Elevated temperature-humidity index induces physiological, blood and milk alterations in Holstein cows in a more pronounced manner than in 1/2 and 3/4 Holstein × Gir

Bos taurus and indicus cattle subspecies present different capabilities in coping with situations of elevated temperatures, the latter being more tolerant to heat stress. Thus, some breeding programs crossed these produce a high producing yet heat-tolerant breed (Girolando). Nineteen Holstein (H100) 19 Girolando cows [(½ × Gir (H50) ¾ (H75)] similar milk production were used six-day experiment evaluate consequences stress due shade deprivation on their physiological, blood traits. Cows exposed non-shaded environment between morning (06:00h; GMT -3:00) evening milking (14:30h; access water ad libitum. Procedures conducted before milkings. Physiological parameters related mechanisms dissipation measured, as well composition. Blood traits evaluated. The temperature-humidity index (THI) was calculated. Statistical procedures included analysis variance, correlation, principal factors. THI during trial negatively impacted milk, H100, H75, H50. Alterations physiology, stability, composition, pronounced H100. presented changes physiological manner reduced capability this dealing THI. similarity levels excludes parameter justification for differences tolerance, genetic composition main reason results.