Farm Animal Metabolism and Nutrition

Chapter 4

Phenethanolamine Repartitioning Agents

D.E. Moody, D.L. Hancock and D.B. Anderson

Research and Development, Elanco Animal Health,

Greenfield, Indiana, USA

Introduction

Phenethanolamine leanness-enhancing

repartitioning agents have been studied in

livestock species for nearly two decades.

Work leading to the discovery of new com-

pounds with repartitioning effects began at

several pharmaceutical laboratories in the

late 1970s. Patents were issued and initial

reports were made in the mid-1980s (e.g.

Asato et al., 1984; Anderson et al., 1987a;

Convey et al., 1987; Veenhuizen et al.,

1987). Since the mid-1980s, data have been

generated to define the physiological

effects and the parameters needed to

optimize the response. One of these com-

pounds manufactured by Hoechst Roussel

Vet, zilpaterol, has been cleared for use and

is being sold in South Africa and Mexico.

Ractopamine, an Elanco Animal Health

products, is cleared for use in swine in the

US.

Several reviews of phenethanolamine

repartitioning agent use in livestock have

been published. Anderson et al. (1991)

provide an extensive review with >360

citations, Moloney et al.(1991) provide a

particularly complete summarization of

the efficacy of various compounds, and

Mersmann (1998) provides an updated

review of mechanism of action. The objec-

tives of this chapter are: (i) to summarize

the effects of phenethanolamines on

growth and carcass traits, including a

review of factors that influence those

effects; (ii) to describe the mode of action

of phenethanolamines in livestock and

explore topics currently under investiga-

tion that could contribute to a better under-

standing of their efficacy; (iii) to present

safety information surrounding the use of

phenethanolamines; and (iv) to discuss

potential implications of the use of

phenethanolamines in the livestock

industry.

Effects of Phenethanolamines

in Livestock

Compounds

The phenethanolamines are a general class

of compounds that have been used success-

fully in human medicine for many years

(Hoffman and Lefkowitz, 1996). More

recently, the potential use of these

compounds in improving the efficiency of

© CAB International2000. Farm Animal Metabolism and Nutrition

(ed. J.P.F. D’Mello) 65

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