Daytime Heat Stress, Thermal Pattern, Hyperthermia and Body Caloric Overload in Tropical Acclimatized Holstein and Jersey Heifers  

作　　者：Edil E. Araúz-Santamaría Bryan G. Mendieta-Araica Roderick A. González-Murray Gustavo A. Crudeli David Berroa-Pinzón Ernesto R. Varillas-Esquivel Edil E. Araúz-Santamaría;Bryan G. Mendieta-Araica;Roderick A. González-Murray;Gustavo A. Crudeli;David Berroa-Pinzón;Ernesto R. Varillas-Esquivel(Chiriqu Research and Teaching Center, Department of Animal Science and Production, Faculty of Agricultural Sciences, University of Panam, David, Panam;Independent Researcher, Managua, Nicaragua;Research and Innovation Institute of Panama, Experimental Station Carlos Ortega, Gualaca, Panam;Department of Basic and Applied Sciences, Veterinary Science Degrees, National University of Chaco Austral, Presidencia Roque Saenz Pea, Argentina;Specialized Veterinarian Services in Production, Health and Reproductive Management in Dairy Cattle, David, Panamá;Independent Researcher, Santiago de Veraguas, Panam)

机构地区：[1]Chiriqu Research and Teaching Center, Department of Animal Science and Production, Faculty of Agricultural Sciences, University of Panam, David, Panam [2]Independent Researcher, Managua, Nicaragua [3]Research and Innovation Institute of Panama, Experimental Station Carlos Ortega, Gualaca, Panam [4]Department of Basic and Applied Sciences, Veterinary Science Degrees, National University of Chaco Austral, Presidencia Roque Saenz Pea, Argentina [5]Specialized Veterinarian Services in Production, Health and Reproductive Management in Dairy Cattle, David, Panamá [6]Independent Researcher, Santiago de Veraguas, Panam

出　　处：《Open Journal of Animal Sciences》2024年第4期260-287,共28页动物科学期刊（英文）

摘　　要：The influence of daytime tropical heat stress in the summer was studied in Holstein and Jersey heifers already acclimatized to tropical environments to determine their physiological response based on body thermal patterns and respiratory alterations according to psychrometric caloric indicators. Daytime psychrometric elements showed a tropical caloric potential for developing moderate to severe heat stress in dairy cattle. Body temperature and respiratory rate increased in both breeds open and pregnant (P < 0.01). Thermal body overload and respiratory works increased from 09 am to 12 md (P < 0.001);reaching and sustaining hyperthermia under the highest caloric pressure from 12 md to 03 pm. Rectal temperature increased +1.5˚C in open Holstein (OH), +1.3˚C in pregnant Holstein (PH), +0.8˚C in open jersey (OJ) and +0.8˚C in pregnant Jersey (PJ). The lowest heat stress index (HSI) was at 06 am, where OH and PH showed a HIS +2.25 and +2.30 and OJ and PJ +2.34 and +2.38. Maximum heat stress occurred at 12 md where OH averaged +3.28 and Pregnant Holsteins showed +3.85 at 03 pm. Open Jersey (OJ) showed a maximum HSI at 12 md (3.54) and PJ resulted in +3.89 at 03 pm. Open and pregnant Jersey heifers were more tolerant to heat stress based on lower body mass, insulation, feed consumption and greater relation between body surface and metabolic body size for thermolysis. Acclimatization between five and twenty-five months under tropical heat stress allowed Holstein and Jersey heifers to develop thermal tolerance. Middle thermal acclimatization lowered thermal sensitivity, hyperthermia and hyperpnea in Holstein and Jersey heifers in the morning;however, pregnant heifers in both breeds showed higher thermal alteration in the afternoon. Tropical acclimatization at low altitudes could be integrated with environmental improvements and nutritional and health management to reduce influences of severe heat stress and improve physiological comfort and welfare in Holstein and Jersey heifers in the summer. Those combined strategiesThe influence of daytime tropical heat stress in the summer was studied in Holstein and Jersey heifers already acclimatized to tropical environments to determine their physiological response based on body thermal patterns and respiratory alterations according to psychrometric caloric indicators. Daytime psychrometric elements showed a tropical caloric potential for developing moderate to severe heat stress in dairy cattle. Body temperature and respiratory rate increased in both breeds open and pregnant (P < 0.01). Thermal body overload and respiratory works increased from 09 am to 12 md (P < 0.001);reaching and sustaining hyperthermia under the highest caloric pressure from 12 md to 03 pm. Rectal temperature increased +1.5˚C in open Holstein (OH), +1.3˚C in pregnant Holstein (PH), +0.8˚C in open jersey (OJ) and +0.8˚C in pregnant Jersey (PJ). The lowest heat stress index (HSI) was at 06 am, where OH and PH showed a HIS +2.25 and +2.30 and OJ and PJ +2.34 and +2.38. Maximum heat stress occurred at 12 md where OH averaged +3.28 and Pregnant Holsteins showed +3.85 at 03 pm. Open Jersey (OJ) showed a maximum HSI at 12 md (3.54) and PJ resulted in +3.89 at 03 pm. Open and pregnant Jersey heifers were more tolerant to heat stress based on lower body mass, insulation, feed consumption and greater relation between body surface and metabolic body size for thermolysis. Acclimatization between five and twenty-five months under tropical heat stress allowed Holstein and Jersey heifers to develop thermal tolerance. Middle thermal acclimatization lowered thermal sensitivity, hyperthermia and hyperpnea in Holstein and Jersey heifers in the morning;however, pregnant heifers in both breeds showed higher thermal alteration in the afternoon. Tropical acclimatization at low altitudes could be integrated with environmental improvements and nutritional and health management to reduce influences of severe heat stress and improve physiological comfort and welfare in Holstein and Jersey heifers in the summer. Those combined strategies

关 键 词：ACCLIMATIZATION Dairy Cattle Heat Stress Index Rectal Temperature Summer Temperature Humidity Index 

分 类 号：R73[医药卫生—肿瘤]