Agriculture Reference
In-Depth Information
bowed front legs and enlarged hocks (Plumlee
et al.
, 1956). Additionally, calcium and
phosphorus levels in the diet have been reported to affect reproductive failure and hence,
sow longevity (Arthur
et al.
, 1983; Koketsu
et al.
, 1996; Kornegay
et al.
, 1984). Other
minerals were also shown to have a beneficial effect on sow longevity and its component
traits. Hagen
et al.
(2000) demonstrated the beneficial effects of supplemental chromium
on sow mortality. However, Crenshaw (2003) pointed out that reducing sow mortality
due to lameness by manipulation of bone mineralization through dietary measures was
not successful. Mahan and Newton (1995) found that a decline in mineral composition
occurred in sows that had completed three parities compared with pregnant gilts. Results
from this study demonstrated that the most notable mineral declines in sows completing
three parities were calcium, phosphorus, magnesium, potassium, sodium, and zinc.
Thus, it is generally recommended that gilts should be provided with greater dietary
concentrations of calcium, phosphorus, copper and zinc compared with diets for grow-
finisher pigs (NRC, 2012) in order to prevent leg problems due to excessive reduction of
mineral reserves during the lactation period (Whitney and Masker, 2010).
19.6
Housing effects on longevity
19.6.1
Space requirements for gilts and sows
Recommendations for space requirements for breeding sows are few and many of them
are based on consumers' perceptions rather than on scientific knowledge. Countries like
the European Union established that the floor area available for group-housed gilts and
sows must be at least 1.64 m
2
and 2.25 m
2
, respectively, with a 10% increase of space
allowance for groups of animals less than six and a similar reduction of 10% for groups
of 40 or more animals. These allowances were made to ensure sow welfare.
From an industry point of view, effects of space requirements on reproduction variables
are of utmost importance. Ford and Teague (1978) did not find differences in average age
at puberty for gilts housed with a 50 or 70% space restriction compared with controls.
The control gilts were housed in a space of 0.37 m
2
with increments of 0.09 m
2
for each
additional 13.6 kg increase in body weight. Cronin
et al.
(1983) observed a 4.2% increase
in undetected oestrous in post-pubertal gilts housed in large groups with <0.9 m
2
of
space allowance per gilt. Young
et al.
(2008) saw no effect on total number of piglets
produced over three parities or on removal rate between gilts housed in 1.13 m
2
or 0.77
m
2
during the rearing period; although gilts reared with the larger space allowance were
more likely to attain puberty at a younger age. In a study by Kuhlers
et al.
(1985), gilts
that were provided with 1.25 m
2
of floor space during the rearing period farrowed larger
litters with more piglets born alive than gilts provided 0.62 m
2
. However, results from
these studies need to be interpreted with caution because space restriction was achieved
by variations in the group size.
Physiological measures were used as indicators of the animal's ability to cope with the
environment in order to evaluate space effects on gilt and sow welfare. Hemsworth
et al.
(1986) observed chronic stress responses in gilts housed at reduced space allowances (1,
