title: Relationships between heat stress and metabolic and milk parameters in dairy cows in Southern Brazil.
abstract: This study approached the relationships between heat stress and metabolic and milk parameters in a commercial herd of Holstein cows located in southern Brazil. A total of 50 multiparous cows at different lactations and lactation stages were selected in order to obtain 450 samples during two consecutive years (2011 and 2012). The animals were fed a partial mixed ration along with ryegrass pasture in a semi-confinement system. Blood, milk, and urine samples were taken during the summer and winter for a total of eight samples. Three intervals of temperature-humidity index (THI) were established during the summer months (January and February) as follows: low group (LOW), THI between 75 and 81 (N = 100); moderate group (MOD), THI between 81 and 82 (N = 150); and severe group (SEV), THI between 83 and 90 (N = 150). The group of cows sampled during winter (July) constituted the control group (CON; THI = 59, N = 50). Increased total protein, albumin, glucose, and cholesterol occurred in heat-stressed cows. Increased AST activity was also observed in heat-stressed cows, but triglycerides and beta-OH-butyrate did not show any difference among groups. Lower lactate and higher pO2 were seen in cows with heat stress than CON. Cows in SEV had a 21 % milk yield decrease, while lactose and protein decreased with fat not being affected. Heat stress had strong effects on metabolic, clinical, and performance parameters in Holstein cows.
authors: School of Veterinary Medicine, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
authors: Alejandra Barrera
authors: AB
authors: Garcia
authors: Natalia
authors: N
authors: Angeli
authors: Letícia
authors: L
authors: Machado
authors: Felipe Cardoso
authors: FC
authors: de Cardoso
authors: Félix
authors: F
authors: Gonzalez
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D001938:Brazil; D002417:Cattle; D002418:Cattle Diseases / Q000503:physiopathology*; D003612:Dairying; D005260:Female; D018882:Heat Stress Disorders / Q000097:blood / Q000503:physiopathology / Q000662:veterinary*; D006358:Hot Temperature; D008892:Milk / Q000378:metabolism*; D012621:Seasons