Front Matter

Chapter 4 The Role of Nutrition in Canine Performance and Rehabilitation 73

popular activities, such as agility and field trial
activities, have been largely ignored, leading to
attempts to translate endurance and sprinting
knowledge into sound nutritional principles
for all athletic dogs. These principles are
addressed here, focusing on three areas: ener-
getics, nutrition for performance, and nutrition
during rehabilitation.

Energetics and the myofiber

Conversion of substrate to energy

The generation of ATP is a universal process in
all cells that occurs through the enzymatic
machinery of the mitochondrial electron trans-
port chain (ETC). In short, the ETC uses free
hydrogen to create an electrochemical gradient
between the inner and outer mitochondrial
membrane. This generates a covalent bond
between ADP and inorganic phosphate to make
ATP, which is the storage form of energy.
ATP generation and hydrolysis becomes a
central theme to appropriate muscle contrac-
tion. ATP is ultimately formed from the genera-
tion of hydrogenated nicotinamide adenine
dinucleotide (NADH) and dihydrogenated
flavin adenine dinucleotide (FADH 2 ) in the

citric acid cycle within mitochondria. The citric

acid cycle is a complex of many enzymes that

convert the byproducts of glucose, protein, and

fat degradation as pyruvate (glucose and some

amino acids) and acetate (fatty acids and some

amino acids) into covalently bound coenzyme

A (CoA) moieties to make acetyl CoA—the

major entry point substrate for the citric acid

cycle (Figure  4.1). No matter where substrates

enter the citric acid cycle they are eventually

turned into carbon dioxide with oxygen as the

reactant in the process for generating ATP

(Shulman & Petersen, 2009).

Glycolysis and beta‐oxidation of

fatty acids

ATP generation occurs through beta‐oxidation

of fat and glucose oxidation through glycolysis,

both of which lead to acetyl CoA production.

Beta‐oxidation of fat is a critical process to

normal daily energy metabolism because fat is

considered the preferred fuel during rest.

Glycolysis is a complex process that begins

with fructose conversion to glucose or glucose’s

immediate entry into the glycolytic pathway.

This breakdown of glucose results in one 6‐carbon

molecule, generating two 3‐carbon precursors,

Succinate

Oxaloacetate

Acetyl CoA

Citrate

GTP

NADH

CO 2

NADH

CO 2

NADH

CO 2

FADH 2

Figure 4.1 The citric acid cycle showing acetyl CoA entry and the formation of NADH and FADH 2 with the liberation
of CO 2 and GTP. NADH and FADH 2 then enter the electron transport chain.