Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Crystal L Levesque


Lysine efficiency, Pregnant gilts, Protein retention, Threonine efficiency


In pregnant pigs, amino acid (AA) requirements represent the sum of those required for maintenance functions, protein retention and efficiency of utilizing AA intake for the aforementioned body processes. The NRC (2012) model assumed AA efficiency is constant across period of gestation; however this is not reflective of the changes in metabolic demand during gestation. Therefore, two experiments were conducted to evaluate the efficiency of utilizing SID Lys and Thr for whole body protein retention (kSIDLys and kSIDThr) in pregnant gilts during early, mid and late gestation. Three 12 d N-balance studies were conducted to represent different periods of gestation. Graded levels of Lys and Thr moderately below the NRC (2012) requirements were used to estimate the AA efficiency within balance periods. Lysine and Thr efficiency using regression analysis could not be determined for early and mid-gestation because of the lack of response in Lys and Thr retention to increasing SID Lys and Thr intake, respectively, which reflects an oversupply of the respective test AA. At the lowest SID Lys and Thr intake, Lys and Thr efficiency were 0.49 and 0.32 for early gestation and 0.61 and 0.52 for mid-gestation, respectively. In contrast, kSIDLys and kSIDThr in late gestation were determined to be 0.54, which is slightly higher than the current NRC (2012) estimate of 0.49 and 0.53 for Lys and Thr, respectively. Evidences from our current study suggest that kSIDLys and kSIDThr are not constant throughout gestation and therefore not reflective of the changes in metabolic demand of pregnant pigs during pregnancy. Also, the lack of response to dietary SID Lys and Thr levels suggest that SID Lys and Thr requirements of pregnant gilts are lower (i.e./d and/d) than the current NRC (2012) recommendation of 11 g SID Lys and 8 g SID Thr/d from d 0 to 90 of gestation; whereas the requirements for SID Lys and Thr during late gestation (>90 d) is reasonably represented in NRC (2012) at 17 and 12 g/d, respectively. Our current research is important for the refinement of the AA requirement model for gestating pigs to ensure diet optimization, nutrient excretion management and improvement of overall farm efficiency.

Library of Congress Subject Headings

Swine -- Feeding and feeds.
Lysine in animal nutrition.
Proteins in animal nutrition.
Swine -- Reproduction.


Includes bibliographical references



Number of Pages



South Dakota State University



Rights Statement

In Copyright