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Background: Longitudinal records of automatically-recorded vaginal temperature (TV) could be a key source of data for deriving novel indicators of climatic resilience (CR) for breeding more resilient pigs, especially during lactation when sows are at an increased risk of suffering from heat stress (HS). Therefore, we derived 15 CR indicators based on the variability in TV in lactating sows and estimated their genetic parameters. We also investigated their genetic relationship with sows' key reproductive traits. Results: The heritability estimates of the CR traits ranged from 0.000 ± 0.000 for slope for decreased rate of TV (SlopeDe) to 0.291 ± 0.047 for sum of TV values below the HS threshold (HSUB). Moderate to high genetic correlations (from 0.508 ± 0.056 to 0.998 ± 0.137) and Spearman rank correlations (from 0.431 to 1.000) between genomic estimated breeding values (GEBV) were observed for five CR indicators, i.e. HS duration (HSD), the normalized median multiplied by normalized variance (Nor_medvar), the highest TV value of each measurement day for each individual (MaxTv), and the sum of the TV values above (HSUA) and below (HSUB) the HS threshold. These five CR indicators were lowly to moderately genetically correlated with shoulder skin surface temperature (from 0.139 ± 0.008 to 0.478 ± 0.048) and respiration rate (from 0.079 ± 0.011 to 0.502 ± 0.098). The genetic correlations between these five selected CR indicators and sow reproductive performance traits ranged from − 0.733 to − 0.175 for total number of piglets born alive, from − 0.733 to − 0.175 for total number of piglets born, and from − 0.434 to − 0.169 for number of pigs weaned. The individuals with the highest GEBV (most climate-sensitive) had higher mean skin surface temperature, respiration rate (RR), panting score (PS), and hair density, but had lower mean body condition scores compared to those with the lowest GEBV (most climate-resilient). Conclusions: Most of the CR indicators evaluated are heritable with substantial additive genetic variance. Five of them, i.e. HSD, MaxTv, HSUA, HSUB, and Nor_medvar share similar underlying genetic mechanisms. In addition, individuals with higher CR indicators are more likely to exhibit better HS-related physiological responses, higher body condition scores, and improved reproductive performance under hot conditions. These findings highlight the potential benefits of genetically selecting more heat-tolerant individuals based on CR indicators. [ABSTRACT FROM AUTHOR]

Background: Genetic selection based on direct indicators of heat stress could capture additional mechanisms that are involved in heat stress response and enable more accurate selection for more heat-tolerant individuals. Therefore, the main objectives of this study were to estimate genetic parameters for various heat stress indicators in a commercial population of Landrace × Large White lactating sows measured under heat stress conditions. The main indicators evaluated were: skin surface temperatures (SST), automatically-recorded vaginal temperature (TV), respiration rate (RR), panting score (PS), body condition score (BCS), hair density (HD), body size (BS), ear size, and respiration efficiency (Reff). Results: Traits based on TV presented moderate heritability estimates, ranging from 0.15 ± 0.02 to 0.29 ± 0.05. Low heritability estimates were found for SST traits (from 0.04 ± 0.01 to 0.06 ± 0.01), RR (0.06 ± 0.01), PS (0.05 0.01), and Reff (0.03 ± 0.01). Moderate to high heritability values were estimated for BCS (0.29 ± 0.04 for caliper measurements and 0.25 ± 0.04 for visual assessments), HD (0.25 ± 0.05), BS (0.33 ± 0.05), ear area (EA; 0.40 ± 0.09), and ear length (EL; 0.32 ± 0.07). High genetic correlations were estimated among SST traits (> 0.78) and among TV traits (> 0.75). Similarly, high genetic correlations were also estimated for RR with PS (0.87 ± 0.02), with BCS measures (0.92 ± 0.04), and with ear measures (0.95 ± 0.03). Low to moderate positive genetic correlations were estimated between SST and TV (from 0.25 ± 0.04 to 0.76 ± 0.07). Low genetic correlations were estimated between TV and BCS (from − 0.01 ± 0.08 to 0.06 ± 0.07). Respiration efficiency was estimated to be positively and moderately correlated with RR (0.36 ± 0.04), PS (0.56 ± 0.03), and BCS (0.56 ± 0.05 for caliper measurements and 0.50 ± 0.05 for the visual assessments). All other trait combinations were lowly genetically correlated. Conclusions: A comprehensive landscape of heritabilities and genetic correlations for various thermotolerance indicators in lactating sows were estimated. All traits evaluated are under genetic control and heritable, with different magnitudes, indicating that genetic progress is possible for all of them. The genetic correlation estimates provide evidence for the complex relationships between these traits and confirm the importance of a sub-index of thermotolerance traits to improve heat tolerance in pigs. [ABSTRACT FROM AUTHOR]

Domesticated sows are motivated to perform nesting behavior prior to farrowing, and nesting material can reduce piglet cold stress. However, nesting material may not be practical in most production systems due to the potential for clogging slurry systems. Therefore, the study objectives were to assess an alternative nesting material provided prior to farrowing on sow welfare and piglet survival, and to investigate the effect of the entire nesting environment on piglet survival and growth performance. We hypothesized that the provision of jute nesting material would decrease sow stress and farrowing duration, and that nesting mat provision would allow piglets to remain euthermic and improve survival and growth. Sows (N  = 20) were randomly assigned to one of two treatments: a farrowing crate with three pieces of 40.6 × 21.6 cm jute nesting material (Nest; n  = 10) and two enriched piglet mats made from an acrylic board (28.0 × 86.4 cm) covered with a microfiber material, or a farrowing crate without nesting material (Control; n  = 10) and one standard plastic piglet mat (28.0 × 86.4 cm). Jute pieces were attached to the front of the crate to prevent substrate from falling through the slatted floors. Saliva samples were collected to measure cortisol and immunoglobulin A (IgA), on days −1, 0, 1, and 2 relative to farrowing, and a final sample was collected at weaning (day 16.9 ± 0.18). Blood was collected from four piglets per litter to measure immunoglobulin G (IgG) at 48 h, day 7, and weaning. Piglet skin temperature (T S) was measured on two piglets per litter using an infrared camera for 3 d after birth at 0800, 1200, 1600, and 2000 h. One piglet was randomly chosen from the heat lamp and nonheat lamp side of the crate to measure T S. Video was continuously coded for observations of jute- and crate-directed interactions. Data were analyzed as a mixed model analysis of variance in SAS 9.4. Nest sows performed less crate-directed behavior than Control sows (P  = 0.02). Cortisol tended to be reduced in Nest sows (P  = 0.08) when compared to Controls, but no differences in IgA concentrations (P  > 0.40) were detected. Nest piglets tended to be heavier on day 7 (P  < 0.10), had greater IgG concentrations (P  = 0.03), and had greater T S (P  = 0.02) versus Controls. No farrowing duration or number of stillbirth differences were observed (P  > 0.70). The jute material and piglet nests positively impacted sow welfare and piglet measures but did not translate into improved piglet survival. [ABSTRACT FROM AUTHOR]

