Abortion in Angora goats

Friday, 16th March 2018

Abortions in Angora goats are not uncommon being higher than in sheep. Producers may experience abortions of up to 5% on a regular occurrence.

Many infectious diseases, stress related farm activities, nutritional deficiencies and toxic plants may cause abortions. 

CAUSES and ‘POTENTIAL CAUSES’ OF ABORTION

  1. NUTRITION

Probably the most important cause of abortion after day 90 of pregnancy is a nutritional energy deficiency.

Most losses occur in the period just before birth until seven days after birth. Nearly 80% of these mortalities are related to the nutrition of the ewe during the last weeks before kidding and the first weeks after kidding. The nutritional requirement of a late pregnant Angora ewe is known to increase more than two fold above the standard maintenance requirements of a dry ewe. This figure is too often forgotten or underestimated.

Trials were performed to determine blood glucose concentration in 20 pregnant ewes receiving a high and low plane of nutrition during the fourth month of gestation (Wentzel, Le Roux and Botha). They concluded a drop in blood glucose levels due to nutritional stress to be the likely trigger for the onset of hormonal changes related to abortion in Angora goat ewes. In addition, the stress of sub-nutrition during the experimental period increased the incidence of perinatal mortality.

Why do Angora goats abort more easily than sheep during nutritional stress?

In a ewe which is energy deficient there is a decrease in blood glucose level which is passed on to the foetus.  This triggers a stress-response by the foetus, causing a rise in cortisol (steroid) production.  As these steroids are oestrogen precursors, this has the ultimate effect of increasing oestrogen production. 

This causes the regression and eventual destruction of the Corpus Luteum (CL), the area of the ovary responsible for progesterone production.

 In Angora goats the CL is the only source of progesterone and is solely responsible for maintaining pregnancy, whereas in sheep, progesterone is also produced by the placenta. For this reason, sheep are significantly less likely to abort during energy shortages.

The aborted foetus is usually well formed, normal in appearance and sometimes still alive when aborted. When energy is supplemented appropriately, abortions will typically stop within two weeks.

It is important that care should be taken when:

  • Ewes are moved to a new type of grazing during this time (e.g. to cultivated pastures or lucerne lands). When such a move takes place the ewe takes time to adapt to the altered diet, and the temporary deficiency created by this can lead to abortions even in the midst of plenty. During such a movement an energy supplement should be supplied, or lucerne hay provided a week before the move until several days after introduction to the lands

 

  • During cold snaps it is important to remember cold stress also increases glucose consumption by up to 66% which is aggravated by restricted grazing at times when goats are housed in sheds. Abortions typically then occur 1-5 days later. Pregnant ewes should therefore when possible be given supplementary feeding when housed.

 

  • Energy deficiencies can occur during handling, kraaling such as at times of crutching, shearing or dosing.

Mineral and Vitamin deficiencies will seldom cause abortions in late pregnancy so deficiencies are often observed as reduced reproductive performance.

Vitamin A is essential in production of progesterone so deficiencies result can result in abortion, poor expression of oestrus, delayed ovulation and birth defects.

Manganese (Mn) deficiencies are mainly characterised by delayed, very short and irregular oestrus, poor conception especially in young ewes, normally developed but still born kids and skeletal abnormalities may occur. High dietary intakes of Ca such as contained in lucerne reduce Mn absorption.

Iodine (I) primary importance is in the Thyroid hormone. Goitrogens found in plants from the Brassica family reduce TH production. Deficiencies result mostly in reduced growth, hair production and reproductive performance. Areas deficient in I are found in the Langkloof valley

 

  1. RIFT VALLEY FEVER (RVF)

 

During a RVF outbreak up to 100% ewes may abort and between 10-100% of kids under 10 days old may die

Kid deaths occur within 12 hours after the fever reaction starts, others may survive longer and die within 12-24 hrs.

