Bringing a Doe into Estrus
The goat is recognized as a “short-day breeder” and in the United States is usually “seasonally polyestrous.” Meaning, she shows evidence of the desire to breed when day length grows shorter; in the late summer, fall, and winter months. She thereby conceives during the time of year when the ambient temperature is most moderate. She then kids or freshens (gives birth) in the spring when nutritional conditions are optimal for neonatal growth, lactation, and browsing as the kids are weaned. The doe will then exhibit a state of anestrous until the end of summer or early fall when she will again show signs of estrus activity. This transition from estrous to anestrous, in seasonal breeders like the goat, occurs on an annual basis. Some factors affecting this transition on individual farms and in individual animals can be as elementary as the number of bucks within a doe’s view, the farm’s physical location with regard to the equator, and even weather.
The initiation of behavioral estrus in the doe is triggered by sensory stimulation, i.e., what information her brain receives with regard to her surroundings. One or more of her senses receive stimulus, the most likely being:
What she sees: A change in daylight hours (photoperiod).
What she hears: The exuberant vocal expressions of the buck.
What she smells: The buck’s odor when in rut.
Sensory stimulus traditionally aids in the kick-start of hormonal activity in the doe. Such activity eventually results in bringing her from a state of seasonal anestrous (not in heat) to estrus (in heat) on a “regular” 18-21 day cycle. This is often preceded by a silent ovulation. This silent ovulation acts to “prime” the brain through a rise in progesterone levels that increases sensitivity to estrogen in the blood stream. This can result in a strong expression of behavioral estrus.
To help determine the “regular” cycle for each AI candidate, the producer should maintain a “breeding diary” of sorts. Good records are a key element and are of primary importance in any breeding program, especially one involving assisted reproduction by artificial means. If the producer is diligent in documenting any changes in the doe’s behavior, a pattern will soon emerge. Details should be kept regarding not only the first signs of estrus, but also the last signs observed as her estrous cycle comes to an end. Over time, the producer can make a fairly accurate determination as to how long the doe can be anticipated to remain in not just a standing heat, but the entire length of her estrous cycle. The producer should be reminded that does remain in estrus for approximately 30 hours; although this can vary from breed to breed. Many producers have witnessed that some Saanen does exhibit estrus for as briefly as 18 hours, whereas it is not uncommon for the Nubian doe exhibit estrus signs for days on end. Each breed will often be different, as can each doe within the breed. For this reason, all observations made by the producer are worthy of note. The only thing that can be relied on, at least to some degree, is that whatever length of estrus is “regular” for an individual doe will likely be repeated year after year.
One should also not fall into the poor habit of making such observations only at feeding or milking time. The producer should make a point of observing the herd’s behavior twice daily for a 15-20 minute period. This practice should be done when the herd is unaware of the producer’s presence. The goal is to witness what the herd is doing when the distractions of food and equipment are not interfering with their “normal” behaviors. Is the doe to be inseminated standing at the fence, as near to the bucks as she can get? Is she flagging or hollering for no good reason? Is she mounting her pen mates or allowing them to mount her? These behaviors are strong indicators that she is in some stage of her estrous cycle and should be noted.
The time in which the doe will stand for a pen mate or buck to mount her is commonly referred to as a time of “standing heat” and is the focus of most producers’ attentions. However, for the purposes of AI, inseminating the doe based on this observation alone would be premature and unlikely to offer even average rates of conception.
Light therapy for inducing off-season estrus
Light therapy is a very cost effective, common practice that has proven useful for commercial goat dairies as a means of bringing a large number of does into estrus. This protocol is often used when the desired result is to facilitate off-season freshening for a year round milk supply. Therapy is accomplished by transitioning the doe’s photoperiod in a controlled environment. Does are housed in a building with adequate ventilation and regular cleaning to maintain good health. However, the design of the building allows no outside light to penetrate the interior. Exposure to sunlight can either be partially or totally eliminated by the herdsman. The producer may choose to release the does to enjoy outside, natural light for a controlled period of time, or he may choose to control the photo stimulus by simply turning on and off the interior lighting. The same results can be accomplished using either regime.
