Examining the effect of non-essential amino acid nitrogen content on lysine requirement for nitrogen retention and growth performance in growing pigs
Date
2023-08-17
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
Low protein (LP) diets with crystalline amino acid (CAA) supplementation have improved nitrogen (N) utilization while maintaining performance in growing pigs. Although LP diets are beneficial, non-essential amino acids (NEAA) or N may become limiting in LP diets, affecting N utilization for N retention (NR). Consequently, the essential amino acid-nitrogen to total nitrogen ratio (EAA-N:TN) may be useful in determining the appropriate amount of EAA and NEAA, or N, that should be provided in LP diets. Therefore, this thesis evaluated the effects of providing a low (LR) or high (HR) EAA-N:TN ratio on lysine (Lys) requirement for NR and growth performance in pigs. An N balance study estimated 1.21% standardized ileal digestible (SID) Lys requirement to maximize NR in pigs fed the HR diets. No breakpoint was achieved for pigs fed the LR diets. Therefore, NEAA or N become limiting in HR diets, whereas Lys is limiting in LR diets. A follow-up growth performance study was conducted using the same LR and HR ratios in the diets, with Lys included at 100% NRC requirements, and at the breakpoint value from the N-balance study, formulated for 20-50 kg pigs. Average daily gain (ADG), average daily feed intake (ADFI), gain:feed (G:F), and N output were measured in the growth performance study. Increasing Lys resulted in increased overall ADG and ADFI, but there was no effect of ratio or interactive effect of ratio and Lys. However, pigs fed the HR diets had improved ADG in week 4, whereas pigs fed LR diets had improved ADG and G:F in week 1. In addition, pigs fed the HR diets with 1.22% SID Lys had lower N output compared to pigs fed the other diets. It was concluded that insufficient dietary N may be more of a concern during periods of general nutrient insufficiency, and that diets deficient in dietary N may require more Lys than what is currently recommended. Overall, an increase in Lys may be required to maximize NR and growth, and that NEAA and N become limiting in HR diets. By incorporating the EAA-N:TN ratio in current diet formulations, along with appropriate dietary inclusion of EAA may result in decreased dietary costs for producers and decreased N excretion into the environment, while improving NR and N utilization in growing pigs.
Description
Keywords
Low protein, amino acids, nitrogen retention, non-essential amino acids, essential amino acid-nitrogen to total nitrogen ratio, growing pigs, lysine
Citation
Degree
Master of Science (M.Sc.)
Department
Animal and Poultry Science
Program
Animal Science