Abortion

Abortion by one or more goats in a herd may signal an infectious disease or some other condition that could be controlled by proper management.

Diagnostic Workup for Abortions

Practitioners are often asked to determine the cause of an abortion or to offer an opinion as to the need for diagnostic testing.

Table 13.2 Guidelines for estimating the gestational age of tropical breeds.

Week Developmental characteristic

10-11 Hairs on eyelids

13- 14 Hairs on dorsum of neck and entire calvarium hard

14- 15 Eyelids separable

16- 17 Body sparsely covered with hair

17- 20 Body densely covered with hair, teeth buds prominent

At birth 1-3 pairs incisors erupted

Source: Based on Sivachelvan et al. 1996.

Norwegian goats (Lyngset 1971), and Australian feral goats (McDonald et al. 1988).

The serious risk of zoonotic disease and prompt disposal of all fetuses or placentas not submitted for diagnostic workup must be stressed. Uterine discharges are an impor­tant source of infection for others in the herd, and thus all aborting does should be isolated at once from the rest of the herd. Pregnant does should be fed from feeders to limit exposure to discharges on the ground. When abortion has occurred outside, the immediate area can be disinfected by burning (straw and diesel fuel). It is also good policy to separate pregnant females of different species, because some abortion storms may cross species lines.

After consulting with the regional diagnostic laboratory, fetus, placenta, and paired sera should be collected. If it is not convenient to submit the entire fetus, fetal tissues and fluids (stomach fluid, heart blood, or thoracic fluid) should be harvested for culture and serology tests and submitted along with formalin-fixed tissues (including brain) for his­tology (see Table 13.3). Impression smears of the cut sur­face of cotyledons may permit identification of infectious agents by special stains or fluorescent antibody techniques when the placenta itself is too autolyzed or contaminated to easily evaluate by culture or routine histology. Exudate from the vagina may be substituted in some tests if pla­centa is not available. Owners should be alerted to the unsuitability of a mummified fetus for many tests, so that long drives and expenses associated with laboratory sub­mission of a mummy can be avoided. Although not ideal, it is possible to freeze the first aborted fetus and placenta, along with serum from the dam, then await the possible development of a herd problem.

Laboratory procedures for identifying the various causes of abortion have been described in Kirkbride’s manual (Kirkbride 1990) and more recently by Holler (2012).

The importance of the placenta cannot be overempha­sized. Table 13.4 summarizes the placental changes that may have diagnostic value. Small white amniotic plaques of proliferating epithelial tissue are inconsistent but nor­mal findings (Lyngset 1971). Unfortunately, many does either eat the placenta or retain it, so that this extremely important tissue is not always available. Also, grossly visible placental lesions are not invariably present.

The diagnosis in an abortion storm often is not available for several days. In fact, absence of placentas, autolysis, bacterial contamination, or submission of unrepresenta­tive fetuses (bad luck) may result in no diagnosis being achieved. It is reasonable to begin treatment of remaining

Table 13.3 Diagnostic samples for abortion testing.

Tissues

Fluids in test tube Fresh bacteriology Fresh virology Formalin-fixed histology

Maternal blood X

Fetal heart blood or thoracic fluid X

Abomasal fluid X

Table 13.4 Changes observed in placentas from aborting goats.

pregnant does with tetracycline in case a susceptible infectious agent is involved. One possible protocol is three subcutaneous injections of long-lasting tetracycline (Biomycin 200®, Boehringer Ingelheim, Ingelheim, Germany) at 20 mg/kg at three-day intervals. The intramuscular route should be avoided because it causes severe muscle necrosis. Obvious nutritional deficiencies should also be addressed.

Early Abortion

In the field it is often impossible to differentiate early abortions from simple failure to conceive and false preg­nancy, unless the animals are followed by ultrasonography (Samir et al. 2016). Similarly, when more corpora lutea than embryos are found in slaughterhouse studies, the con­tribution of fertilization failure cannot be determined (Lyngset 1968a). One possible genetic cause of early embry­onic death, the Robertsonian translocation, is discussed later in this chapter.

Veterinarians occasionally prescribe progesterone main­tenance therapy for goats that have aborted repeatedly and may have inadequate hormone levels. It may be inappro­priate to assist in reproducing reproductive misfits. The presence of a live fetus should also be verified (real-time ultrasound) before progesterone administration is begun. Experimentally, progesterone in oil (25 mg daily) prevented abortion in three ovariectomized goats (Meites et al. 1951).

Drug-Induced Malformations

Before attachment of the blastocyst at day 15, the uterus contains a fluid of increased pH that accumulates high concentrations of acidic drugs administered to the dam. Even after attachment, drugs may disrupt organogenesis. Specific information related to the goat is lacking, but in general unnecessary drugs, including anthelmintics and anesthetics, should be avoided during the first 35 days of pregnancy. Diazepam, xylazine, and acetylpromazine are potentially deleterious drugs, whereas thiopental, thia- mylal, ketamine, and the major inhalation anesthetic agents are not believed to be teratogenic (Ludders 1988).

Sheep and Goat Hybrids

When flocks of sheep and goats are kept together, breeding usually only occurs between members of the same species. However, if does are housed with a fertile male sheep and no buck is available, interbreeding occurs. An embryo forms, but usually does not survive beyond the second month of pregnancy. Fertilization rarely occurs when a ewe is bred by a buck (Kelk et al. 1997).

