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Cited by 25Effects of Environmental Stressors on LivestockThermoregulation and physiological responsesAnimal Nutrition and Physiology

Theoretical model of heat balance in pigs

Fialho, F. B., Bucklin, R. A., Zazueta, F. S., Myer, R. O.·2004·Animal Science
DOI 10.1017/s135772980005459x
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Abstract

AbstractA theoretical model was developed to predict the heat balance and body temperature of growing and finishing pigs subjected to different environments. The heat transfer modes considered in the model were convection to the surrounding air, conduction to the floor, long-wave radiation between the animal and the surrounding walls, shortwave radiation from the sun, evaporation on the skin surface, evaporation and heating of air in the respiratory tract and heating of ingested food and water. The heat balance is the net heat gain or loss from the environment due to all these processes, added to the animal's heat production. Body temperature is calculated over time using the heat balance, the animal's mass and the specific heat of the animal's body. Behavioural responses to heat and cold environments, such as vasoconstriction, vasodilatation, posture changes and huddling were expressed as changes in heat transfer coefficients and exposed surface area. The increase in evaporation under hot conditions was also considered. It was assumed that the animal's reaction to the environment may be expressed as a function of mean body temperature. The animal's heat production was considered an input to the model, which should reflect the increased metabolic rate in cold environments. Although further research is still needed to determine precisely some of the parameters, the model may be integrated with other models in order to compose a complete pig model.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper presents a theoretical heat-balance model for growing and finishing pigs that predicts heat loss and mean body temperature using body temperature as the main feedback mechanism. Simulations of a 70-kg pig illustrate the relative importance of skin, floor, respiratory, solar-radiation, wallowing and ingested-food/water heat exchanges.

Key findings

The model partitions total heat loss among shaded skin, sunlit skin, floor, breathing and ingested matter, and calculates body temperature from heat balance, body mass and specific heat. In a 70-kg pig simulation at 30°C with no sunlight or wallowing, body temperature was 40·4°C and total heat loss was 206 W; with 0·40 of skin exposed to sunlight at noon, body temperature rose to 42·4°C and total heat loss fell to 111 W, while at midnight it was 40·3°C and 205 W. Allowing wallowing so up to 0·40 of skin could be wet kept body temperature at 39·2°C, with evaporation from shaded skin at 60 W/m² and breathing heat loss only 8 W. Heating ingested food and water accounted for only 0·02 to 0·04 of total heat loss; changing water temperature from 30°C to 20°C produced a very small change in body temperature.

Methods

The study developed a theoretical simulation model of pig heat balance, incorporating conduction to the floor, convection, long-wave radiation, short-wave solar radiation, skin evaporation, respiratory ventilation and heating of ingested food and water. The model was implemented in C++ and tested by simulating a 70-kg pig under four environmental conditions, with critical body temperatures set to 38·5, 39·5 and 40·5°C. A sensitivity check reran the simulations using critical body temperatures of 38·8, 39·2 and 41·3°C.

Limitations

The paper states that further research is needed to determine some parameters precisely, that the tests do not attempt to validate the model but only demonstrate relative importance of heat-loss modes and logical/robust behaviour, and that validation is done in a companion paper. It also states that mean body temperature is very difficult, if not impossible, to measure precisely, and that the critical body temperatures used were arbitrary regulation values rather than precise indications of actual body temperature. The text makes evident that the simulations use only one 70-kg pig and no empirical validation data are presented in this paper.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1017/s135772980005459x

Cites

18 of 18 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

2 of 36 cited sources checked · 1 supported · 0 flagged · accuracy not yet measured

  • Findingown data
    § Test of the model

    In simulation run 1, most heat loss was through the exposed skin, mainly by convection and long-wave radiation.

    “Still, most heat loss was through the exposed skin, mainly by convection and long-wave radiation, as shown in Table 1.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Body surface area is proportional to body weight to the power 2/3.
    • The authors state this as an assumption: Heat transfer is zero for skin in contact with animals.
    • The authors state this as an assumption: Pigs tend to maximize contact area with a cool floor in a hot environment, or with a warm floor in a cold environment; otherwise they try to stay away from the floor.
    • The authors state this as an assumption: There is enough space in the pen for all animals to be comfortably lying down without necessarily having to be in contact with each other.
    • The authors state this as an assumption: The value of ka is maximum for Tb < Tcb and zero for Tb > Teb, with intermediate values given by transition functions.
    • The authors state this as an assumption: The value of ks will be maximum for Tb < Tcb; for Tb > Teb, ks is given by an equation.
    • The authors state this as an assumption: The value of rv is minimum for Tb < Teb and maximum for Tb > Thb, with intermediate values calculated by a transition function.
  • Findingnone given
    § Test of the model

    In thermoneutral conditions of run 3, Tb (39.1C) was similar to the value observed previously.

