box.
d.. Never expose semen to direct ultraviolet light.
e.. Never refreeze semen that has been thawed as it will be destroyed.
f.. Check for proper identification on ampule or straw.
g.. A defective ampule may blow up after it is removed from the tank. This is due to a small leak that allows nitrogen to enter the ampule. When removed from the tank, the gas expands too rapidly to vent back out the hole and it explodes the glass. A hissing sound is usually audible when it is removed. Keep your hand between the ampule and your face when putting it into thaw box.
h.. Always wear gloves and goggles for your own protection when working inside a liquid nitrogen tank.
Methods for semen thawing vary among manufacturers, and it is best to follow their recommendation. The thawing procedure for 1cc ampules, the most common for goat semen, is generally the ice water bath.
Ice water (38-42F) is placed in a styrofoam box long enough before-hand to allow temperature to equilibrate. Remove the ampule from tank and place immediately into thaw box. Ampule may be placed in a small plastic cup with holes in the bottom. This prevents ice from coming into direct contact with ampule. Ampule should thaw in 3 to 5 minutes. Check for slushiness and allow more time if needed. Ampule may sit in ice water for as long as 30 minutes with no damage. Once removed, the semen must be used right away. The layer of ice on the ampule must be peeled off before opening to avoid possible contamination. The ice water thaw method is especially good during winter breeding of does because of low risk of cold shock to thawed and exposed semen. Thawing of semen can be done from -320F rapidly, but any subsequent exposure to lower temperatures after thawing will kill many or all of the sperm.
The warm water method of thawing is more exact than the ice water method, but probably will not work in cold weather, although it may give somewhat better results the rest of the year. The procedure is basically the same as for the ice water thaw except that the water must be maintained at 92 to 98F. This requires a source of warm water and an accurate thermometer. Thawing will be complete in about 1 minute with no ice layer formation of the ampule. Ampules thawed with the warm water method should be used within 5 minutes. Straws (0.5 or 0.25 m
l) can be thawed by either of the previous two methods. A given amount of semen in a straw will take about one half as long to thaw as an equal amount in an ampule. Many inseminators simply thaw straws by placing them into their shirt or pants pocket.
Materials needed for artificial insemination:
b.. Sterile lubricating jelly (K-Y)
c.. Thaw box
d.. Inseminating pipette with bulb or syringe (ampules only) or Inseminating gun (straws only)
e.. Paper towels
f.. Facility for securing doe (stanchion, fence, rope hoist)
g.. Recording journal for breeding dates, buck's name, etc.
2.. Place bulb or syringe on exposed end.
3.. Thaw ampule according to the described methods.
4.. Dry ampule after thawing, hold in paper towel and scribe (with proper tool) one side of ampule collar. Some ampule types do not need to be scribed, but can be snapped open.
5.. Pull syringe back 1/2 cc on plunger or squeeze bulb closed before placing pipette into ampule. Tip ampule to slight angle and maintain constant suction on pipette while it is slowly inserted into the ampule. Try to get all the semen into the pipette, keeping the semen column down near the end of the pipette.
6.. When filled, the pipette should have a semen column with no air spaces, with the bottom of the column being 1 to 2'' from the pipette tip. Do not draw semen into the syringe or bulb.
7.. Keep the ampule for information to complete breeding records.
8.. Keep the pipette away from sunlight or cover with paper towels.
9.. The semen is now ready to be placed into the doe in estrus.
2.. Place straw in thaw box.
3.. Remove when thawed, wipe dry. Check buck information.
4.. Pull plunger on gun back 4 to 6'' and insert straw into gun, cotton plug end first (towards plunger).
5.. Hold gun in upright position, allowing air bubble to rise to the sealed end.
6.. Cut sealed end of straw with scissors. Take care to cut straw squarely for proper seating.
7.. Install the sheath over the gun, fastening it down with the provided O-ring. Install it so that the wider side of the ring faces the straw, with the narrower side facing the syringe end.
Assuming that the doe has been observed in heat, has been suitably restrained (i.e. in stanchion) and the steps for preparing the ampule or straw have been followed. The next steps are:
b.. Hold pipette or inseminating gun, wrapped in a paper towel, in your mouth; or let someone else hold it if extra hands are available.
c.. Turn head light on and insert lubricated speculum in a slow and gentle manner. Begin entrance at a somewhat upward angle for the first several inches. This is to prevent the speculum from scraping across the vaginal floor, possibly doing damage to the urethral opening.
d.. Complete insertion of speculum and locate cervix. Center the end of the speculum over the os uteri (entrance to cervical canal).
e.. Cervix should be of a red-purple coloration with a viscous whitish mucus present if doe is truly in heat.
f.. Insert pipette or inseminating gun into speculum to the cervix. Gently manipulate the instrument through the cervical canal (cervix is 1 to 2'' long) to the 4th or 5th annular ring.
g.. Deposit semen near the uterine end of the cervix or just inside the uterus. Do not enter too far into the uterus as the semen will then tend to be dumped into one horn or the other. If the semen is pushed into the wrong horn (i.e. egg produced in left ovary, semen dumped into right horn) then fertilization may not occur.
h.. Deposit semen slowly, taking at least five seconds.
i.. Slowly withdraw instrument without release of syringe or depressed bulb, then carefully remove the speculum.
j.. Record all pertinent breeding information.
k.. Carefully discard all disposable materials. Arrange to sanitize reuseable items and sterilize the speculum (if it is a non-disposable type).
In France, a doe is usually restrained by a second person who straddles the doe's neck and elevates the hindquarters to a vertical position while holding the hind limbs tightly flexed. The inseminator is free to stand in a comfortable position. He holds the speculum and the goat's tail in one hand and the pipette or straw gun in the other hand. If excess mucus is a problem, the assistant lowers the goat's hindquarters almost to the ground; if the mucus does not run out of the speculum, the latter is removed and shaken to clear it. The goat is then lifted to its former position. If many goats are to be bred, the assistant may tire using this technique. If the doe is not held in a vertical position, it is often impossible to adequately visualize and penetrate the cervix. Various slings have been devised to suspend the goat in the appropriate position.
About the author: Extension Goat Handbook - This material was contributed from collections at the National Agricultural
Library. However, users should direct all inquires about the contents to
authors or originating agencies.|
G. F. W. Haenlein; R. Caccese; U. Delaware, Newark
D. L. Ace; Pennsylvania State U., University Park
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