The theory is to mimic the decreasing daylight hours that naturally occurs during the fall and winter months. When beginning the program, does could be exposed to perhaps 20 hours of light per day. Over a succession of weeks the hours of light exposure are gradually decreased until an estrous response is induced and breeding can begin.
Therapy should begin between the months of December through February depending on the desired date of freshening. For optimum response to the therapy, an ideal completion date of extended photoperiods should be March 1. The following protocol is suitable for employing light therapy based on current research and field experience:
- Photo stimulation should be provided using incandescent light intensity equal to 12-15 foot candles at the animal’s eye level for 18-22 hours per day over a 45-60 day period. This light intensity can be achieved by using bulbs giving 400 watts of incandescent light for each 12 x 12 square foot block of the barn. This provision of light should bring about an anestrous period in the subjected herd of does.
- Following the 45-60 day period of light stimulus, the does should be exposed to decreasing length of the daily photoperiods. If done correctly, this will mimic the onset of fall and winter daylight hours. Six to eight weeks following the termination of the extended light period, the does should be exposed to bucks in rut. Once the bucks are introduced, fertile estrus can be expected 10-20 days later.
If natural service is the desired means of mating, it can be quite beneficial to subject the donor bucks to the same light therapy protocol. This will stimulate the bucks to begin their own breeding cycle, evidenced by their condition of rut.
Utilizing the buck effect for the induction of estrous
Utilizing the buck effect is a very simple and cost effective means of inducing estrous in the doe earlier than would naturally occur. It is, however, not 100% reliable in its results and is not nearly as effective as light therapy in initiating off-season estrous. This protocol is more useful when the goal is to bring one or several does out of seasonal anestrous and into estrous as many as several weeks earlier than would normally be expected. This can be accomplished with reasonable success by first removing buck(s) of any age from the doe’s line of sight and sense of smell for an extended period of time, perhaps as long as several months. Three to seven days prior to the time of desired estrus in the does, a buck(s) should be brought within immediate fence line contact. A young, virile buck, in his prime, will facilitate sensory stimulation by his odor, behavior, and vocal expressions. Within a few days behavioral estrus should begin to be seen in many, if not all, of the exposed does.
Progestagen treatment is commonly accomplished by using some type of implant designed for the controlled breeding of goats. Progesterone implants are the most commonly used device and fool the doe’s system into thinking it is pregnant, thereby preventing hormonal activity that would induce a state of estrous. Once removed, the decrease in progesterone in the doe’s system stimulates the production of a variety of hormones and behavioral estrus can be expected within 24-36 hours. Although not yet approved for use with goats in the United States, progesterone implants are commonly used in many countries and come in a variety of forms.
- Previously, many producers utilized an implant labeled for cattle, known as Syncro-Mate B™, with good success. Although at the time of this writing Syncro-Mate B™ is not currently available, its future use is still worthy of consideration in the event the implant again becomes available.
This norgestomet implant resembles a small pellet and is “injected” using an applicator made specifically for this purpose. The implant is often cut in half to provide a 3 mg dose (half the bovine dose), and is deposited just under the surface of the loose skin found at the side of the tail web of the goat. Though less recommended, it may also be implanted at the base of the ear as is done with cattle. An experienced technician should be employed for both the insertion and the removal of the cylindrical shaped implant. For easy removal it is important that the implant be deposited just under the first layers of tissue, and not deep in the fat that may be present in the tail. If not deposited properly, the implant can migrate deeper into the fatty tissues making removal difficult. Prior to the implant’s removal, a small injection of anesthetic just under the skin is necessary to deaden pain in the surrounding tissue. The implant can then be easily and painlessly removed by way of a small incision made with a scalpel at one end of the implant. Using a forcep or tweezer the implant should be extracted, and once removed, an antibiotic ointment applied to the small incision.