    “In the thermoneutral conditions of simulation run 3, Tb (39·1ºC) was similar to the value observed previously.”
    Quote in the paperNot a substantial claim
  • Findingown data
    § Test of the model

    The effect of heating ingested food and water to body temperature was only 0.02 to 0.04 of total heat loss.

    “The effect of heating ingested food and water to body temperature was only 0·02 to 0·04 of total heat loss, and is included in the model for completeness.”
    Quote in the paperNot a substantial claim
  • Findingreasoning
    § Test of the model

    When simulations were rerun with critical body temperatures 38.8, 39.2, 41.3, simulated Tb was higher than Table 1 for runs 1 (40.7), 2 (43.1 and 40.7), 4 (40.6), due to increase in critical body temperature scale for hot environments.

    “As expected, simulated Tb was higher than the values in Table 1 for simulation runs 1 (40·7ºC), 2 (43·1 and 40·7ºC) and 4 (40·6ºC), due to the increase in the critical body temperature scale for hot environments.”
    Quote in the paperNot a substantial claim
  • Findingreasoning
    § Test of the model

    In simulation run 2, the simulated pig ate only at night, after body temperature decreased back to a tolerable level.

    “The simulated pig ate only at night, after body temperature decreased back to a tolerable level.”
    Quote in the paperSubstantial claim
  • May combine two claims. 21
  • Classified as probably not a substantial claim. 18

  • May combine two claims.

    Premisecitation
    § Other modes of heat transfer

    Schiavon and Emmans (2000) reported similar values, with water intake approximately doubling over the range of temperatures studied.

    “Schiavon and Emmans (2000) reported similar values, with water intake approximately doubling over the range of temperatures studied.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Schiavon and Emmans, 2000 source

  • May combine two claims.

    Premisecitation
    § Other modes of heat transfer

    Schiavon and Emmans (2000) verified an increase in water intake with body weight, although the analysis of their data suggest that the relationship is not linear.

    “Schiavon and Emmans (2000) verified an increase in water intake with body weight, although the analysis of their data suggest that the relationship is not linear.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Schiavon and Emmans, 2000 source

      The Evaluation section reports a positive slope of 76 (SE 10) g of measured water intake per kg of body weight, supporting the increase with weight. It does not report that the weight–intake relationship is nonlinear; its low R² values are attributed to other sources of variation. The nonlinearity inference is therefore not supported by the cited paper’s analysis. (LLM, conf=0.84)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data
    § Test of the model

    The model behaves as logically expected under the simulated conditions.

    “They also demonstrate that the model behaves as logically expected under the simulated conditions”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Test of the model

    In simulation run 2, body temperature increased sharply above the upper critical temperature during the day, inhibiting food intake and growth, in order to reduce heat production.

    “In this condition, body temperature increased sharply above the upper critical temperature during the day, inhibiting food intake and growth, in order to reduce heat production.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The value of ka is maximum for Tb < Tcb and zero for Tb > Teb, with intermediate values given by transition functions.
    • The authors state this as an assumption: The value of ks will be maximum for Tb < Tcb; for Tb > Teb, ks is given by an equation.
    • The authors state this as an assumption: The value of rv is minimum for Tb < Teb and maximum for Tb > Thb, with intermediate values calculated by a transition function.

  • May combine two claims.

    Findingown data
    § Test of the model

    In simulation run 2, the net total heat loss rate at noon was much smaller than at midnight, due to solar radiation, although heat loss by all other means was greater.

    “As shown in Table 1, the net total heat loss rate at noon was much smaller than at midnight, due to solar radiation, although heat loss by all other means was greater.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Test of the model

    The model behaved similarly using both sets of critical body temperatures; apart from a small difference in noon values of run 2, the remaining heat loss estimates were nearly identical.

    “As shown in Figure 3, the model behaved similarly using both sets of critical body temperatures. Apart from a small difference in the noon values of simulation run 2, the remaining heat loss estimates were nearly identical.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Test of the model

    In simulation run 3, body temperature was within the thermoneutral zone, and breathing rate was normal.

