Evaluation of the optimal true-ileal-digestible lysine and threonine requirement for nursery pigs (2004)

N A Lenehan,C W Hastad,J L Usry,Michael D Tokach,Steven S Dritz,Robert D Goodband,Joel M Derouchey,Jim L Nelssen

doi:10.4148/2378-5977.6884

Abstract

A total of 1800 pigs (Exp 1, 360; Exp. 2, 1440) were used in two experiments to evaluate the true ileal digestible (TID) lysine and threonine requirement for 24to 44-lb pigs. In Exp. 1, there were eight pens per treatment, with five pigs (Genetiporc, initially 23.6 lb and 34 d of age) per pen. Experiment 1 was conducted as a combination of two separate trials to simultaneously examine both the TID lysine and threonine requirement, and hence, determine the appropriate threonine-to-lysine ratio. The first part of the trial consisted of five treatments formulated to contain 0.9, 1.0, 1.1, 1.2, or 1.3% TID lysine, with TID threonine at 66% of lysine. The second part consisted of five treatments formulated to 1.3% TID lysine with increasing TID threonine (0.60, 0.66, 0.73, 0.79, or 0.85%). Other amino acids were formulated to either meet or exceed requirement estimates, thereby ensuring lysine and threonine were first limiting. The highest concentrations of both lysine and threonine (1.3% and 0.85%, respectively) were combined in a single diet, which was used in both trials, to give a total of 10 treatments. From d 0 to 17, ADG and feed efficiency (F/G) improved as TID lysine (quadratic, P<0.02) and threonine (ADG, linear, P<0.03; F/G, quadratic, P<0.04) increased. Regression analysis showed that 95% or more of the maximum response was obtained at a TID threonine-to-lysine ratio of approximately 64% for ADG and 66% for F/G. In Exp. 2, there were 48 pigs per experimental unit (2 pens sharing a fenceline feeder) and six replications per treatment. Pigs (PIC, 24 lb and 39 d of age) were fed experimental diets containing 1.1% TID lysine (calculated to be less than their requirement estimate), with added Lthreonine to give TID threonine concentrations of 0.55, 0.60, 0.66, 0.72, or 0.77% and TID threonine-to-lysine ratios of 50, 55, 60, 65, and 70%. For the 21-d trial, ADG (quadratic, P<0.07) and F/G (quadratic, P<0.01) improved with increasing TID threonine. The best ADG and F/G were observed at 0.72% TID threonine. Hence, it seems that pigs weighing between 22 and 44 lb require approximately 0.72% TID threonine (0.81% total threonine) when fed 1.1% TID lysine, which corresponds to a TID threonine-tolysine ratio of 65%, similar to results in Exp. 1. Data from these two studies indicate an optimal TID threonine-to-lysine ratio of approximately 64 to 66% for 24to 44-lb pigs.

Highlights

There is an increased interest in synthetic threonine supplementation in swine diets because it has become more commercially available and economically viable
Experiment 1 was conducted as a combination of two separate trials to simultaneously examine both the true ileal digestible (TID) lysine and threonine requirement, and determine the appropriate threonine-to-lysine ratio
The first part of the trial consisted of five treatments formulated to contain 0.9, 1.0, 1.1, 1.2, or 1.3% TID lysine, with TID threonine at 66% of lysine

Summary

Introduction

There is an increased interest in synthetic threonine supplementation in swine diets because it has become more commercially available and economically viable. The current National Research Council (NRC) requirement estimate for true-ileal-digestible lysine and threonine for a 24- to 44-lb pig are 1.01 and 0.63% of the diet, respectively, suggesting a TID threonine-to-lysine ratio of 62%. Lysine and threonine requirement estimates from the NRC are less than those currently being used in commercial production. The objective of these experiments was to determine the optimal ratio of threonine to lysine, and to characterize the optimal use of synthetic threonine in diets to maximize growth performance of the nursery pig

Results

Discussion

Conclusion