Agriculture Reference
In-Depth Information
in late gestating sows fed graded levels of dietary lysine (NRC, 2012). Because of the
limited number of such studies for other essential amino acids, NRC (2012) had to
estimate unique efficiency values for each amino acid to calculate the digestible amino
acid requirements of the gestating sow. Nonetheless, these estimated efficiency values
remain to be validated with empirical values generated for gestating sows. These efficiency
estimates are presented in Table 6.6.
Lactation protein pools
Amino acid requirements for lactation are defined by the amino acid composition of
two pools (maternal body and milk) and their relative contribution to protein accretion
over the course of lactation. Again, these two pools have unique amino acid profiles (i.e.
amino acid:lysine), as shown in Table 6.7. Milk protein production is the single largest
contributor to amino acid requirements of lactating sows, implying that the amino acid
requirement pattern during lactation is rather constant and determined largely by the
amino acid profile of milk protein.
Efficiency of digestible amino acid deposition in milk protein.
The efficiency of 67% for standardized ileal digestible lysine deposition into milk
protein was directly calculated based on a number of closely controlled and published
studies as described in NRC (2012). There are currently insufficient empirical data on
the requirement of other essential amino acids for milk production in sows to allow
for calculation of unique efficiency values as calculated for lysine. Except for lysine,
the efficiency values of standardized ileal amino acid utilization for milk production
presented in Table 6.6 were model-derived (NRC, 2012) and remain to be validated with
Table 6.6. Efficiency of dietary ileal digestible amino acid utilization for protein gain in gestation and milk
protein output in lactation (adapted from NRC, 2012).
Amino acid
Gestation
Lactation
Arginine
0.960
0.816
Histidine
0.636
0.722
Isoleucine
0.491
0.698
Leucine
0.588
0.723
Lysine
0.490
0.670
Methionine
0.495
0.675
Total sulfur
0.402
0.662
Phenylalanine
0.542
0.733
Total aromatic
0.537
0.705
Threonine
0.527
0.764
Tryptophan
0.467
0.674
Valine
0.549
0.583
N × 6.25
0.555
0.759