 

In subacute casers (usually adult goats) clinical signs may be seen which include:

  • fever,
  • increased respiratory rate,
  • Nasal and eye discharge may occur.
  • The goats may show abdominal pain, are reluctant to move and are weak and lack c0-ordination.
  • The goat often develop a haemorrhagic diarrhoea. Goats that do survive show signs of jaundice.
  • Older or resistant goats may have a fever and decreased appetite with a few abortions.

 

For more information on RVF see our website

https://www.angoras.co.za/page/rift_valley_fever#33

 

  1. WESSELSBRON DISEASE

 

Wesselsbron disease is usually associated with Rift Valley Fever (RVF) as the conditions and vectors (mosquitos) are similar. 

New-born Angora kids are most susceptible and deaths are seen whereas in adult goats cases are usually subclinical, although abortions may occur.

.

Clinical signs show after an incubation period of 1–3 days in kids which include

  • Non-specific signs of fever, anorexia, listlessness, weakness, and increased respiration.
  • Icterus (jaundice)
  • Death may occur within 72 hr (up to 30% of kids may die)

 

Clinical signs in adult goats:

  • Occasional abortions,
  • Congenital CNS malformations with arthrogryposis,
  • Hydrops amnii (severe distension of the abdomen) can be seen in pregnant ewes.

 

Wesselsbron disease and Rift Valley fever share many clinical and pathologic features. However, Wesselsbron disease is usually milder, producing much lower mortality, fewer abortions, and less destructive liver lesions.

 

  1. ENZOOTIC ABORTION

 

Enzootic abortion (chlamydiosis) a contagious disease in Angora goats and sheep caused by Chlamydophila abortus (previously) Chlamydia psittaci. Outbreaks are usually seen a year or two after new sheep or goats were introduced onto a farm.

For more detail on Enzootic abortion see SAMGA website:

https://www.angoras.co.za/page/abortion-enzootic-abortion#144

 

 

  1. LIVE VACCINES

 

The use of ‘live’ vaccines such as RVF or Enzootic abortion must not be given to pregnant ewes as this may cause abortions and congenital abnormalities

 

  1. LUCERNE and oestrogen containing pastures

Lucerne may contain phytoestrogens which can lower Angora goat fertility.

Environmental factors, stage of growth and biological stress in lucerne/alfalfa (Medicago sativa) is the major determinant of oestrogenicity.  Studies in Israel, North America, Europe, New Zealand and Australia have confirmed that coumestans in cause a loss of reproductive efficiency in herbivores, e.g., Angora goats, sheep, cattle.

When sufficiently exposed peri-conception, coumestrol, sometimes present in lucerne, be it as pasture, hay, silage, pellets or meal is associated with what can be an insidious, asymptomatic, infertility syndrome. Most livestock research with oestrogenic lucerne has been conducted with sheep. Ewes may be at risk when the coumestrol concentration in their diet exceeds 25 mg/kg. In studies where lambing was compared for lucerne and a phytoestrogen-free treatment, the mean decrease in lambs born/ewe was 13%.

  1. GENETIC- HERITABLE Abortion in Angora goats

The hypothesis that the abortion phenomenon was heritable was first proposed by van Heerden (1963,1964). Van Rensburg (1965) subsequently confirmed this hypothesis when he found, on small numbers of goats, that mohair production characters (with a fairly high inheritance) were linked with abortion.

Habitual abortion is caused by chronic over activity of the ewe’s adrenal cortex. It is closely associated with stress abortion, which is usually due to feed disturbance, causing blood sugar levels to drop.

In feed-stress abortions, apparently normal, well-developed kids are expelled after the 90th day of pregnancy. Abortion due to the doe’s overactive adrenal cortex shows signs of oedema (unnatural collection of fluid) in the foetus. The heart rate is slow and heart failure occurs. This has largely been eliminated through selection.

  1. BRUCELLOSIS

 

Brucellosis in Angora goats is caused by Brucella melitensus. This is to date an extremely rare condition in Angora goats and only a few isolated cases have ever been diagnosed in goats South Africa.

