Characterizing the acute heat stress response in gilts: I. Thermoregulatory and production variables

Abstract

Identifying traits associated with susceptibility or tolerance to heat stress (HS) is a prerequisite for developing strategies to improve efficient pork production during the summer months. Study objectives were to determine the relationship between the thermoregulatory and production responses to acute HS in pigs. Prepubertal gilts (n = 235; 77.9 ± 1.2 kg BW) were exposed to a thermoneutral (TN) period (P1, 24 h; 21.9 ± 0.5 °C, 62 ± 13% RH; fed ad libitum) followed immediately by a subsequent acute HS period (P2, 24 h; 29.7 ± 1.3 °C, 49 ± 8% RH; fed ad libitum). Rectal temperature (TR), skin temperature (TS), and respiration rate (RR) were monitored and BW and feed intake (FI) were determined. All pigs had increased TR, TS, and RR (0.80 °C, 5.65 °C, and 61.2 bpm, respectively; P < 0.01) and decreased FI and BW (29% and 1.10 kg, respectively; P < 0.01) during P2 compared to P1. Interestingly, body temperature indices did not explain variation in FI during P2 (R2 ≤ 0.02). Further, the percent change in BW during P2 was only marginally explained by each body temperature index (R2 ≤ 0.06) or percent change in FI (R2 = 0.14). During HS, TR was strongly correlated with P1 TR (r = 0.72, P < 0.01), indicating a pig's body temperature during TN conditions predicts the severity of hyperthermia during HS. Additionally, the change in TR (ΔTR, HS TR - TN TR) was larger in pigs retrospectively classified as susceptible (SUS) as compared to tolerant (TOL) pigs (1.05 vs. 0.51 °C, respectively; P < 0.01). In summary, thermoregulatory responses and production variables during acute HS are only marginally related. Further, changes in BW and FI were unexpectedly poorly correlated during acute HS (r = 0.34; P < 0.01). Collectively, suboptimal growth is largely independent on the thermoregulatory response and hypophagia during acute HS. Consequently, incorporating solely body temperature indices into a genetic index is likely insufficient for substantial progress in selecting HS tolerant pigs.

Effect of Floor Cooling on Behavior and Heart Rate of Late Lactation Sows Under Acute Heat Stress

“…Reduced feed intake has been reported in pigs to be one of the main physiological responses to prevent body temperature from increasing ( 5 , 14 , 42 – 44 ). However, this strategy appears to be temperature and/or time dependent.…”

Characterization of the acute heat stress response in gilts: III. Genome-wide association studies of thermotolerance traits in pigs

“…Detailed description of experimental designs and how the body temperature variables were calculated during prepubertal and postpubertal development have been described in two other studies that established the HS phenotypes. (Graves et al, 2018;Seibert et al, 2018). Seibert et al (2018) established the production phenotypes in response to HS while Graves et al (2018) utilized a subset of the same group of gilts and established the repeatability of the phenotypes later in life and the relationship between the HS response and reproductive success.…”

“…(Graves et al, 2018;Seibert et al, 2018). Seibert et al (2018) established the production phenotypes in response to HS while Graves et al (2018) utilized a subset of the same group of gilts and established the repeatability of the phenotypes later in life and the relationship between the HS response and reproductive success. Collectively, crossbred gilts (n = 235; PIC maternal × Duroc terminal sire) from the same cohort were received on the 24th day of age and arrived immediately after weaning.…”

“…Due to logistical constraints of the facilities, the experiment was conducted in five replications (n = 44 to 48/replicate). The initial BW from replications 1 to 5 were 59 ± 1.0, 64 ± 1.2, 77 ± 1.2, 88 ± 1.1, and 103 ± 1.6 kg, respectively (Seibert et al, 2018). During the experiment, water and feed were provided ad libitum during the entire experiment.…”

Polymorphisms associated with the number of live-born piglets in sows infected with the PRRS virus in southern Sonora Mexico

“…Por una parte, el SNP rs81276080 (asociado a LNV1) se localiza en la región 5' del gen TTR (Transthyretin), el cual codifica la síntesis de una proteína transportadora de hormonas tiroideas en plasma y fluido cerebroespinal. El TTR ha sido propuesto como un potencial gen candidato asociado a la respuesta fisiológica de cerdos sometidos a estrés por calor, el cual limita seriamente la capacidad reproductiva (27) , ya que disminuye la calidad de los ovocitos y la viabilidad embrionaria, intensificando los efectos negativos del PRRS sobre la fertilidad de cerdas infectadas. Por otra parte, el SNP rs80893794 (asociado a LNV2) se localiza en una región intrónica del gen CWH43 (Cell wall biogenesis 43 C-terminal homolog).…”