The effects of the exposure to daily maximum temperature-humidity index (THI) and daily THI fluctuations (∆THI, maximum–minimum THI) around birth (−2 d, birth date [0 d], +2 d, and +7 d) on serum total protein (STP) and health of preweaned Holstein heifers were evaluated. Heifer calves exposed to small ∆THI (<20 units) at 0 d had greater STP compared with medium ∆THI (≥20 to ≤30 units). At all exposure periods, heat stress (THI > 70 units) increased the occurrence of scours at earlier age, whereas small and large ∆THI favored the presentation of scours and respiratory disease, respectively.

Read the full article in the Journal of Animal Science.