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Thermoregulatory responses of cattle to controlled dehydration during heat challenge
Author(s) -
Scharf Brad Allan,
Evans Tim,
Spiers Donald E.
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.991.8
Subject(s) - dehydration , rectal temperature , zoology , heat stress , thermoregulation , respiration rate , chemistry , body weight , respiration , biology , endocrinology , biochemistry , botany
Few studies have quantified the impact of dehydration on bovine thermal status during heat stress. Angus steers (n=8) in trial 1 were dehydrated and rehydrated over 6 days at thermoneutrality (TN; 19–21°C), with 4 month recovery. Trial 2 consisted of 5 days of cyclic heat stress (HS; 26–36°C) followed by water restriction and rehydration as in trial 1. Measurements included respiration rate (RR) and rectal temperature (Tre) taken 6 times daily, with body weight (BW), feed intake (FI), and sweat rate (SR) determined at selected times. Dehydration‐induced reductions in FI (70–75%), BW (4–9%), and RR (~15bpm) were similar in magnitude regardless of ambient temperature. FI and BW quickly returned to baselines after 1 day rehydration, while RR took 4 days. SR approached 100 g/m2h during HS, declined to 30 g/m2h with dehydration, and did not recover until after 3 days rehydration. Tre exhibited no significant change with dehydration, due to reduction in FI that counterbalanced decreases in RR and SR. Rehydration decreased Tre (~0.5°C), with slow recovery over 4 days. Surprisingly, dehydration of cattle did not result in a change in thermal status during heat stress. USDA Agreement No. 58‐6227‐3‐016