    “Body temperature was within the thermoneutral zone, and breathing rate was normal, as shown on Table 1 by the small value of heat loss through breathing.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning
    § Test of the model

    In simulation run 1, simulated body temperature was within the evaporative zone, meaning breathing rate was above normal.

    “Simulated body temperature was within the evaporative zone, meaning breathing rate was above normal.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The value of rv is minimum for Tb < Teb and maximum for Tb > Thb, with intermediate values calculated by a transition function.

  • May combine two claims.

    Findingown data
    § Test of the model

    In simulation run 4, changing water temperature to 20C caused a very small change in body temperature and a slightly smaller breathing rate.

    “The effect of this change was a very small change in body temperature and a slightly smaller breathing rate.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Model description

    The heat and mass transfer equations originate from physical principles, which may be found in the ASHRAE handbook.

    “The heat and mass transfer equations originate from physical principles, which may be found in the ASHRAE handbook (American Society of Heating, Refrigerating and AirConditioning Engineers, 1989).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites American Society of Heating, Refrigerating and AirConditioning Engineers, 1989

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given
    § Heat transfer across the skin

    Most of the heat lost from the skin to the surrounding environment is produced in the inner core of the animal's body.

    “Most of the heat lost from the skin to the surrounding environment is produced in the inner core of the animal's body.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given
    § Heat transfer across the skin

    Ct is minimum in a cold environment when Tb < Tcb and maximum in a hot environment when Tb > Teb.

    “C t is minimum ( C t0 , W/m 2 per ºC) in a cold environment, when Tb &lt; Tcb and maximum ( Ct1 , W/ m 2 per ºC) in a hot environment, when Tb &gt; Teb .”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given
    § Heat transfer across the skin

    Heat is transferred between the skin and the floor by conduction.

    “Heat is transferred between the skin and the floor by conduction.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Zones of the thermal environment

    Changes in ambient temperature alter metabolism and affect the level of heat production and heat loss.

    “Changes in ambient temperature ( T a , ºC) alter metabolism and affect the level of heat production and heat loss, as shown in Figure 2.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Mount, 1974 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Zones of the thermal environment

    Between Tc and Te, the animal is in the thermoneutral zone, where metabolism is stable.

    “Between T c and T e , the animal is considered to be in the thermoneutral zone, where metabolism is stable.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Mount, 1974 source

  • May combine two claims.

    Premisecitation
    § Zones of the thermal environment

    When Ta > Th, food intake stops, heat production decreases to a minimum after digestion of remaining food in the gut, and respiration and perspiration rates are maximum, although there is still a slight increase in evaporative heat loss due to the reduction in relative humidity of air as temperature rises.

    “When T a &gt; T h , food intake stops, heat production decreases to a minimum (after digestion of remaining food in the gut) and respiration and perspiration rates are maximum, although there is still a slight increase in evaporative heat loss due to the reduction in relative humidity of air as temperature rises.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Giles, 1992

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation
    § Zones of the thermal environment

    If ambient temperature rises above the evaporative critical temperature Te, evaporative heat loss increases and food intake is inhibited, reducing metabolism and heat production.

    “If T a rises above the evaporative critical temperature ( T e , ºC), evaporative heat loss increases and food intake is inhibited, reducing metabolism and heat production.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Mount, 1974 source

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given
    § Zones of the thermal environment

    As ambient temperature rises above Th, heat loss continues to decrease or becomes heat gain, with no decrease in heat production.

    “As ambient temperature rises above T h , heat loss continues to decrease (or becomes heat gain), with no decrease in heat production.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § Heat transfer across the skin

    Black et al. (1986) assumed that vasodilatation reduces tissue insulation to 0.25 of the maximum value.

    “Black et al. (1986) assumed that vasodilatation reduces tissue insulation to 0·25 of the maximum value, such that the value of Ct1 may be calculated by a similar relationship:”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Black et al. (1986)

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Interpretationreasoning
    § Model description

    Improvements may be made on one part of the model without altering the other part.

    “Improvements may be made on one part of the model without altering the other part.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § Heat transfer across the skin

    These values show that water diffusion only accounts for around 0.04 of the skin being wetted, and that this value does not change much as temperature rises.

    “These values show that water diffusion only accounts for around 0·04 of the skin being wetted, and that this value does not change much as temperature rises.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationnone given
    § Model description

    The heat balance model described in the paper simulates the pig's heat loss (or gain) to the environment, heat balance and body temperature variations.

