Agriculture Reference
In-Depth Information
annually; and, the average removal parity ranges from 3.3 to 3.8 (D'Allaire
et al.
, 1987;
Lucia
et al.
, 2000b). In Europe, the average annual removal rate varies from 43 to 52%
and average removal parity ranges from 4.3 to 4.6 (Boyle
et al.
, 1998; Dijkhuizen
et al.
,
1989; Engblom
et al.
, 2007). Such early culling is detrimental to producer profitability as
breeding females should be retained in the herd until at least the initial investment cost
associated with their replacement is recouped. Stalder
et al.
(2003) and Carroll (2011)
suggested that sows should remain in the breeding herd for at least three parities to pay
for themselves; however, they advised that the number of parities required to recoup
the initial investment costs varies between farms and production systems. Irrespective
of the production system, the longer a sow stays in the herd, the more litters and pigs
her initial replacement cost can be spread over. Sehested (1996) reported that improving
sow longevity by a single parity showed the same economic impact as improving lean
meat content by 0.5%; however, he also reported that this impact had little effect beyond
parity five.
A high removal rate increases the number of non-productive days, increases the number
of gilts in the herd resulting in lower mean litter size and lower number of pigs weaned per
sow per year. (Hughes and Varley, 2003). Additionally, piglets from first parity sows are
lighter at birth and at weaning and have higher mortality risk and disease susceptibility
compared with pigs produced from older parity sows (Smits, 2011). Furthermore, as the
sow herd accounts for approximately 20% of feed costs in a commercial farrow to finish
farm, low removal rates could have a small direct effect on herd feed conversion due to
changes in breeder feed consumption because replacement gilts must be maintained for
6-12 weeks before their first mating (Smits, 2011). Therefore, it is of vital importance to
identify and to understand different factors and/or practices that impact sow longevity in
order to increase the time a sow stays in the breeding herd and increase farm profitability.
19.2
Common metrics used to evaluate sow longevity
There is no clear consensus regarding the definition of sow longevity in the scientific
literature and it usually refers to length of productive lifetime rather than the sow's natural
lifespan. However, the definition of sow longevity differs depending on the objective
of the studies or the purpose for which longevity is evaluated. D'Allaire
et al.
(1992)
suggested that there are several methods to evaluate sow longevity including length of
life, herd life, productive life, and stayability (binary trait that indicates whether a sow
survived to a defined parity or time point). Other measures for sow longevity also include
removal rate, culling rate, replacement rate, percent of gilts in the herd, mean parity of
females in inventory, and mean parity at removal. Additionally, sow longevity can also
be measured using economic indicators such as pigs weaned per day of life, number
of herd days per pig weaned, or parity at which a positive net present value is attained
(Culbertson and Mabry, 1995; Stalder
et al.
, 2003). In many cases, management practices
employed by commercial operations make it difficult to apply some definitions of sow
longevity. For instance, length of life, defined as the number of days between date of birth
and date of removal, can only be approximated when replacement gilts are purchased and
their birth dates are not provided (Stalder
et al.
, 2007a).
