Hormonal Causes of Infertility in the Doe

Carol Raczykowski
Reviewed by Dr. William Holleman

(Reprinted from Pygmy Goat WORLD magazine with permission)

Infertility in does falls into many categories: hormonal, infectious, post parturition, chronic illness, malnutrition, old age and congenital problems.

With all the possible reasons why a doe may not conceive, it seems a miracle that any do. Fortunately, infertility problems tend to be exceptions rather than the norm. Healthy, sound does conceive easily and give birth to a high percentage of twins, triplets and sometimes quads. The number of kids is dependent on many factors, including genetic makeup, uterine overcrowding, mother's age, time of year the doe is bred, and so on.

Before we talk about infertility, we must learn something about the reproductive cycle. In most mammals, sexual receptivity is restricted to recurring periods called estrus. Does comes into heat, or estrus, every 18-24 days, often year round, depending on factors such as weather, nutrition and daylight hours. Pygmy does are precocious animals and can have their first estrus as early as six weeks old. Estrus typically lasts from 24-48 hours. Before and during estrus, hormones regulate changes in the does sex organs and make her receptive to a buck both physiologically and psychologically.

Signs of estrus are numerous, some obvious, some more discreet. The doe usually flags her tail side-to-side when around a buck, presumably to send attractive pheromones from the her reproductive tract into the environment that a buck finds attractive. Her vulva may be more pink than normal, appear swollen, and have some clear or white-colored discharge with the consistency of egg white. This discharge usually starts clear and becomes more white as the heat progresses. Others signs include more frequent urination and restless behavior. She may also talk more than usual, sometimes bleating very loudly at the edge of the fenceline nearest the buck. Decreased appetite and milk production are also reported. The doe is in a standing heat when she stands willingly and lets a buck mount. Standing heat usually lasts from 1-24 hours. If a buck is not present, does often mount their herdmates or stand for other does to mount them.

Ovulation is the most important event that takes place during estrus. This is a series of events, each triggering the next. A follicle on the ovary starts developing and producing estrogen. Increased estrogen triggers the release of  follicle-stimulating hormone (FSH) and luteinizing hormone (LH) which matures the follicle. The number of follicles which develop during each estrus cycle depends on hereditary and environmental factors. The follicle, similar in appearance to a water blister, grows until it finally ruptures, releasing the egg. The egg, with its genetic contribution from the mother, is released from the ovary when the follicle bursts. The egg then floats down toward the oviduct. After ovulation, the collapsed follicle transforms into a new endocrine structure called the corpus luteum (CL) which produces progesterone to prepare the uterus for pregancy and to maintain the pregancy. If the egg meets healthy sperm in the oviduct/fallopian tube and fertilization takes place, the fertilized egg travels down the fallopian tube to the uterus where it implants itself.

When the doe conceives, the corpus luteum will remain throughout the pregnancy, secreting both estrogenic and progestational steroids. If the doe does not conceive, the uterus produces prostaglandin that dissolves the CL)  leaving a small scar where the follicle was, and a new cycle begins.

The new cycle begins with a new follicle. Each doe is born with a certain number of follicles and when those follicles are used up, so is the possibility of pregnancy. This is called menopause in women.

To recap, a number of hormonal changes must take place for a doe to become pregnant. First, she must produce enough hormones to produce a follicle. The follicle must produce enough estrogen to trigger the release of LH and FSH, maturing the follicle and causing it to rupture. A corpus luteum must develop to prepare the uterus and maintain the pregnancy. Variance in any one of these areas can create problems.

Before you decide your doe has a conception problem, be sure she is not already pregnant. The most common cause of failure to cycle is pregnancy. Did a buck recently perform a great escape? Did a young buck stay with the herd too long? Did you record the breeding date(s) on a calendar? These questions need to be asked before giving any fertility treatments. Further, many times just exposing a doe to a buck (his odor) will bring her into heat. It is also possible for a bred doe to show signs of estrus, although her signs will not be as strong. This is where patience come in handy and maybe  the key to treatment. But, if you have determined that your doe is definitely not pregnant, she was seen to be serviced and has still not settled, theres a list of hormone balance problems to consider.

