Calculate metabolic energy requirements for fibre production

Calculates the energy requirement for fibre production (MJ/head/day), defined as the additional energy required for the synthesis of animal fibre (e.g. wool or hair).

Usage

calc_metabolic_energy_req_fibre(
  species_short,
  cohort_short,
  fibre_yield_year = 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)

fibre_yield_year

Numeric. Annual production yield of fibre, such as wool, cashmere, mohair (kg/head/year). Required only for species = CML, SHP, and GTS.

Value

Numeric. Energy required for the synthesis of fibre for SHP, GTS and CML. Assumed to be 0 for other species. (MJ/head/day). Expressed as net energy for CTL, BFL, SHP, GTS and as metabolizable energy for CML and PGS (MJ/head/day).

Details

This component follows the IPCC Tier 2 partitioning approach and is applied only to fibre-producing species and relevant cohorts, which are assumed to be FA, FS, MA, and MS.

Species-specific approach:

• SHP and GTS (IPCC, 2006; IPCC, 2019):

  For sheep and goats, fibre production energy is calculated assuming a fixed net energy cost of \(24\) MJ per kilogram of fibre produced. Annual fibre production is converted to a daily requirement as:

  $$ metabolic\_energy\_req\_fibre = \frac{24 \times fibre\_yield\_year}{365} $$

  where:

  • \(fibre\_yield\_year\) is annual fibre production (kg/head/year),

  • \(24\) is the net energy requirement per kilogram of fibre (MJ/kg fibre),

  • division by \(365\) converts annual production to a daily basis.

• CML (AFRC, 1998; Cannas et al., 2007):

  For camels, fibre energy requirements are first calculated on a net energy basis and then converted to metabolizable energy using a net-to-metabolizable energy efficiency coefficient:

  $$ metabolic\_energy\_req\_fibre = \frac{24}{0.43} \times \frac{fibre\_yield\_year}{365} $$

  where:

  • \(24\) is the net energy requirement per kilogram of fibre (MJ/kg fibre),

  • \(0.43\) is the efficiency of conversion from metabolizable energy to net energy for fibre production (fraction),

  • \(fibre\_prod\) is annual fibre production per animal (kg/head/year),

  • \(365\) to convert annual production to a daily basis.

  The efficiency coefficient of \(0.43\) is adopted by analogy with goats, assuming a dietary metabolizability of approximately 0.55, following AFRC guidance and the synthesis by Cannas et al. (2007).

• Other species: Fibre production energy is assumed to be zero.

This function is part of the run_metabolic_energy_req_module().

References

AFRC (1998) The Nutrition of Goats. CAB International, Wallingford, UK.

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.

Cannas, A., Atzori, A. S., Boe, F., & Teixeira, I. (2007). Energy and protein requirements of goats. In: Dairy sheep nutrition (pp. 31-49). 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 10.12.

IPCC. (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Chapter 10: Emissions from Livestock and Manure Management, Equation 10.12.

See also

run_metabolic_energy_req_module,