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Foetal loss in dairy goats: An epidemiological study in 22 herds
Small Ruminant Research 30 (1998) 37±48
Foetal loss in dairy goats: An epidemiological study in 22 herds Inge Vogt Engelanda,*, Harald Waldelandb, éystein Andresena, Torleiv Lùken1,c, Camilla BjoÈrkmand, Inge BjerkaÊse a
Department of Reproduction and Forensic Medicine, Norwegian College of Veterinary Medicine, P.O. Box 8146 Dep., NO-0033 Oslo, Norway b Department of Sheep and Goat Research, Norwegian College of Veterinary Medicine, P.O. Box 264, NO-4301 Sandnes, Norway c Central Veterinary Laboratory, NO-0033 Oslo, Norway d Department of Cattle and Sheep Diseases, Swedish University of Agricultural Sciences, P.O. Box 7019, SE-750 07 Uppsala, Sweden e Department of Morphology, Genetics and Aquatic Biology, Norwegian College of Veterinary Medicine, P.O. Box 8146 Dep., NO-0033 Oslo, Norway Accepted 19 November 1997
Abstract In this study, 22 herds comprising 1439 dairy goats presumed to be pregnant were studied during the gestation period 1990± 91. Altogether, 160(11.1% of the total number of goats) experienced foetal loss following conception. In all, 85(53%) of these goats aborted, 45(28%) delivered dead foetuses at full term and from 30(19%) goats no discharge or foetus was observed. The incidence of foetal loss in the different herds varied from 3±38%. The proportion of foetal loss was >20% in three herds comprising a total of 169 goats. In 10 herds comprising 677 goats the proportion of foetal losses were <10%. In most of the herds, the foetal loss occurred in goats aged 3 years. Decomposed foetuses expelled during the last 2 months of pregnancy was the most common observation. Usually, no other symptoms of disease were observed. Listeric abortion was diagnosed in ®ve (3.1%) goats and in seven (4.3%) goats serological or parasitological examination indicated foetal loss from toxoplasmosis. A herd history of foetal loss was signi®cantly associated with a high incidence of loss during the present examination. Other diseases and routine ¯ock management procedures were not found to be signi®cant. However, some environmental conditions such as inferior natural lighting in the stables, pre-heated drinking water and a building design with a combined feeding and milking platform involving large and crowded pens were associated with a high incidence of foetal loss. # 1998 Elsevier Science B.V. All rights reserved. Keywords: Goat; Abortion; Foetal loss; Epidemiology; Questionnaires
1. Introduction *Corresponding author. Tel.: 0047 2296 4853; fax: 0047 2256 5704; e-mail: [email protected] 1 Present address: Department of Large Animal Clinical Sciences, Norwegian College of Veterinary Medicine, P.O. Box 8146 Dep., NO-0033 Oslo, Norway.
Foetal loss is a serious problem in Norwegian goat husbandry. Melby et al. (1986) found an abortion rate of 8.5% in 27 goat herds, whereas 1.2% of the goats had pseudopregnancy and 3.2% either returned to service or were empty. In an epidemiological study
0921-4488/98/$ ± see front matter # 1998 Elsevier Science B.V. All rights reserved. PII S0921-4488(98)00084-4
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I.V. Engeland et al. / Small Ruminant Research 30 (1998) 37±48
in 30 herds, Lùken (1990) observed foetal loss in 9.8% of the does. Waldeland and Lùken (1991) studied the incidence of foetal loss in 24 selected goat herds, and found that 15.6% of the animals either aborted, delivered dead kids at full term, or were empty. In that study Listeria monocytogenes or Toxoplasma gondii was found to be the cause of foetal loss in only 9(2.4%) out of 369 goats. Corresponding results have also been reported from other countries (Wentzel, 1982; Merrall, 1985; Orr et al., 1987). These reports suggest that abortion in goats from non-identi®ed causes constitutes a substantial loss. Since infectious causes were found in relatively few cases of foetal loss in goats in Norway, Waldeland and Lùken (1991) suggested that nutritional and environmental factors may be important. In studies on South African Angora goats, submaintenance energy feeding during pregnancy was found to increase the incidence of abortion (Van der Westhuysen and Roelofse, 1971; Wentzel et al., 1974). Recent experiments on Norwegian goats revealed that feeding with silage of poor quality from aerobically damaged round bales during the indoor period combined with low energy intake between 91±120 days of gestation increased the rate of abortion (Hussain et al., 1996). The aim of the present study was to survey foetal loss in dairy goats under ®eld conditions, and to investigate the in¯uence of various herd factors related to disease, environment and management procedures on the incidence of foetal loss from unidenti®ed causes. 2. Materials and methods 2.1. Herds and management We studied 22 commercial dairy herds comprising a total of 1498 goats in the region of Hallingdal and Valdres in Norway. Most of the goats were of the Norwegian breed, while a few were crosses between the Norwegian and Saanen breeds. The goats were kept outdoors during daytime for the ®rst month after mating, and indoors for the rest of the pregnancy. Inclement weather during the gestation period were recorded. In one herd, most of the goats were mated during July, and in the other herds mating mostly occurred in
August or September. A few goats (5%) were arti®cially inseminated. All farmers kept one or two bucks in a separate pen during the whole breeding season and gestation period. During the ®rst two months after the mating started, all goats were observed for oestrus in the presence of a buck twice daily. The goats were hand-mated and the dates of mating registered. Goats were carefully observed for oestrus in the presence of a buck for 10±15 min twice daily 19±23 days after mating, and again at days 40±44. A goat was presumed to be pregnant if signs of oestrus were not observed in the latter two periods. Only goats presumed to be pregnant, totally 1439, were included in the study. The goats were fed grass silage (19 herds) or hay (3 herds) ad-libitum during pregnancy. In 16 of the herds fed silage, smaller amounts of hay were also given. In addition, the animals were individually fed commercial concentrates containing proteins, vitamins and minerals. The quantity of concentrates offered was reduced for a short period in the last half of pregnancy to terminate milk production. Foot trimming was carried out once or twice during pregnancy. Treatment against nematodes and lice during the second month of pregnancy, shearing during the third month of pregnancy and vaccination against clostridial infections prior to kidding were done in most herds. 2.2. Design of the study The study was based on herd as the unit of analysis with the incidence of foetal loss as the dependent variable. Foetal loss was de®ned as either abortion, delivery of an immature dead foetus or foetal remnants at full term, or being empty at term after having been registered as pregnant. Abortion was de®ned as expulsion of an immature foetus or of bloody vaginal discharges. The farmers checked the goats twice each day for any sign of abortion throughout pregnancy. The date of foetal loss was recorded. The herds were visited three or four times during the gestation period. During these visits, questionnaires on 67 subjects were ®lled out. The questions covered different aspects concerning diseases in the herds, environmental conditions such as building design and natural light conditions in the stable, and ¯ock management procedures such as feeding and vaccina-
I.V. Engeland et al. / Small Ruminant Research 30 (1998) 37±48
tion routines. Herds with an incidence of foetal loss >10% during the last three years, were de®ned as having previous foetal loss. Rooms for 35 goats with 2m2 windows, were de®ned as having inferior natural lighting. All variables were recorded, if possible, before the outcome of pregnancy was known. A herd was visited when a goat aborted or delivered an immature dead foetus. The goats were observed clinically and materials for laboratory examinations were collected. Samples from vaginal discharges were collected on swabs (swab transport pack, Amies medium, Difco) from goats that were suspected of having aborted. All farms were also visited after the kidding season to record the total reproductive performance. Aborted materials from the goats were examined for infectious agents known to cause reproductive loss. Serological screening was also done for certain other diseases prevalent in Norway. Information on the incidence of foetal loss during the 10-year period from 1984/85 to 1993/94 in herds 1±7 were obtained from the farmers' records. These herds were selected mainly on the basis of foetal loss from 1987±1990, when the incidence was >15% in ®ve of the seven herds and <13% in the remaining two herds. 2.3. Examination of aborted material Aborted foetuses and foetal membranes were subjected to gross inspection, routine bacteriological examination, modi®ed Ziehl Neelsen staining (Waldeland and Lùken, 1991) and examination for T. gondii (Waldeland, 1976a). The swabs collected from vaginal discharges were subjected to bacteriological examination. Materials for histological examination for Neospora caninum were obtained from diencephalon/cerebrum from foetuses aborted in a suitable fresh condition. Brain sections, ®xed in 10% neutral, buffered formalin and embedded in paraf®n, were stained with haematoxylin and eosin and immunostained by the avidin±biotin peroxidase complex method (Vector Laboratories, Burlingame, CA, USA) (BjerkaÊs and Presthus, 1988), using rabbit anti-N. caninum antibodies as the primary antiserum (obtained from Dr. J.P. Dubey, Agricultural Research Service, MD, USA). Sections from a dog with neosporosis were included as positive controls.