    “The heat balance model described in this paper simulates the pig's heat loss (or gain) to the environment, heat balance and body temperature variations.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The thermal effects of the environment on the animal can be completely expressed by the animal's mean body temperature.

  • May combine two claims.

    Premisecitation
    § Heat transfer across the skin

    Otherwise, heat is transferred by conduction to the floor, convection to the surrounding air, long-wave radiation from the surrounding walls, short-wave radiation from the sun and evaporation from the skin surface.

    “Otherwise, heat is transferred by conduction to the floor, convection to the surrounding air, long-wave radiation from the surrounding walls, short-wave radiation from the sun and evaporation from the skin surface (Ingram and Mount, 1975).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Ingram and Mount, 1975 source

  • May combine two claims.

    Premisecitation
    § Heat transfer across the skin

    Skin exposed to a shaded environment is subjected to long-wave radiation from the surrounding walls, convection by movement of air and heat loss by evaporation of water.

    “The skin exposed to a shaded environment is subjected to long-wave radiation from the surrounding walls, convection by movement of air and heat loss by evaporation of water (Ingram and Mount, 1975).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Ingram and Mount, 1975 source

  • May combine two claims.

    Premisecitation
    § Zones of the thermal environment

    At a hot environment above Te, physiological mechanisms increase evaporation rate and food intake decreases gradually until the upper critical temperature Th is reached.

    “At the other extreme, when temperature rises in a hot environment (above T e ), physiological mechanisms increase evaporation rate and food intake decreases gradually, until the upper critical temperature ( T h , ºC) is reached (Giles, 1992).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Giles, 1992

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Premisecitation
    § Zones of the thermal environment

    It is not possible to express Tc and Te values properly without defining the conditions in which the animal is in.

    “Therefore, it is not possible to express their values properly without defining the conditions in which the animal is in (Mount, 1975).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Mount, 1975 source

  • May combine two claims.

    Interpretationnone given
    § Conclusions

    Body temperature is used to characterize environmental conditions and regulate feedback mechanisms which control heat loss.

    “Body temperature is used to characterize the environmental conditions and regulate the feedback mechanisms which control heat loss.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

    Interpretationreasoning
    § Applications

    The complete model may be used to optimize feeding strategies under different environmental conditions, and evaluate changes in the production system.

    “This complete model may be used to optimize feeding strategies under different environmental conditions, and evaluate changes in the production system.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Heat transfer across the skin

    Black et al. (1986) assumed that the pig is able to wet up to 0.15 of the skin by water and urine, which would make rww1 equal to 0.15.

    “They assumed that the pig is able to wet up to 0·15 of the skin by these means, which would make r ww1 equal to 0·15.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Black et al. (1986)

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationnone given
    § Applications

    The principle of using body temperature as a central regulation mechanism may also be applied in other models.

    “The principle of using body temperature as a central regulation mechanism may also be applied in other models.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Heat transfer across the skin

    Bruce and Clark (1979) and Black et al. (1986) use values of 0.1 for kf0 and 0.2 for kf1.

    “Bruce and Clark (1979) and Black et al. (1986) use values of 0·1 for k f0 and 0·2 for k f1 .”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Bruce and Clark, 1979 source
    • cites Black et al., 1986

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Heat transfer across the skin

    The saturation vapour pressure for air at a given absolute temperature T* is given by a common psychrometric function pws(T*).

    “The saturation vapour pressure for air at a given absolute temperature T * is given by a common psychrometric function pws ( T * ) (ASHRAE, 1989):”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites ASHRAE, 1989

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Interpretationreasoning
    § Applications

    Through simulation, the effect of changes on thermal comfort and economic impact may be estimated before they are implemented.

    “Through the use of simulation, the effect of these changes on the thermal comfort of the animal and their economic impact may be estimated before they are actually implemented.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Heat transfer across the skin

    For a typical skin temperature of 32oC, hL is 2425 J/g, with the proportional variation in this value being less than ±0.01 for a skin temperature range of 22 to 42oC.

    “For a typical skin temperature of 32ºC (Bruce and Clark, 1979), hL is 2425 J/g (ASHRAE, 1989), with the proportional variation in this value being less than ± 0·01 for a skin temperature range of 22 to 42ºC.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Bruce and Clark, 1979 source
    • cites ASHRAE, 1989

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationnone given
    § Conclusions

    The model may be integrated with other models in order to compose a complete pig model.

