Agriculture Reference
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reproductive tissues are lost from the sow body. The uterus, in contrast, regresses during
the first week after farrowing, which causes release of nutrients that may be utilized
for milk production. The amount of energy supplied from the regressing uterus to the
sow circulation is of minor importance and can be neglected, but substantial amounts
of protein and essential amino acids are released to the blood and should ideally be
accounted for when feeding transition sows. It is not known whether sow feeding affects
growth and regression of placental and uterine tissues, but it is likely that the nutritional
impact is rather low because these traits are associated with offspring survival, which is
highly prioritized.
7.2.5
Mammary growth
Substantial mammary growth occurs in the last third of gestation, but 10 d before
parturition mammary development is still quite small. The pattern of growth rate of
mammary glands during late gestation is not known in details, but without doubt the
growth rate is accelerated during the last 10 d of gestation based on visual evaluation
of udder development of late gestating sows. The mammary glands continue to grow
until approximately d 10 of lactation (Kim et al. , 1999a), but their growth rate after
parturition is slower than before parturition (Noblet et al. , 1985) and this impacts the
nutrient requirements. Moreover, if mammary glands for some reasons are not suckled
after parturition, these glands will regress during the first week after parturition (Kim et
al. , 2001; Theil et al. , 2006) and, consequently, substantial amounts of amino acids and
minor amounts of energy will be recirculated to the blood. In modern high-prolific sows,
however, the number of non-suckled mammary glands is low due to the large number
of suckling piglets and mobilization of amino acids from regressing mammary glands
can be overlooked. From a productivity point of view, it would indeed be interesting
to know whether mammary gland growth can be enhanced by nutritional means. This
aspect is covered in Chapter 4 (Farmer and Hurley, 2015), but it is evident that there is a
lack of information on the impact of feeding during the transition period on mammary
development in sows.
7.2.6
Farrowing process: duration, birth intervals, stillbirth rate and
piglet vitality
Optimal sow feeding to reduce farrowing length, stillbirth rate or to improve piglet
vitality at birth has not received a lot of scientific attention. Expectedly, feeding during
the last few days before parturition is important for the farrowing process and, therefore,
altered nutrition may be a way of increasing sow productivity, for instance via a reduction
in stillbirth rate. Data from 5 Danish studies carried out at Research Centre Foulum
from 2007 to 2013 revealed that the mean duration of 126 farrowings was 343±15
min (Vadmand et al. , unpublished data). On an individual basis, the farrowing length
varied from 87 to 935 min, which means that the fastest sow spent only 1.5 h farrowing,
whereas the slowest one spent 15.5 h. All sows gave birth to more than 10 piglets and on
average 16.1 piglets were born alive while 1.1 piglets per litter were stillborn. Farrowing
length was not associated with the total number of piglets born, but it was greater for
sows with stillborn piglets (Figure 7.1). However, it is not clear whether the presence of
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