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2.4. Serological examinations All goats in herds 1±7 were bled during the ®rst month of pregnancy and again after foetal loss or kidding. Goats with foetal loss in the other 15 herds were bled immediately after the loss was detected. Goats found empty at term were bled after the expected date of delivery. Serum samples were stored at ÿ208C until the time of analysis. All sera collected from goats with foetal loss were examined for antibodies against T. gondii by the Sabin±Feldman dye test (Waldeland, 1976b). The sera collected in herds 1±7 were examined for neutralising antibodies at twofold dilutions against the cytopathogenic NADL strain of bovine pestivirus and a Norwegian isolate of caprine herpesvirus (kindly supplied by Prof. B. Hylseth, Norwegian College of Veterinary Medicine) (Lùken et al., 1982). Undiluted sera were screened in immunodiffusion test for antibodies against caprine arthritis encephalitis (CAE) virus (Capriclear 300 test kit, Central Veterinary Laboratory, Weybridge, Surrey, UK) (Cutlip et al., 1977) (see Table 2). Sera from the goats with foetal loss in herds 1±7 were also examined in complement ®xation tests at twofold dilutions for antibodies against Chlamydia psittaci (Ornithosis antigens, Behringwerke AG, Marburg, Germany) and Coxiella burnetii (Q-fever antigen, Behringwerke AG, Marburg, Germany) (Waldeland and Lùken, 1991). These sera were also diluted in twofold dilutions from 1 : 20 and analysed for the presence of antibodies to N. caninum with an indirect ¯uorescent antibody test (IFAT) as modi®ed by BjoÈrkman et al. (1994), as were sera selected at random from 27 animals with normal pregnancy. 2.5. Statistical analysis Correlation coef®cients between the herd incidence of foetal loss of unidenti®ed causes and each of the recorded variables were calculated. Furthermore, a stepwise forward regression analysis with, and without weighting for the herd-size effect was performed. The variables with the highest absolute value of the correlation coef®cients and variables which remained in the ®nal step of the regression procedure were selected for graphical presentation. Some variables of special veterinary interest are also presented graphically.
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Data from examinations for herpesvirus and CAEvirus were subjected to univariate and multivariate logistic regression analysis. 3. Results 3.1. Outcome of pregnancy Of the total of 1498 goats, 59 were omitted from the study either due to hydrometra (8 goats), slaughtering (24 goats), slaughtering because of lack of sign of oestrous (11 goats), sale (6 goats), dead because of mastitis (1 goat), dead because of chronic pneumonia (1 goat) or because they did not conceive (8 goats). The incidences of foetal loss in the 22 herds with a total of 1439 goats presumed to be pregnant are shown in Table 1. The rate of goats with foetal loss in the
different herds varied from 3±38%. In three herds (Nos. 1, 6 and 21) comprising 169 goats, >20% of the does had foetal loss. In 10 other herds comprising 677 goats, the rate was <10%. Altogether, 160(11.1%) of the 1439 goats experienced foetal loss, of which 85(53%) aborted, 45(28%) delivered dead foetuses at full term and 30(19%) were found empty at term after having been registered as pregnant. Out of the 45 goats that delivered a dead foetus at full term, 15 also delivered a live twin kid. Also, 40(30%) goats experienced foetal loss before Day 91 of gestation, 45(35%) between Day 90 and 141 and 45(35%) after Day 140. Only ®ve goats that aborted showed anorexia and fever in connection with abortion. Of these, three goats belonged to Herd 13, and the remaining two goats to herds 7 and 18, respectively. The prevalence of foetal loss increased with age. Only 7% of goats 2 years lost their foetus, while the ®gure for goats 3 years was 18%.
Table 1 Foetal loss during one gestation in 22 dairy goat herds Herd No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Total a
Number of goats total
empty a
aborted
delivered dead foetuses at full term
total with foetal loss
73 64 74 90 78 59 78 63 60 105 49 51 59 85 37 50 80 93 52 54 37 48 1439
1 2 0 1 2 1 1 0 0 0 5 2 4 0 0 0 1 0 0 1 6 3 30
4 2 5 4 8 10 6 5 3 3 3 0 4 5 1 2 2 2 1 7 6 2 85
12 2 5 5 5 3 1 2 0 0 1 0 0 0 0 0 1 2 2 0 2 2 45
17 6 10 10 15 14 8 7 3 3 9 2 8 5 1 2 4 4 3 8 14 7 160
Found empty at term after having been registered as pregnant.
Incidence of foetal loss (%)
23.3 9.4 13.5 11.1 19.2 23.7 10.3 11.1 5.0 2.9 18.4 3.9 13.6 5.9 2.7 4.0 5.0 4.3 5.8 14.8 37.8 14.6 11.1
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Fig. 1. Mean (SEM) incidence of foetal loss in seven dairy goat herds during the gestation periods 1984/85 to 1993/94.
No connection was found between foetal loss and routine ¯ock management procedures such as vaccination, treatment for endo- and ectoparasites or foot trimming. Changes in the weather did not seem to in¯uence the outcome of pregnancy. The mean incidence (SEM) of foetal loss in herds 1±7 for the gestation periods 1984/85±1993/94 are shown in Fig. 1. The mean incidence and standard error of the mean during all 10 years was 13.75.0%. In one of these herds, the mean incidence of foetal loss was below 10% during this period. In the other herds, the main trend was an increasing level during the ®rst part of the period, followed by a decline.
foetuses were delivered together with a live twin. Also, two goats delivered triplets comprising one normal live kid, one stillborn and one decomposed foetus. Malformation of the skeleton was seen in one of the dead triplets from a doe in Herd 7. In 15 herds, most of the aborted foetuses had a decomposed appearance. In all herds, 50% or more of the foetuses were decomposed or mummi®ed. No signi®cant histo-pathological lesions were found in the 23 examined foetal brains. The immunostaining for N. caninum was negative.
3.2. Examination of aborted materials
No infectious agent was isolated from 125(95%) of the 132 aborted or stillborn kids. In Herd 13, L. monocytogenes was isolated from two aborted sets of twins and also from the vaginal discharges of another doe, where no foetus was observed. This agent was also isolated from a total of three foetuses from two goats in herds 7 and 18, respectively (Table 2). No other signi®cant organisms were detected by microscopy or by culture from the maternal placental tissues, foetal stomach contents or organs.
Dead foetuses, foetal remnants or vaginal discharges were registered in a total of 130 goats. Altogether, 132 foetuses from 102 goats and 12 swabs of vaginal discharges from 12 other goats were examined. From the remaining 16 goats, materials were not examined due to circumstances out of our control. Of the examined foetuses, 21(16%) had a relatively fresh appearance, 25(19%) were mummi®ed to various degrees and 86(65%) were decomposed. In eight of the latter cases, the number of foetuses were dif®cult to estimate due to advanced decomposition or maceration. Further, four foetuses with a relatively fresh appearance and nine decomposed or mummi®ed
3.3. Microbiological examination
3.4. Serological examinations Indication of abortion from infection with T. gondii (titre 1 : 1024) was found in six of the nine goats
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Table 2 Serological examination of goats with foetal loss, and microbiological examination of aborted materials Microorganism
Toxoplasma gondii a Listeria monocytogenes b Pestivirus c Caprine herpesvirus c CAE-virus d Neospora caninum e Chlamydia psittaci f Coxiella burnetii f
Number of: examined goats with normal pregnancy
examined goats with foetal loss
herds represented
positive goats with normal pregnancy
positive goats with foetal loss
positive herds
0 0 436 436 436 27 0 0
160 114 80 80 80 80 80 80
22 21 7 7 7 7 7 7
± ± 4 169 74 0 ± ±
8g 5 0 29 19 0 20 h 0
3 3 3 7 7 0 3 0
a
Sabin±Feldman dye test; titres 1 : 256. Bacteriological examination. c Neutralisation test; positive titres for pestivirus 1 : 4; for herpesvirus 1 : 2. d Immunodiffusion test; screening of undiluted sera. e Indirect fluorescent antibody test; positive titres 1:40. f Complement fixation test; positive titres for Chlamydia psittaci 1 : 5; for Coxiella burnetii 1 : 2. g Six goats had titres 1 : 1024, and two had titres of 1 : 256. T. gondii was not detected from a fresh foetus of one of the goats with titre 1 : 256, and from the remainder, the foetus was too decomposed for parasitological examination. h Elementary bodies indicating Chlamydia psittasi were not detected in any of the foetuses or placentas by staining with modified Ziehl Neelsen. b
examined in Herd 11. One of the goats that aborted from each of the herds 10 and 22 had a titre of 1 : 256 (Table 2). One of these two goats (Herd 22) gave birth to a relatively fresh dead foetus with one live kid. T. gondii was not detected in the aborted materials. From the other seropositive goat (Herd 10), the aborted materials were too decomposed for parasitological examination. In the other goats that aborted the titres against T. gondii ranged from negative to 1/64 by the dye test. Conversion from negative to positive titres was not observed in any of the goats that aborted in herds 1±7. The results from the other serological examinations are given in Table 2. None of the goats positive for pestivirus aborted (titre 1 : 4). In the examination for herpesvirus (positive titre 1 : 2), the maximum titre of 1/256 was found in a goat that had a normal pregnancy. Antibodies against N. caninum and C. burnetii were not detected. All goats positive for C. psittaci had titres 1 : 20. The univariate and multivariate analyses revealed no signi®cant association between foetal loss and antibodies against herpesvirus or CAE-virus.