    “and may be integrated with other models in order to compose a complete pig model.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given
    § Applications

    The heat balance model may be integrated with models of other physiological systems to create a larger model of the pig.

    “The heat balance model may be integrated with models of other physiological systems, in order to create a larger model of the pig.”
    Quote in the paperNot a substantial claim
36 of 36

  • The authors state this as an assumption.

    The thermal effects of the environment on the animal can be completely expressed by the animal's mean body temperature.

    “It assumes that the thermal effects of the environment on the animal can be completely expressed by the animal's mean body temperature ( T b , ºC).”

  • The paper relies on this without support.

    Body temperature is affected by all modes of heat transfer.

    “Since body temperature is affected by all modes of heat transfer, it is thought to be a more accurate variable than ambient temperature with which to model the thermal environment zones.”

  • The paper relies on this without support.

    A pig loses heat by breathing and heating ingested food and water to body temperature.

    “Additionally, a pig loses heat by breathing and heating ingested food and water to body temperature.”

  • The paper relies on this without support.

    Under hot conditions, pigs may gain heat from the environment, especially if exposed to the sun.

    “Under hot conditions, pigs may gain heat from the environment, especially if exposed to the sun.”

  • The paper relies on this without support.

    Within the thermoneutral zone, the animal changes posture, behaviour and peripheral blood flow in order to maintain mean body temperature approximately constant.

    “Within the thermoneutral zone, the animal changes posture, behaviour and peripheral blood flow in order to maintain mean body temperature approximately constant.”

  • The paper relies on this without support.

    Although core body temperature may remain constant, skin temperature may change in response to the environment.

    “Although core body temperature may remain constant, skin temperature may change in response to the environment.”

  • The authors state this as an assumption.

    If the skin is in contact with another portion of skin, heat transfer is zero.

    “If the skin is in contact with another portion of skin, either by being folded over itself or in contact with other animals, heat transfer is assumed to be zero.”

  • The authors state this as an assumption.

    One way to implement the model is to assume that heat flows laterally within the floor and that floor temperature is equal to air temperature (Tf = Ta).

    “One way to implement the model is to assume that heat flows laterally within the floor and that floor temperature is equal to air temperature ( Tf = Ta ), as done by Bruce and Clark (1979).”

  • The authors state this as an assumption.

    In a hot environment when Tb > Teb, the animals do not huddle, and the value of N used in the previous equation should be equal to one.

    “In a hot environment (when Tb &gt; Teb ), the animals do not huddle, and the value of N used in the previous equation should be equal to one.”

  • The authors state this as an assumption.

    Assuming Tr* ≈ Tse* ≈ (Ta + 273.15), which is reasonable in absolute temperatures, (Tse*4 - Tr*4) may be approximated by 4·(Ta+273.15)^3·(Tse - Tr).

    “Assuming Tr * ≈ Tse * ≈ ( Ta + 273·15), which is reasonable in absolute temperatures, ( T * se 4 -T * r 4 ) may be approximated by 4 · ( Ta + 273·15) 3 · ( Tse -T r ), and qRe can be rewritten as:”

  • The authors state this as an assumption.

    Both el and er are parameters which may be assumed equal to 0.95.

    “Both e l and e r are parameters which may be assumed to be equal to 0·95 (Curtis, 1983).”

  • The authors state this as an assumption.

    The pig could be represented as a cylinder for calculating hC.

    “Assuming that the pig could be represented as a cylinder, Bruce and Clark (1979) calculated hC as a function of air speed ( Va , m/ s) and body weight ( Wb , kg):”

  • The authors state this as an assumption.

    The model assumes that an increase in sweating only occurs in heat stress situations, when Tb is above Teb.

    “The model assumes that an increase in sweating only occurs in heat stress situations, when Tb is above Teb .”

  • The paper relies on this without support.

    Pigs do not sweat in response to temperature change.

    “Pigs do not sweat in response to temperature change.”

  • The paper relies on this without support.

    Water diffusion through the skin is responsible for a certain amount of heat loss.

    “However, water diffusion through the skin is responsible for a certain amount of heat loss.”

  • The authors state this as an assumption.

    Assuming Tr* ≈ Tss* ≈ (Ta + 273.15), which is reasonable in absolute temperatures, (Tss*4 - Tr*4) may be approximated by 4·(Ta+273.15)^3·(Tss - Tr).

