Agriculture Reference
In-Depth Information
Herd life is defined as the number of days between date of entry in the breeding herd
and date of removal. Lucia
et al.
(2000b) reported a mean heard life of 583 d for gilts and
sows; however, it increased to 691 d when gilt removals were excluded from the data. A
similar herd life of 682 d was reported by Koketsu (2003), and Babot
et al.
(2003) reported
a herd life of 1105 d for Spanish commercial females. Productive life is the number of
days between first conception or first farrowing and date of removal. Rodríguez-Zas
et
al.
(2003) found a mean productive life of 467 d from first service to removal for U.S.
commercial females, whereas Engblom
et al.
(2007) reported a mean productive life of
735 d from first conception to removal in Swedish commercial sows. Finnish purebred
Landrace and Large White populations and crossbred sows remained in the herd on
average 439 d (Serenius and Stalder, 2004) and 536 d (Serenius and Stalder, 2007) from
first farrowing, respectively. In Austria, Large White sows remained in the herd on average
for 531 d from first farrowing, whereas Landrace sows averaged 615 d of productive life
(Mészáros
et al.
, 2010). In Swiss nucleus, average productive life for Large White sows was
602 d from first farrowing (Tarrés
et al.
, 2006a). Swedish Yorkshire and Landrace sows
remained in the herd on average 353 d (Yazdi
et al.
, 2000a) and 618 d post first farrowing
(Yazdi
et al.
, 2000b), respectively.
Culling rate is the number of sows that are removed from the herd due to health and/
or performance problems or management decision, excluding deaths and euthanasia.
Mean annual culling rates in commercial herds reported in different countries varied
from 43 to 50% (Boyle
et al.
, 1998; Dijkhuizen
et al.
, 1989; Engblom
et al.
, 2007; Koketsu,
2007; PigCHAMP, 2012). Lucia
et al.
(2000b) and Knauer
et al.
(2011) reported that the
proportion of females removed as gilts was 19% and 28%, respectively. Furthermore,
Lucia
et al.
(2000b) reported that 46% of females were removed before the third parity
with a detrimental economic effect for pig producers. Removal rate includes culling,
natural death, and euthanasia. It is defined as the number of animals removed from
the herd during a year, divided by the average inventory, and multiplied by 100. The
inventory may refer to sows only or sows and gilts, with gilts being introduced at different
times in their production cycle. For a better standardization of terminology, it has been
suggested that only mated females be considered in the calculation of removal rate. On
some farms, however, culling of gilts introduced into the breeding herd but not yet mated
is very high and may require more investigation. Annual removal rates of 35-55% for
sows were reported in different studies (Boyle
et al.
, 1998; Dagorn and Aumaître 1979;
D'Allaire
et al.
, 1987; Dijkhuizen
et al.
, 1989; Engblom
et al.
, 2007; Friendship
et al.
, 1986;
Knauer
et al.
, 2007). A target of 39-40% is recommended with 35-36% for culling and
3-5% for death (Dial
et al.
, 1992; Muirhead, 1976). Such target values should be adjusted
for individual farms as removal rate is influenced by several farm-specific factors such as
herd size, desired genetic turnover, breed, definition of the average inventory, etc. Market
trends and economic conditions also influence a producer's culling decision and timing
(Stalder
et al.
, 2004).
Longevity of sows in the herd can also be evaluated by the replacement rate, which is
defined as the total number of animals entering the herd divided by the average inventory
and multiplied by 100. The removal rate and replacement rate should be similar in a
stable herd if the inventory remains constant. However, in a herd undergoing expansion,