3.5. Foetal loss and predisposing factors Analysis of the predisposing in¯uence of various factors on the incidence of foetal loss was performed in the 20 herds, where infections could be ruled out as main cause of the problem. Individual goats in these herd were excluded if infections were detected or suspected as the cause of reproductive loss. A total of 1328 goats, of which 140 experienced foetal loss, were on this basis included in this part of the study. Some of the 67 recorded variables are presented graphically in Figs. 2±9 and 10±13. The variables chosen for graphical presentation are those most strongly associated with the incidence of foetal loss and also some other variables of special veterinary interest. On the basis of both correlation coef®cients and forward stepwise regressions, the following variables were associated with a high incidence of foetal loss: previous foetal loss; inferior natural lighting in the stable; pre-heated drinking water; and a combined feeding and milking platform. No association was found between the incidence of foetal loss and other health problems or routine ¯ock management procedures such as the feeding regime.
I.V. Engeland et al. / Small Ruminant Research 30 (1998) 37±48
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Figs. 2±9. Mean (SEM) incidence of foetal loss (f.l.) (%) from unidentified causes in 20 dairy goat herds with 1328 goats, of which 140 lost their foetus from unidentified causes. Stepwise regression showed statistically significant association with a high incidence of foetal loss for the variables marked `*'.
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Figs. 10±13. Incidence of foetal loss (%) from unidentified causes in 20 dairy goat herds with 1328 goats, of which 140 lost their foetus from unidentified causes. Stepwise regression showed no statistically significant association with a high incidence of foetal loss for these variables.
4. Discussion Under current systems of management in which male and female goats are housed together during the breeding season, most of the goats conceive (Williams, 1986). A teaser or breeding buck is best able to elicit and detect sign of oestrus in the doe. A goat in oestrus is generally easy to identify, as there is an obvious display of the signs of heat such as a plaintive voice, increased incidence of urination, decreased appetite, and a decrease in milk yield. The vulva also becomes somewhat swollen and the doe's tail wags vigorously (Smith and Sherman, 1994). On this basis, and since all farmers had a long experience with goats, a goat was presumed to be pregnant if she did not return to service within 6 weeks of mating. The 30 mated goats that were found to be empty at term may have experienced an early embryonic death with resorption of the embryo or abortion which was not recognised by the farmer. However, it is possible that a small number of these empty goats had not conceived, but instead had a prolonged luteal phase or established anoestrus.
The mean incidence (11.1%) of foetal loss found in the present study is similar to that reported by Melby et al. (1986) (8.5%) and Lùken (1990) (9.8%). The clinical manifestation of foetal loss varied between the herds. However, in most of the herds the foetal loss was characterised as follows: 1. 2. 3. 4. 5.
abortion of decomposed or mummi®ed foetuses; the affected doe was 3 years of age; the loss occurred after Day 90 of pregnancy; there were no symptoms of general disease; and infectious causes were not found.
Foetal loss was allocated to the day on which abortion or birth of a dead foetus occurred, but the time of foetal death was dif®cult to estimate. Ultrasound examination of goats that had received inoculations of T. gondii or pestivirus, showed that decomposed foetuses may have been dead less than one week before expulsion, and mummi®ed foetuses for over one week (Engeland et al., 1996; Lùken and BjerkaÊs, 1991). Based on these observations, 107(81%) of the 132 examined foetuses were probably aborted within one week of death.
I.V. Engeland et al. / Small Ruminant Research 30 (1998) 37±48
Based on microbiological examination, an etiologic diagnosis was made in only ®ve goats, from which L. monocytogenes was isolated. Of these, three belonged to Herd 13, where altogether four goats aborted and another four were empty. It is possible that early embryonic death had also occurred due to L. monocytogenes infection in the latter four goats. Serological indications of foetal death from toxoplasmosis were found in Herd 11. While not con®rming the presence of Toxoplasma abortion, the high titres (>1/1024) are strongly suggestive of this diagnosis as has been reported in sheep (Waldeland, 1977; Dubey, 1987) and goats (Dubey, 1981). In the goat with a titre of 1/256 in Herd 10, toxoplasmosis cannot be ruled out as cause of abortion. Another goat that aborted in this ¯ock was serological negative. Of the total of 152 other goats with foetal loss, 33 had titres in the 1/16±1/64 range. This is in the range commonly found in chronically infected animals, and it is unlikely that toxoplasmosis was the cause of abortion in any of these. Even if low titres may be observed in some goats that abort from toxoplasmosis, high titres should be found in other animals that abort in the same herd as observed in goats by Dubey (1981) and in sheep by Waldeland (1977). Although there is no report in the available literature on foetal loss in goats from infection with CAEvirus, the goats were also checked for antibodies against this virus which is widely distributed in Norway (Nord, 1994). The presence of antibodies against caprine herpesvirus were also studied as this infection causes vulvovaginitis in Norwegian goats during pregnancy (Hyllseth et al., 1985). There was no association between positive titres to CAE-virus or herpesvirus and foetal loss (Table 1). The serological examination for C. psittaci showed only low titres (1:20) or negative reactions, and microscopic examination of aborted material was negative. This micro-organism has never been found in aborted materials from sheep or goats in Norway, and positive reactions were probably due to cross-reactions with strains of C. psittaci responsible for extra-uterine infections such as conjunctivitis. Antibodies against N. caninum were not detected, and the histological examinations were negative. This parasite causes bovine abortion in the USA (Andersson et al., 1991), and has also been isolated from
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aborted foetuses from goats (Dubey et al., 1992; Barr et al., 1992). Since N. caninum has been detected in dogs in Norway (BjerkaÊs et al., 1984) and antibodies have been detected in Norwegian cattle (BjoÈrkman and Fossen, unpublished ®ndings 1995), infection with this parasite had to be considered in the present study. The minor importance of infections as a cause of foetal loss in goats found in the present study is in accordance with earlier reports (Melby et al., 1986; Lùken, 1990; Waldeland and Lùken, 1991). Older individuals are supposed to have acquired immunity to infectious abortifacients commonly present in the environment. Thus, in the present study, the occurrence of foetal loss mainly in goats that were 3 years or older supports the diagnosis of non-infectious causes. It should also be noted that both herds with, and without, reproductive problems participated in a cooperative breeding circle and also shared mountain pasture, which result in extensive contact between animals from the different herds. The conceptus presents antigens that are foreign to its mother. Protective immunological mechanisms responsible for the maintenance of pregnancy, as well immunological mechanisms responsible for pregnancy wastage exist (Beer and Billingham, 1978). Corbel (1972) demonstrated the production of antibodies to placental antigens in pregnant sheep infected in-utero with Aspergillus fumigatus. Of these 11 sheep, it was found that 10 aborted after 16-37 days. In the study by Waldeland and Lùken (1991), antibodies against placental tissues were not detected in sera from Norwegian goats that aborted. However, it still remains to be established whether other immunological mechanisms are involved in unexplained miscarriage in the goat. It appears that luteolysis was not the only precipitating factor for foetal loss in the present study, because 15 of the foetuses delivered dead at full term were twins to live kids. Many of these dead foetuses were decomposed. It is therefore possible that individual factors, possibly of a genetic nature, may be involved. However, knowledge of such factors is sparse, and further studies are needed to clarify this aspect of foetal loss in the goat. The analysis of the in¯uence of 67 various factors on the incidence of foetal loss was performed on 20 herds. One should keep in mind that analyses invol-
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ving so many variables may produce some signi®cant associations purely by chance. The incidence of foetal loss was signi®cantly correlated with the incidence in the previous years (Fig. 2). Some farmers have reported a pattern of occurrence of abortion in which abortion is a problem in a herd over a period of successive seasons followed by some years without major problems. After an interval, this pattern may recur. In the seven herds selected for retrospective studies, the variation in incidence of foetal loss seemed to follow a biphasic pattern during the 10-year period (Fig. 1). It is possible that the proportion of goats 3 years, which were found to be more prone to abort, was higher during the years 1987 to 1990. Goats that abort are usually culled, and replaced by younger animals. The lower incidence of foetal loss in these younger goats together with the increased proportion of younger goats may have resulted in a drop in the incidence of foetal loss during the following years. However, it was not possible to obtain information about the age distribution in the previous years to con®rm this hypothesis. In addition, some cases of previous foetal loss caused by infections may have been included in this result, since examinations of aborted materials and serological examinations were not performed in the previous years. Further studies in these seven herds concerning individual traits and various blood parameters and their relationship to reproductive performance are described elsewhere (Engeland et al., 1997, 1995). The natural light conditions in the stable seemed to affect the reproductive performance. In three of the four herds with light conditions judged as inferior (total windows area 2m2), the incidence of foetal loss was very high (Fig. 3). Although the lux intensity was not measured, it is nevertheless interesting that an association between this variable and the incidence of foetal loss was found. Knowledge of the effects of light on pregnancy is sparse, and further studies on this aspect of reproductive performance are required. Pre-heating of drinking water was also signi®cantly associated with increased incidence of foetal loss (Fig. 4). It is possible that micro-organisms in heated drinking water can multiply and produce toxins which may in¯uence the Corpus luteum and induce abortion. An increase in heavy metal, like copper and lead, may also be present in pre-heated drinking water. However, since the drinking water was pre-heated in only four of
the 20 herds, it is dif®cult to justify a general conclusion. The common design of buildings for goats in Norway is a central feeding passage with barrier to each side where the goats run free in pens. If milking is performed in the pens and not in a separate milking parlour, the common layout is a raised platform up to the feeding passage. The goats are ®xed in the feeding yokes when milked. There was a higher incidence of foetal loss in herds that used a combined feeding and milking platform (Fig. 5). The mean number of pens was lower (3.0 vs. 5.5), the mean number of goats in each pen higher (21 vs. 13) and the mean ¯oor space per goat smaller (0.6 m2 vs. 0.8 m2) than in the six herds without the combined feeding and milking platform. Higher numbers of goats in each pen and less ¯oor space per goat may constitute a situation of continuous stress that may inhibit luteal function and result in foetal loss. In sheep, management procedures such as con®nement, trucking, dipping and shearing have been found to increase the level of plasma cortisol (Kilgour and de Langen, 1970), which is commonly used as an indicator of stress. Thorburn et al. (1972) and Wentzel and Roelofse (1975) found that an elevated level of plasma cortisol may result in abortion in goats. Other variables concerning environmental conditions, diseases in the herd or routine ¯ock management procedures, such as the feeding regime, apparently, were not associated with the incidence of foetal loss (Figs. 6±13). It is surprising that indicators of a high general level of exposure of infection in a herd like high incidence of symptoms from the respiratory system, bad ventilation and participating in a cooperative breeding circle or shared mountain pasture and milking facilities during the summer revealed no such association. The same holds true for stress indicators such as inclement weather or handling of the animals several times during the gestation. 5. Conclusion In most herds, the foetal loss occurred in goats aged 3 years. Decomposed foetuses expelled during the last two month of pregnancy was the most common observation. There were no symptoms of general disease, and infectious causes played a minor role.