Gestating sows are particularly sensitive to heat stress due to their large mass and greater metabolic heat production associated with increased reproductive organ and fetal development. Unfortunately, the heat stress sensitivity of gestating sows has increased over the past decades due to genetic and genomic advances that have improved litter sizes and reproductive efficiency. When combined with the greater frequency and severity of heat waves and high temperatures, it is likely that reproductive issues associated with heat stress exposure will continue to be a concern for the swine industry. It is well understood that high temperatures pose a challenge to gestating sows and their developing offspring. Research from 50 to 60 yr ago demonstrated that heat exposure results in a decrease in viable embryos and an increase in embryonic mortality, particularly when gestating sows are subjected to heat stress in the first trimester. Additionally, late gestation heat stress exposure can increase the rate of stillborn piglets and reduce the total number of liveborn piglets. Although the reasons for these losses are multifactorial, the direct influence of maternal body temperature and total stress load on the intrauterine environment can play a significant role during these critical stages. For offspring that survive to birth, prospects for a healthy, productive, and stress-free life are at risk due to the long-lasting effects of in utero heat stress, which include greater postnatal stress sensitivity and decreased productivity. Therefore, understanding and mitigating gestational heat stress in pigs is of great importance to ensure the sustainability and profitability of swine production. [ABSTRACT FROM AUTHOR]

The maternal response to heat stress (HS) has detrimental effects on swine offspring in the form of in utero heat stress (IUHS). Long-term effects of IUHS include reduced postnatal growth performance and lean muscle deposition. As such, developing mitigation strategies that reduce IUHS is essential to maximize economic return. Therefore, the study objective was to investigate whether genomic selection for HS tolerance (TOL) or HS sensitivity (SEN) would impact the postnatal growth of IUHS and in utero thermoneutral (IUTN) pigs from birth to market. We hypothesized that the IUHS pigs born to TOL dams would have improved growth relative to IUHS pigs born to SEN dams, but overall, IUHS pigs would have reduced growth compared with IUTN pigs. Pregnant gilts (n = 15 TOL and 13 SEN) were exposed to thermoneutral (TN; 17-20ºC; n = 7 TOL and 6 SEN) or heat stress (HS; cycling 26 to 36ºC; n = 8 TOL and 7 SEN) conditions from d 6 to 70 of gestation, and then all gilts were exposed to TN conditions until farrowing. Thirtysix offspring (barrows) were selected to represent each possible treatment combination: TOL+IUTN (n = 9), TOL+IUHS (n = 9), SEN+IUTN (n = 9), and SEN+IUHS (n = 9). Barrows were group-housed and fed a corn-soybean based diet that was provided with water ad libitum. Body weight (BW) of all barrows was measured at d 1, 21, 28, 35, 42, 49, 56, 84, 105, 126, 147, 168, and 189 of life to evaluate growth from birth (d 1) to market (d 189). Data were analyzed using the PROC GLIMMIX procedure of SAS with pig as the experimental unit and random effects being pen and litter. Body weights for each treatment group were fitted to a generalized Michaelis-Menten (GMM) function using the Nonlinear MIXED procedure of SAS with pig specific random effects for mature BW. On d 1, 126, and 168, IUHS pigs tended to have reduced BW (P < 0.10; 1.19 ± 0.07, 58.37 ± 4.94, 91.18 ± 7.26 kg, respectively) when compared with IUTN pigs (1.32 ± 0.07, 68.95 ± 4.94, 106.25 ± 7.26 kg, respectively). Overall, final BW was reduced (P = 0.04) for IUHS (111.08 ± 7.91 kg versus IUTN (128.79 ± 7.91 kg) pigs, and estimated days to a market weight of 125 kg tended to be greater (P = 0.06) for IUHS (219.8 ± 10.8 d) versus IUTN (188.1 ± 10.21 d) barrows. The GMM model predicted that IUHS+TOL and IUTN+TOL barrows had different shaped BW growth curves with decreased age to achieve one-half of their predicted mature BW than IUHS+SEN and IUTN+SEN barrows. In conclusion, IUHS resulted in reduced growth rates overall; however, TOL improved some aspects of growth [ABSTRACT FROM AUTHOR]

Heat stress (HS) decreases lactation output in sows due to an attempt to reduce metabolic heat production. However, this negatively affects litter growth performance. Therefore, the study objective was to determine whether electronically controlled cooling pads (ECP) would improve indirect measures of lactation output (e.g., total heat production [THP]) and litter growth performance in HS exposed sows. Over two repetitions, 12 multiparous (2.69 ± 0.85) lactating sows (265.4 ± 26.1 kg body weight [BW]) and litters were assigned to either an ECP (n = 3/repetition) or a non-functional ECP (NECP; n = 3/repetition) and placed into farrowing crates within indirect calorimeters from days 3.7 ± 0.5 to 18.7 ± 0.5 of lactation. Litters were standardized across all sows (11.4 ± 0.7 piglets/litter), and sows were provided ad libitum feed and water. All sows were exposed to cyclical HS (28.27 ± 0.26 °C nighttime to 33.09 ± 0.19°C daytime). On days 4, 8, 14, and 18 of lactation, indirect calorimetry was performed on each individual sow and litter to determine THP and THP/kg BW0.75. Body temperature (TB) was measured hourly using vaginal implants, and respiration rate (RR; breaths per minute [bpm]) was measured daily at 0700, 1100, 1300, 1500, and 1900 h. Sow feed intake (FI) was assessed daily. Litter weights were obtained at birth, on days 4, 8, 14, and 18 of lactation, and at weaning. Data were analyzed using PROC GLIMMIX with sow and/or litter as the experimental unit. An overall decrease (P < 0.01; 25 bpm) in RR and maximum daily TB (P = 0.02; 0.40 °C) was observed in ECP vs. NECP sows. An increase in THP (P < 0.01; 20.4%) and THP/kg BW0.75 (P < 0.01; 23.1%) was observed for ECP when compared with NECP sows and litters. Litter average daily gain and weaning weight were increased (P < 0.05; 25.0 and 19.2%, respectively) for ECP vs. NECP litters. No FI differences were observed (P = 0.40) when comparing ECP (5.66 ± 0.31 kg/d) and NECP (5.28 ± 0.31 kg/d) sows. In summary, ECPs improve litter growth, thermoregulatory measures, and bioenergetic parameters associated with greater milk production in lactating sows exposed to cyclical HS. [ABSTRACT FROM AUTHOR]

The metabolic heat production of modern pigs has increased by an average of 16%, compared with sows of 30 years ago. Therefore, it is likely that temperature recommendations require updating to meet the needs of modern pigs. The objective of this study was to evaluate whether different reproductive stages of sows altered thermal preference and if current recommendations required updating. Twenty multiparous sows (3.4 ± 1.2 parity) in different reproductive stages (nonpregnant: n = 7; mid-gestation: 58.5 ± 5.68 d, n = 6; and late-gestation: 104.7 ± 2.8 d, n = 7) were tested. Thermal preference was individually tested, and sows could freely choose a temperature, using a thermal gradient between 10.4 and 30.5 °C. Sows were given 24 h to acclimate to the thermal apparatus. Before testing began, sows were given daily feed allotment and returned to the apparatus. Video from the 24-h test period was used to record sow behavior (time spent inactive), posture (upright and sternal and lateral lying), and location using instantaneous scan samples every 15 min. Data were analyzed using PROC MIXED procedure in SAS 9.4. A cubic regression model was used to calculate the sow’s most preferred temperature based on the location, or temperature, in which they spent the most time. The preference range was calculated using peak temperature preference ±SE for each sow. The reproductive stage altered where sows spent their time within the thermal gradient (P < 0.01). Late-gestation sows preferred cooler temperatures (14.0 °C) than mid-gestation (14.8 °C; P < 0.01) and nonpregnant sows (14.8 °C; P < 0.01). In summary, sow thermal preferences were within the lower half of the current recommended range (10 to 25 °C). This indicates that temperatures at the higher end of the recommended range could be uncomfortable to sows and that the thermal comfort zone of sows may be narrower than recommendations indicate. [ABSTRACT FROM AUTHOR]

