Sow longevity - The Gestating and Lactating Sow - page 417

The possibility of disease transmission to susceptible gilts is increased by the stress related
to loading, mixing, and transportation of these animals (Loula, 2000; Wrathall et al. , 2003).

19.4 Why sows commonly leave the breeding herd?

19.4.1 Voluntary and involuntary culling

Sows can be replaced in the herd for both voluntary and involuntary reasons. Voluntary
culling occurs when management makes a decision to remove a female from the breeding
herd. For example, when a sow reaches some predefined maximum parity and is culled or
when the female's production levels become unacceptable and she is culled. Involuntary
culling occurs when the producer must remove the sow from the breeding herd because
she is unproductive due various reasons such as reproductive failure (non-return into
oestrus or absence of fertilization), lactation failure (low milk production or insufficient
number of piglets at weaning) and locomotion problems (Dagorn and Aumaître, 1979;
D'Allaire et al. , 1987), in which instances the culling decision is essentially automatically
made due to the sow's condition. Unfortunately, younger parity females are often removed
due to involuntary culling (Pinilla and Lecznieski, 2014).

Old age is a relative term and its definition can greatly vary between herds (D'Allaire et
al. , 1987). However, this removal reason is not frequently used prior to parity five or six. It
has been reported that 9 to 31% of female removals are due to old age (Boyle et al. , 1998;
D'Allaire et al. , 1987; Dijkhuizen et al. , 1989; Friendship et al. , 1986; Lucia et al. , 2000b;
Engblom et al. , 2007; Hughes et al. , 2010).

Reproductive failure, which includes failures to cycle, failure to conceive, and failure to
farrow, is the most frequent involuntary culling reason and accounts for 20 to 43% of all
removals (Boyle et al. , 1998; D'Allaire et al. , 1987; Dijkhuizen et al. , 1989; Engblom et al. ,
2007; Hughes et al. , 2010; Lucia et al. , 2000b; Tarrés et al. , 2006b). Between 34 and 43%
of the females removed due to reproductive problems are younger parity sows (D'Allaire
et al. , 1987; Hughes et al. , 2010; Lucia et al. , 2000b). Additionally, sows removed for
reproductive failure have lower number of piglets born alive per year, and more lifetime
non-productive days when compared with females culled for other reasons (Sasaki and
Koketsu, 2011). This could partly be due to genetic factors, but improved reproductive
management practices are needed in order to reduce the number of females culled.

Poor litter performance, including small farrowed and/or weaned litter size, low piglet
birth weight, low individual pig weaning weight, udder problems, and poor mothering
ability, accounts on average for 20 to 30% of culled sows, with studies reporting a range
between 11 to 56% of culled sows (Boyle et al. , 1998; D'Allaire et al. , 1987; Dijkhuizen
et al. , 1989; Engblom et al. , 2007; Hughes et al. , 2010; Lucia et al. , 2000b; Tarrés et al. ,
2006b). Generally, young females are allowed to express their reproductive capabilities
before being culled for poor litter performance. Accordingly, for mature sows (i.e. sows
parity three and above) litter performance and age start to increase in importance as
removal reasons, while culling for reproductive failure gradually decreases in importance