I.V. Engeland et al. / Small Ruminant Research 30 (1998) 37±48
The incidence of foetal loss was signi®cantly associated with previous loss in the herds. Some environmental conditions such as inferior natural lighting in the stable and a building design with a combined feeding and milking platform involving large and crowded pens were found to be associated with a high incidence of foetal loss. Variables associated with nonreproductive diseases in the herd or routine ¯ock management procedures were not found to have any in¯uence on foetal loss. Acknowledgements Financial support was received from the Research Council of Norway. References Andersson, M.L., Blanchard, P.C., Barr, B.C., Dubey, J.P., Hoffman, R.L., Conrad, P.A., 1991. Neospora-like protozoan infection as a major cause of abortion in California dairy cattle. J. Am. Vet. Med. Assoc. 198, 241±244. Barr, B.C., Anderson, M.L., Woods, L.W., Dubey, J.P., Conrad, P.A., 1992. Neospora-like protozoal infections associated with abortion in goats. J. Vet. Diagn. Invest. 4, 365±367. Beer, A.E., Billingham, R.E., 1978. Immunoregulatory aspects of pregnancy. Federation Proc. 37, 2374±2378. BjerkaÊs, I., Mohn, S.F., Presthus, I., 1984. Unidentified cystforming sporozoon causing encephalomyelitis and myositis in dogs. Z. Parasitenkd. 70, 271±274. BjerkaÊs, I., Presthus, J., 1988. Immuno-histochemical and ultrastructural characteristics of a cyst-forming sporozoon associated with encephalomyelitis and myositis in dogs. APMIS 96, 445±454. BjoÈrkman, C., LundeÂn, A., Holmdahl, J., Barber, J., Trees, A.J., Uggla, A., 1994. Neospora caninum in dogs: Detection of antibodies by ELISA using an iscom antigen. Parasite Immunol. 16, 643±648. Corbel, M.J., 1972. Production of antibodies to placental antigens by pregnant ewes experimentally infected with Aspergillus fumigatus. Br. Vet. J. 128, x1iv±x1vi. Cutlip, R.C., Jackson, T.A., Laird, G.A., 1977. Immunodiffusion test for ovine progressive pneumonia. Am. J. Vet. Res. 38, 1081±1084. Dubey, J.P., 1981. Epizootic toxoplasmosis associated with abortion in dairy goats in Montana. J. Am. Vet. Med. Assoc. 178, 661±670. Dubey, J.P., 1987. Serodiagnosis of postnatally and prenatally induced toxoplasmosis in sheep. Am. J. Vet. Res. 48, 1239± 1243. Dubey, J.P., Acland, H.M., Hamir, A.N., 1992. Neospora caninum (Apicomplexa) in a stillborn goat. J. Parasitol. 78, 532±534.
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Engeland, I.V., Waldeland, H., Andresen, é., Tverdal, A., 1997. Foetal loss in dairy goats: an epidemiological study in 515 individual goats. Anim. Reprod. Sci. 49, 45±53. Engeland, I.V., Ropstad, E., Andresen, é., Waldeland, H., Kindahl, H., Eik, L.O., Djùnne, B.K., Tverdal, A., 1995. Reproductive failure in dairy goats: The relationship between reproductive performance and certain blood parameters In: I.V. Engeland (Dr. scient. thesis), Reproductive failure in goats. Norwegian College of Veterinary Medicine, Oslo, pp. 59±83. Engeland, I.V., Waldeland, H., Kindahl, H., Ropstad, E., Andresen, é., 1996. Effect of Toxoplasma gondii infection on the development of pregnancy and on endocrine foetal±placental function in the goat. Anim. Reprod. Sci. 67, 61±74. Hussain, Q., Waldeland, H., Havrevoll, é., Eik, L.O., Andresen, é., Engeland, I.V., 1996. Effects of type of roughage and energy level on reproductive performance in pregnant goats. Small Rumin. Res. 21, 97±103. Hyllseth, B., Andresen, é., Larsen, H.J., 1985. Genital herpesvirus infection in goats in Norway. Abstract, 44. Proceedings of the 1985 Symposium of European Society Against Virus Disease, Oslo, Norway. Kilgour, R., de Langen, H., 1970. Stress in sheep resulting from management practices. Proc. N. Z. Soc. Anim. Prod. 30, 65±76. Lùken, T., Hyllseth, B., Larsen, H.J., 1982. Border disease in Norway. Serological examination of affected sheep flocks. Acta Vet. Scand. 23, 46±52. Lùken, T., 1990. Pestivirus infection in Norway. Epidemiological studies in goats. J. Comp. Pathol. 103, 1±10. Lùken, T., BjerkaÊs, I., 1991. Experimental pestivirus infections in pregnant goats. J. Comp. Pathol. 105, 123±140. Melby, H.P., Aursjù, J., Binde, M., Grùnstùl, H., 1986. Diseases and mortality in 27 dairy goat farms. Nord. Vet. Med. 38, 403± 411. Merrall, M., 1985. The aborting goat. Proceedings of a course in goat husbandry and medicine. Massay University, N. Z., Publ. No. 106, Veterinary Continuing Education, pp. 181±198. Nord, K., 1994. Prevalence of antibodies to caprine arthritis encephalitis virus and control of the disease in Norway. In: Hansson S.J. (Ed.), XVII Nordic Veterinary Congress, 26±29 July, 1994, Reykjavik, Iceland, Proceedings and Abstracts, vol. 1, p. 116. Orr, M., Montgomery, H., Gill, J., Smith, R., 1987. Abortion in goats: A field study. Surveillance 14, 5±6. Smith, M.C., Sherman, D.M., 1994. Reproductive system, in Smith M.C., Sherman, D.M. (Eds.), Goat Medicine. Lea and Febiger, Philadelphia, pp. 411±463. Thorburn, G.D., Nicol, D.H., Bassett, J.M., Shutt, D.A., Cox, R.I., 1972. Parturition in the goat and sheep: Changes in corticosteroids, progesterone, oestrogens and prostaglandin F. J. Reprod. Fertil. Suppl. 16, 61±84. Van der Westhuysen, J.M., Roelofse, C.S., 1971. Effect of shelter and different levels of dietary energy and protein on reproductive performance in Angora goats with special reference to the habitual aborter. Agroanimalia 3, 129±132. Waldeland, H., 1976a. Toxoplasmosis in sheep. The relative importance of the infection as a cause of reproductive loss in sheep in Norway, Acta Vet. Scand. 17, pp. 412±425.
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Waldeland, H., 1976b. Toxoplasmosis in sheep. The reliability of a microtiter system in Sabin and Feldman's dye test, Acta Vet. Scand. 17, pp. 426±431. Waldeland, H., 1977. Toxoplasmosis in sheep. Influence of various factors on the antibody contents. Acta Vet. Scand. 18, 237±247. Waldeland, H., Lùken, T., 1991. Reproductive failure in goats in Norway: An investigation in 24 herds. Acta Vet. Scand. 32, 535±541. Wentzel, D., Morgenthal, J.C., Van Niekerk, C.H., Roelofse, C.S., 1974. The habitually aborting Angora doe: II. The effect of an
energy deficiency on the incidence of abortion. Agroanimalia 6, 129±132. Wentzel, D., Roelofse, C.S., 1975. The habitually aborting Angora doe. VII. Induction of abortion by administration of cortisone acetate. Agroanimalia 7, 45±48. Wentzel, D., 1982. Non-infections abortion in Angora goats. Proceedings. Third International Conference on Goat Production and Disease, Tucson, Arizona, pp. 155±161. Williams, C.S.F., 1986. Pregnancy diagnosis. In: Morrow D.A. (Ed), Current Therapy in Theriogenology. 2nd. edn., Saunders, Philadelphia, pp. 587±588.