For more information on brucellosis see the SAMGA website:

https://www.angoras.co.za/page/abortion-brucellosis-melitensis#145

 

  1. Q-FEVER (Coxiella burnetii)

 

Q - fever, Coxiella burnetii, in Angora goats can potentially be associated with abortions and peri-natal deaths although the incidence is unknown and more research is required. The role of Q-fever in abortions is also uncertain as antibodies have been detected in goats aborting as well as those not aborting.

For more information see the SAMGA website

https://www.angoras.co.za/article/q-fevercoxiella-burnetii#230

 

  1. TOXOPLASMOSIS

 

Toxoplasmosis as a cause of abortion in Angora goats in South Africa has not been diagnosed.

It potentially could be a cause where goats and cats may be in close proximity. Toxoplasma has been diagnosed as a cause of abortions in Angora goats in Europe ( Slosarkova, Literak, et al) and New Zealand (K.D. McSporran,C. McCaughan,J.H.S. Currall &A. Demsteegt 1984)

The cause of abortion in Angora goats in South Africa was extensively investigated by Malherbe and Van Heerded in the 1950’s and Toxoplasmosis was discarded as a potential cause of Abortions in Angora goats in South Africa for a number of reasons.

 For more info on Toxoplasmosis see the SAMGA website https://www.angoras.co.za/article/toxoplasmosis#274

  1. CAMPYLOBACTER

 

Campylobacter (Campylobacter fetus fetus) is NOT a current reproductive issue in Angora goats but is a major problem effecting fertility in cattle in South Africa (Campylobacter fetus venerealis).

Campylobacteriosis  ( Campylobacter fetus) has been referred to as ‘Vibriosis’ in the past. It can cause abortion during the last 6 weeks of pregnanacy but can result in early neonatal loss. For more information see the SAMGA website https://www.angoras.co.za/article/campylobacter#270

 

  1. LISTERIOSIS

 

Listeriosis  has not been diagnosed in Angora goats in the Karoo and is not economically important. It potentially, but rarely, effects most farm animals as well as humans.

Listeriosis is caused by a bacterium Listeria monocytogenes and can cause abortion.

For more information see the SAMGA website

https://www.angoras.co.za/article/listeriosis#255

 

  1. HAIRY SHAKER, BORDER DISEASE

Border disease (Britain) or hairy shaker disease (Australia and New Zealand) is a congenital disorder of lambs characterized by low birth weight and viability, poor conformation, tremor, and an excessively hairy birth coat. Goat kids may also be affected. See SAMGA website https://www.angoras.co.za/article/hairy-shaker-disease-border-disease#271

 

  1. LEPTOSPIROSIS

Leptospirosis has not been diagnosed in Angora goats in South Africa.

The dry and hot conditions in the Karroo, where most Angora goats occur, are very unfavourable to leptospirosis. Leptospirosis in South Africa has mostly been reported from areas with relatively high rainfall such as Mpumalanga, KwaZulu Natal and the coastal area of the Eastern Cape provinces. However, it has also been diagnosed in the drier Limpopo and North West provinces.

Leptospirosis is rare in sheep and goats but possible clinical signs include

  • Acute death
  • Redwater resulting from infection with Leptospira pomona .
  • Septicemia
  • Leptospira hardjo - abortion may be the only sign,
  • Milk drop syndrome similar to one observed in cattle can be seen in lactating ewes

For more information see the SAMGA website https://www.angoras.co.za/article/leptospirosis#272

REFERENCES

  1. F. M. Reed

Reed Pasture Science, Brighton East 3187, Australia; rps@eftel.net.au

Academic Editor: Secundino López

Received: 29 May 2016; Accepted: 20 July 2016; Published: 30 July 2016

 

© SA Mohair Growers - 2018 | Links | Abortion in Angora goats

Website Design and Search Engine Optimisation (SEO) by ZAWebs Designs | Web Hosting by ZAWebs Hosting