    “Assuming Tr * ≈ Tss * ≈ ( Ta + 273·15), which is reasonable in absolute temperatures, ( T * ss 4 -T * r 4 ) may be approximated by 4 · ( Ta + 273·15) 3 · ( Tss -T r ), and qRs can be rewritten as:”

  • The authors state this as an assumption.

    A pig can be considered a cylinder with its axis perpendicular to the sun, so θ can be estimated as arcsin(2/π) ≈ 40º.

    “Assuming again that a pig could be considered a cylinder with its axis perpendicular to the sun, the value of θ may be estimated by the ratio between skin surface and cross-section area as arcsin(2/ π ), which is approximately 40º.”

  • The authors state this as an assumption.

    Body surface area is proportional to body weight to the power 2/3.

    “The animal's body surface area ( Ab , m 2 ) is assumed to be proportional to body weight to the power 2/3, as a result of the relation between area and volume:”

  • The authors state this as an assumption.

    Heat transfer is zero for skin in contact with animals.

    “The fraction of body surface area in contact with animals ( k a ), where heat transfer is assumed zero, is a function of the environment.”

  • The authors state this as an assumption.

    Pigs tend to maximize contact area with a cool floor in a hot environment, or with a warm floor in a cold environment; otherwise they try to stay away from the floor.

    “The model assumes that the pigs will tend to maximize contact area with a cool floor in a hot environment, or with a warm floor in a cold environment. Otherwise, they will try to stay away from the floor, in an approach similar to that used by Green and Whittemore (2003).”

  • The authors state this as an assumption.

    There is enough space in the pen for all animals to be comfortably lying down without necessarily having to be in contact with each other.

    “The model assumes that there is enough space in the pen for all animals to be comfortably lying down without necessarily having to be in contact with each other.”

  • The authors state this as an assumption.

    Air leaves the respiratory tract at an intermediate temperature between air temperature and core temperature, saturated with water at that temperature.

    “The model assumes that the air leaves the respiratory tract at an intermediate temperature between air temperature and core temperature, saturated with water at that temperature.”

  • The authors state this as an assumption.

    Water intake is proportional to the metabolic weight of the animal, expressed as Wb^0.75.

    “In the absence of better estimates, water intake was assumed to be proportional to the metabolic weight of the animal, expressed as Wb 0·75 .”

  • The authors state this as an assumption.

    The rate of water consumption increases under heat stress, varying between a minimum of 0.18 and a maximum of 0.35 kg/day per kg0.75.

    “Based on this information, the rate of water consumption ( Wi , kg/ day per kg 0·75 ) was assumed to increase under heat stress, varying between a minimum ( Wi0 ) of 0·18 kg/ day per kg 0·75 , for Tb &lt; Teb , and a maximum ( Wi1 ) of 0·35 kg/day per kg 0·75 , for Tb &gt; Thb , with intermediate values of Wi being calculated using the transition functions.”

  • The authors state this as an assumption.

    The value of ka is maximum for Tb < Tcb and zero for Tb > Teb, with intermediate values given by transition functions.

    “The value of k a is maximum for Tb &lt; Tcb and zero for Tb &gt; Teb , with intermediate values given by the transition functions.”

  • The authors state this as an assumption.

    The value of ks will be maximum for Tb < Tcb; for Tb > Teb, ks is given by an equation.

    “The value of k s will be maximum ( k s1 ) for Tb &lt; Tcb . For Tb &gt; Teb , k s is given by:”

  • The authors state this as an assumption.

    The value of rv is minimum for Tb < Teb and maximum for Tb > Thb, with intermediate values calculated by a transition function.

    “The value of r v is minimum ( r v0 , l/s) for Tb &lt; Teb and maximum ( r v1 , l/s) for Tb &gt; Thb , with intermediate values calculated by a transition function.”
27 of 27

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Existing mechanistic models have not succeeded in explicitly interpreting panting and vasodilatation, which significantly influence the prediction ability of mechanistic models.