Cystic ovaries occur when the follicles do not rupture and continue to produce estrogen. Heat cycles become become frequent (6-14 days) or nonexistent. Does may exhibit bucky behaviorby riding other does or being overly aggressive. If a doe with cystic ovaries is undiagnosed and untreated, she can become permanently sterile. These does eventually begin to look 'bucky.' If the condition is caught early, a shot of chorionic gonadotrophin may restore reproductive function.

If you suspect more than one doe of having cystic ovaries, your feeding program may be at fault. High estrogen levels in sweet clover and some alfalfa, or diets high in calcium and low in phosphorus may cause temporary problems.

There is evidence to support a hereditary predisposition to cystic ovaries from both the dam's side and the sire's side.

Another common theme is a 5-day cycle , a different condition than cystic ovaries. When this happens, the doe has a normal heat and the follicle matures but does not release the egg. The doe has another normal heat 5 to 7  days later, at which time the egg is released. There is diversity of opionion among experienced breeders about eggs not being released on the first of the 5-day cycles - some say that eggs can be released on both cycles and breed on both cycles to maximize the number of conceptuses. This condition may be related to the presence of multiple follicles - some rupture and some don't until the second heat.

If a doe has a hormone imbalance, she may exhibit no signs of heat at all, and the term for this is anestrus. The doe's ovaries are simply not producing follicles. A shot of prostaglandin may start her cycling. Anestrus may also be related to cystic ovaries. Silent heats between regular estrus cycles is not uncommon. This is where all the necessary physiologic and histologic events take place but the doe shows no outward signs of estrus. Fortunately, the buck always knows and a successful breeding may be accomplished if they are together. If the time between estrus periods is unusually long, silent heats may be the cause. [Ed. note: Anestrus for several-month periods may signal embryonic mortality if the doe had been bred.] The most probable cause is a lack of proper balance of hormones affecting the onset of estrus.

False pregnancy is another hormonal problem that can occur in pygmy goats. Pseudopregnancy is like normal pregnancy in every way. There are two ways to differentiate a normal pregnancy from a false one: (1) ultrasound or X-ray at around 60-90 days, or (2) wait until the end of pregnancy and see what is delivered. There is no known reason for pseudopregnancy but it may be a hormonal imbalance or early embryonic death with resorption of the fetus and membranes. If a false pregnancy is detected, a shot of prostaglandin will end it. Most does will not repeat this process and can be bred successfully on the next cycle.

Implantation failure in the uterus can create another infertile situation. If a fertilized egg fails to implant in the uterus, it simply deteriorates and a new cycle begins. Progesterone may play a big role in the preimplantation uterine changes. If progesterone is not released to prepare the uterus for pregnancy, the fertilized egg will simply be sloughed off. The uterine lining must be equipped for the egg to implant, like a lush shag carpet. The uterine lining of a doe that doesn't produce enough progesterone looks similar to an indoor-outdoor carpet. This type of uterine problem may be due to a uterine infection after the last delivery or an ageing uterus that finally fails. The prognosis is usually very guarded to negative for either of these conditions.

The occasional doe may have a retained corpus luteum that tells the doe she is still pregnant. This typically transpires after kidding and can be easily corrected with one or two injections of prostaglandin to restart normal cycles.

Detection of hormone problems is more difficult in Pygmy goats because of their small stature. With a cow or mare, a veterinarian can periodically feel the reproductive tract and follow its cycle. This is not possible with Pygmy goats. Many times trial and error is the best method. Your decision to pursue differing treatments should be based in part on the value of the animal. Is she worth the cost? Hundreds of dollars can be spent trying to identify the cause of an infertility problem. A series of hormonal screens can be done to either eliminate or identify potential problems, a laparoscopy can be done to explore the reproductive tract, or hormonal treatments can be given.

 

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