Agriculture Reference
In-Depth Information
protein in these animal by-products is of very good quality, with a high digestibility and
high methionine concentration. These products however tend to be rather expensive so
economic considerations often prevent them from entering least-cost diet formulations
for sows (Patience
et al.
, 1995).
Crystalline amino acids, including L-lysine, L-threonine, DL-methionine, and
L-tryptophan are readily available commercially in pure crystalline form. Each crystalline
amino acid can be included individually in diets for lactating sows. Of these, L-lysine is
by far the most utilized, and to some extent L-threonine, depending on the cereal grains
used. Amino acids in crystalline form are 100% digestible and can be supplemented in a
very precise amount to correct small deficiencies.
6.4.5
Applying dietary amino acid needs to requirements
Recommended daily requirement for key amino acids of gestating and lactating sows
at varying levels of performance and when fed corn and soybean meal based diets, are
presented in Table 6.2 and Table 6.3. These values are derived from NRC (2012) but
include a typical 10% added safety margin to account for imprecision in diet formulation
and preparation, as well as in estimation of nutrient requirements. Hence, amino acid
requirements presented in Table 6.2 and Table 6.3 are referred to as 'recommended'
requirements or allowances.
For gestating sows, these values illustrate the substantially higher daily amino acid
requirements during late gestation (after d 85) as compared with early and mid-gestation
(d 1 to 90). These greater requirements are reflective of the amino acid requirements for
the exponential increase in protein accretion of the products of conception during late
gestation (Figure 6.3). When comparing early and mid gestation with late gestation, the
increases in amino acid requirements are larger than the increase in energy requirements.
Therefore, the optimal dietary amino acid to energy ratio is increased during late
gestation. Based on these concepts, phase-feeding gestating sows should be considered,
whereby both the feeding level and diet composition may be changed around d 90 of
gestation. Amino acid requirements of gestating sows decrease quite substantially with
increasing parity, reflecting the gradual decline in maternal body protein deposition as
sows approach mature body protein mass. In large sow operations, the use of parity
segregated gestation diets may be considered in order to more closely meet the amino
acid requirements of different groups of sows, and to reduce feed costs and nutrient losses
into the environment while maintaining sow productivity. With the rapid development of
computer controlled feeding equipment and identification of individual sows, it will be
feasible to optimize blends of two or more basal diets so that individual sows meet their
unique amino acid requirements. In that situation, basal diets may be formulated to meet
requirements of sows with the highest (e.g. late gestation parity 1) and lowest (e.g. early
gestation parity 4+ sows) dietary amino acid requirements.
As is the case with energy requirements, litter growth rate is by far the most important
determinant of amino acids requirements for lactating sows. Failure to meet these
requirements will lead to reduced milk output and will increase mobilization of maternal