Gestating sows may be more susceptible to increasing dry bulb temperatures (T DB ) due to greater metabolic heat production and increased body mass, especially as gestation advances. However, there are few studies on the thermoregulatory and physiological responses of sows at differing gestation stages exposed to gradually increasing temperatures. The study objective was to determine the thermoregulatory and physiological responses of nonpregnant (n = 12; parity 3.27 ± 0.86), mid-gestation (59.7 ± 9.6 d pregnant, n = 12; parity 3.25 ± 0.83), and late-gestation (99.0 ± 4.8 d pregnant, n = 12; parity 3.33 ± 0.75) sows exposed to increasing TDB. Prior to the experiment (5.0 ± 0.7 d), jugular catheters were placed in all sows. During the experiment, the TDB was increased incrementally by 2.45 ± 0.43 °C every 60 min from 19.84 ± 2.15 to 35.54 ± 0.43 °C over 400 min, and relative humidity was recorded at 40.49 ± 18.57%. Respiration rate (RR), heart rate (HR), skin temperature, and vaginal temperature were measured, and blood samples were obtained via the jugular catheter every 20 min. Data were analyzed using PROC MIXED in SAS 9.4. RR increased at a lower TDB (P < 0.01) in late-gestation sows compared with mid-gestation and nonpregnant sows, but no differences were detected between mid-gestation and nonpregnant sows. Overall, late-gestation sows had greater RR (P < 0.01; 23 ± 2 breaths per min [ brpm ]) compared with mid-gestation (16 ± 2 brpm) and nonpregnant (15 ± 2 brpm) sows. Late-gestation sows had an overall greater HR (P < 0.01; 84 ± 5 beats per min [ bpm ]) than mid-gestation (76 ± 5 bpm) and nonpregnant (69 ± 5 bpm) sows. Late-gestation sows had overall reduced bicarbonate and total carbon dioxide levels (P = 0.02; 23.89 ± 1.97 and 25.41 ± 2.07 mmol/L, respectively) compared with mid-gestation (27.03 ± 1.97 and 28.58 ± 2.07 mmol/L, respectively) and nonpregnant (26.08 ± 1.97 and 27.58 ± 2.07 mmol/L, respectively) sows. Moreover, late-gestation sows had overall greater nitric oxide levels (P < 0.01; 248.82 ± 34.54 µM) compared with mid-gestation (110.47 ± 34.54 µM) and nonpregnant (41.55 ± 34.54 µM) sows. In summary, late-gestation sows appear to be more sensitive to increasing TDB as indicated by thermoregulatory and physiological responses when compared with mid-gestation or nonpregnant sows. The results from this study provide valuable information regarding thermoregulatory thresholds of sows at differing gestation stages. [ABSTRACT FROM AUTHOR]

Climatic resilience (CR) can be defined as the ability of an animal to maintain euthermia under thermally stressful conditions. However, CR based on longitudinal physiological variables has not been included in current swine genetic selection schemes. This is the first study deriving novel CR indicators using automatically recorded vaginal temperatures (TV) and estimating genetic parameters for them. Therefore, the study objectives were to: 1) derive novel indicators of CR based on automatically recorded vaginal temperature (TV); and 2) estimate (co)variance components and genetic parameters for these indicators. TV of 1,381 lactating sows (parities 2 to 7; Landrace × Large White) were measured automatically every 10 minutes from June 5th, 2021 to July 30th, 2021 using a vaginally implanted thermochron data recorder. A total of 1,639 F1 (Landrace x Large White) sows within the studied population were genotyped using the PorcineSNP50K Bead Chip. A total of 18 HS indicators derived from Tv, their definitions, heritability estimates, and mean genomic estimated breeding value (GEBV) accuracies are shown in Table 1. Multi-trait animal models were fitted for estimating the (co)variance components, considering the effects of week of data collection, parity, and location (barn and room within barn) as fixed. Heritability estimates for these resilience traits ranged from 0.0004 ± 7.16E-6 (SlopeDe) to 0.291 ± 0.047 (HSAB). Most traits derived directly from vaginal temperature (e.g., Duration: 0.201 ± 0.033, MaxTv: 0.203 ± 0.032) are moderately heritable with substantial additive genetic variance. Besides, LnVar(Med) that is derived from the deviation between the real and predicted value had moderate heritability (0.196 ± 0.041) and high mean GEBV accuracy (0.616 ± 0.042). The indicators defined based on the slope of Tv and time had low heritability estimates, which are close to zero, and low mean GEBV accuracy (0.106 ± 0.050 - 0.337 ± 0.065). Among all the CR indicators, Duration, MaxTv, Nor_medvar, Nor_avevar, HSAA, and HSAB outperformed the other indicators with moderate heritability estimates and high average GEBV accuracies. Genetic correlations were estimated among the six indicators with moderate heritability and high mean GEBV accuracy. Moderate to high positive genetic correlations (0.508 ± 0.034 to 0.992 ± 0.025) were estimated among Duration, MaxTv, Nor_medvar, HSAB, and HSAA. LnVar(Med) showed low negative genetic correlations (-0.218 ± 0.028 to -0.039 ± 0.018) with the traits Duration, MaxTv, HSAA, and HSAB, except with Nor_medvar, which was positive (0.156 ± 0.022). Thus, Duration, LnVar(Med), MaxTv, Nor_medvar, HSAB, and HSAA might be promising CR indicator and contribute toward improving lactating sows' resilience to thermal stress through genetic selection. New studies about the relationship between these new indicators and other economic important traits in pigs are required before including them in selection indexes. [ABSTRACT FROM AUTHOR]

Pre-weaned piglets prefer higher temperatures than lactating sows. To address this, swine producers use heating lamps or pads in combination with maintaining farrowing room macroenvironment temperatures at the upper end of the thermoneutral zone (24-25℃) of the lactating sow. This may inadvertently cause thermal stress for lactating sows resulting in decreased feed consumption, and ultimately, reduced milk production and litter growth. Therefore, the objective was to determine the sow level macroenvironment temperature that would improve both sow and litter productivity. In two repetitions, 37 lactating sows (parity = 3.1 ± 1.7) and their litters (d 1 litter size = 12.0 ± 1.0) were housed within 1 of 3 farrowing rooms set to different macroenvironment temperatures: LOW (n = 12 sows and litters; 15.0 ± 0.4℃), MID (n = 13 sows and litters; 19.3 ± 0.2℃), and HIGH (n = 12 sows and litters; 24.6 ± 0.8℃). Lactating sows and their litters were on trial from the onset of farrowing until weaning (19.8 ± 0.9 d of age). Individual farrowing crate temperatures were recorded throughout the trial in 0.14 s intervals using thermocouples mounted at sow head height. Piglets were provided a 0.34 x 1.52 m heating pad with a verified steady state of 35.0℃. Sow body weight (BW) was recorded at 24 h post-farrowing and at weaning, and piglet weights were measured on d 1, 7, 14 and at weaning to determine average daily BW gain (ADG). Liveborn piglet mortality was recorded throughout the trial. Sow feed intake (FI) was recorded daily from d 1 post-farrowing until weaning. The sow was considered the experimental unit for sow level measures and the litter was considered the experimental unit for piglet measures. Data were analyzed using PROC GLIMMIX in SAS 9.4 and using GLM in JMP 15. Regression models were used to determine the optimal macroenvironment temperature to improve sow FI and piglet ADG. Sow FI was greater (P < 0.01) for LOW (7.91 ± 0.38 kg) and MID (7.32 ± 0.37 kg) versus HIGH (6.37 ± 0.39 kg) sows, but similar for LOW and MID sows. Piglet ADG was greater from d 1 to weaning (P < 0.01) for LOW (0.25 ± 0.01 kg) and MID (0.26 ± 0.01 kg) versus HIGH (0.21 ± 0.01 kg) piglets, but similar for LOW and MID piglets. Pre-weaning mortality was similar (P = 0.32; 15.6%) among all treatments. A quadratic effect was observed (P < 0.01) where sow FI was maximized at a macroenvironment temperature of 17.2℃. A cubic effect was observed (P < 0.01) where piglet ADG was greatest at 17.0℃. In summary, these data have implications towards housing lactating sows and their litters at lower macroenvironment temperatures to improve growth performance. [ABSTRACT FROM AUTHOR]