    “Based on the best knowledge of the authors, the existing mechanistic models (Bjerg, Pedersen, Morsing, &amp; Zhang, 2017; Bruce &amp; Clark, 1979; Fialho, Bucklin, Zazueta, &amp; Myer, 2004; McArthur, 1987; Turnpenny, McArthur, Clark, &amp; Wathes, 2000a; Turnpenny, Wathes, Clark, &amp; McArthur, 2000b) have not succeeded in explicitly interpreting the two most essential interactions between the t”

    From A two-node mechanistic thermophysiological model for pigs reared in hot climates – Part 1: Physiological responses and model development (2021) · cites this paper as Fialho et al., 2004

    The paper explicitly represents both responses. In “Heat transfer across the skin” (page unavailable), it models vasodilatation through changes in the peripheral-tissue heat-transfer coefficient; in “Other modes of heat transfer” (page unavailable), it models increased breathing under heat stress and its contribution to heat loss. This contradicts the claim that this model did not explicitly interpret those responses. (LLM, conf=0.90)

    Checked by a reasoning model — may be wrong.

    Experimental — accuracy not yet measured

  • Heat balance models predict the effect of the thermal environment on variables such as body temperature.

    “Heat balance models, such as the one described by Fialho et al. (2004) and Turnpenny et al. (2000a and b), predict the effect of the thermal environment on some variables, like body temperature.”

    From Modelling the effect of heat stress on food intake, heat production and growth in pigs (2004) · cites this paper as Fialho et al. (2004)

  • Heat loss is not very sensitive to the critical body temperatures Tcb and Teb.

    “The best values for these critical body temperatures may be different, but, as demonstrated by Fialho et al . (2004), heat loss is not very sensitive to these parameters.”

    From Modelling the effect of heat stress on food intake, heat production and growth in pigs (2004) · cites this paper as Fialho et al., 2004

  • Heat loss is affected little by the parameter Thb.

    “Although the true value of Thb may be different, heat loss is affected little by this parameter (Fialho et al ., 2004).”

    From Modelling the effect of heat stress on food intake, heat production and growth in pigs (2004) · cites this paper as Fialho et al., 2004

  • The three thresholds employed in Eqs. (9) and (11) were set arbitrarily in the study by Fialho et al. (2004).

    “In addition, it should be noted that the three thresholds employed in Eqs. (9) and (11) were set arbitrarily in the study by Fialho et al. (2004).”

    From A two-node mechanistic thermophysiological model for pigs reared in hot climates – Part 2: Model performance assessments (2021) · cites this paper as Fialho et al. (2004)

Cites

Flagged first, then by citations

Research works printed but not linked: 3

  1. Giles L. R. 1992. Energy expenditure of growing pigs at high ambient temperatures. Ph. D. thesis, University of Sydney.
  2. 1989, Handbook of fundamentals, SI edition
  3. Ouwerkerk E. N. J. van. 1992. Modelling the heat balance of pigs at animal and housing levels. In CIGR second report of working group on climatization of animal houses, pp. 1–17. Centre for Climatization of Animal Houses, State University of Ghent.

Cited by

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Related

Authors
Fialho, F. B., Bucklin, R. A., Zazueta, F. S., & Myer, R. O.
Affiliations
Embrapa Uva e Vinho (BR)
Corresponding author
Fialho, F. B.
ORCID
Venue
Animal Science
Publisher
Cambridge University Press (CUP)
Published
2004-04
Volume
79
Issue
1
Pages
121-134
ISSN
  • 1357-7298 (ISSN-L)
  • 1748-748X
DOI
10.1017/s135772980005459x
OpenAlex
W2944659065
Semantic Scholar
dfd3cf2ffcf68254e81b1bec4a0b34a72b7c7e0a
Cited by
25
References
18
Citations by year
2026: 3 · 2025: 3 · 2023: 2 · 2022: 2 · 2021: 4 · 2020: 2 · 2018: 1 · 2014: 1 · 2013: 3 · 2012: 1
FWCI
0.54
Type
journal article
Language
en
Open access
closed
Licence
www.cambridge.org/core/terms (unspecified, 4522 d)
Locations
Animal Science (publishedVersion)
Funders
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Topics
  • Life Sciences › Agricultural and Biological Sciences › Animal Science and Zoology › Effects of Environmental Stressors on Livestock
  • Health Sciences › Medicine › Physiology › Thermoregulation and physiological responses
  • Life Sciences › Agricultural and Biological Sciences › Animal Science and Zoology › Animal Nutrition and Physiology
Keywords
heat balance, pigs, body temperature, heat transfer, convection, radiation, evaporation, respiratory heat exchange, thermogenesis, behavioral thermoregulation, vasoconstriction, huddling, fattening pigs, ambient temperature

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-11.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-11.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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