- A progesterone-containing vaginal sponge or pessary, such as Veramix®, inserted into the vaginal cavity is a very easy means for the goat producer to maintain progesterone levels in the doe. The vaginal sponge is a porous sponge-like material that is comfortably retained by the vagina until its time of scheduled removal. The “sponge” can be properly inserted deep into the doe’s vaginal cavity using a well lubricated, large sized speculum or oversized syringe that has been cut off and sanded to smoothness. For removal, depending on the manufacturer, a fine piece of “fish line” type material or string is attached to the sponge and protrudes from the doe’s vulva while implanted. The sponge is removed by pulling gently on the string.
One disadvantage of the vaginal sponge is the porous material of which it is constructed. Although the texture affords good comfort for the doe, it also acts as a host to bacteria and trap to other debris that may enter the vaginal cavity. Bacterial growth can occur that may cause a potential vaginal or uterine infection. In some cases, fetal abnormalities have been reported when vaginal sponges have been used.
- Controlled Intravaginal Drug Release (CIDR) devices are another progesterone delivering, intravaginal vehicle and a favorite method for most ET programs. Unlike the porous material of the sponge, the CIDR is made of an inert silicone elastomer that is non-porous and does not readily absorb bodily fluids. The producer is cautioned to only use CIDR’s designed and sized for use in goats, not bovines. Depending on the manufacturer, the CIDR made for use in goats delivers 0.3 g of progesterone; a CIDR for use in bovines delivers a substantially greater level and is physically much too large for the goat’s small vaginal cavity. Once inserted, a cattle size CIDR will readily and almost immediately be expunged by the doe. Nor can such bovine devices be carved or cut down to accommodate the smaller size of the doe’s vagina. First, because there is no absolute means to determine the amount of progesterone being delivered by the remaining “piece” of the device, and second, because the resulting rough edges would grossly irritate the interior of the vagina and lay potential for open sores in the vaginal walls.
A CIDR designed for goat use, when used with full-sized goats and according to manufacturer’s instruction, can be used both safely and effectively with no vaginal trauma or other negative results. The CIDR has been found to be the most cost effective device providing ease of use for the producer. Like the sponge, it can be inserted using a cut off and sanded syringe with lubricant, a large sized speculum or, although slightly more costly, an applicator designed specifically for this use can be purchased. Specialized caprine reproduction services can assist you in locating such an applicator. Once properly inserted deep into the doe’s vagina, the CIDR unfolds into a “T” like formation that aids in retention. Be aware that it is not uncommon for pen mates to grasp the clear plastic line that protrudes from the doe’s vulva and remove the device. Some producer’s have found that cutting off the bulbous tip at the end of the line, helps to avoid pen mates taking notice of the device’s existence in the doe. Daily monitoring of the device is advisable to confirm that it has not been inadvertently removed. Some producers running large herds choose to color the clear plastic line with a brightly colored paint or enamel. Although this may cause more notice by pen mates, it enables easy monitoring of the device during routine feeding and as a daily management protocol.
CIDR and applicator
Loaded CIDR applicator
Whatever form of implant selected by the producer, it is best to follow the manufacturer’s labeled instruction on its proper use and application. No device of any kind should be considered for re-use. All implants are designed by their manufacturer and labeled for single use. Some manufacturer’s recommend leaving the device inserted for as long as 18-21 days. However, producers have found in goats 9-14 days are sufficient to induce the desired result. Once the implant is removed, a majority of does will be in estrus within 24-48 hours. However, insemination should not occur until proper timing is achieved for the technique the producer wishes to use. It should also be noted that intravaginal progesterone delivering devices could lend some additional “color” to vaginal mucus. This can be deceiving to an inexperienced technician unfamiliar with working with such a device and who is using mucus color and consistency to gauge a doe’s stage of estrus.
For AI with frozen semen, some manufacturers recommend a 200-400 iu dose of PMSG be given up to 48 hours prior to the device’s removal. Some manufacturers further recommend that insemination using a laparoscope or cervical technique be performed within 48 hours of the device’s removal.