Foetal loss in dairy goats: An epidemiological study in 22 herds Inge Vogt Engelanda,*, Harald Waldelandb, éystein Andresena, Torleiv Lùken1,c, Camilla BjoÈrkmand, Inge BjerkaÊse a
Department of Reproduction and Forensic Medicine, Norwegian College of Veterinary Medicine, P.O. Box 8146 Dep., NO-0033 Oslo, Norway b Department of Sheep and Goat Research, Norwegian College of Veterinary Medicine, P.O. Box 264, NO-4301 Sandnes, Norway c Central Veterinary Laboratory, NO-0033 Oslo, Norway d Department of Cattle and Sheep Diseases, Swedish University of Agricultural Sciences, P.O. Box 7019, SE-750 07 Uppsala, Sweden e Department of Morphology, Genetics and Aquatic Biology, Norwegian College of Veterinary Medicine, P.O. Box 8146 Dep., NO-0033 Oslo, Norway Accepted 19 November 1997
Abstract In this study, 22 herds comprising 1439 dairy goats presumed to be pregnant were studied during the gestation period 1990± 91. Altogether, 160(11.1% of the total number of goats) experienced foetal loss following conception. In all, 85(53%) of these goats aborted, 45(28%) delivered dead foetuses at full term and from 30(19%) goats no discharge or foetus was observed. The incidence of foetal loss in the different herds varied from 3±38%. The proportion of foetal loss was >20% in three herds comprising a total of 169 goats. In 10 herds comprising 677 goats the proportion of foetal losses were <10%. In most of the herds, the foetal loss occurred in goats aged 3 years. Decomposed foetuses expelled during the last 2 months of pregnancy was the most common observation. Usually, no other symptoms of disease were observed. Listeric abortion was diagnosed in ®ve (3.1%) goats and in seven (4.3%) goats serological or parasitological examination indicated foetal loss from toxoplasmosis. A herd history of foetal loss was signi®cantly associated with a high incidence of loss during the present examination. Other diseases and routine ¯ock management procedures were not found to be signi®cant. However, some environmental conditions such as inferior natural lighting in the stables, pre-heated drinking water and a building design with a combined feeding and milking platform involving large and crowded pens were associated with a high incidence of foetal loss. # 1998 Elsevier Science B.V. All rights reserved. Keywords: Goat; Abortion; Foetal loss; Epidemiology; Questionnaires
1. Introduction *Corresponding author. Tel.: 0047 2296 4853; fax: 0047 2256 5704; e-mail: [email protected] 1 Present address: Department of Large Animal Clinical Sciences, Norwegian College of Veterinary Medicine, P.O. Box 8146 Dep., NO-0033 Oslo, Norway.
Foetal loss is a serious problem in Norwegian goat husbandry. Melby et al. (1986) found an abortion rate of 8.5% in 27 goat herds, whereas 1.2% of the goats had pseudopregnancy and 3.2% either returned to service or were empty. In an epidemiological study
0921-4488/98/$ ± see front matter # 1998 Elsevier Science B.V. All rights reserved. PII S0921-4488(98)00084-4
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in 30 herds, Lùken (1990) observed foetal loss in 9.8% of the does. Waldeland and Lùken (1991) studied the incidence of foetal loss in 24 selected goat herds, and found that 15.6% of the animals either aborted, delivered dead kids at full term, or were empty. In that study Listeria monocytogenes or Toxoplasma gondii was found to be the cause of foetal loss in only 9(2.4%) out of 369 goats. Corresponding results have also been reported from other countries (Wentzel, 1982; Merrall, 1985; Orr et al., 1987). These reports suggest that abortion in goats from non-identi®ed causes constitutes a substantial loss. Since infectious causes were found in relatively few cases of foetal loss in goats in Norway, Waldeland and Lùken (1991) suggested that nutritional and environmental factors may be important. In studies on South African Angora goats, submaintenance energy feeding during pregnancy was found to increase the incidence of abortion (Van der Westhuysen and Roelofse, 1971; Wentzel et al., 1974). Recent experiments on Norwegian goats revealed that feeding with silage of poor quality from aerobically damaged round bales during the indoor period combined with low energy intake between 91±120 days of gestation increased the rate of abortion (Hussain et al., 1996). The aim of the present study was to survey foetal loss in dairy goats under ®eld conditions, and to investigate the in¯uence of various herd factors related to disease, environment and management procedures on the incidence of foetal loss from unidenti®ed causes. 2. Materials and methods 2.1. Herds and management We studied 22 commercial dairy herds comprising a total of 1498 goats in the region of Hallingdal and Valdres in Norway. Most of the goats were of the Norwegian breed, while a few were crosses between the Norwegian and Saanen breeds. The goats were kept outdoors during daytime for the ®rst month after mating, and indoors for the rest of the pregnancy. Inclement weather during the gestation period were recorded. In one herd, most of the goats were mated during July, and in the other herds mating mostly occurred in
August or September. A few goats (5%) were arti®cially inseminated. All farmers kept one or two bucks in a separate pen during the whole breeding season and gestation period. During the ®rst two months after the mating started, all goats were observed for oestrus in the presence of a buck twice daily. The goats were hand-mated and the dates of mating registered. Goats were carefully observed for oestrus in the presence of a buck for 10±15 min twice daily 19±23 days after mating, and again at days 40±44. A goat was presumed to be pregnant if signs of oestrus were not observed in the latter two periods. Only goats presumed to be pregnant, totally 1439, were included in the study. The goats were fed grass silage (19 herds) or hay (3 herds) ad-libitum during pregnancy. In 16 of the herds fed silage, smaller amounts of hay were also given. In addition, the animals were individually fed commercial concentrates containing proteins, vitamins and minerals. The quantity of concentrates offered was reduced for a short period in the last half of pregnancy to terminate milk production. Foot trimming was carried out once or twice during pregnancy. Treatment against nematodes and lice during the second month of pregnancy, shearing during the third month of pregnancy and vaccination against clostridial infections prior to kidding were done in most herds. 2.2. Design of the study The study was based on herd as the unit of analysis with the incidence of foetal loss as the dependent variable. Foetal loss was de®ned as either abortion, delivery of an immature dead foetus or foetal remnants at full term, or being empty at term after having been registered as pregnant. Abortion was de®ned as expulsion of an immature foetus or of bloody vaginal discharges. The farmers checked the goats twice each day for any sign of abortion throughout pregnancy. The date of foetal loss was recorded. The herds were visited three or four times during the gestation period. During these visits, questionnaires on 67 subjects were ®lled out. The questions covered different aspects concerning diseases in the herds, environmental conditions such as building design and natural light conditions in the stable, and ¯ock management procedures such as feeding and vaccina-
I.V. Engeland et al. / Small Ruminant Research 30 (1998) 37±48
tion routines. Herds with an incidence of foetal loss >10% during the last three years, were de®ned as having previous foetal loss. Rooms for 35 goats with 2m2 windows, were de®ned as having inferior natural lighting. All variables were recorded, if possible, before the outcome of pregnancy was known. A herd was visited when a goat aborted or delivered an immature dead foetus. The goats were observed clinically and materials for laboratory examinations were collected. Samples from vaginal discharges were collected on swabs (swab transport pack, Amies medium, Difco) from goats that were suspected of having aborted. All farms were also visited after the kidding season to record the total reproductive performance. Aborted materials from the goats were examined for infectious agents known to cause reproductive loss. Serological screening was also done for certain other diseases prevalent in Norway. Information on the incidence of foetal loss during the 10-year period from 1984/85 to 1993/94 in herds 1±7 were obtained from the farmers' records. These herds were selected mainly on the basis of foetal loss from 1987±1990, when the incidence was >15% in ®ve of the seven herds and <13% in the remaining two herds. 2.3. Examination of aborted material Aborted foetuses and foetal membranes were subjected to gross inspection, routine bacteriological examination, modi®ed Ziehl Neelsen staining (Waldeland and Lùken, 1991) and examination for T. gondii (Waldeland, 1976a). The swabs collected from vaginal discharges were subjected to bacteriological examination. Materials for histological examination for Neospora caninum were obtained from diencephalon/cerebrum from foetuses aborted in a suitable fresh condition. Brain sections, ®xed in 10% neutral, buffered formalin and embedded in paraf®n, were stained with haematoxylin and eosin and immunostained by the avidin±biotin peroxidase complex method (Vector Laboratories, Burlingame, CA, USA) (BjerkaÊs and Presthus, 1988), using rabbit anti-N. caninum antibodies as the primary antiserum (obtained from Dr. J.P. Dubey, Agricultural Research Service, MD, USA). Sections from a dog with neosporosis were included as positive controls.
