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Amino acid (AA) requirements of sows may be greater in the late pregnancy. Mainly due to the accelerated growth of products of conception after d 70 of pregnancy, such as protein and fat accretions in the foetus and the rapid growth of the mammary gland during the last third of gestation. The objective of this study was to determine the Trp requirement, Phe kinetics, and energy expenditure in early (d 35 to 53) and late (d 92 to 111) pregnancy using the indicator amino acid oxidation method and indirect calorimetry. Six pregnant Large White x Landrace sows in the second parity were each fed 6 dietary Trp levels in a 6 x 6 Latin square designs in both early and late pregnancy.
Dietary Trp contents ranged from deficient to excess compared with the estimated requirements (2.5g/d of total Trp). Dietary Trp levels in early pregnancy were 20 to 120% of the estimated requeriments. Dietary Trp levels for the same sows in late pregnancy were 60 to 180% of the estimated requirement. Feed allowance was constant for each sow at 2.41 kg/d (SE 0.029). Expired air and blood were collected every 30 min for 5 1/2 h. After three 30-min periods to determine background 13C enrichment in expired CO2 and plasma Phe, L[1- 13C]Phe was given orally at a rate of 2 mg/(kg BW·h) with 8 1/2 hourly meals. Requirements were determined as the breakpoint of 2-phase linear models.
The Trp requirement was 1.7 g/d (P = 0.001) in early pregnancy and 2.6 g/d (P = 0.013) in late pregnancy, or 0.7 g/kg and 1.1 g/kg diet of total Trp, respectively, for a feed allowance of 2.4 kg/d. The Trp requirement in late pregnancy tended (P = 0.056) to be greater than in early pregnancy. Quantitative Phe kinetics was not affected by Trp intake except for a quadratic response of Phe oxidation and retention (P < 0.1) to Trp intake in early pregnancy. In late pregnancy, sows oxidized less Phe and retained more Phe (P = 0.001) than in early pregnancy, indicating that young, growing pregnant sows increase the efficiency of utilizing AA in late pregnancy to maintain protein synthesis in both maternal and fetal tissues. Oxidation and body protein breakdown contributed less to Phe flux in late than early pregnancy while protein synthesis contributed more (P < 0.01). To meet both energy and AA requirements in late gestation, a phase feeding program with 2 diets is recommended.
Franco, D.J., Josephson, J.K., Moehn, S., Pencharz, P.B. and Ball, R. O. 2014. Tryptophan requirement of pregnant sows. J. Anim. Sci. 2014.92:4457–4465 doi:10.2527/jas2013-7023
