Pseudopregnancy (PPG) is an important pathological condition, as it represents one of the main causes of temporary infertility in dairy goats (Matthews,2009; Menzies,2019). As far as we know, no previous study reported the prevalence rate of PPG in the M-G breed does, so far. Moreover, we also didn’t find any report investigating the prevalence rate and risk factors of PPG in dairy goats in Iran, at least in this population scale. The reported range for the prevalence of PPG is from 1.37–30.4%, but most previous studies reported a rate of 9–12% which is in accordance with the prevalence of PPG in our study (Almubarak et al., 2018; Batista et al., 2001; Desire et al., 2018; Hesselink, 1993.a; Lopes Júnior et al., 2004; Maia et al.,2019; Barna et al., 2017). Several factors including breed and genetic predisposition, age, milk production, pregnancy loss, reproductive management, days in milk, systems of production, and nutritional management were reported to be associated with PPG occurrence (Almubarak et al., 2018; Hesselink, 1993.a; Hesselink,1996; Maia et al., 2019; Van den Brom et al., 2019).
Three is a consensus about higher prevalence of PPG in aged does, but inconsistent finding about its relationship with parity exist (Almubarak et al., 2018; Hesselink, 1993.a; Maia et al., 2019; Van den Brom et al., 2019; Wittek et al.;1997). The persistence of corpus luteum is prevalent after the second year of lactation without being mated (Matthews, 2009). In this study, the average age was higher in the diseased does compared to the normal group and significant differences in the rate of PPG existed between various age and also parity groups. In fact, similar to most previous reports, the lowest rate of PPG was found in the age group of 1–2 and primiparous does and the prevalence rate was elevated by increasing age and parity, except for parity number of three and age of ≥ 4. Moreover, no significant relationship between age (and parity) and prevalence of PPG was found generally, which can be explained by a surprisingly lower prevalence of PPG in does with a parity number of three and an age of ≥ 4. This can be explained by changing prevalence in certain ages and/or milk production groups, and lacking of a significant increasing trend by elevated age and milk production. Moreover, considering the recurrent nature of the disease and its long-term negative impacts on reproductive efficiency (Maia et al., 2020), the policy of the herd for culling aged does with reproductive problems and a history of infertility may affect the prevalence of PPG and result in lower prevalence in aged does with high parity number, and cause this discrepancy. Controversial reports about the association between milk production and PPG were presented (Almubarak et al., 2018; Hesselink,1993.b; Wittek et al., 1997). Lacking a significant relationship between milk production and prevalence of PPG despite tending to be significant or significantly higher milk production), among 2–3 years old does (P = 0.08), 3–4 years old (P = 0.04) PPG does, and in general (P = 0.07) indicates that relationship between milk production and PPG is significant only in certain ages. The lowest and highest prevalence of PPG occurred in does with less than 1 kilogram and 1–2 kilograms of milk production per day, respectively and this can be explained by the effect of age, as the high production are younger and have a lower risk of developing PPG. Significantly increased prevalence of PPG by elevating milk production in higher aged groups compared to young does and also in aged does only with production level of higher than 1 Kg/day, indicated higher sensitivity of aged does to develop PPG by increasing level of production and the effect of milk production level on increasing rate of PPG, in ages does. This finding may be related to metabolic complications of aged does with high milk production, which is suggested to be investigated in future research.
There are some reports about a higher prevalence of PPG in cases of cyclicity out of the breeding season (Duquesnel et al., 1992; Barna et al., 2017). Moreover, a positive genetic correlation between out-of-season kidding ability (and also extended lactation and whole-life days in milk, as a result) with PPG was reported. The persistence of milk production in M-G goats is heritable, (Menéndez-Buxadera et al., 2010) and based on the explained findings, this may affect the genetic predisposition of individuals to PPG in this species. According to our provided results for M-G does, there was no difference in the prevalence of PPG during the breeding season and out of it, which is in agreement with recently published reports (Almubarak et al., 2018). This might have occurred due to the low geographic latitude of the place where the studied farm is located, which diminishes does' seasonality.
The PPG itself is defined as a sterile fluid accumulation in the uterus, but as it imitates pregnancy, resolving it through cloudburst mimics parturition and may predispose sterile uterine environment to bacterial contamination, which can be detrimental due to suppressed uterine immunity as a result of chronic high plasma progestogen concentration. A standard therapy regimen of repeated prostaglandin administration 11–12 days apart, increased the rate of successful treatment and improved post-therapy pregnancy rate by reducing the chances of disease reoccurrence. It's supposed that drainage of the remnant uterine fluids by second injection, following induction of luteolysis and cloudburst by first injection is responsible for this improved response to therapy. The cure rate in the first and the second groups of the study was 66.8% (8/12) and 75% (9/12) respectively. After rebreeding, the pregnancy rate was 75% (6/8) and 88.8% (8/9) in the recovered cases of the first and second groups of the study. The cure rate of 59% and pregnancy rate of 48% following two prostaglandin injections were reported before (Hesselink, 1993.b), which is lower than our finding. In another study, despite a 95% cure rate after the second prostaglandin administration, a pregnancy rate of 45% following treatment with three doses of prostaglandin was reported (Maia et al., 2018.b), another study reported conception rate of 64%, which is comparable to our result (Barna et al., 2017). Antibiotic administration improved the cure rate and pregnancy rate numerically, and the lack of significant results might be due small number of observations in each group of the study.