39
2.4. Serological examinations All goats in herds 1±7 were bled during the ®rst month of pregnancy and again after foetal loss or kidding. Goats with foetal loss in the other 15 herds were bled immediately after the loss was detected. Goats found empty at term were bled after the expected date of delivery. Serum samples were stored at ÿ208C until the time of analysis. All sera collected from goats with foetal loss were examined for antibodies against T. gondii by the Sabin±Feldman dye test (Waldeland, 1976b). The sera collected in herds 1±7 were examined for neutralising antibodies at twofold dilutions against the cytopathogenic NADL strain of bovine pestivirus and a Norwegian isolate of caprine herpesvirus (kindly supplied by Prof. B. Hylseth, Norwegian College of Veterinary Medicine) (Lùken et al., 1982). Undiluted sera were screened in immunodiffusion test for antibodies against caprine arthritis encephalitis (CAE) virus (Capriclear 300 test kit, Central Veterinary Laboratory, Weybridge, Surrey, UK) (Cutlip et al., 1977) (see Table 2). Sera from the goats with foetal loss in herds 1±7 were also examined in complement ®xation tests at twofold dilutions for antibodies against Chlamydia psittaci (Ornithosis antigens, Behringwerke AG, Marburg, Germany) and Coxiella burnetii (Q-fever antigen, Behringwerke AG, Marburg, Germany) (Waldeland and Lùken, 1991). These sera were also diluted in twofold dilutions from 1 : 20 and analysed for the presence of antibodies to N. caninum with an indirect ¯uorescent antibody test (IFAT) as modi®ed by BjoÈrkman et al. (1994), as were sera selected at random from 27 animals with normal pregnancy. 2.5. Statistical analysis Correlation coef®cients between the herd incidence of foetal loss of unidenti®ed causes and each of the recorded variables were calculated. Furthermore, a stepwise forward regression analysis with, and without weighting for the herd-size effect was performed. The variables with the highest absolute value of the correlation coef®cients and variables which remained in the ®nal step of the regression procedure were selected for graphical presentation. Some variables of special veterinary interest are also presented graphically.
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Data from examinations for herpesvirus and CAEvirus were subjected to univariate and multivariate logistic regression analysis. 3. Results 3.1. Outcome of pregnancy Of the total of 1498 goats, 59 were omitted from the study either due to hydrometra (8 goats), slaughtering (24 goats), slaughtering because of lack of sign of oestrous (11 goats), sale (6 goats), dead because of mastitis (1 goat), dead because of chronic pneumonia (1 goat) or because they did not conceive (8 goats). The incidences of foetal loss in the 22 herds with a total of 1439 goats presumed to be pregnant are shown in Table 1. The rate of goats with foetal loss in the
different herds varied from 3±38%. In three herds (Nos. 1, 6 and 21) comprising 169 goats, >20% of the does had foetal loss. In 10 other herds comprising 677 goats, the rate was <10%. Altogether, 160(11.1%) of the 1439 goats experienced foetal loss, of which 85(53%) aborted, 45(28%) delivered dead foetuses at full term and 30(19%) were found empty at term after having been registered as pregnant. Out of the 45 goats that delivered a dead foetus at full term, 15 also delivered a live twin kid. Also, 40(30%) goats experienced foetal loss before Day 91 of gestation, 45(35%) between Day 90 and 141 and 45(35%) after Day 140. Only ®ve goats that aborted showed anorexia and fever in connection with abortion. Of these, three goats belonged to Herd 13, and the remaining two goats to herds 7 and 18, respectively. The prevalence of foetal loss increased with age. Only 7% of goats 2 years lost their foetus, while the ®gure for goats 3 years was 18%.
Table 1 Foetal loss during one gestation in 22 dairy goat herds Herd No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Total a
Number of goats total
empty a
aborted
delivered dead foetuses at full term
total with foetal loss
73 64 74 90 78 59 78 63 60 105 49 51 59 85 37 50 80 93 52 54 37 48 1439
1 2 0 1 2 1 1 0 0 0 5 2 4 0 0 0 1 0 0 1 6 3 30
4 2 5 4 8 10 6 5 3 3 3 0 4 5 1 2 2 2 1 7 6 2 85
12 2 5 5 5 3 1 2 0 0 1 0 0 0 0 0 1 2 2 0 2 2 45
17 6 10 10 15 14 8 7 3 3 9 2 8 5 1 2 4 4 3 8 14 7 160
Found empty at term after having been registered as pregnant.
Incidence of foetal loss (%)
23.3 9.4 13.5 11.1 19.2 23.7 10.3 11.1 5.0 2.9 18.4 3.9 13.6 5.9 2.7 4.0 5.0 4.3 5.8 14.8 37.8 14.6 11.1
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41
Fig. 1. Mean (SEM) incidence of foetal loss in seven dairy goat herds during the gestation periods 1984/85 to 1993/94.
No connection was found between foetal loss and routine ¯ock management procedures such as vaccination, treatment for endo- and ectoparasites or foot trimming. Changes in the weather did not seem to in¯uence the outcome of pregnancy. The mean incidence (SEM) of foetal loss in herds 1±7 for the gestation periods 1984/85±1993/94 are shown in Fig. 1. The mean incidence and standard error of the mean during all 10 years was 13.75.0%. In one of these herds, the mean incidence of foetal loss was below 10% during this period. In the other herds, the main trend was an increasing level during the ®rst part of the period, followed by a decline.
foetuses were delivered together with a live twin. Also, two goats delivered triplets comprising one normal live kid, one stillborn and one decomposed foetus. Malformation of the skeleton was seen in one of the dead triplets from a doe in Herd 7. In 15 herds, most of the aborted foetuses had a decomposed appearance. In all herds, 50% or more of the foetuses were decomposed or mummi®ed. No signi®cant histo-pathological lesions were found in the 23 examined foetal brains. The immunostaining for N. caninum was negative.
3.2. Examination of aborted materials
No infectious agent was isolated from 125(95%) of the 132 aborted or stillborn kids. In Herd 13, L. monocytogenes was isolated from two aborted sets of twins and also from the vaginal discharges of another doe, where no foetus was observed. This agent was also isolated from a total of three foetuses from two goats in herds 7 and 18, respectively (Table 2). No other signi®cant organisms were detected by microscopy or by culture from the maternal placental tissues, foetal stomach contents or organs.
Dead foetuses, foetal remnants or vaginal discharges were registered in a total of 130 goats. Altogether, 132 foetuses from 102 goats and 12 swabs of vaginal discharges from 12 other goats were examined. From the remaining 16 goats, materials were not examined due to circumstances out of our control. Of the examined foetuses, 21(16%) had a relatively fresh appearance, 25(19%) were mummi®ed to various degrees and 86(65%) were decomposed. In eight of the latter cases, the number of foetuses were dif®cult to estimate due to advanced decomposition or maceration. Further, four foetuses with a relatively fresh appearance and nine decomposed or mummi®ed
3.3. Microbiological examination
3.4. Serological examinations Indication of abortion from infection with T. gondii (titre 1 : 1024) was found in six of the nine goats
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Table 2 Serological examination of goats with foetal loss, and microbiological examination of aborted materials Microorganism
Toxoplasma gondii a Listeria monocytogenes b Pestivirus c Caprine herpesvirus c CAE-virus d Neospora caninum e Chlamydia psittaci f Coxiella burnetii f
Number of: examined goats with normal pregnancy
examined goats with foetal loss
herds represented
positive goats with normal pregnancy
positive goats with foetal loss
positive herds
0 0 436 436 436 27 0 0
160 114 80 80 80 80 80 80
22 21 7 7 7 7 7 7
± ± 4 169 74 0 ± ±
8g 5 0 29 19 0 20 h 0
3 3 3 7 7 0 3 0
a
Sabin±Feldman dye test; titres 1 : 256. Bacteriological examination. c Neutralisation test; positive titres for pestivirus 1 : 4; for herpesvirus 1 : 2. d Immunodiffusion test; screening of undiluted sera. e Indirect fluorescent antibody test; positive titres 1:40. f Complement fixation test; positive titres for Chlamydia psittaci 1 : 5; for Coxiella burnetii 1 : 2. g Six goats had titres 1 : 1024, and two had titres of 1 : 256. T. gondii was not detected from a fresh foetus of one of the goats with titre 1 : 256, and from the remainder, the foetus was too decomposed for parasitological examination. h Elementary bodies indicating Chlamydia psittasi were not detected in any of the foetuses or placentas by staining with modified Ziehl Neelsen. b
examined in Herd 11. One of the goats that aborted from each of the herds 10 and 22 had a titre of 1 : 256 (Table 2). One of these two goats (Herd 22) gave birth to a relatively fresh dead foetus with one live kid. T. gondii was not detected in the aborted materials. From the other seropositive goat (Herd 10), the aborted materials were too decomposed for parasitological examination. In the other goats that aborted the titres against T. gondii ranged from negative to 1/64 by the dye test. Conversion from negative to positive titres was not observed in any of the goats that aborted in herds 1±7. The results from the other serological examinations are given in Table 2. None of the goats positive for pestivirus aborted (titre 1 : 4). In the examination for herpesvirus (positive titre 1 : 2), the maximum titre of 1/256 was found in a goat that had a normal pregnancy. Antibodies against N. caninum and C. burnetii were not detected. All goats positive for C. psittaci had titres 1 : 20. The univariate and multivariate analyses revealed no signi®cant association between foetal loss and antibodies against herpesvirus or CAE-virus.
