Table 3. Definitions of key milk productivity traits in dairy cows

Variable name Definition
Milk yield (kg/day) The amount of milk produced per cow per day (in kilograms).
Milk fat (%) The percentage of fat content in milk.
Milk protein (%) The percentage of protein content in milk.
SNF (%) The proportion of non-fat solids in milk, excluding milk fat.
Somatic cell count (×103/mL) The number of somatic cells per milliliter of milk, used as an indicator of udder health.
MUN (mg/dL) The concentration of urea nitrogen in milk, reflecting the balance of dietary protein.
305-day milk yield (kg) The total amount of milk produced over a standardized 305-day lactation period.
305-day milk fat yield (kg) The total amount of milk fat produced over 305 days.
305-day milk protein yield (kg) The total amount of milk protein produced over 305 days.
305-day solids-not-fat yield (kg) The total amount of SNF (non-fat solids) produced over 305 days.
Mature equivalent milk yield (kg) Estimated milk yield adjusted to a standard age (72 months) and lactation length.
Mature equivalent milk fat yield (kg) Estimated milk fat yield adjusted to a standard cow maturity.
Mature equivalent milk protein yield (kg) Estimated milk protein yield adjusted to a standard cow maturity.
Mature equivalent SNF yield (kg) Estimated SNF yield adjusted to a standard cow maturity.
SNF, solids-not-fat; MUN, milk urea nitrogen.