Topic 7: Water - Introductory Animal Nutrition and Feeding

Vocabulary-style flashcards covering the physiological functions, requirements, compartments, and management of water in animal nutrition.

Universal solvent of life

A descriptor for water, which makes up $99\%$ of all molecules in an animal and $50-80\%$ of its body mass.

Biological functions of water

Medium for metabolic reactions, transportation (blood, lymph), gas transfer in lungs, thermoregulation, and lubricant/cushion (synovial fluid).

Solvation

The process of attraction and association of particles of solute and molecules of solvent.

Total Body Water (TBW) in neonates

Approximately $70-88\%$ of body mass (BM).

Total Body Water (TBW) in adults

Approximately $50-75\%$ of body mass (BM), varying inversely with fat content.

Methods to measure TBW

Desiccation, bioelectrical impedance spectroscopy, and marker dilution using isotopically labeled water ($^{3}H_2O$ or $^{2}H_2O$).

Extracellular fluid (ECF)

Water outside the cells, comprising $30-40\%$ of TBW; measured by markers like polyethylene glycol (PEG) or inulin.

Intracellular fluid (ICF)

Water inside the cells (cytosol), comprising $60-70\%$ of TBW; measured by the difference between TBW and ECFV.

Vascular subcompartment

The blood/plasma portion of the ECF, comprising $25\%$ of ECF ($5-7\%$ of BM), measured by Evans blue or radio-labeled RBC.

Free water

Drinking water from sources such as streams, lakes, rain, snow, or troughs.

Preformed water

Water contained within the food or feed consumed by an animal.

Oxidative or metabolic water

Water produced as a product of the oxidation of organic compounds containing hydrogen.

Metabolic water yield: Carbohydrate

$\approx 0.6\,g\,H_2O / g$ substrate.

Metabolic water yield: Lipid

$\approx 1.12\,g\,H_2O / g$ substrate.

Metabolic water yield: Protein

$\approx 0.37\,g\,H_2O / g$ substrate.

Dry matter (DM)

The residue remaining after food is dried at $100-105^{\circ}C$; it allows for nutrient content to be standardized.

Total Dissolved Solids (TDS)

A measure of water quality; levels $< 1000\,mg/L$ are safe, while levels $> 7000\,mg/L$ pose considerable risk and should be avoided.

Water Flux (WF)

The turnover or amount of body water which is replaced each day, calculated as $WF = b \times (TBW)$, where $b$ is the fractional turnover rate.

UWL

Urinary water loss, one of the components in the factorial approach to estimating total water loss (WL).

EWL

Evaporative water loss, which includes water lost through breathing and sweating.

Factorial method: Supply equation

$WI = FWI + PW + MW + RW + (IW)$, where WI is total water intake.

PDS-Pneumatic Drinker system

A management tool that can change line pressure or automatically flush drinker lines to provide cool water in hot weather.

Medicator

A treatment injector that typically uses a $1:128$ dilution (1 ounce per gallon) to treat a whole flock with vitamins, vaccines, or antibiotics.