title: The use of simple physiological and environmental measures to estimate the latent heat transfer in crossbred Holstein cows.
abstract: The aim of the present study was to estimate the heat transfer through cutaneous and respiratory evaporation of dairy cows raised in tropical ambient conditions using simple environmental and physiological measures. Twenty-six lactating crossbred cows (7/8 Holstein-Gir) were used, 8 predominantly white and 18 predominantly black. The environmental variables air temperature, relative humidity, black globe temperature, and wind speed were measured. Respiratory rate and coat surface temperature were measured at 0700, 0900, 1100, 1300, and 1500 h. The environmental and physiological data were used to estimate heat loss by respiratory (ER) and cutaneous evaporation (EC). Results showed that there was variation (P < 0.01) for respiratory rate depending on the times of the day. The highest values were recorded at 1100, 1300, and 1500 h, corresponding to 66.85 ± 10.20, 66.98 ± 7.80, and 65.65 ± 6.50 breaths/min, respectively. Thus, the amount of heat transferred via respiration ranged from 19.21 to 29.42 W/m2. There was a variation from 31.6 to 38.8 °C for coat surface temperature; these values reflected a range of 55.52 to 566.83 W/m2for heat transfer via cutaneous evaporation. However, throughout the day, the dissipation of thermal energy through the coat surface accounted for 87.9 % total loss of latent heat, and the remainder (12.1 %) was via the respiratory tract. In conclusion, the predictive models based on respiratory rate and coat surface temperature may be used to estimate the latent heat loss in dairy cows kept confined in tropical ambient conditions.
authors.affiliation: Federal University of Paraíba, Areia, Paraíba, Brazil. guilhermeufpb@gmail.com.
authors.forename: Severino Guilherme Caetano Gonçalves Dos
authors.initials: SG
authors.lastname: Santos
authors.affiliation: Federal University of Paraíba, Areia, Paraíba, Brazil.
authors.forename: Edilson Paes
authors.initials: EP
authors.lastname: Saraiva
authors.affiliation: Federal University of Paraíba, Areia, Paraíba, Brazil.
authors.forename: Edgard Cavalcanti
authors.initials: EC
authors.lastname: Pimenta Filho
authors.affiliation: Federal University of Paraíba, Areia, Paraíba, Brazil.
authors.forename: Severino
authors.initials: S
authors.lastname: Gonzaga Neto
authors.affiliation: Federal University of Paraíba, Areia, Paraíba, Brazil.
authors.forename: Vinicus França Carvalho
authors.initials: VF
authors.lastname: Fonsêca
authors.affiliation: Federal University of Paraíba, Areia, Paraíba, Brazil.
authors.forename: Antônio da Costa
authors.initials: AD
authors.lastname: Pinheiro
authors.affiliation: Federal University of Paraíba, Areia, Paraíba, Brazil.
authors.forename: Maria Elivania Vieira
authors.initials: ME
authors.lastname: Almeida
authors.affiliation: Federal University of Paraíba, Areia, Paraíba, Brazil.
authors.forename: Mikael Leal Cabral Menezes
authors.initials: ML
authors.lastname: de Amorim
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation; D002417:Cattle / Q000502:physiology*; D005260:Female; D006813:Humidity; D008954:Models, Biological; D012143:Respiratory Physiological Phenomena; D056152:Respiratory Rate; D012879:Skin Physiological Phenomena; D013696:Temperature; D014329:Tropical Climate; D014919:Wind
keywords: Hot climate; Prediction model; Respiration rate; Surface temperatrure; Thermoregulation