PET Food Processing - March 2021 - 37

FORMULATION

OBTAINING
amino acid balance
It's not just exceeding recommendations.
By Michelina Crosbie, Cara Cargo-Froom, James R. Templeman and Anna K. Shoveller, PhD, University of Guelph

┬ęSergey Tarasov - stock.adobe.com

P

Protein is considered an essential nutrient; however, like
humans, companion animals do not have a requirement
for protein, but rather a requirement for indispensable
amino acids (AA) and sufficient nitrogen. Indispensable
AAs must be supplied in the diet because companion
animals cannot synthesize them. Sufficient intake of indispensable AAs, as well as adequate provision of nonessential AAs, which can be synthesized by the animal if
enough nitrogen and carbon sources are provided in the
diet, allows for the maintenance of whole-body protein
reserves (i.e. lean muscle) and the synthesis of secondary metabolites (i.e. the skin pigment melanin is synthesized from phenylalanine and tyrosine) (Biourge and
Sergheraert 2002).
Current recommendations for indispensable AA
requirements established by the National Research
Council (NRC) for adult dogs are based off limited studies where minimum requirements of the majority of indispensable AAs -histidine, isoleucine, leucine, lysine,
phenylalanine, tyrosine, threonine, tryptophan, and valine - are based only on the lowest concentrations reported in a doctoral dissertation and one empirical peerreviewed report (NRC 2006). In these studies, adult
dogs were fed low-crude protein diets for an extended
period of time and displayed no observable clinical signs
of AA deficiency leading to definition of the minimum
requirements. Both studies that contributed to the recommendations of these AA requirements in adult dogs
used the beagle as a representation of all dog breeds
(Ward 1976) (Sanderson, et al. 2001). This one breed
serves as a basis for suggested requirements of a num-

ber of indispensable AAs for adult dogs of all breeds and
breed sizes, so these reports do not account for potential
differences among dog breeds in physical characteristics
(e.g. conformation), genetics, or lifestyles (e.g. activity
level). These differences may also cause variation in the
way a particular breed utilizes dietary AAs, as well as the
concentration of each indispensable AA that the breed
needs to maintain an ideal bodyweight and/or sustain
metabolic processes and may also affect the dogs' metabolism through a myriad of different processes.
Currently, the most conventional and commonly utilized method for estimating AA requirements is measuring nitrogen balance and growth performance in growing
animals fed diets containing various levels of the specific
AA being estimated and with all other dietary components held constant (NRC 2006) (Milner 1979) (Burns
and Milner 1982) (Czarnecki and Baker 1982). Nitrogen
balance techniques consist of determining the difference
between dietary nitrogen intake and nitrogen excretion
(Tessari 2006). While these techniques may be practical for
generating estimates of AA requirements for growing animals, results from these studies must be carefully considered when extrapolating these requirements to adult dogs
(Just 1982). For example, while growth is typically correlated to nitrogen retention in growing animals (Baker 1986),
changes in nitrogen balance, bodyweight, and whole-body
protein stores occur at slower rates in adult animals since
they are no longer growing (Moughan 1995). As well, this
methodology neglects the secondary metabolic utilization
of an AA, which may have a more profound effect on the
requirements of adult animals than for growing animals

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PET Food Processing - March 2021

Table of Contents for the Digital Edition of PET Food Processing - March 2021

PET Food Processing - March 2021 - Intro
PET Food Processing - March 2021 - 1
PET Food Processing - March 2021 - 2
PET Food Processing - March 2021 - 3
PET Food Processing - March 2021 - 4
PET Food Processing - March 2021 - 5
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PET Food Processing - March 2021 - 7
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http://digital.petfoodprocessing.net/sosland/pfp/pet-food-processing-march-2021
http://digital.petfoodprocessing.net/sosland/pfp/2020_12_01
http://digital.petfoodprocessing.net/sosland/pfp/2020_10_01
http://digital.petfoodprocessing.net/sosland/pfp/2020_09_01
http://digital.petfoodprocessing.net/sosland/pfp/2020_06_01
http://digital.petfoodprocessing.net/sosland/pfp/2020_03_01
http://digital.petfoodprocessing.net/sosland/pfp/2019_12_01
http://digital.petfoodprocessing.net/sosland/pfp/2019_10_01
http://digital.petfoodprocessing.net/sosland/pfp/2019_09_01
http://digital.petfoodprocessing.net/sosland/pfp/2019_06_01
http://digital.petfoodprocessing.net/sosland/pfp/2019_03_01
http://digital.petfoodprocessing.net/sosland/pfp/2018_12_01
http://digital.petfoodprocessing.net/sosland/pfp/2018_09_01
http://digital.petfoodprocessing.net/sosland/pfp/2018_06_01
http://digital.petfoodprocessing.net/sosland/pfp/2018_03_01
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