In field trials, producers have gained the highest rate of success when practicing the following protocol involving a progesterone device that delivers 0.3 g of Progesterone.
- Day one; insert progesterone implant.
- Day thirteen; 2 cc of prostaglandin administered intramuscular (IM) with dosage dependent on product label and doe body weight.
- Day fourteen; 1.5 cc dose of PG600 administered IM and device removed.
- Day fifteen; doe shows sign of estrus.
- Day sixteen; doe is carefully monitored and inseminated.
Protocols for the same implants may differ when intended for use in an ET program rather than simple insemination methods. Some commercial ET services offer a regiment which involves the repeated daily use of FSH for a period of four days, accompanied by a single dose of prostaglandin for the donor doe, and a single dose of PMSG for the recipient does. Some ET technicians report that superior results are obtained if the implants are removed from the recipients 12 hours before they are removed from the donor does. The producer is advised to consult with the intended ET service provider for their preferred methods of preparation of any animal intended for use in an ET program. Each ET technician’s own techniques and schedules, often based on personal experience, may affect their individual requirements.
MGA feed supplement
Sheep producers and researchers are currently involved in field trials and controlled studies that have returned favorable preliminary results using a progesterone feed supplement, melengestrol acetate (MGA). This supplement is currently used with reported success in cattle and horses. However, at the time of this writing, adequate data to suggest a reliable protocol for goats has not yet been established. Such a protocol is on the horizon and MGA feed supplementation, as a means for herd estrous synchronization, could be of value to the producer in the near future.
As with any feed supplement, constant monitoring of each animal’s intake is necessary and can prove labor intensive for the large producer. Certainly electronic and mechanized apparatuses can assist in feeding and intake regulation and are being used by some large producers. In group-fed animals given unrestricted feed access, dominant animals will invariably disrupt each animal from ingesting a proper dose. Individual feeding or other methods of solving this problem may prove impractical for the average producer. However, with proper management and equipment design, a feeding program utilizing a progesterone feed supplement is worthy of consideration.
Although not affording the same reliability and consistency of results as progestagen therapies, prostaglandin injections have also proven a cost effective means of producing a synchronized heat for the producer. It is good to note that protocols as labeled and described for cattle use have proven unreliable for goats when using some forms of this product. There are a large variety of opinions for off-label use of this veterinarian prescribed, controlled product in goats. The dosage prescribed seems to range from 0.5 cc to 3 cc IM, depending upon purpose of use, product label, and intended technique and protocol. The length of time in which the producer can expect an apparent estrus response, if indeed one is even achieved, also varies considerably according to dosage administered, breed of goat, geographic location of the animal, and time of year. Time of year is important to the producer because prostaglandin is only effective if a corpus luteum is present on the doe’s ovary. If no corpus luteum exists, the prostaglandin injection is useless in stimulating estrus. Another discouraging result of prostaglandin use can be a showing of behavioral estrous, but no ultimate ovulation. This may be due to a variety of reasons including the lack of sufficient LH in the doe’s system to elicit such a response.
In field trials by producers across the United States the most favorable results have occurred with the following protocol:
- Day one; 2-3 cc of prostaglandin administered IM according to the product label and doe’s body weight (2 cc for does under 100 lbs and 3 cc for does over 100 lbs).
- Day eleven, hour one; 2-3 cc of prostaglandin administered IM according to the product label and doe’s body weight (2 cc for does under 100 lbs and 3 cc for does over 100 lbs).
- Hour 48-52; doe shows signs of estrus.
- Hour 48-72; doe is carefully monitored for stage of estrus.
- When evidence that proper stage of estrus is observed, doe is inseminated.
It is good for the producer to recognize that prostaglandin in any dosage could initiate a fetal abortion in a pregnant animal. Great care and caution should be taken in the exposure of such a product to animals at any stage of gestation if a termination of pregnancy is not the desired result.