Background: The study objective was to test the hypothesis that 1) lowering dietary crude protein (CP) increases dietary energetic efficiency and reduces metabolic heat associated with lactation, and 2) excessive dietary leucine (Leu) supplementation in a low CP diet decreases dietary energetic efficiency and increases metabolic heat associated with lactation. Methods: Fifty-four lactating multiparous Yorkshire sows were allotted to 1 of 3 isocaloric diets (10.80 MJ/kg net energy): 1) control (CON; 18.75% CP), 2) reduced CP with a near ideal or optimal AA profile (OPT; 13.75% CP) and 3) diet OPT with excessive Leu (OPTLEU; 14.25% CP). Sow body weight and backfat were recorded on day 1 and 21 of lactation and piglets were weighed on day 1, 4, 8, 14, 18, and 21 of lactation. Energy balance was measured on sows during early (day 4 to 8) and peak (day 14 to18) lactation, and milk was sampled on day 8 and 18. Results: Over 21-day lactation, sows fed OPT lost body weight and body lipid (P < 0.05). In peak lactation, sows fed OPT had higher milk energy output (P < 0.05) than CON. Sows fed OPTLEU tended (P = 0.07) to have less milk energy output than OPT and did not differ from CON. Maternal energy retention was lower (P < 0.05) in OPT and OPTLEU compared to CON sows, and did not differ between OPTLEU and OPT sows. Sows fed OPT had higher (P < 0.05) apparent energy efficiency for milk production compared to CON. Heat production associated with lactation was lower (P < 0.05) or tended to be lower (P = 0.082), respectively, in OPT and OPTLEU compared to CON sows. Conclusion: The OPT diet, in peak lactation, improved dietary energy utilization for lactation due to less urinary energy and metabolic heat loss, and triggered dietary energy deposition into milk at the expense of maternal lipid mobilization. Leucine supplementation above requirement may reduce dietary energy utilization for lactation by decreasing the energy partitioning towards milk, partially explaining the effectiveness of OPT diet over CON diets. [ABSTRACT FROM AUTHOR]

The ability to determine total heat production (THP) in individual sows and litters can be logistically difficult and often requires the use of multiple animals to generate data on a per room basis. Furthermore, these systems may be costly to construct, precluding their use by many researchers. Therefore, the objective was to develop a low-cost indirect calorimetry system to determine THP in individual lactating sows and litters. Six indirect calorimeters were constructed to house 1 sow and litter in a crate throughout farrowing and a 21-d lactation period. Farrowing crates were placed within a high-density polyethylene pan filled with water and then a polyvinyl chloride frame was constructed around the crate. The frame provided a structure to hold the inlet and outlet air pipes, feed and water inlets, air circulation fans, and a polyethylene plastic sheet that was secured at the bottom of the frame and submerged under water to maintain an air tight seal. Chamber accuracies for O2 and CO2 were evaluated by ethanol combustion. One week pre-farrowing, 6 pregnant multiparous sows (parity 2.9 ± 0.9; 218.3 ± 38.6 kg BW) were housed individually in each farrowing crate and the calorimeters were maintained at thermoneutral conditions (20.9 ± 2.6°C and 43.7 ± 18.6% relative humidity) throughout lactation. On lactation day 4, 8, 14, and 18, indirect calorimetry was performed on all sows and their litters, as well as 2 piglets from a sentinel litter to determine THP and the respiratory quotient (RQ). Sentinel piglet data were used to estimate THP and RQ for the sows independent of the litter. Sow + litter THP (kcal/h) increased (P = 0.01; 16.6%) on day 8 compared to day 4 and was greater (27.3%) on day 14 and day 18 compared to day 4 and day 8. Sow THP was greater (P = 0.01) on day 8 (401.19 ± 17.15 kcal/h) and day 14 (430.79 ± 12.42 kcal/h) compared to day 4 (346.16 ± 16.62 kcal/h), and was greater on day 14 compared to day 8, and on day 18 (386.16 ± 20.02 kcal/h) compared to day 14. No sow + litter RQ differences (P = 0.21; 1.02 ± 0.04) were detected by day of lactation. However, sow RQ was reduced (P = 0.01) on day 14 (0.98 ± 0.02) compared to day 4 (1.03 ± 0.03), day 8 (1.02 ± 0.02), and day 18 (1.04 ± 0.03). In summary, this cost-effective system (total cost: $1,892 USD) can allow researchers to accurately evaluate THP in individual lactating sows and their litters. [ABSTRACT FROM AUTHOR]

The ability to determine total heat production (THP) in individual sows and litters can be logistically difficult and often requires the use of multiple animals to generate data on a per room basis. Furthermore, these systems may be costly to construct, precluding their use by many researchers. Therefore, the objective was to develop a low-cost indirect calorimetry system to determine THP in individual lactating sows and litters. Six indirect calorimeters were constructed to house 1 sow and litter in a crate throughout farrowing and a 21-d lactation period. Farrowing crates were placed within a high-density polyethylene pan filled with water and then a polyvinyl chloride frame was constructed around the crate. The frame provided a structure to hold the inlet and outlet air pipes, feed and water inlets, air circulation fans, and a polyethylene plastic sheet that was secured at the bottom of the frame and submerged under water to maintain an air tight seal. Chamber accuracies for O2 and CO2 were evaluated by ethanol combustion. One week pre-farrowing, 6 pregnant multiparous sows (parity 2.9 ± 0.9; 218.3 ± 38.6 kg BW) were housed individually in each farrowing crate and the calorimeters were maintained at thermoneutral conditions (20.9 ± 2.6°C and 43.7 ± 18.6% relative humidity) throughout lactation. On lactation day 4, 8, 14, and 18, indirect calorimetry was performed on all sows and their litters, as well as 2 piglets from a sentinel litter to determine THP and the respiratory quotient (RQ). Sentinel piglet data were used to estimate THP and RQ for the sows independent of the litter. Sow + litter THP (kcal/h) increased (P = 0.01; 16.6%) on day 8 compared to day 4 and was greater (27.3%) on day 14 and day 18 compared to day 4 and day 8. Sow THP was greater (P = 0.01) on day 8 (401.19 ± 17.15 kcal/h) and day 14 (430.79 ± 12.42 kcal/h) compared to day 4 (346.16 ± 16.62 kcal/h), and was greater on day 14 compared to day 8, and on day 18 (386.16 ± 20.02 kcal/h) compared to day 14. No sow + litter RQ differences (P = 0.21; 1.02 ± 0.04) were detected by day of lactation. However, sow RQ was reduced (P = 0.01) on day 14 (0.98 ± 0.02) compared to day 4 (1.03 ± 0.03), day 8 (1.02 ± 0.02), and day 18 (1.04 ± 0.03). In summary, this cost-effective system (total cost: $1,892 USD) can allow researchers to accurately evaluate THP in individual lactating sows and their litters. [ABSTRACT FROM AUTHOR]

