Milk Composition and Consumption Flashcards

Vocabulary flashcards covering milk composition, breed differences, milk production metrics, lactose intolerance, mastitis effects, and dietary precursors for milkfat and protein synthesis based on ANMLTEC 3167T lecture notes.

Milk Solids (Total Solids)

The portion of milk that is not water, comprising fat, protein, lactose, ash, and other components (about $13\%$ of milk total), often referring specifically to fat and protein in industry contexts.

Total Solids Non-Fat

The total milk solids remaining after subtracting the fat content, representing the components found in skim milk.

Milkfat

Lipids dispersed in milk in the form of small globules as an oil-in-water emulsion, composed mainly of triglycerides that are lighter than the rest of the milk.

Casein

A class of protein unique to milk that accounts for approximately $80\%$ of total milk protein, serves as the basis for cheese making, and is used to manufacture products like glue, plastics, and sizing.

Whey Proteins

A class of milk protein making up approximately $20\%$ of total protein, including lactalbumin, lactoglobulin, and lactoferrin.

Immune Globulins

Antibodies present at approximately $0.1\%$ in normal milk and in much higher concentrations in colostrum to provide passive immunity to offspring.

Lactose Molecular Structure

A sweet disaccharide sugar synthesized exclusively by cells of the lactating mammary gland, composed of galactose and glucose subunits.

Lactose Intolerance

A condition resulting from an intestinal lactase deficiency that prevents proper digestion of lactose, leading to bloating, cramping, and diarrhea.

Prevalence of Lactose Intolerance

The global geographic distribution of lactose intolerance rate, ranging from $0\text{--}20\%$ in Northern Europe and North America to $80\text{--}100\%$ in parts of Africa, Asia, and South America.

Colostrum

The first milk produced post-calving, containing very high total solids including approximately $14\%$ protein and high levels of immunoglobulins.

Mastitis Effects on Milk

Mammary gland inflammation that causes decreases in lactose, fat, casein, calcium, phosphorus, potassium, and cheese yield, while increasing globulins, salts ($\text{NaCl}$), acidity, and somatic cell count.

De Novo Fatty Acid Synthesis

The synthesis of milkfat inside the mammary gland using volatile fatty acids (primarily acetate and butyrate) derived from ruminal fermentation of carbohydrates.

Preformed Fatty Acids

Milkfat originating directly from dietary fat or body fat mobilization (adipose tissue breakdown yielding $\text{NEFA}$ and chylomicra/$\text{VLDL}$).

Acetic Acid (Acetate)

A short-chain volatile fatty acid produced by fiber digestion in the rumen that serves as the primary precursor for de novo milkfat synthesis.

Propionic Acid (Propionate)

A volatile fatty acid produced during rumen fermentation of sugars and starches that serves as the primary precursor for lactose synthesis.

Butyric Acid (Butyrate)

A volatile fatty acid formed during rumen fermentation of carbohydrates that functions as a precursor for de novo milkfat synthesis.

Butterfat Depression

A reduction in milk fat percentage caused by high-grain, low-hay diets that lower rumen $\text{pH}$ below $6.0$, shifting fermentation away from acetic acid toward propionic acid.

Limiting Amino Acids (Barrel Analogy)

The nutritional concept illustrating that milk production or component synthesis is limited by whichever essential amino acid is in shortest supply (such as methionine or lysine), represented as wooden barrel staves.

Global Milk Production by Source (2022)

The worldwide breakdown of milk production in 2022 led by cattle milk ($753\text{ million tons}$), followed by buffalo ($143\text{ million tons}$), goat ($19.1\text{ million tons}$), sheep ($10.9\text{ million tons}$), and camel milk ($4.1\text{ million tons}$).

USDA Average Holstein Milk Components (2024)

The average composition of Holstein milk reported per USDA in 2024, consisting of $87\%$ water, $4.23\%$ fat, $3.29\%$ protein, $4.8\%$ sugar, $0.7\%$ ash, and $0.2\%$ other.

Fat Variation During Milking

The increase in milk fat percentage from the start to the end of a single milking session, where the first portion contains the lowest fat percentage and the fourth portion contains the highest fat percentage.

Lactation Curve vs. Component Percentage

The inverse relationship during a cow's lactation cycle where daily milk yield peaks early (around weeks $6\text{--}8$) while fat and protein percentages drop, followed by declining milk yield as fat and protein percentages increase.

Seasonal Factors in Milk Production

The seasonal trend where milk volume increases and component percentages (fat and protein) decrease in summer, whereas milk volume decreases and component percentages increase in winter.

Jersey Breed Milk Composition

Milk produced by Jersey cattle, which features the highest fat percentage ($5.03\%$) and protein percentage ($3.76\%$) among major dairy breeds according to 2023 DHI averages.

Holstein Breed Milk Yield

Milk produced by Holstein cattle, characterized by the highest overall milk yield ($26,164\,lb$), total fat ($1,097\,lb$), and total protein ($859\,lb$) per lactation among major dairy breeds, with $4.21\%$ fat and $3.29\%$ protein.