The goat has 60 chromosomes, all acrocentric. The sheep has 54 chromosomes, 6 of which are metacentric while the rest are acrocentric. The hybrid embryo has 57 chromo­somes, 3 of which are metacentric (Ilbery et al. 1967). Some hybrid embryos fail to attach to the maternal caruncles. Histologically, those that attach show evidence of rejection of the trophoblastic tissue that invades the caruncles (Hancock et al. 1968; Dent et al. 1971). The embryo degen­erates and is expelled. Passage of the placenta may astound an owner who had not realized that a pregnancy had been initiated. Occasionally mummification occurs and the fetus is expelled at a later date. Rejection typically occurs in the sixth week of pregnancy (or sooner, in goats carrying a hybrid embryo for the second time). Only very rarely has a hybrid fetus (documented by karyotype) survived to term (Bunch et al. 1976; Denis et al. 1988; Stewart-Scott et al. 1990; Letshwenyo and Kedikilwe 2000; Mine et al. 2000).

Goat-lambs (or “geep”) are a different, artificial phenom­enon produced by manipulation and combination of a goat embryo and a sheep embryo. The resulting chimera is then implanted in a recipient sheep or goat (Fehilly et al. 1984). If the chimeric embryo is constructed in such a way that the trophectoderm and thus the chorionic epithelium arise entirely from cells of the same species as the recipient, rejection of the embryo is avoided.

Toxoplasmosis

It is reasonable to suspect that infection of a doe with Toxoplasma gondii in early gestation might occasionally lead to early embryonic death, rather than overt abortion. Animals affected in this way might return to estrus after an irregular interval or merely be found open when partu­rition was expected. Early embryonic loss has been docu­mented in experimental infections with Toxoplasma (Dubey 1988), but is difficult to confirm in field cases (Calamel and Giauffret 1975; Nurse and Lenghaus 1986). Some early deaths may be the result of the febrile response in the infected doe, rather than of invasion of the placenta and fetus. In a serologic study of sheep from farms where toxoplasmosis had been identified as a cause of abortion, a significantly larger proportion of barren ewes than of lambing ewes had high titers for toxoplas - mosis (Johnston 1988). T. gondii has been detected in the semen of bucks after experimental infection (Dubey and Sharma 1980) and of naturally infected rams at an insem­ination center (Bezerra et al. 2014). It is conceivable that a buck could be the source of infection and early embry­onic loss in does. Such a scenario was produced experi­mentally where 4 of 5 does inseminated with semen containing live tachyzoites of T. gondii experienced early embryonic loss between days 21 and 49 of gestation (Wanderley et al. 2013).

Nutritional Factors

Deficiencies of several trace minerals have been associated with lowered conception rates and abortions in controlled experiments with goats. These include copper and iodine (Anke et al. 1977). Experimental selenium deficiency leads to a lowered apparent conception rate, but not to early abortions (Anke et al. 1989). Conversely, prolonged sele­nium toxicosis (caused by excess selenium in soil and therefore in feeds) has been reported to cause abortion and failure of conception in goats in India (Gupta et al. 1982).

Under adverse field conditions, such as prolonged drought, deficiencies of several nutrients (e.g., protein, magnesium, and copper) have been suspected to cause abortion, based on lowered concentrations in the blood of does aborting early in pregnancy (Unanian and Feliciano- Silva 1984), but the exact cause of the abortions remains unproven.

Studies in Angoras have suggested that simultaneous deficiencies of energy and protein (rather than just one or the other) are required for early embryonic mortality to occur (Van der Westhuysen and Roelofse 1971). Dairy does for which both energy and protein were restricted had a lower ovulation rate and increased embryonic losses when compared with goats on a control, maintenance diet. Circulating progesterone concentrations were not affected (Mani et al. 1992, 1995). A protein and mineral supplement should be offered if reproductive failure coincides with probable nutritional deprivation. Supplementation of a low-protein grass diet with leguminous browse has decreased abortion losses in West African Dwarf goats (Pamo et al. 2006). However, toxic species such as Mimosa Ienuiflora have caused early embryonic loss (Dantas et al. 2012). Other long-term feeding trials of does have suggested that energy is more critical to successful repro­duction in goats than is protein (Sachdeva et al. 1973). This suggests that a supplement that does not improve the digestible nutrients in the ration may not be effective in restoring reproduction.

Prevention of Early Losses by Flushing

Flushing is the technique of increasing energy intake just before breeding to increase ovulation rate. Maintaining the improved nutrition through the first month of gestation is advised to give the embryos ample opportunity to survive this critical period. Flushing is often interpreted as feeding grain. In range or grazing animals, other management options appear to be useful to improve the nutritional bal­ance. These include moving to a better pasture, deworming at this strategic time, or shearing (Angoras). Shearing prob­ably stimulates an increase in feed intake until a protective layer of fleece grows back. A study by Hart et al. (1999) failed to show an increase in conception rate or litter size with increases in either energy or protein fed to Spanish meat goats, whereas Shahneh et al. (2008) found that feed­ing barley resulted in an improved pregnancy rate in Iranian goats.