Several management practices and technologies have been developed to mitigate thermal stress in swine. However, recommended temperature thresholds for implementing thermal stress mitigation are variable and may not accurately reflect the thermal requirements of non-pregnant and gestating sows with modern genetics. Therefore, a tool to support environmental management decisions for non-pregnant and gestating sows was created. The decision support tool is based on several published works by our group that characterized responses of non-pregnant, mid-gestation, and late-gestation sows across a wide temperature range. Cool, comfortable, and warm ranges were identified based upon behavioral thermal preferendum, and physiological responses were used to determine mild, moderate, and severe heat stress thresholds. The inflection points of respiration rate and body temperature as a function of dry bulb temperature were used to establish heat stress thresholds by gestation stage. Non-pregnant, mid-gestation, and late-gestation sow mild heat stress thresholds differed (P < 0.05) and occurred at 25.5, 25.1, and 24.0 °C, respectively. Body temperature inflection points indicative of moderate heat stress differed by gestation stage (P < 0.05) and occurred at 28.1, 27.8, and 25.5 °C, respectively. Severe heat stress inflection points were lower (P < 0.05) for late-gestation sows (30.8 °C) but were similar for non-pregnant and mid-gestation sows (32.9 °C). Dewpoint influenced heat stress response for mid- and late-gestation sows (P < 0.05) but did not have an effect on non-pregnant sows (P > 0.05). Heat stress threshold data were integrated with behavioral thermal preferendum data. For non-pregnant and midgestation sows, similar (P > 0.05) cool (< 13.2°C) and comfortable (13.2 to 16.4°C) temperature ranges were observed. However, late-gestation sows had lower (P < 0.05) cool (< 12.6°C) and comfortable (12.6 to 15.6°C) temperature ranges relative to non-pregnant and midgestation sows. The dry bulb temperature (TDB) that non-pregnant, mid-gestation, and late-gestation sows found to be warm was estimated as TDB preference range < TDB < mild heat stress. The decision support tool was integrated into a smartphone application called HotHog. This smartphone application provides hourly and daily predictions of thermal comfort and stress in non-pregnant, mid-gestation, and lategestation sows. Users can set geographical locations, either manually or by current location, for thermal index predictions. Additionally, hourly and daily precipitation, and temperature predictions are displayed for the selected location. Management observations and mitigation options, as well as expected physiological and behavioral changes, are provided for each thermal index category to help users identify stressed pigs and assist with management decisions. HotHog will support swine producers in making more informed decisions related to in-barn environmental management to reduce the negative effects of thermal stress on sows and their gestating offspring. Furthermore, the tool may be helpful for teaching thermal management to livestock technicians and students. [ABSTRACT FROM AUTHOR]

Increased global temperatures pose challenges to livestock agriculture. Domestic swine are particularly sensitive to hotter environments due to their inability to sweat, litter bearing nature, difficulty in expressing natural cooling behaviors, and intense genetic selection for production traits. Since animal welfare is central to livestock production as a matter vital to efficiency as much as ethics, developing novel traits that may be genetically related to heat tolerance may assist in improving and sustaining animal welfare. The objective of this study was to develop novel traits of behavior using an ethogram designed for efficiency in production settings, estimate the variance components, and correlate these traits with indicators of heat tolerance and maternal ability. This study considered 1,312 individual Landrace-Large White cross production sows between 6 and 19 days of lactation. Animals were housed in farrowing crates in a commercial setting in southern North Carolina in June and July of 2021, an environment susceptible to potential heat stress. These sows were subjected to a standardized procedure involving a person removing hair from both hips using an electric clipper while an observer was positioned in front of the sow to record behaviors. Scores were later applied to the variations in behavior both for changes in positions and types of vocalizations displayed by the animals during handling. Genotypes were obtained from hair follicles and captured by a 50K porcine SNP panel. Variance components for novel behavior traits were obtained using the BLUPF90+ programs and genomic relationship matrix to estimate genetic correlations of behavior with several indicators of heat tolerance and maternal ability. Heritabilities for behavior traits ranged from 0.131 for vocalization score to 0.072 for shaving time, while heritabilities for heat tolerance and maternal ability ranged from 0.15 to 0.03 for vaginal temperature and respiration efficiency, respectively. The maternal ability traits were based on the single current litter and had the lowest heritabilities ranging from 0.101 to 0.04 for number born alive and number of mummies, respectively. High and positive genetic correlations indicate a potential for coupled selection for both fewer mummified piglets and a greater number of liveborn using the behavior trait of vocalization score. These correlations between favorable maternal traits and behavior traits suggest the potential that one or more complex biological pathways exist that share relevancy between these traits. However, genetic correlations between the behavior traits and heat tolerance indicators were low to negligible, most with a magnitude falling below 0.10, revealing the need for other traits to be used as selection parameters for heat tolerance. Further studies may be able to capture additional environmental effects to improve models of behavior and create indirect measures more obtainable than direct measures of heat tolerance. [ABSTRACT FROM AUTHOR]

Lactating sows are among the most heat stress sensitive population in the swine herd. Exposure to high ambient temperatures causes a marked decrease in production measures and welfare in lactating sows and may have a negative downstream impact on piglet growth due to impaired sow lactogenesis. Genomic selection for improved heat stress (HS) tolerance may be a viable method to reduce the negative impacts of HS on lactating sows and their offspring. However, selection for HS tolerance is generally associated with decreased productivity. Therefore, the study objective was to evaluate the impact of genomic selection for thermotolerance on indirect measures of sow milk production under HS conditions. We hypothesized that heat tolerant sows would have a decrease in indirect measures of milk production when compared with heat sensitive sows. A total of 20 multiparous lactating sows (Large White x Landrace; parity = 4.85 ± 0.75) divergently genomically selected for heat tolerance (TOL; n = 11) or heat sensitivity (SEN; n = 9) were subjected to cyclic HS temperatures (28 to 32° C) from day 2.5 ± 1.0 post-farrowing until weaning (d 21.3 ± 1.1). On d 4, 8, 14, and 18 of lactation, indirect calorimetry was used to estimate total heat production (THP) on an individual sow basis following previously published methods by our group. In addition, sow respiration rate (RR) was measured daily at 0800, 1200, 1600, and 2000 h. All data were analyzed using PROC GLIMMIX in SAS 9.4 with individual sow included as the experimental unit. It was determined that TOL sows had an overall increase (P = 0.04; 5.68 ± 0.24 kcal·sow· kg BW0.75(-1)) in THP when compared with SEN sows (4.74 ± 0.18 kcal·sow· kg BW0.75(-1)). A treatment by day effect was observed where THP was greater (P < 0.01; 88%) for TOL sows on d 4 of lactation when compared with SEN sows. Preliminary evidence suggests that TOL sows had an overall increase (P = 0.01) in RR (78 ± 5 bpm) when compared with SEN sows (73 ± 5 bpm). Taken together, these data suggest that genomic selection methods used to increase lactating sow thermotolerance may have had a positive impact on indirect measures of lactogenesis under HS conditions. [ABSTRACT FROM AUTHOR]