3.5. Foetal loss and predisposing factors Analysis of the predisposing in¯uence of various factors on the incidence of foetal loss was performed in the 20 herds, where infections could be ruled out as main cause of the problem. Individual goats in these herd were excluded if infections were detected or suspected as the cause of reproductive loss. A total of 1328 goats, of which 140 experienced foetal loss, were on this basis included in this part of the study. Some of the 67 recorded variables are presented graphically in Figs. 2±9 and 10±13. The variables chosen for graphical presentation are those most strongly associated with the incidence of foetal loss and also some other variables of special veterinary interest. On the basis of both correlation coef®cients and forward stepwise regressions, the following variables were associated with a high incidence of foetal loss: previous foetal loss; inferior natural lighting in the stable; pre-heated drinking water; and a combined feeding and milking platform. No association was found between the incidence of foetal loss and other health problems or routine ¯ock management procedures such as the feeding regime.
I.V. Engeland et al. / Small Ruminant Research 30 (1998) 37±48
43
Figs. 2±9. Mean (SEM) incidence of foetal loss (f.l.) (%) from unidentified causes in 20 dairy goat herds with 1328 goats, of which 140 lost their foetus from unidentified causes. Stepwise regression showed statistically significant association with a high incidence of foetal loss for the variables marked `*'.
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Figs. 10±13. Incidence of foetal loss (%) from unidentified causes in 20 dairy goat herds with 1328 goats, of which 140 lost their foetus from unidentified causes. Stepwise regression showed no statistically significant association with a high incidence of foetal loss for these variables.
4. Discussion Under current systems of management in which male and female goats are housed together during the breeding season, most of the goats conceive (Williams, 1986). A teaser or breeding buck is best able to elicit and detect sign of oestrus in the doe. A goat in oestrus is generally easy to identify, as there is an obvious display of the signs of heat such as a plaintive voice, increased incidence of urination, decreased appetite, and a decrease in milk yield. The vulva also becomes somewhat swollen and the doe's tail wags vigorously (Smith and Sherman, 1994). On this basis, and since all farmers had a long experience with goats, a goat was presumed to be pregnant if she did not return to service within 6 weeks of mating. The 30 mated goats that were found to be empty at term may have experienced an early embryonic death with resorption of the embryo or abortion which was not recognised by the farmer. However, it is possible that a small number of these empty goats had not conceived, but instead had a prolonged luteal phase or established anoestrus.
The mean incidence (11.1%) of foetal loss found in the present study is similar to that reported by Melby et al. (1986) (8.5%) and Lùken (1990) (9.8%). The clinical manifestation of foetal loss varied between the herds. However, in most of the herds the foetal loss was characterised as follows: 1. 2. 3. 4. 5.
abortion of decomposed or mummi®ed foetuses; the affected doe was 3 years of age; the loss occurred after Day 90 of pregnancy; there were no symptoms of general disease; and infectious causes were not found.
Foetal loss was allocated to the day on which abortion or birth of a dead foetus occurred, but the time of foetal death was dif®cult to estimate. Ultrasound examination of goats that had received inoculations of T. gondii or pestivirus, showed that decomposed foetuses may have been dead less than one week before expulsion, and mummi®ed foetuses for over one week (Engeland et al., 1996; Lùken and BjerkaÊs, 1991). Based on these observations, 107(81%) of the 132 examined foetuses were probably aborted within one week of death.
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Based on microbiological examination, an etiologic diagnosis was made in only ®ve goats, from which L. monocytogenes was isolated. Of these, three belonged to Herd 13, where altogether four goats aborted and another four were empty. It is possible that early embryonic death had also occurred due to L. monocytogenes infection in the latter four goats. Serological indications of foetal death from toxoplasmosis were found in Herd 11. While not con®rming the presence of Toxoplasma abortion, the high titres (>1/1024) are strongly suggestive of this diagnosis as has been reported in sheep (Waldeland, 1977; Dubey, 1987) and goats (Dubey, 1981). In the goat with a titre of 1/256 in Herd 10, toxoplasmosis cannot be ruled out as cause of abortion. Another goat that aborted in this ¯ock was serological negative. Of the total of 152 other goats with foetal loss, 33 had titres in the 1/16±1/64 range. This is in the range commonly found in chronically infected animals, and it is unlikely that toxoplasmosis was the cause of abortion in any of these. Even if low titres may be observed in some goats that abort from toxoplasmosis, high titres should be found in other animals that abort in the same herd as observed in goats by Dubey (1981) and in sheep by Waldeland (1977). Although there is no report in the available literature on foetal loss in goats from infection with CAEvirus, the goats were also checked for antibodies against this virus which is widely distributed in Norway (Nord, 1994). The presence of antibodies against caprine herpesvirus were also studied as this infection causes vulvovaginitis in Norwegian goats during pregnancy (Hyllseth et al., 1985). There was no association between positive titres to CAE-virus or herpesvirus and foetal loss (Table 1). The serological examination for C. psittaci showed only low titres (1:20) or negative reactions, and microscopic examination of aborted material was negative. This micro-organism has never been found in aborted materials from sheep or goats in Norway, and positive reactions were probably due to cross-reactions with strains of C. psittaci responsible for extra-uterine infections such as conjunctivitis. Antibodies against N. caninum were not detected, and the histological examinations were negative. This parasite causes bovine abortion in the USA (Andersson et al., 1991), and has also been isolated from
45
aborted foetuses from goats (Dubey et al., 1992; Barr et al., 1992). Since N. caninum has been detected in dogs in Norway (BjerkaÊs et al., 1984) and antibodies have been detected in Norwegian cattle (BjoÈrkman and Fossen, unpublished ®ndings 1995), infection with this parasite had to be considered in the present study. The minor importance of infections as a cause of foetal loss in goats found in the present study is in accordance with earlier reports (Melby et al., 1986; Lùken, 1990; Waldeland and Lùken, 1991). Older individuals are supposed to have acquired immunity to infectious abortifacients commonly present in the environment. Thus, in the present study, the occurrence of foetal loss mainly in goats that were 3 years or older supports the diagnosis of non-infectious causes. It should also be noted that both herds with, and without, reproductive problems participated in a cooperative breeding circle and also shared mountain pasture, which result in extensive contact between animals from the different herds. The conceptus presents antigens that are foreign to its mother. Protective immunological mechanisms responsible for the maintenance of pregnancy, as well immunological mechanisms responsible for pregnancy wastage exist (Beer and Billingham, 1978). Corbel (1972) demonstrated the production of antibodies to placental antigens in pregnant sheep infected in-utero with Aspergillus fumigatus. Of these 11 sheep, it was found that 10 aborted after 16-37 days. In the study by Waldeland and Lùken (1991), antibodies against placental tissues were not detected in sera from Norwegian goats that aborted. However, it still remains to be established whether other immunological mechanisms are involved in unexplained miscarriage in the goat. It appears that luteolysis was not the only precipitating factor for foetal loss in the present study, because 15 of the foetuses delivered dead at full term were twins to live kids. Many of these dead foetuses were decomposed. It is therefore possible that individual factors, possibly of a genetic nature, may be involved. However, knowledge of such factors is sparse, and further studies are needed to clarify this aspect of foetal loss in the goat. The analysis of the in¯uence of 67 various factors on the incidence of foetal loss was performed on 20 herds. One should keep in mind that analyses invol-
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I.V. Engeland et al. / Small Ruminant Research 30 (1998) 37±48
ving so many variables may produce some signi®cant associations purely by chance. The incidence of foetal loss was signi®cantly correlated with the incidence in the previous years (Fig. 2). Some farmers have reported a pattern of occurrence of abortion in which abortion is a problem in a herd over a period of successive seasons followed by some years without major problems. After an interval, this pattern may recur. In the seven herds selected for retrospective studies, the variation in incidence of foetal loss seemed to follow a biphasic pattern during the 10-year period (Fig. 1). It is possible that the proportion of goats 3 years, which were found to be more prone to abort, was higher during the years 1987 to 1990. Goats that abort are usually culled, and replaced by younger animals. The lower incidence of foetal loss in these younger goats together with the increased proportion of younger goats may have resulted in a drop in the incidence of foetal loss during the following years. However, it was not possible to obtain information about the age distribution in the previous years to con®rm this hypothesis. In addition, some cases of previous foetal loss caused by infections may have been included in this result, since examinations of aborted materials and serological examinations were not performed in the previous years. Further studies in these seven herds concerning individual traits and various blood parameters and their relationship to reproductive performance are described elsewhere (Engeland et al., 1997, 1995). The natural light conditions in the stable seemed to affect the reproductive performance. In three of the four herds with light conditions judged as inferior (total windows area 2m2), the incidence of foetal loss was very high (Fig. 3). Although the lux intensity was not measured, it is nevertheless interesting that an association between this variable and the incidence of foetal loss was found. Knowledge of the effects of light on pregnancy is sparse, and further studies on this aspect of reproductive performance are required. Pre-heating of drinking water was also signi®cantly associated with increased incidence of foetal loss (Fig. 4). It is possible that micro-organisms in heated drinking water can multiply and produce toxins which may in¯uence the Corpus luteum and induce abortion. An increase in heavy metal, like copper and lead, may also be present in pre-heated drinking water. However, since the drinking water was pre-heated in only four of
the 20 herds, it is dif®cult to justify a general conclusion. The common design of buildings for goats in Norway is a central feeding passage with barrier to each side where the goats run free in pens. If milking is performed in the pens and not in a separate milking parlour, the common layout is a raised platform up to the feeding passage. The goats are ®xed in the feeding yokes when milked. There was a higher incidence of foetal loss in herds that used a combined feeding and milking platform (Fig. 5). The mean number of pens was lower (3.0 vs. 5.5), the mean number of goats in each pen higher (21 vs. 13) and the mean ¯oor space per goat smaller (0.6 m2 vs. 0.8 m2) than in the six herds without the combined feeding and milking platform. Higher numbers of goats in each pen and less ¯oor space per goat may constitute a situation of continuous stress that may inhibit luteal function and result in foetal loss. In sheep, management procedures such as con®nement, trucking, dipping and shearing have been found to increase the level of plasma cortisol (Kilgour and de Langen, 1970), which is commonly used as an indicator of stress. Thorburn et al. (1972) and Wentzel and Roelofse (1975) found that an elevated level of plasma cortisol may result in abortion in goats. Other variables concerning environmental conditions, diseases in the herd or routine ¯ock management procedures, such as the feeding regime, apparently, were not associated with the incidence of foetal loss (Figs. 6±13). It is surprising that indicators of a high general level of exposure of infection in a herd like high incidence of symptoms from the respiratory system, bad ventilation and participating in a cooperative breeding circle or shared mountain pasture and milking facilities during the summer revealed no such association. The same holds true for stress indicators such as inclement weather or handling of the animals several times during the gestation. 5. Conclusion In most herds, the foetal loss occurred in goats aged 3 years. Decomposed foetuses expelled during the last two month of pregnancy was the most common observation. There were no symptoms of general disease, and infectious causes played a minor role.
