Supplemental Table 1. Effects of heat stress and dietary organic acid and pure botanical supplementation on dry matter intake of weaned Holstein calves.

In a completely randomized design, 62 bull and heifer calves were assigned to one of five groups during the first week of life: thermoneutral conditions (TN-Con; n = 12, 6 heifers and 6 bulls), heat stress with no organic acids and pure botanicals (OA/PB) (HS-Con; n = 12, 6 heifers and 6 bulls), thermoneutral conditions pair-fed to HS-Con (TN-PF; n = 11, 6 heifers and 5 bulls), HS with low-dose OA/PB (75 mg/kg of body weight [BW]; AviPlus R; VetAgro S.p.A., Italy; HS-Low; n = 14; 8 heifers and 6 bulls), and HS with a high-dose of OA/PB (150 mg/kg of BW; AviPlus R; HS-High; n = 13, 7 heifers and 6 bulls). Calves unsupplemented with OA/PB received a placebo containing matching dose of triglyceride. After weaning, calves (62 ± 2 d of age) were transported to a new facility where they were acclimated for 7 d in thermoneutrality (20 ± 1.7°C; 68 ± 0.4 % relative humidity; 63 ± 2 temperature-humidity index [THI]). Thereafter, calves were exposed to environmental conditions of TN (20 ± 1.3°C; 71 ± 0.3 % relative humidity; 67 ± 2 THI) or HS (32 ± 3.3°C; 41 ± 0.4 % relative humidity; 79 ± 2 THI).

本研究采用完全随机设计，将62头公犊牛与母犊牛于出生后第一周随机分为5组：热中性对照组（TN-Con；n=12，母犊牛、公犊牛各6头）；无有机酸与纯植物提取物（OA/PB）的热应激组（HS-Con；n=12，母犊牛、公犊牛各6头）；配对饲喂HS-Con组的热中性组（TN-PF；n=11，母犊牛6头、公犊牛5头）；低剂量OA/PB热应激组（剂量为75 mg/kg体重[BW]，AviPlus®，意大利VetAgro S.p.A.公司生产，HS-Low；n=14，母犊牛8头、公犊牛6头）；高剂量OA/PB热应激组（剂量为150 mg/kg体重，AviPlus®，HS-High；n=13，母犊牛7头、公犊牛6头）。未补充OA/PB的犊牛将饲喂含有等剂量甘油三酯的安慰剂。断奶后，日龄为62±2 d的犊牛被转运至新养殖设施，先在热中性环境中适应7 d，该环境参数为：温度20±1.7℃，相对湿度68±0.4%，温度湿度指数（temperature-humidity index, THI）63±2。此后，犊牛分别被置于热中性（TN，环境参数：温度20±1.3℃，相对湿度71±0.3%，THI 67±2）或热应激（HS，环境参数：温度32±3.3℃，相对湿度41±0.4%，THI 79±2）环境中。