In utero heat stress negatively impacts fetal development and alters postnatal phenotypes in swine. However, the effects of heat stress (HS) on fetal growth during early gestation is relatively unknown. The study objective was to evaluate the effects of gestational HS on measures of fetal growth in early gestation. Twentythree gestating gilts were exposed to HS (n = 12; cyclic 26-38°C) or thermoneutral (TN; n = 11; 18.5 ± 1.2°C) conditions from gestation d 6 ± 0.9 to 33 ± 1.7. Vaginal temperature was recorded in 15 min intervals using data loggers. Respiration rates (RR) were recorded daily at 0800, 1200, 1600, and 2000 h. All gilts were individually-housed, and limit-fed 1.82 kg/d. Gilt body weights (BW) were measured weekly and average daily gain and gain:feed were calculated. At gestation d 33 ± 1.7, gilts were harvested and fetal weights and counts were recorded. Data were analyzed using PROC GLIMMIX. Vaginal temperatures and RR were greater (P < 0.01) in HS (38.5 ± 0.1°C and 59 ± 2 bpm, respectively) versus TN gilts (38.0 ± 0.1°C and 29 ± 2 bpm, respectively). Although no initial BW differences were observed (P = 0.39; 148.8 ± 4.1 kg), final BW tended to be greater (P < 0.07) for HS (166.5 ± 3.8 kg) versus TN (156.8 ± 4.0 kg) gilts. Average daily gain was increased (P < 0.01) for HS (0.5 ± 0.1 kg/d) versus TN (0.3 ± 0.1 kg/d) gilts. Gain:feed was greater (P < 0.01) for HS (0.27 ± 0.03) versus TN (0.16 ± 0.03) gilts. No fetal weight (P = 0.23; 4.3 ± 0.2 g/fetus) or count (P = 0.15; 15.2 ± 0.9 fetuses/gilt) differences were detected. In conclusion, HS-exposure during early gestation improved measures of growth performance in gestating gilts but did not impact fetal growth or count. [ABSTRACT FROM AUTHOR]

Accurate estrus detection can improve sow conception rates and increase swine production efficiency. Unfortunately, current practices based on individual animal behavior may be inefficient due to large sow populations at commercial farms and the associated labor required. Therefore, the study objective was to characterize body temperature and activity changes in replacement gilts at the onset of estrus in order to provide initial data to develop a remote estrus detection system for commercial swine operations. Twelve replacement gilts (130.2±1.9 kg BW) were administered altrenogest to synchronize estrus, and data loggers that detect vaginal temperature (T V ) and quantify total activity 24 h/d in 5 min intervals were attached to a blank controlled internal drug release device and inserted intra-vaginally for 7 d prior to expected estrus. Activity was quantified as counts per minute (cnt/min) using an internal accelerometer. During the 7 d of monitoring, gilts were checked for estrus twice daily (0800 and 1500 h) by two trained individuals. To standardize data, only the day of estrus detection (d E ) and the 3 d prior (d −3 , d −2 , d −1 , n =4 total days) were used in the final analysis since gilts came into estrus on different days. Data were analyzed using the PROC MIXED procedure in SAS 9.4. Overall, T V was reduced ( P <0.01; 0.26 °C) on d E compared to the previous 3 d; however, no differences were detected between d −3 , d −2 , and d −1 . Activity was increased ( P <0.01; 37.8%) on d E compared to d −3 and d −2 , but no differences were detected between d E and d −1 . In summary, T V was reduced and activity was increased at the onset of estrus in replacement gilts. [ABSTRACT FROM AUTHOR]

Lactating sows are especially sensitive to heat stress (HS) due to high metabolic demands resulting from milk output. Therefore, there is a need to develop effective cooling technologies that reduce the impact of HS on lactating sows. The study objective was to determine whether electronically controlled cooling pads (ECP) would allow sows to remain euthermic under HS conditions. Twelve multiparous (2.69 ± 0.85) lactating sows (265.4 ± 26.1 kg) and litters (11.4 ± 0.7 piglets/litter) were assigned to either a non-functional ECP (NECP; n = 6) or an ECP (n = 6), housed in farrowing crates, and tested over two repetitions. Sows were provided feed and water ad libitum and all sows were exposed to HS (28.27 ± 1.42°C nighttime to 35.14 ± 0.70°C daytime). Body temperature (TB), was measured hourly using vaginal implants, and respiration rate (RR) was measured in 30 min intervals from 0600 to 2100 hrs over 2 d representing mid- and late lactation. Mixed model periodic regression equations were fitted to the TB and RR to time. The final model for TB included the effect of replicate, random effect of sow, day of lactation as a covariate, single-phase sine and cosine variables for each treatment and 2-phase sine and cosine periodic regression variables. The final model for RR included the random effect of sow, effect of treatment, replicate, day of lactation, sleeping, and single-phase sine and cosine functions for each treatment. An interaction (P < 0.05) between treatment and sine or cosine was observed for TB. For RR there was no interaction for treatment and cosine (P = 0.07), but an interaction (P < 0.05; -9.94) was observed for sine. The significant treatment by wavelength interactions observed indicate a change in RR and TB patterns when sows are placed on ECPs. [ABSTRACT FROM AUTHOR]

Heat stress (HS) decreases lactation output in sows due to an attempt to reduce metabolic heat production; however, this negatively affects litter growth performance. Therefore, the study objective was to determine whether electronically controlled cooling pads (ECP) would improve indirect measures of lactation output (e.g., metabolic heat production) and litter growth performance in HS exposed sows. Over two repetitions, 12 multiparous (2.69 ± 0.85) lactating sows (265.4 ± 26.1 kg) and litters were assigned to either an ECP (n = 6) or a non-functional ECP (NECP; n = 6) and placed into farrowing crates within indirect calorimeters from d 3.7 ± 0.5 to d 18.7 ± 0.5 of lactation. Litters were standardized across all sows (11.4 ± 0.7 piglets/litter), and sows were provided ad libitum feed and water. All sows were exposed to cyclical HS (28.27 ± 1.42°C nighttime to 35.14 ± 0.70°C daytime). On d 4, 8, 14, and 18 of lactation, indirect calorimetry was performed on each individual sow and litter to determine total heat production (THP). Body temperature (TB), was measured hourly using vaginal implants, and respiration rate (RR) was measured daily at 0700, 1100, 1300, 1500, and 1900 h. Litter weights were obtained at birth and weaning. An overall decrease (P < 0.01; 25 bpm) in RR and maximum daily TB (P = 0.02; 0.40°C) was observed in ECP versus NECP sows. An increase in THP (P < 0.01; 20.4%) and THP/kg0.75 (P < 0.01; 23.1%) was observed for ECP when compared to NECP sows and litters. Litter growth rate was increased (P < 0.01; 20.8%) in ECP versus NECP sows. In summary, the use of ECP improves litter growth, thermoregulatory measures, and bioenergetic parameters associated with greater milk production in lactating sows exposed to cyclical heat stress. [ABSTRACT FROM AUTHOR]

