Agriculture Reference
In-Depth Information
amino acids other than lysine and valine have not been tested thoroughly as has been
done with growing pigs, but Soltwedel
et al.
(2006) reported that lysine and threonine
were the first and second limiting amino acids for lactating sows fed diets based on corn
and soybean. Instead, recommended levels of dietary amino acids are often established
based on the concentrations found in sow milk (relative to lysine), which implies that
all essential amino acids (digested) are used for milk synthesis with identical efficiency.
Severe restriction of feed from an average of 5.3 kg/d to 2.6 kg/d (i.e. severe restriction
of all dietary nutrients including energy, protein and essential amino acids) also reduced
sow milk yield from 10.1 to 6.6 kg/d on days 18 to 24 of lactation (Verstegen
et al.
, 1985).
However, in the same study, only a small reduction in milk yield was seen on days 7 to
14 (from 8.3 to 7.0 kg/d). These studies emphasize that nutrition of the lactating sow is
important, but that if dietary supply is inadequate, lactating sows use their body fat and
muscles as nutrient buffers to support milk production. This was demonstrated elegantly
by King and Dunkin (1986), where sows were fed lactation diet at one of six levels (1.5
to 4.8 kg/d). The study revealed that sows compensated for insufficient feed intake by
increasing nutrient mobilization from the body. Piglet growth, which was used as an
indicator of milk production, was only compromised in the fourth week of lactation,
whereas sows were able to compensate for insufficient dietary supply during the first
three weeks of lactation. However, it must be kept in mind that severe body mobilisation
during lactation is well known to have negative impacts on subsequent performance of
reproduction (Quesnel, 2009), such as compromised litter uniformity at birth (Wientjes
et al.,
2013) or increased weaning-to-oestrus interval. Preventing low feed intake by sows
during lactation is therefore essential for sow longevity.
From a practical point of view, it is more interesting to know how we can improve the
appetite of lactating sows and how we can improve the milk yield of sows having a
good appetite and being fed suitable lactation diets. Ramanau
et al.
(2004) showed that
supplementation with L-carnithine increased sow milk yield and, in turn, growth of their
piglets. This is an example of a bioactive stimulation of milk production, because the sows
received only a minor daily supplementation of L-carnithine (250 mg/d). Alterations in
macrochemical dietary composition have also been studied and dietary fat has received
some attention. Some fat sources (8% animal fat or 8% rapeseed oil) increased the
energy secreted in milk compared with 8% fish oil or a low fat control diet (3% animal
fat supplemented). However, the increased transfer of energy to the piglets was obtained
partly by increased milk yield and partly by increased milk fat content, as neither milk
yield nor milk composition was significantly affected (Lauridsen and Danielsen, 2004).
Nevertheless, most studies with dietary fat inclusion show no impact on milk yield (Theil
et al.
, 2004; Tilton
et al.
, 1999).
Another nutritional aspect is the feeding curve, which influences sow milk yield
(Danielsen, 2003). If sows are fed
ad libitum
from day 7 of lactation onward, their milk
yield (8.3 kg/d) is numerically higher than when fed
ad libitum
from day 14 of lactation
(8.1 kg/d) or from parturition (7.9 kg/d) onward and significantly higher compared to
sows fed
ad libitum
during the last week prior to farrowing and throughout lactation
(7.4 kg/d). These findings suggest that feeding sows too heavily around parturition is
detrimental to subsequent milk production and that a setpoint of milk yield is established
