Agriculture Reference
In-Depth Information
(2.6 MJ/d), mammary growth (1.6 MJ/d), and uterus, placenta, fluids and membranes
(0.3 MJ/d). Heat loss is required for maintenance purposes and for colostrum production,
fetal growth, mammary growth and growth of uterine tissues. The energy requirement
is fairly constant in late gestation and hardly increases from d 105 to parturition because
the metabolic live weight (kg
0.75
) of sows increases only slightly. After parturition, the
energy requirement is low for a couple of days mainly because no nutrients are retained
in fetuses, placenta or uterine tissues, and because large quantities of colostrum and milk
likely are not synthesized during the first 1.5 d after parturition. From d 2 of lactation
onwards, the energy requirement increases substantially each day due to a greater milk
production (Hansen
et al.
, 2012b) and to increasing amounts of heat associated with milk
production. On d 10 of lactation, sows require approximately 81 MJ/d of metabolizable
energy, of which 53% is secreted in milk (42.8 MJ/d), another 12 MJ/d is lost as heat
due to milk production and the remaining 25.7 MJ/d is lost as heat due to maintenance.
The regressing uterus supplies only a minor amount of energy during the first week of
lactation and this contribution slightly reduces the daily energy requirement (-1.6 MJ/d).
Finally, the energy required for mammary growth (0.6 MJ/d) is negligible (Kim
et al.
,
1999b). It is interesting to note that the proportion of additional heat lost (heat loss
exceeding that required for maintenance) is 19 to 20% prior to parturition, whereas it is
only 13 to 15% after parturition. The greater proportion lost before parturition is likely
explained by a greater level of physical activity in late gestation vs. early lactation (6 vs. 4 h
of standing activity; Theil
et al.
, 2002, 2004), but it may also be speculated that conversion
of metabolizable energy to colostrum is less efficient than utilizing metabolizable energy
for milk production.
7.4.3
Lysine requirement
During transition, lysine is mainly required for reproduction whereas minor amounts are
required for sow maintenance (Feyera and Theil, 2014; Figure 7.6). During the last 10 d of
gestation, the lysine requirement increases by approximately 24% due to the exponential
increase in fetal growth (Noblet
et al.
, 1985). The increase in lysine requirement may be
even greater than 24% if mammary growth follows an exponential growth curve like
fetal growth in late gestation. However, it is currently unknown how the requirements
for mammary growth and colostrum production change in the pre- and post-farrowing
period. If we assume that all colostrum is produced uniformly during the last 10 d
of gestation, it can be calculated that as much as 59% (d 106) and 48% (d 115) of the
daily lysine requirement is needed for mammary growth and colostrum synthesis. At
parturition, the lysine requirement drops abruptly because most of the lysine is needed
for reproduction and only sparse amounts are required for sow maintenance. The lysine
requirement then increases dramatically from d 2 and throughout the transition period,
because sows have a very high requirement of lysine for milk production. Wu and Knabe
(1994) reported that milk contains 29 mmol/l of lysine, which is equivalent to 4.12 g of
lysine per kg of milk (assuming that milk density is 1.029 kg/l). However, after parturition
the regressing uterus supplies approximately 2.6 g/d of lysine, and this amount is higher
than the amount required for sow maintenance. In total, the uterine supply accounts for
approximately 13% of the total requirement for lysine on d 2 and 8% on d 7 of lactation.
These quantities are valid only if the uterine degradation after parturition happens