Determining total heat production (THP) in individual sows and litters can be difficult and often requires the use of multiple animals to generate data on a per room basis. These systems may be costly to construct precluding their use by many researchers. The study objective was to develop a low cost indirect calorimetry system to determine THP in individual lactating sows and litters. Six indirect calorimeters were constructed to house 1 sow and litter in a crate throughout farrowing and a 21-d lactation period. Chamber accuracies for O2 and CO2 were evaluated by ethanol combustion. One-week pre-farrowing, 6 pregnant multiparous sows (parity 2.9 ± 0.9; 218.3 ± 38.6 kg BW) were housed individually in each farrowing crate and maintained in thermoneutral conditions (20.9 ± 2.6°C and 43.7 ± 18.6% relative humidity) throughout lactation. On lactation d 4, 8, 14, and 18, indirect calorimetry was performed on all sows and their litters, as well as 2 piglets from a sentinel litter to determine THP. Sentinel piglet data were used to estimate THP for the sows independent of the litter. Sow + litter THP (kcal/h) increased (P = 0.01; 16.6%) on d 8 compared to d 4 and was greater (27.3%) on d 14 and d 18 compared to d 4 and d 8. Sow THP was greater (P = 0.01) on d 8 (401.19 ± 17.15 kcal/h) and d 14 (430.79 ± 12.42 kcal/h) compared to d 4 (346.16 ± 16.62 kcal/h), and was greater on d 14 compared to d 8 and on d 18 (386.16 ± 20.02 kcal/h) compared to d 14. In summary, this cost-effective system can allow researchers to accurately evaluate THP in individual lactating sows and their litters [ABSTRACT FROM AUTHOR]

We hypothesized that lactating sows fed a reduced CP (RCP) diet with supplemental AA to improve AA balance produce less metabolic heat (HP) compared with feeding a conventional diet (control). The objective was to measure HP of sows (n = 24) fed control (19.6% CP) or RCP (14.2% CP) under thermoneutral (TN, 21 ± 1.5°C) or cycling heat stress (HS, 32 ± 1.5°C daytime and 24 ± 1.5°C nighttime). Diets contained 0.90% SID Lys and 2,580 kcal/kg. Positive pressure indirect calorimeters were used to measure gas exchange in individual sows with litters (sow + litter), and individual piglets on lactation d 4, 8, 14 and 18, and HP determined overnight (1900–0700) and during daytime (0700–1900). Sow and litter weights were recorded on d 1, 10 and 21. Sow HP was calculated by subtracting litter HP from sow + litter HP based on BW0.75. Model included the fixed effect of diet, random effects of block and sow, sow feed intake as a regression variable and day as the repeated measurement. Compared to control, HP (kcal/h·kg0.75) of RCP was lower (P < 0.01) overnight (5.25 vs. 5.96 ± 0.38), during daytime (6.33 vs. 6.94 ± 0.23), and over 24-h (5.78 vs. 6.46 ± 0.24) under HS. Under TN, HP of RCP tended to differ (P = 0.107) overnight (5.20 vs. 5.90 ±0.57) and over 24-h (5.93 vs. 6.48 ± 0.50) and did not differ (P = 0.190) during daytime (6.66 vs. 7.06 ± 0.52). Under HS, lactation day affected HP (P < 0.05) overnight and over 24-h, with HP increasing from d 1 to 14 and decreasing from d 14 to 18. Under TN, day of lactation did not affect sow HP. Feeding RCP diet to lactating sows decreased HP, and this effect was more pronounced in sows housed under HS. [ABSTRACT FROM AUTHOR]

This study was designed to evaluate the effects of electronically controlled cooling pads on measures of physiological responses in HS gilts. The study utilized 12 gilts randomly assigned into one of three treatment groups [Control(CN), flush 2.0 L cool water over 30 s every 4 min(F4), or flush 2.0 L over 30 s every 8 min(F8)] in a Latin Square design and replicated 12 times(2 repetitions/d over 6 d). Gilts were housed in farrowing crates and fed 1.2 kg at 0700 and 1300 h daily. On d 1 to 3(6 repetitions) the room was gradually heated from 18ºC to 32ºC, while on d 4 to 6 the room was gradually heated from 18ºC to 35ºC starting at 0730 or 1330 h. Once the temperature was achieved, cooling pads were turned on and the temperature was maintained for 2.5 h. Two baseline measurements were taken of respiration rates(RR), skin temperature through thermal imaging(IRTemp), and vaginal temperature(VTemp) before room heating began and then recorded every 20 minutes after pads were turned on. Measurements at the end of HS(PostH) and the change in values during the HS period(DIFF) were evaluated using PROC mixed of SAS. Gilts in F4 and F8 had lower RR than CN for PostH for both 32ºC and 35ºC (P< .05). DIFF in RR was less in F4 and F8 than in CN[(32ºC, P=.097) and (35ºC, P=.005)]. There was a tendency for DIFF in Vtemp at 32ºC between treatments (P=.064) but had no effect by treatment for PostH (P=.534). There was no effect in PostH and DIFF for IRTemp between treatments for 32ºC and 35ºC. PostH and DIFF for VTemp were significant at 35ºC (P=.009 and P=.001). PostH for RR was different at 35 ºC and 32 ºC (P=.0074; P=.0472) with F4 and F8 lesser and CN. In conclusion, cooling pads, regardless of flush rate, had positive impacts on physiological indicators of HS. [ABSTRACT FROM AUTHOR]

Heat stress (HS) during summer months can negatively affect reproductive efficiency and sow productivity. This study was designed to evaluate potential relationships between HS sensitivity and behavior with litter characteristics in replacement gilts. A total of 61 replacement gilts (108.8± 10.4 kg BW; 8 repetitions; 9d/repetition), were tested from February to May 2020 at the USDA-ARS Food Animal Behavior Laboratory in West Lafayette, IN. Pigs were housed (2/pen) in thermoneutral (TN; 22.6± 1.6°C) conditions and their behavior was recorded for 5 d. On d 6, gilts were subjected to an open field test and novel object test. Heart rate, number of escape attempts, and vocalizations were recorded during behavior testing. Vaginal temperature monitors were inserted to record body temperature (TB) every 15 min. Gilts were individually housed and exposed to cyclic HS (28.2± 0.97°C nighttime to 36.9± 1.9°C daytime; 46± 15.4% relative humidity) on d 7 to 9. Feed was provided ad libitum and feed intake was recorded daily. During the HS challenge, respiration rate (RR), skin (ear, shoulder, rump, and tail) temperature, and posture were recorded every 2 h from 0800 to 2000 h. Following the HS challenge, gilts were transported to the Purdue University swine farm, and gilts that displayed signs of estrus were artificially inseminated (253±29 d of age) between May and September 2020. At farrowing, litter characteristics were obtained and included total number of piglets born, total number of piglets born alive, average litter birth weight, total number of piglets weaned, and average weaning weight of the litter. Correlations between behavior, HS response, and litter characteristics were obtained using JMP 15 software. The preliminary analysis indicated no significant interactions (P < 0.05) between RR or TB with litter characteristics. However additional records are currently being collected, which might reveal important trends among the traits analyzed. [ABSTRACT FROM AUTHOR]

