Risk factors for stillbirths in two swine farms in the south of Brazil
Introduction
Stillborn piglets are those that are apparently normal but die shortly before or during the parturition (Christianson, 1992, Dial et al., 1992). The main cause of stillbirths is anoxia (English and Wilkinson, 1982, Christianson, 1992, Herpin et al., 2001), which is common in cases of dystocia. Additionally, stillbirths can be related to environment, nutrition and to sire and dam factors (Christianson, 1992).
Stillborn risks are highly variable in different countries (English and Wilkinson, 1982, Marsh et al., 1992, King and Xue, 1996), which commonly reflects differences in the sow:personnel ratio attributed to differences in labor costs (Holyoake et al., 1995). High stillborn risks are related negatively to breeding-herd efficiency, because they are associated with reduction in both the number of pigs weaned per litter and the number of pigs weaned per female per year (Wilson et al., 1986, Dial et al., 1992). Thus, identification of risk factors associated with stillbirths could help to optimize reproductive efficiency. However, risk factors for stillbirths have not been characterized clearly. Our objectives were to describe the distribution of litters having stillborn piglets and to characterize stillbirth risk factors in two commercial swine farms in Brazil.
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Material and methods
This study was conducted in two different commercial swine farms located in the Rio Grande do Sul State, in the southern region of Brazil. In the first farm (Farm A, which had an average breeding-herd inventory of 400 females), the study was conducted during March 1999. In the second farm (Farm B, with an average breeding-herd inventory of 1050 females), the study period was September and October 1999. The difference between the study periods was because the same technicians were used in both
Results
Farm-specific parity and stillborn distributions are in Table 1 and descriptive statistics are shown in Table 2. In Farm A, 39% of the litters farrowed during the period of interest had stillborn piglets and 12% of a total of 1565 piglets born were stillborns. In Farm B, 25% of all litters farrowed had stillborn piglets and 2% of the 3997 piglets born during that period were stillborns.
Table 3 shows farm-specific frequency distributions of individual risk factors. Factors offered to the
Discussion
The stratification by farm was justified by the difference of almost 10% points between the stillborn risks observed in the two analyzed farms. According to industry benchmarks (King and Xue, 1996), the risk observed for Farm A (12%) would be considered extremely high. Stillborn risks commonly observed in Brazil are lower than those observed in other countries such as USA, Canada and Japan (King and Xue, 1996) probably as a function of the lower labor cost in Brazil.
Total litter size was the
Conclusions
High-parity females and litters having ≥12 piglets require special attention in the farrowing room due to higher stillborn risk. Practices aimed to reduce stillborn risk, such as use of oxytocin and obstetric intervention through vaginal palpation, should be conducted carefully because they can be associated with higher stillbirth risk, if used incorrectly.
Acknowledgements
This research was funded by CNPq (Conselho Nacional de Desenvolvimento Cientı́fico e Tecnológico), Grant No. 300702/97-3.
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