Reproductive Physiology

Females

Relative to body size, the nonpregnant reproductive tract of SAC is relatively small. The uterine morphology is similar to that of a mare with relatively short horns and uterine body. The cervix can be felt on rectal palpation and has 2 or 3 rings. The urethra opens into the floor of the vagina. A suburethral diverticulum is present.

Ovarian activity typically begins at ~10–12 mo of age. Camelids are induced ovulators. At the onset of puberty, follicular waves occur with a dominant follicle developing every 12–14 days. Due to the small size of females and the potential for dystocia associated with early breeding, females are usually not bred until they are >18 mo old and weigh 40 kg (alpaca) or 90 kg (llama). If a female is truly receptive, she will usually assume a position of sternal recumbency (cushing) within seconds to a few minutes after introduction of a male and allow the male to breed. While mounting, the male will typically begin a vocalization described as “orgling.” The volume of the ejaculate is relatively small (2–5 mL) and is mostly deposited directly into the body of the uterus. Ejaculation occurs over an extended period of time. An ovulation induction factor in the semen stimulates reflex ovulation ~24 hr after mating. The fertilized oocyte is usually found in the uterus by day 7 after mating, with implantation occurring by ~30 days of gestation. The type of placentation is diffuse epitheliochorial, developing in both horns. While ovulation occurs bilaterally, ~95% or more of the pregnancies are carried in the left horn. Live births of twins are extremely uncommon; most twins are resorbed or aborted early in gestation.

A female with a functional corpus luteum (CL), will aggressively refuse the male's efforts to mount. An indication of pregnancy is the female's rejection of the male if he is reintroduced >15 days after the initial breeding. Progesterone concentrations of >1.0 ng/mL are typical in females with a functional CL and can be used for confirmation of both ovulation at 6–9 days after mating and pregnancy at >21 days after mating. Persistent CL are periodically seen and account for most false-positive results when using serum progesterone for pregnancy confirmation. Rectal palpation is practical in llamas at >45 days of gestation. It is usually not possible to safely perform rectal palpation in alpacas, unless the palpator has small hands. Pregnancy can positively be diagnosed by transrectal ultrasound from ~28 days of gestation, although it is possible to be suspicious as early as 10–12 days based on presence of fluid and be reasonably sure by day 21 when a hyperechoic “embryo” is observed. Ultrasonographic transabdominal approach from 45−60 days can be expected to produce positive results.

Normal gestation in camelids is ~342 ± 10 days, with alpacas being somewhat less. Most normal births (>70%) occur in the morning. Dystocias due to excessively large crias are rare. There are few reliable indications of pending delivery. Stage I labor typically lasts 1–6 hr and may be accompanied by increased frequency of urination, increased “humming,” and separation from the herd. Stage II labor is rapid (typically <30 min), with delivery of a cria weighing 5.5–8.0 kg (alpaca) or 11–16 kg (llama). Stage III should be complete within 4–6 hr. All stages are usually longer in a first-time delivery. Retained placentas are rare. Uterine involution begins shortly after birth, and most females can conceive within 14–21 days after delivery. Females have 4 teats and do not exhibit significant mammary enlargement during the prepartum period. Mastitis is rare.

Males

Both testicles should be fully descended at birth. Testes should be at least ~2 × 4 cm and 3 × 6 cm in mature alpacas and llamas, respectively. Relative to body size, the testes are smaller than those of many other domestic livestock species and are held close to the body wall. The urethra is relatively small and contains a urethral diverticulum at the level of the ischial arch, making retrograde catheterization difficult to impossible. The unstimulated prepuce points backward, accounting for the rear directed urination, while the forward-pointing penis is fibrous, with a sigmoid flexure. A cartilaginous process is present at the tip of the penis, and the urethra opens 1–2 cm back from the tip. Urinary calculi are relatively common and have a poor prognosis due to the small urethral diameter (3.5–5 French).

Although androgen production may begin at <8 mo of age, and some sperm can be collected by vaginal retrieval as early as 14 mo of age, normal preputial adhesions prevent full penile extension and copulation until 18–24 mo of age or older. Most males enter breeding programs when 18–24 mo old, and most are fertile by 30 mo of age. Sexual maturity may be later in alpacas than in llamas.

Semen evaluation is difficult in camelids due to the small total volume of semen and the dribble ejaculation. While males can be trained to mount a phantom or dummy, equipped with an artificial vagina, semen collection usually requires heavy sedation or anesthesia and electroejaculation. Semen collection, even from males of known fertility, is inconsistent. The most reliable semen evaluation is afforded by postbreeding retrieval from the vagina of a receptive dam.

Management of Reproductive Problems

Fertility problems are relatively common in llamas and alpacas. Although most problems primarily involve females, problems with males include hypoplastic testes, penile injuries, and heat stress, which is characterized by scrotal edema, decreased activity, and reluctance to breed. Fertility can be permanently impaired or reduced for up to 6 wk. Shearing, adequate shade, and sufficient water help prevent the problem. When working with inexperienced males, vaginal intromission should be visually confirmed.

Due to the relatively high incidence of congenital anomalies, anatomic problems must be considered as causes of infertility in nulliparous animals. In multiparous animals, vaginal strictures, uterine infections, and cervical damage are also relatively common. Complete uterine strictures are possible sequelae of dystocia. The diagnostic approach to all these conditions is similar to that used in mares, except that rectal palpation cannot usually be safely done in alpacas unless sedated. If uterine biopsies or cultures are appropriate, they should be performed when the dam has a dominant follicle, which relaxes the cervix.

Rupture of a mature follicle (>7 mm) can reliably be induced with human chorionic gonadotropin or GnRH. Increased progesterone concentration (>1.0 ng/mL) 7 days after copulation or hormonal treatment is indicative of CL formation. Although persistent CL have been identified, they are relatively rare. Prostaglandin treatment will result in regression of a persistent CL and abortion throughout gestation. Induction of parturition with prostaglandins or glucocorticoids is not recommended. Rapid death of llamas and alpacas has occurred following prostaglandin therapy, especially at high doses and when administered by other than SC route.

Last full review/revision July 2011 by LaRue W. Johnson, DVM, PhD