Date Published: July 1, 2008
Publisher: BioMed Central
Author(s): Linda Engblom, Lena Eliasson-Selling, Nils Lundeheim, Katinka Belák, Kjell Andersson, Anne-Marie Dalin.
The aim of this study was to get information on post mortem diagnoses of sows found dead or euthanised and to understand the diagnoses aetiology (causative background). Moreover, the study was to evaluate the association between the clinical symptoms observed on farm and post mortem findings.
A large Swedish herd was studied from January to September 2006. During the 32-week period 3.9% of the removed sows and gilts (old enough to be mated) were found dead, 12.0% were euthanised and the rest were sent to slaughter. Of 32 sows/gilts found dead 17 (53%) were post mortem examined, and of 98 sows euthanised 79 (81%) were examined. The 96 examined carcasses were after 70 sows and 26 gilts. The findings at examination were together with data from the herd monitoring program PigWin Sugg the base for the descriptive statistics presented.
The average parity number at removal was 2.8 for those found dead and 2.1 for those euthanised. The highest number euthanised and found dead was in parity 0 (gilts). The main proportion of post mortem examinations was made on sows being in the period = 28 d of gestation at death (37.5%), followed by weaning to next service period (24.0%). Arthritis, with an incidence of 36.4% was the most common main finding of pathological-anatomical diagnosis (PAD). Of sows/gilts found dead were circulatory/cardiac failure (23.5%) and trauma related injuries (23.5%) most common PAD. The most commonly observed clinical symptom and reason for euthanasia of the sows/gilts was lameness. Notably, in 43% of the cases with PAD arthritis, the clinical symptoms suggested it being a fracture. Further one or more abscesses (38.5%) and teeth injuries (31.0%) were common findings when also incidental findings were included.
This post mortem study based on carcasses from sows/gilts found dead or euthanised showed that arthritis was a significant problem in the studied herd and that post mortem examination was important to get proper diagnosis.
Sow mortality includes sows found dead. However, sows euthanised on farm due to trauma or disease are generally also included in studies on mortality. Both of these two kinds of unplanned removal lead to urgent need for replacement gilts, loss of income from slaughter, and an extra cost for destruction of the carcasses. Besides the loss in production, there is a risk that the sows are suffering from pain during their last days alive. Annual mortality rates reported previously, mainly including sows found dead, varied from 3.4% to 6.9% of sows in production [1-3]. Risk factors for sow mortality have been identified. Higher mortality was reported during summer months [2,4,5], both during the days before expected farrowing and the days just after farrowing [4,6,7].
This study was based on material collected from a sow pool with 2200 crossbred Landrace × Yorkshire sows in the south central part of Sweden. The sow pool had a central unit supplying 13 satellite units with pregnant sows within a leasing system. In the central unit the newly weaned sows were housed in groups of 50 on deep straw bedding for one week. During this period oestrus was checked twice daily starting three days after weaning and artificial insemination was used. During the first eight weeks of pregnancy the sows were kept in smaller groups (9–15 sows per pen) on concrete/partially slatted floor with access to straw. Pregnancy check was performed twice with ultrasound scan, at 4 and 8 weeks. After the second check, pregnant sows were moved to large pens (50 sows per pen) with deep straw or peat bedding.
During the 32-week period, 816 sows (n = 709) and gilts (n = 107) were removed from the sow pool including the multiplying unit. Average parity number at removal was 4.1. Of the removed sows/gilts, 3.9% were found dead, 12.0% were euthanised and the rest were sent to slaughter. This corresponds to an annual removal rate of sows at 46.7% of sows in production.
This study was based on material from one herd, but the proportion of sows/gilts found dead and euthanised agrees with the findings in a larger study based on 21 Swedish piglet producing herds . The high proportion of euthanised sows/gilts in both studies (12% and 10.5%) is partly due to the animal welfare legislation in Sweden, which states that only sows and gilts in normal body condition and without lameness are allowed to be transported to slaughter.
The results from present study show the importance of post mortem examination to obtain the proper diagnoses for sows found dead or being euthanised. The finding that most of the post mortem examined sows had arthritis as main finding needs to be confirmed on a larger number of animals and herds. If this is a general problem, further investigation is needed to find out more about the aetiology so prophylactic measures can be implemented.
The authors declare that they have no competing interests.
LE participated in the design of the study, evaluated the post mortem findings, performed the descriptive statistics and drafted the manuscript. LES participated in the design of the study, evaluated the post mortem findings and helped to draft the manuscript. NL applied for funding of the project, participated in the design of the study and helped to draft the manuscript. KB participated in the design of the study, evaluated the post mortem findings and helped to draft the manuscript. KA participated in the design of the study and helped to draft the manuscript. AMD participated in the design of the study, evaluated the post mortem findings and contributed significantly to the manuscript. All authors read and approved the final manuscript.