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Calculate milk production

Source: R/core_model_production.R
calc_milk_production.Rd

Calculates total milk production for the producing cohort (FA) of milk-producing species (CML, CTL, BFL, SHP, GTS) over the assessment period and returns multiple production metrics: total milk mass, milk protein, and fat-protein-corrected milk (FPCM) (kg/cohort/assessment period).

Usage

calc_milk_production(
  species_short,
  cohort_short,
  milk_yield_day,
  simulation_duration,
  cohort_stock_size,
  lactating_females_fraction,
  milk_protein_fraction,
  milk_fat_fraction,
  milk_lactose_fraction,
  milk_protein_fraction_standard,
  milk_fat_fraction_standard,
  milk_lactose_fraction_standard
)

Arguments

species_short

Character. Code identifying the livestock species. Supported values include:

  • PGS: pigs

  • CML: camels

  • CTL: cattle

  • BFL: buffalo

  • SHP: sheep

  • GTS: goats

cohort_short

Character. Sex- and age-specific cohort code describing the production stage of the animals. Supported values include:

  • FA: adult females (from age at first parturition)

  • FS: sub-adult females (from weaning to age at first parturition)

  • FJ: juvenile females (from birth to weaning)

  • MA: adult males (from age at first breeding)

  • MS: sub-adult males (from weaning to age at first breeding)

  • MJ: juvenile males (from birth to weaning)

milk_yield_day

Numeric. Average milk yield per milk-producing animal during the assessment duration (kg/head/day). This value is calculated as the total quantity of milk produced for human consumption by milk-producing animals during the assessment period, divided by the number of milk-producing animals, and the length of the assessment period (days). Required only for species = CML, CTL, BFL, SHP, and GTS.

simulation_duration

Numeric. Length of the assessment period (days).

cohort_stock_size

Numeric. Average population size in each of the 6 sex–age cohorts (# heads). (cohorts=FJ, FS, FA, MJ, MS, MA).

lactating_females_fraction

Numeric. Proportion of adult females that are lactating during the assessment period (fraction). Required only for species: CML, CTL, BFL, SHP, and GTS.

milk_protein_fraction

Numeric. Milk protein fraction (kg protein/kg milk). Required only for species = CML, CTL, BFL, SHP, and GTS.

milk_fat_fraction

Numeric. Milk fat fraction (kg fat/kg milk). Required only for species = CML, CTL, BFL, SHP, and GTS.

milk_lactose_fraction

Numeric. Milk lactose fraction (kg lactose/kg milk). Required only for species = CML, CTL, BFL, SHP, and GTS.

milk_protein_fraction_standard

Numeric. Standard protein content of milk, used to calculate Fat-protein-corrected milk (FPCM), (kg protein/kg milk). Suggested value = 0.033.

milk_fat_fraction_standard

Numeric. Standard fat content of milk, used to calculate Fat-protein-corrected milk (FPCM), (kg fat/kg milk). Suggested value = 0.04.

milk_lactose_fraction_standard

Numeric. Standard lactose content of milk, used to calculate Fat-protein-corrected milk (FPCM), (kg lactose/kg milk). Suggested value = 0.048.

Value

A named list with:

milk_production_mass_cohort

Numeric. Total milk production produced over the assessment period (kg/cohort/assessment period).

milk_production_protein_cohort

Numeric. Total milk protein production produced over the assessment period (kg protein/cohort/assessment period).

milk_production_fpcm_cohort

Numeric. Total fat-protein-corrected milk (FPCM) produced over the assessment period (kg/cohort/assessment period).

Details

Milk production outputs are computed as follows:

  • milk_production_mass_cohort is computed as:

    \(milk\_production = milk\_yield\_day \times simulation\_duration \times cohort\_stock\_size \times lactating\_females\_fraction\)

  • milk_production_protein_cohort is computed as:

    \(milk\_protein\_production = milk\_production \times milk\_protein\_fraction\)

  • milk_production_fpcm_cohort is computed using the ratio of energy content of actual versus standard milk:

    \(FPCM = milk\_production \times \frac{E_{milk}}{E_{standard}}\)

    where milk energy content (Mcal/kg) is computed as (IDF, 2022):

    \(E_{milk} = 0.0929 \times milk\_fat\_fraction + 0.0547 \times milk\_protein\_fraction + 0.0395 \times milk\_lactose\_fraction\)

    \(E_{standard} = 0.0929 \times milk\_fat\_fraction\_standard + 0.0547 \times milk\_protein\_fraction\_standard + 0.0395 \times milk\_lactose\_fraction\_standard\)

Non-zero milk outputs are only expected for adult female cohorts of milk-producing species.

This function is part of the run_production_module().

References

International Dairy Federation (IDF). 2022. The IDF Global Carbon Footprint Standard for the Dairy Sector. Bulletin of the IDF No. 520/2022. International Dairy Federation (ed.), Brussels, Belgium. Equation 10.

See also

run_production_module