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Calculate metabolic energy requirements for maintenance

Source: R/core_model_metabolic_energy_req.R
calc_metabolic_energy_req_maintenance.Rd

Calculates the energy requirement for maintenance by cohort (MJ/head/day), defined as the energy required to maintain basal physiological functions at equilibrium, with no net gain or loss of body energy.

Usage

calc_metabolic_energy_req_maintenance(
  species_short,
  cohort_short,
  live_weight_cohort_average,
  lactating_females_fraction = NA_real_,
  offtake_rate = NA_real_,
  age_first_parturition = NA_real_
)

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)

live_weight_cohort_average

Numeric. Average live weight over the cohort stage. Computed by accounting for the share of offtaken animals within the cohort, using their slaughter weight, and the potential final weight of animals that remain in the cohort (kg).

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.

offtake_rate

Numeric. Annual proportion of animals removed from the herd for each sex-age cohort (fraction).

age_first_parturition

Numeric. Age at first parturition for female breeding animals (days)

Value

Numeric. Energy required for maintenance, defined as the amount of energy needed to keep the animal at equilibrium such that body energy is neither gained nor lost. Expressed as net energy for CTL, BFL, SHP, GTS and as metabolizable energy for CML and PGS (MJ/head/day).

Details

This approach follows the IPCC Tier 2 partitioning method and applies:

\(metabolic\_energy\_req\_maintenance = cmain \times average\_weight^{0.75}\)

where \(cmain\) is a category-specific coefficient (MJ/day/kg\(^{0.75}\)) that reflects basal metabolic requirements and varies by species, physiological status, and sex.

For selected cohorts, \(cmain\) is computed as a weighted average to account for:

  • CTL, BFL: lactating vs. non-lactating females

  • CTL, BFL, SHP: intact vs. castrated males - Offtaken animals assumed castrated

  • SHP: animals below vs. above one year of age

Specific coefficients by species and cohort:

CTL and BFL (NRC, 1996; AFRC, 1993):

  • FA: \(cmain = 0.386 \times lactating\_females\_fraction + 0.322 \times (1 - lactating\_females\_fraction)\)

  • FS, FJ, MJ: \(cmain = 0.322\)

  • MA, MS: \(cmain = 0.322 \times offtake\_rate + 0.370 \times (1 - offtake\_rate)\)

CML (Wardeh, 2004):

  • All cohorts: \(cmain = 0.435\)

GTS (AFRC, 1993):

  • All cohorts: \(cmain = 0.315\)

SHP (AFRC, 1993):

  • FA: \(cmain = 0.217\)

  • FJ: \(cmain = 0.236\)

  • FS: \(cmain = 0.236 \times (365/age\_first\_parturition) + 0.217 \times ((age\_first\_parturition - 365)/age\_first\_parturition)\)

  • MA: \(cmain = 0.217 \times offtake\_rate + (0.217 \times 1.15) \times (1 - offtake\_rate)\)

  • MJ: \(cmain = 0.236 \times offtake\_rate + (0.236 \times 1.15) \times (1 - offtake\_rate)\)

  • MS: \(cmain = (0.217 \times offtake\_rate + (0.217 \times 1.15) \times (1 - offtake\_rate)) \times ((age\_first\_parturition - 365)/age\_first\_parturition) + (0.236 \times offtake\_rate + (0.236 \times 1.15) \times (1 - offtake\_rate)) \times (365/age\_first\_parturition)\)

PGS (NRC, 1998):

  • All cohorts: \(cmain = 0.4435\)

This function is part of the run_metabolic_energy_req_module().

References

NRC (1998). Nutrient Requirements of Swine, 10th Revised Edition. National Academies Press, Washington, DC.

NRC (1996). Nutrient Requirements of Beef Cattle, 7th Revised Edition. National Academies Press, Washington, DC.

AFRC (1993). Energy and Protein Requirements of Ruminants. An Advisory Manual Prepared by the AFRC Technical Committee on Responses to Nutrients. CAB International, Wallingford, UK.

IPCC. (2019). 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Chapter 10: Emissions from Livestock and Manure Management, Equation 10.3; Table 10.4.

IPCC. (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Chapter 10: Emissions from Livestock and Manure Management, Equation 10.3; Table 10.4.

Wardeh, M. F. (2004). The nutrient requirements of the dromedary camel. Journal of Camel Science, 1(1):37-45. The Camel Applied Research and Development Network (CARDN), Arab Center for the Studies of Arid Zones and Dry Lands (ACSAD).

See also

run_metabolic_energy_req_module, calc_avg_weights