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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]

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]

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]

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]

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]

Maintaining metabolic balance is a key factor in the health of dairy cattle during the transition from pregnancy to lactation. Little is known regarding the role of the circadian timing system in the regulation of physiological changes during the transition period. We hypothesized that disruption of the cow's circadian timing system by exposure to chronic light–dark phase shifts during the prepartum period would negatively affect the regulation of homeostasis and cause metabolic disturbances, leading to reduced milk production in the subsequent lactation. The objective was to determine the effect of exposure to chronic light–dark phase shift during the last 5 wk prepartum of the nonlactating dry period on core body temperature, melatonin, blood glucose, β-hydroxybutyric acid (BHB) and nonesterified fatty acid (NEFA) concentrations, and milk production. Multiparous cows were moved to tiestalls at 5 wk before expected calving and assigned to control (CTR; n = 16) or phase-shifted (PS; n = 16) treatments. Control cows were exposed to 16 h of light and 8 h of dark. Phase-shifted cows were exposed to the same photoperiod; however, the light–dark cycle was shifted 6 h every 3 d until parturition. Resting behavior and feed intake were recorded daily. Core body temperature was recorded vaginally for 48 h at 23 and 9 d before expected calving using calibrated data loggers. Blood concentrations of melatonin, glucose, BHB, and NEFA were measured during the pre- and postpartum periods. Milk yield and composition were measured through 60 DIM. Treatment did not affect feed intake or body condition. Cosine fit analysis of 24-h core body temperature and circulating melatonin indicated attenuation of circadian rhythms in the PS treatment compared with the CTR treatment. Phase-shifted cows had lower rest consolidation, as indicated by more total resting time, but shorter resting period durations. Phase-shifted cows had lower blood glucose concentration compared with CTR cows (4 mg/mL decrease), but BHB and NEFA concentrations were similar between PS and CTR cows. Milk yield and milk fat yield were greater in PS compared with CTR cows (2.8 kg/d increase). Thus, exposure to chronic light–dark phase shifts during the prepartum period attenuated circadian rhythms of core body temperature, melatonin, and rest–activity behavior and was associated with increased milk fat and milk yield in the postpartum period despite decreased blood glucose pre- and postpartum. Therefore, less variation in central circadian rhythms may create a more constant milieu that supports the onset of lactogenesis. [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]

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]