Sow longevity - The Gestating and Lactating Sow - page 419

sow herds should not exceed 3%. Even though, risk factors for mortality have not been
widely investigated, larger herd size, parity, the peripartum period (i.e. 3 d before the
predicted farrowing date to 3 d after farrowing), short lactation length and weaning have
been identified as risk factors (Chagnon et al. , 1991; D'Allaire, 1992; Koketsu, 2000; Sanz
et al. , 2007; Sasaki and Koketsu, 2008; Tiranti et al. , 2003; USDA, 2001).
Mortality rates increase as herd size increases (Abiven et al. , 1998; Koketsu, 2000). he
USDA (2001) reported that mortality rates increased from 2.5 in farms with less than 250
females to 3.7% in farms with more than 500 females. This could be related to the greater
number of sows per person to work with and the resultant lack of individual attention
(Koketsu, 2000).
Mean parity at death varies between 3.4 and 4.2 (Chagnon et al. , 1991; D'Allaire et al. ,
1987; Madec, 1984). Moreover, the incidence for certain sow mortality causes appears
to be age related. Sudden death and some locomotion problems occur more frequently
in sows of parity one and two (Dewey et al. , 1993; Sanz et al. , 2007), whereas cystitis-
pyelonephritis occurs more frequently in older sows (Madec, 1984).
Engblom et al. (2007) reported that the greatest death rate among females in commercial
breeding herds was observed right after farrowing, whereas the proportion of euthanized
sows was greater in the week after farrowing and in the four weeks after weaning.
According to Anil et al. (2006) the peripartum period is the period of greatest risk in
the reproductive cycle, with 42% of sow deaths occurring during this short interval
(Chagnon et al., 1991).
There are several reasons for mortality reported in the scientific literature and they vary
between studies. Several factors, such as size and number of herds, breed, nutrition,
geographical area, etc., can be responsible for these differences. Chagnon et al. (1991)
reported heart failure (31%), torsions and accidents of abdominal organs (15%), and
cystitis-pyelonephritis (8%) as the major causes of sow death in Canadian breeding herds.
In 13% of the cases, death was caused by either endometritis or uterine prolapse. In
French sow herds, high prevalence of urinary tract infections, metritis, or lameness were
identified as risk factors for a high death rate (Abiven et al. , 1998). Kirk et al. (2005)
investigated the causes of sow mortality in Danish sow herds and indicated that death was
mainly caused by gastrointestinal system (45%) and reproductive system (24%) lesions.
In Swedish sow herds, circulatory or cardiac failure (24%) and bone fracture or internal
trauma-related injuries (24%) were commonly observed in females found dead (Engblom
et al. , 2008). Kirk et al. (2005) reported that arthrosis was almost a constant secondary
diagnosis both among sows that spontaneously died (93%) or were euthanized (88%).
Locomotive system disorders were the main cause for euthanasia in over 70% of the cases
of death; arthritis was the main post-mortem finding for 24 to 44% of euthanized females
and bone fracture for 13 to 16% (Engblom et al. , 2008; Kirk et al. , 2005). Similarly, Sanz et
al. (2007) reported arthritis as the most common post-mortem finding with a frequency
of 37% among euthanized sows in a U.S. herd.