Agriculture Reference
In-Depth Information
ingredients containing higher levels of fiber or proteins have a lower NE content. For
instance, corn (yellow, dent) and soybean meal (dehulled, solvent extracted) contain
similar levels of ME, i.e. 3,395 vs. 3,294 kcal, respectively, but the NE of corn is relatively
higher than that of soybean meal, i.e. 2,672 vs. 2,087 kcal. The ME system overestimates
the 'truly available' energy concentration of feed ingredients of higher fiber or protein
concentrations. Use of the NE system as opposed to the DE or ME system will become
increasingly relevant with the use of purified amino acid supplements or co-products
high in fiber content. In sows, high-fiber feeds are of particular interest during gestation
to increase feed bulkiness, control appetite (Chapter 5; Meunier-Salaün and Bolhuis,
2015), and reduce the incidence of constipation (Chapter 10; Peltoniemi and Oliviero,
2015), dystocia and mastitis-metritis-agalactia (MMA) syndrome.
A concern with using the current NE system is that it only considers the impact of dietary
energy source (i.e. dietary nutrient) on energetic efficiencies. This makes it difficult to
integrate NE systems with estimating energy requirements for various body functions
(e.g. maintenance, body protein and body lipid gain, milk production), as energetic
efficiencies are also influenced by the body function for which energy is used. For this
reason, NRC (2012) introduced the concept of effective ME, which accounts for the effect
of dietary energy source on energetic efficiencies, and effective ME requirements are
estimated based on energy requirements for various body functions taking into account
their associated energetic efficiencies.
In the next section of this chapter, the determinants of energy requirements for gestation
and lactation are discussed in details. The ME requirement of a pregnant sow is equivalent
to the amount of energy needed for maintenance (i.e. basal metabolism) and retained in
the products of conception and in the maternal body, whereas the ME requirement of
a lactating sow is equivalent to the amount of energy needed for maintenance and the
energy retained in milk (NRC, 2012). As illustrated in Figure 6.1, ME includes the heat
associated with basal metabolism and the heat increment associated with protein, fat, and
glycogen deposition during pregnancy or with protein, fat and lactose production during
lactation. Thus the heat increment associated with the development of conceptus or with
milk synthesis represents the single difference between ME and NE requirements of the
gestating or lactating sow, respectively. Therefore, the NE requirement for gestation or
lactation is equivalent to the energy needed for basal metabolism and energy retained (or
recovered) in the conceptus or milk, respectively.
6.3.2
Determinants of energy requirements
Gestation
The main determinants of energy requirements in gestating sows are body maintenance
functions, growth of conceptus and changes in maternal energy stores, including the uterus
and mammary tissue. In NRC (2012), and based on an extensive review of the available
literature, energy requirements for these processes were quantified and related to parity,
sow body weight, level of sow productivity (litter size and average piglet weight at birth),
and environmental conditions (effective environmental temperature, floor type and sow