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The incidence of foetal loss was signi®cantly associated with previous loss in the herds. Some environmental conditions such as inferior natural lighting in the stable and a building design with a combined feeding and milking platform involving large and crowded pens were found to be associated with a high incidence of foetal loss. Variables associated with nonreproductive diseases in the herd or routine ¯ock management procedures were not found to have any in¯uence on foetal loss. Acknowledgements Financial support was received from the Research Council of Norway. References Andersson, M.L., Blanchard, P.C., Barr, B.C., Dubey, J.P., Hoffman, R.L., Conrad, P.A., 1991. Neospora-like protozoan infection as a major cause of abortion in California dairy cattle. J. Am. Vet. Med. Assoc. 198, 241±244. Barr, B.C., Anderson, M.L., Woods, L.W., Dubey, J.P., Conrad, P.A., 1992. Neospora-like protozoal infections associated with abortion in goats. J. Vet. Diagn. Invest. 4, 365±367. Beer, A.E., Billingham, R.E., 1978. Immunoregulatory aspects of pregnancy. Federation Proc. 37, 2374±2378. BjerkaÊs, I., Mohn, S.F., Presthus, I., 1984. Unidentified cystforming sporozoon causing encephalomyelitis and myositis in dogs. Z. Parasitenkd. 70, 271±274. BjerkaÊs, I., Presthus, J., 1988. Immuno-histochemical and ultrastructural characteristics of a cyst-forming sporozoon associated with encephalomyelitis and myositis in dogs. APMIS 96, 445±454. BjoÈrkman, C., LundeÂn, A., Holmdahl, J., Barber, J., Trees, A.J., Uggla, A., 1994. Neospora caninum in dogs: Detection of antibodies by ELISA using an iscom antigen. Parasite Immunol. 16, 643±648. Corbel, M.J., 1972. Production of antibodies to placental antigens by pregnant ewes experimentally infected with Aspergillus fumigatus. Br. Vet. J. 128, x1iv±x1vi. Cutlip, R.C., Jackson, T.A., Laird, G.A., 1977. Immunodiffusion test for ovine progressive pneumonia. Am. J. Vet. Res. 38, 1081±1084. Dubey, J.P., 1981. Epizootic toxoplasmosis associated with abortion in dairy goats in Montana. J. Am. Vet. Med. Assoc. 178, 661±670. Dubey, J.P., 1987. Serodiagnosis of postnatally and prenatally induced toxoplasmosis in sheep. Am. J. Vet. Res. 48, 1239± 1243. Dubey, J.P., Acland, H.M., Hamir, A.N., 1992. Neospora caninum (Apicomplexa) in a stillborn goat. J. Parasitol. 78, 532±534.
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Engeland, I.V., Waldeland, H., Andresen, é., Tverdal, A., 1997. Foetal loss in dairy goats: an epidemiological study in 515 individual goats. Anim. Reprod. Sci. 49, 45±53. Engeland, I.V., Ropstad, E., Andresen, é., Waldeland, H., Kindahl, H., Eik, L.O., Djùnne, B.K., Tverdal, A., 1995. Reproductive failure in dairy goats: The relationship between reproductive performance and certain blood parameters In: I.V. Engeland (Dr. scient. thesis), Reproductive failure in goats. Norwegian College of Veterinary Medicine, Oslo, pp. 59±83. Engeland, I.V., Waldeland, H., Kindahl, H., Ropstad, E., Andresen, é., 1996. Effect of Toxoplasma gondii infection on the development of pregnancy and on endocrine foetal±placental function in the goat. Anim. Reprod. Sci. 67, 61±74. Hussain, Q., Waldeland, H., Havrevoll, é., Eik, L.O., Andresen, é., Engeland, I.V., 1996. Effects of type of roughage and energy level on reproductive performance in pregnant goats. Small Rumin. Res. 21, 97±103. Hyllseth, B., Andresen, é., Larsen, H.J., 1985. Genital herpesvirus infection in goats in Norway. Abstract, 44. Proceedings of the 1985 Symposium of European Society Against Virus Disease, Oslo, Norway. Kilgour, R., de Langen, H., 1970. Stress in sheep resulting from management practices. Proc. N. Z. Soc. Anim. Prod. 30, 65±76. Lùken, T., Hyllseth, B., Larsen, H.J., 1982. Border disease in Norway. Serological examination of affected sheep flocks. Acta Vet. Scand. 23, 46±52. Lùken, T., 1990. Pestivirus infection in Norway. Epidemiological studies in goats. J. Comp. Pathol. 103, 1±10. Lùken, T., BjerkaÊs, I., 1991. Experimental pestivirus infections in pregnant goats. J. Comp. Pathol. 105, 123±140. Melby, H.P., Aursjù, J., Binde, M., Grùnstùl, H., 1986. Diseases and mortality in 27 dairy goat farms. Nord. Vet. Med. 38, 403± 411. Merrall, M., 1985. The aborting goat. Proceedings of a course in goat husbandry and medicine. Massay University, N. Z., Publ. No. 106, Veterinary Continuing Education, pp. 181±198. Nord, K., 1994. Prevalence of antibodies to caprine arthritis encephalitis virus and control of the disease in Norway. In: Hansson S.J. (Ed.), XVII Nordic Veterinary Congress, 26±29 July, 1994, Reykjavik, Iceland, Proceedings and Abstracts, vol. 1, p. 116. Orr, M., Montgomery, H., Gill, J., Smith, R., 1987. Abortion in goats: A field study. Surveillance 14, 5±6. Smith, M.C., Sherman, D.M., 1994. Reproductive system, in Smith M.C., Sherman, D.M. (Eds.), Goat Medicine. Lea and Febiger, Philadelphia, pp. 411±463. Thorburn, G.D., Nicol, D.H., Bassett, J.M., Shutt, D.A., Cox, R.I., 1972. Parturition in the goat and sheep: Changes in corticosteroids, progesterone, oestrogens and prostaglandin F. J. Reprod. Fertil. Suppl. 16, 61±84. Van der Westhuysen, J.M., Roelofse, C.S., 1971. Effect of shelter and different levels of dietary energy and protein on reproductive performance in Angora goats with special reference to the habitual aborter. Agroanimalia 3, 129±132. Waldeland, H., 1976a. Toxoplasmosis in sheep. The relative importance of the infection as a cause of reproductive loss in sheep in Norway, Acta Vet. Scand. 17, pp. 412±425.
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I.V. Engeland et al. / Small Ruminant Research 30 (1998) 37±48
Waldeland, H., 1976b. Toxoplasmosis in sheep. The reliability of a microtiter system in Sabin and Feldman's dye test, Acta Vet. Scand. 17, pp. 426±431. Waldeland, H., 1977. Toxoplasmosis in sheep. Influence of various factors on the antibody contents. Acta Vet. Scand. 18, 237±247. Waldeland, H., Lùken, T., 1991. Reproductive failure in goats in Norway: An investigation in 24 herds. Acta Vet. Scand. 32, 535±541. Wentzel, D., Morgenthal, J.C., Van Niekerk, C.H., Roelofse, C.S., 1974. The habitually aborting Angora doe: II. The effect of an
energy deficiency on the incidence of abortion. Agroanimalia 6, 129±132. Wentzel, D., Roelofse, C.S., 1975. The habitually aborting Angora doe. VII. Induction of abortion by administration of cortisone acetate. Agroanimalia 7, 45±48. Wentzel, D., 1982. Non-infections abortion in Angora goats. Proceedings. Third International Conference on Goat Production and Disease, Tucson, Arizona, pp. 155±161. Williams, C.S.F., 1986. Pregnancy diagnosis. In: Morrow D.A. (Ed), Current Therapy in Theriogenology. 2nd. edn., Saunders, Philadelphia, pp. 587±588.