Postnatal heat stress (HS) effects on pig physiology and performance are widely studied but prenatal HS studies, albeit increasing, are still limited. The objective of this study was to evaluate the chronic prenatal HS effects in growing pigs raised in postnatal thermoneutral (TN) or in HS environment. For prenatal environment (PE), mixed-parity pregnant sows were exposed to either TN (PTN; cyclic 18 to 24 °C; n = 12) or HS (PHS; cyclic 28 to 34 °C; n = 12) conditions from day 9 to 109 of gestation. Two female offspring per sow were selected at 10 wk of age and allotted to one of two postnatal growing environments (GE): GTN (cyclic 18 to 24 °C; n = 24) and GHS (cyclic 28 to 34 °C; n = 24). From 75 to 140 d of age, GTN pigs remained in GTN conditions, while GHS pigs were in GTN conditions from 75 to 81 d of age and in GHS conditions from 82 to 140 d of age. Regardless of PE, postnatal HS increased rectal and skin temperatures (+0.30 and +1.61 °C on average, respectively; P < 0.01) and decreased ADFI (-332 g/d; P < 0.01), resulting in lower ADG and final BW (-127 g/d and -7.9 kg, respectively; P < 0.01). The GHS pigs exhibited thicker backfat (P < 0.01), lower carcass loin percentage (P < 0.01), increased plasma creatinine levels (P < 0.01), and decreased plasma glucose, nonesterified fatty acids, T3, and T4 levels (P < 0.05). Prenatal HS increased feed intake in an age-dependent manner (+10 g·kg BW-0.60·d-1 for PHS pigs in the last 2 wk of the trial; P = 0.02) but did not influence BW gain (P > 0.10). Prenatal HS decreased the plasma levels of superoxide dismutase on day 3 of GHS (trend at P = 0.08) and of T4 on day 49 (P < 0.01) but did not affect T3 on day 3 nor 49 (P > 0.10). Prenatal HS increased rectal and skin temperatures and decreased temperature gradient between rectal and skin temperatures in GTN pigs (+0.10, +0.33 and -0.22 °C, respectively; P < 0.05) but not in GHS pigs (P > 0.10). There were also PE × GE interactions found with lower BW (P = 0.06) and higher backfat (P < 0.01) and perirenal adiposity (P < 0.05) for GHS-PHS pigs than the other groups. Overall, increased body temperature and altered thyroid functions and physiological stress responses suggest decreased heat tolerance and dissipation ability of pigs submitted to a whole-gestation chronic prenatal HS. Postnatal HS decreased growth performance, increased carcass adiposity, and affected metabolic traits and thyroid functions especially in pigs previously submitted to prenatal HS.

中文翻译：

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慢性产前热应激会改变遭受产后热应激的生长猪的生长，car体组成和生理反应。

产后热应激（HS）对猪的生理和性能的影响已得到广泛研究，但产前HS研究虽然有所增加，但仍然有限。这项研究的目的是评估出生后热中性（TN）或HS环境中生长的猪的慢性产前HS效应。对于产前环境（PE），从当天开始，将混合胎的母猪暴露于TN（PTN;周期性18至24°C; n = 12）或HS（PHS;周期性28-34°C; n = 12）的条件下妊娠9到109。每头母猪在10周龄时选出两个雌性后代，并分配给两个出生后生长环境（GE）：GTN（循环温度18至24°C； n = 24）和GHS（循环温度28至34°C； n = 24）。从75到140天大，GTN猪仍处于GTN条件下，而GHS猪的GTN条件为75至81 d，而GHS的条件为82至140 d。无论使用哪种PE，产后HS都会使直肠和皮肤温度升高（分别平均为+0.30和+1.61°C； P <0.01）和ADFI降低（-332 g / d； P <0.01），从而导致ADG和最终BW降低（分别为-127 g / d和-7.9 kg； P <0.01）。GHS猪的背脂较厚（P <0.01），car体腰肉百分比较低（P <0.01），血浆肌酐水平升高（P <0.01），血浆葡萄糖，非酯化脂肪酸，T3和T4水平降低（P <0.05 ）。产前HS以年龄相关的方式增加了采食量（在试验的最后两周，PHS猪的体重增加了10 g·kg BW-0.60·d-1； P = 0.02），但不影响体重增加（P> 0.10） ）。产前HS在GHS第3天（趋势P = 0.08）和T4第49天（P <0.01）降低了血浆超氧化物歧化酶的水平（P <0.01），但在第3天或第49天未影响T3（P> 0.10）。产前HS使GTN猪的直肠和皮肤温度升高，直肠和皮肤温度之间的温度梯度降低（分别为+ 0.10，+ 0.33和-0.22°C； P <0.05），而在GHS猪中则没有（P> 0.10）。与其他组相比，GHS-PHS猪的BW（P = 0.06）和背脂（P <0.01）和肾周围脂肪增多（P <0.05）也有PE×GE相互作用。总体而言，体温升高和甲状腺功能改变以及生理应激反应改变表明，接受全胎慢性产前HS的猪的耐热性和耗散能力降低。产后HS降低了生长性能，