Agriculture Reference
In-Depth Information
with very lean gilts (i.e. <10 mm of backfat). Yang
et al.
(1989) suggested that gilts should
be mated with at least 125 kg of body weight and with a minimum backfat thickness of
13 mm. On the other hand, Tarrés
et al.
(2006b) reported that backfat thickness of less
than 16 mm at the end of the growth period increased the culling risk after the third
farrowing, mainly due to low productivity. The same authors reported that sows with
backfat thickness at first farrowing greater than 19 mm had a significantly increased
culling risk. Additionally, sows with backfat thickness under 15 mm and loin depths less
than 40 mm at first farrowing were associated with a greater culling risk due to greater
lameness problems. Geiger
et al.
(1999) found that sow mortality increased in sows with
<18 mm of backfat at farrowing. Challinor
et al.
(1996) reported that gilts with 18 to 22
mm of backfat at an average weight of 150 kg produced, on average, 7.2 more piglets
over five parities compared with gilts with 14 to 16 mm of backfat. However, results of
Rozeboom
et al.
(1996) suggest that there is no negative effects on longevity when young
gilts have less back fat (i.e. 12.5 mm) at breeding (at puberty or second oestrus) compared
with gilts with more back fat (i.e. 48 mm) at breeding.
Age at puberty and first farrowing
There is a common consensus among pig producers that if gilts reach puberty at an earlier
age, sow longevity and/or reproductive performance will be improved. Chapman
et al.
(1978) found that selecting gilts that reached puberty and conceived earlier improved
their reproductive performance. These results appear to be supported by Young and King
(1981), who found that differences due to initial breeding on first versus third oestrus for
the total number of pigs born, number of pigs born alive and number of pigs weaned, and
weaning to oestrus interval after weaning the first or second litter were not significant,
however maintaining gilts until third oestrus would require approximately 105 kg of
additional feed, thus increasing production cost. Similarly, Holder
et al.
(1995) reported
a greater percentage of gilts producing five parities when they reached puberty 11 days
earlier (58.8 vs. 39.4%), though it was not statistically significant. These results are contrary
to those reported by Brooks and Smith (1980) where puberty was induced at 160 or 200
d of age and no differences were found in the number of sows completing five parities, or
the number or weight of pigs born from the first five parities between the two sow groups.
MacLean
et al.
(2001) also reported no difference in total born piglets between gilts that
reached puberty at 155-174 d, 174-195 d, or >199 d. Furthermore, Patterson
et al.
(2010)
did not find an association between age at puberty and the retention of crossbred gilts in
the herd until the third farrowing, and MacPherson
et al.
(1977) reported no difference
in total number of pigs born at the end of three parities from gilts bred on either their
first, second, or third oestrus.
A younger age at first conception or at first farrowing is associated with superior expected
longevity (Le Cozler
et al.
, 1998; Saito
et al.
, 2011), but also appears to be related with
smaller litter size at first parity (Le Cozler
et al.
, 1998; Saito
et al.
, 2011; Schukken
et al.
,
1994; Serenius
et al.
, 2008; Tummaruk
et al.
, 2001). Immature gilts should not be bred
and according to Schukken
et al.
(1994), an optimal age at first conception is 200 to 220
d. Similarly, Serenius and Stalder (2007) recommended breeding gilts at 200 to 210 d of
age. However, Babot
et al.
(2003) reported greater longevity and lifetime reproduction
