Chapter 1
Female infertility

The normal female goat

In temperate regions, female goats are seasonally polyoestrus. Most goats are totally anoestrus in the northern hemisphere between March and August, although fertile matings have been recorded in all months of the year. Anglo-Nubian and pygmy goats in particular have extremely long breeding seasons. Recently imported goats from the southern hemisphere may take time to adjust to a new seasonality. The breeding season is initiated largely in response to decreasing day length, but is also dependent on temperature, the environment (particularly nutrition) and the presence of a male. Decreasing day length also stimulates reproductive activity in the buck. Table 1.1 details the reproductive aspects of the goat.

Table 1.1 Reproduction in the goat

Breeding season September to March (northern hemisphere) Puberty 5 months Age at first service 4 to 6 months (male)
7 to 18 months (female) Oestrus cycle 19 to 21 days (dairy goats)
18 to 24 days (Pygmy goats) Duration of oestrus 24 to 96 hours (usually 36 to 40 hours) Ovulation 24 to 48 hours after start of oestrus Gestation length 150 days (145 to 156 days) Weight at first mating 60-70% of predicted adult weight
~30 kg for meat goats
30-40 kg for dairy goats

Investigation of female infertility

Because of the seasonal pattern of breeding, infertility must be investigated as early as possible in the breeding season.

The investigation of female infertility in the goat presents major difficulties when compared with the cow because of the inability to palpate the ovaries and because of the seasonal pattern of breeding - does are often presented towards the end of the season, limiting the time available for remedial measures. Figure 1.1 lists possible causes of infertility in the doe.

Figure 1.1 Causes of female infertility.

Initial assessment

The preliminary history should consider:

• Individual or herd/flock problem.
• Feeding, including mineral supplementation.
• Management practices - hand-mating, artificial insemination (AI), buck running with does.
• Disease status of herd/flock.

If there is a herd problem, investigate:

• Male infertility (Chapter 3).
• Intercurrent disease - parasitism, footrot, etc.
• Nutritional status - energy or protein deficit, mineral deficiency (phosphorus, copper, iodine, manganese).
• Stress - overcrowding, recent grouping of goats.
• Poor heat detection.
• Services at incorrect time.

Assessment of individual doe

General assessment

• Conformation.
• Body condition.
• Dentition.
• Clinical examination.

Any obvious clinical signs such as debility, anaemia or lameness should be investigated and corrected where possible before commencing specific therapy aimed at correcting a reproductive disorder.

In the UK overfeeding is probably a greater cause of infertility than poor condition.

Specific examination

• Specific examination of the reproductive and mammary systems. Include, where necessary, examination of the vagina and cervix with a speculum to identify anatomical abnormalities.

Specific history

• Date of last kidding/stage of lactation.
• Daily milk yield.
• Presence or absence of obvious oestrus signs.
• Length of oestrus cycles.
• Date of last service.
• Willingness to stand for male.
• Kidding difficulties last time - malpresentation/manipulation, metritis, retained placenta, abortion, mummified fetus, stillbirths.

Further investigations

• Specific laboratory tests:
• Progesterone assay
• Oestrone sulphate assay
• Bacteriological examination of vaginal or uterine samples
• Feed analysis
• Real-time ultrasound scanning
• Laparoscopy or laparotomy.

Individual infertility problems

Individual infertility problems will generally fall into one of four categories:

1. 1 Difficulty at service.
2. 2 Anoestrus.
3. 3 Irregular oestrus cycles.
4. 4 Regular oestrus cycles.

Difficulty at service

• Doe not in season.
• Doe scared - common with maiden animals, particularly if a large buck is used on a small doe.
• Persistent hymen or vaginal constriction.

Anoestrus

Always consider the possibility of an undetected pregnancy (even if the owner insists that no mating has occurred) before attempting treatment, particularly with prostaglandins.

The causes of anoestrus are listed in Table 1.2 and discussed below.

• Seasonal. Most goats are totally anoestrus between March and August.
• Pregnancy.
• Poor heat detection.

Table 1.2 Causes of anoestrus

Seasonal Pregnancy Poor heat detection Malnutrition Post-kidding anoestrus Lactational anoestrus Adhesions following surgery Hydrometra Intersex Freemartin Ovarian malfunction

Although some dairy goats show only minor behavioural changes during oestrus, oestrus detection is generally easier than in Angora goats, with most does showing obvious signs of tail wagging, frequent bleating, urination near the buck, swelling of the vulva and a mucous vaginal discharge. The signs are generally accentuated in the presence of a male or even a 'billy rag', that is a cloth that has been rubbed on the head of a buck and stored in a sealed jar.

Oestrus can be determined visually by means of a speculum. At the onset of heat, the cervix changes from its normal white colour, becoming hyperaemic, and the cervical secretions are thin and clear. The secretions rapidly thicken, becoming grey/white and collecting on the floor of the vagina. Conception is best when mating occurs at the stage at which the cervical mucus is cloudy and the cervix is relaxed.

Unlike cows, most does will not stand to be ridden by other females even when in oestrus. Riding behaviour is sometimes seen as an expression of dominance in the herd or as part of the nymphomaniac behaviour of goats with cystic ovaries. Many young bucks will mount and serve females that are not in true standing oestrus if the female is restrained, although older bucks are more discriminating. The doe will stand to be mated only when she is in oestrus.

In the milking doe, a rise in milk production may occur 8 to 12 hours before the start of oestrus and milk production may fall below normal during oestrus.

When the buck is running with the flock or herd, sire harnesses with raddles or marker paste will aid oestrus detection. A marked vasectomised ('teaser') buck can be used to detect (and help initiate) the start of oestrus in a group of does.

• Malnutrition. An energy or protein deficit due either to poor nutrition or intercurrent disease may cause anoestrus. Deficiencies of minerals such as cobalt, selenium, manganese, zinc, phosphorus, iodine and copper and deficiencies of vitamins B12 and D are all reported to cause infertility.
• Post-kidding anoestrus. Many does will not show signs of oestrus for 3 months or more after kidding, even if kidding takes place during the normal breeding season.
• Lactational anoestrus. Some high yielding does do not exhibit marked signs of oestrus. These animals may respond to prostaglandin injections with careful observation for oestrus 24 to 48 hours later. Animals that do not respond may need a further injection 11 days later.
• Adhesions following surgery. The goat's reproductive tract is sensitive to handling and adhesions will occur unless very high standards of surgery are maintained during embryo transplant or other surgical procedures. Talc from surgical gloves will produce a marked tissue reaction.

False pregnancy (hydrometra, cloudburst)

False pregnancy occurs when aseptic fluid accumulates in the uterus in the absence of pregnancy, but in the presence of a persistent corpus luteum, which continues to secrete progesterone. The incidence of false pregnancies is fairly high, particularly in some strains of dairy goats and incidences of between 3 and 30% have been reported in commercial herds.

Aetiology

• A persistent corpus luteum following an oestrus cycle in which pregnancy did not occur. This may occur in any sexually mature female but is particularly common in goats in their second year of a lactation ('running through') without being mated. Certain families seem prone to develop the condition.
• A...