Simple Summary: This study evaluated the effects of exposure of the porcine fetus to in utero heat stress (IUHS) during the first half of gestation on carcass and meat quality attributes when market weight was reached. Pigs exposed to IUHS had lower head and heart weights at slaughter compared to the thermoneutral group. Most measures of carcass quality were not impacted by the treatments, but lower loin muscle area was observed for IUHS carcasses. Additionally, the loins from the heat stressed pigs were found to be tougher, regardless of the duration of aging. Accordingly, minimizing heat stress experienced by gestating pigs would be considered an important factor in improving both yield and quality of pork production systems. This study evaluated the impacts of in utero heat stress (IUHS) on the carcass and meat quality traits of offspring when market weight was reached. Twenty-four F1 Landrace × Large White gilts were blocked by body weight and allocated among thermoneutral (IUTN) or IUHS treatments from d 6 to d 59 of gestation. The offspring were raised under identical thermoneutral conditions, and gilts (n = 10/treatment) at market weight (117.3 ± 1.7 kg) were harvested. At 24 h postmortem, the loins (M. longissimus lumborum) were obtained, and sections were allocated among 1 d and 7 d aging treatments at 2 °C. Carcasses from IUHS pigs had lower head and heart weights (p < 0.05), as well as decreased loin muscle area (p < 0.05) compared to IUTN pigs. Loins from the IUHS group had a higher shear force value than the IUTN group (p < 0.05). Treatments had no other impacts on carcass and meat quality traits (p > 0.05), and Western blots suggested increased toughness of IUHS loins would not be attributed to proteolysis. These results suggest minimizing IUHS during the first half of gestation may be beneficial in improving pork yield and quality, though in general the effects of IUHS would be minimal. [ABSTRACT FROM AUTHOR]

An electronically controlled cooling pad has been developed to remove excess heat from sows using water cooled by flowing through underground pipes. This study was designed to evaluate different water flush rates on physiological measures of heat stress on day 16 to 21 of lactation. Twelve sows were randomly assigned to 3 treatments (control (CN), flush 2.0 L over 30 sec every 2.5 minutes (F2.5), or flush every 5 minutes (F5)) in a Latin square design. Feed intake (FI) was recorded daily at 0700 h. Temperatures were gradually increased from 22°C at 0800 h to 32°C by 0930 h. Then 32°C was maintained until 1500 h, when cooling of the room began. After 1800 h, the cooling pads were flushed every 9 minutes. Rectal temperature (RTemp), skin temperature (STemp), and respiration rates (RR) were measured at 0700, 0730, 0900, 1200, 1500, and 1800 h daily, with thermal imaging (IR) being taken at 1200 and 1500 h. The effects of flush rate (amount of water flushed) on STemp were linear (P=0.023), with means of 35.9, 35.0, and 35.9°C for the CN, F2.5, and F5.0 treatments. Pad flush rate effects of RTemp were linear (P< 0.001) and were greater in CN sows compared to F2.5 and F5 (39.3°, 38.8°, and 38.9°C), P< 0.0001). RR was affected by treatment (60 vs 42 and 50 breaths/min, P< 0.005 for CN, F2.5, and F5.0 treatments). Treatment by time interactions were significant for RR (P=0.0003) and RTemp (P=< 0.0001), with the greatest differences at 1200 and 1500 times (RR = 89, 48, & 65; and RTemp 39.9, 39.0, & 39.2°C for CN, F2.5, and F5.0 treatments). Skin temps measured by thermal imaging were not different among treatments (P=0.38) nor DFI (P=0.41). Cooling pad use with a flush rate of 2.0 L/2.5 min reduced body temperature to euthermia without increasing RR most effectively. This has implications toward reducing energy expenditure for thermoregulatory processes, which can increase nutrient availability for lactation during HS. [ABSTRACT FROM AUTHOR]

The study objective was to evaluate the impact of electronically controlled cooling pads on physiological measurements of heat stress during early lactation. Twelve sows (d 3 to 11 of lactation) were provided with a specially designed cooling pad. Sows randomly received no cooling (CONTROL, n=6) or pads set to flush 2L cool water every 30s when aluminum plate reached 29.5°C (TREAT, n=6). Respiration rates (RR), rectal temperatures (RT) and skin temperatures (ST, 15 cm posterior to the ear) were recorded daily (0700 and 1500 h) for seven days of early lactation. Feed intake (DFI) was measured daily at 0700 h. RR, RT, and ST were fitted to a model that included the effects of day, time, parity, cooling pad treatment, and interactions. DFI was fitted to the same model, excluding time of day. For RR: treatment, day, time, treatment by day, treatment by time, and day by time interactions were significant (P< 0.0004, CONTROL=49, TREAT= 30). Pad treatment had greater impact on RR during the first two days of the trial when the temperature was greater (32°C maximum CONTROL mean=66 vs. TREAT mean=30) than the following five days: 42, and 30 respectively). There was greater treatment impact on RR at 1500 versus 0700 h (0700 h: CONTROL= 35, TREAT= 25; 1500 h: CONTROL= 61, TREAT= 36). For RT: treatment, day, time, parity and interaction of day by time were significant (P< 0.01, CONTROL= 37, treat= 35.). For ST: treatment, day, time, parity and the interactions of time by parity, treatment by time, and day by time were significant (P< 0.0006, mean CONTROL=36.5, TREAT= 35.1). For DFI: day and the interaction of day by treatment were significant. The difference in feed intake between treatments increased as day increased. The use of electronically controlled cooling pads reduced measures of heat stress in early lactating sows. [ABSTRACT FROM AUTHOR]

Pregnant sows, especially during late-gestation, may be susceptible to heat stress due to increased metabolic heat production and body mass. Therefore, the study objective was to determine the thermoregulatory and physiological responses of sows exposed to increasing ambient temperature (TA) at 3 reproductive stages. In 3 repetitions, 27 multiparous sows (parity 3.22±0.89) were individually housed and had jugular catheters placed 5.0±1.0 d prior to the experiment. To differentiate between reproductive stages, sows were categorized as open (not pregnant, n=9), mid-gestation (59.7±9.6 days pregnant, n=9), or late-gestation (99.0±4.8 days pregnant, n=9). During the experiment, sows were exposed to 6 consecutive 1 h periods of increasing TA (period 1, 14.39±2.14°C; period 2, 16.20±1.39°C; period 3, 22.09±1.87°C; period 4, 26.34±1.39°C; period 5, 30.56±0.81°C; period 6, 35.07±0.96°C), with 1 h transition phases in between each period. Respiration rate (RR), heart rate (HR), skin temperature, and vaginal temperature (TV) were measured every 20 min and the mean was calculated for each period. At the end of each period, blood gases, leukocytes, and red blood cell counts were measured. Overall, RR and HR were greater (P=0.04; 45.6% and 12.9%, respectively) in late-gestation versus mid-gestation sows. Compared to mid-gestation and open sows, TV tended to be greater (P=0.06) during period 4 (0.18°C and 0.29°C, respectively) and period 5 (0.14°C and 0.18°C, respectively) in late-gestation sows. Blood O2 increased (P< 0.01; 18.1%) for all sows with advancing period, regardless of reproductive stage. Late-gestation sows had reduced (P=0.02; 16.1%) blood CO2 compared to mid-gestation sows, regardless of period. In summary, late-gestation sows appear to be more sensitive to increasing TA as indicated by increased RR, HR, TV, and blood O2, and reduced blood CO2 when compared to mid-gestation or open sows. This change in O2 and CO2, due to increasing RR and heat stress sensitivity of late-gestation sows, may suggest an alteration to the acid-base balance, leading to respiratory alkalosis. [ABSTRACT FROM AUTHOR]