Thermoneutral Period Research Articles

Tissue specific responses to oxidative fuel source preference during heat stress in lactating dairy cows

Prolonged exposure to high environmental temperatures results in an accumulated heat load that induces a heat stress (HS) response in dairy cattle. Heat stress compromises dairy farm profitability by reducing milk yield, altering milk composition, and hindering reproductive performance. The ability to alternate between carbohydrate and lipid sources for energy production is termed metabolic flexibility (Met Flex). The objective of this study was to evaluate the Met Flex of mammary, muscle, and liver tissue in lactating dairy cows under HS and thermoneutral (TN) conditions. Sixteen Holstein cows were assigned to 1 of 2 treatment groups: pair feeding in a TN environment (PFTN) or HS. All cows experienced a 4 d TN period with ad libitum intake followed by a 4 d treatment period. Heat stress cows were exposed to a temperature humidity index (THI) ranging from 76 to 80 and the PFTN cows were exposed to a THI of 64. Milk production and health data were recorded twice daily. Semitendinosus biopsies were obtained on d 4 of each period and post-mortem mammary and liver samples were obtained on d 4 of period 2. All tissue samples were assayed for Met Flex. Activity of mitochondrial (Mit) enzymes were assessed in skeletal muscle only. Four d of HS decreased milk yield, altered milk composition, and increased respiration rate and rectal temperatures. No differences in Met Flex were observed in mammary or liver tissue during period 2. However, HS, but not PFTN conditions, lowered Met Flex of skeletal muscle by 18.3% when compared with TN ad libitum feed intake conditions of period 1. No treatment differences were observed in skeletal muscle Mit enzyme activity indicating the decrease in Met Flex occurred independently of changes in Mit function. The reduction in Met Flex of skeletal muscle during HS may contribute to reduced milk yield and warrants further investigation.

82 Effects of a red-clover containing mineral on heifer behavior and fertility

Abstract Heat stress reduces reproductive efficiency in beef cattle. Recent evidence suggests that supplementation of red clover can alleviate the physiological impacts of fescue toxicosis which could decrease heat stress. Our objective was to determine the effect of supplementing heifers grazing endophyte-infected tall fescue (E+ TF) with a conventional mineral containing red-clover leaf. We hypothesized that heifers supplemented with the red-clover leaf mineral would have greater conception rates to AI (CRAI) in times of possible heat stress compared with heifers supplemented with conventional mineral. A grazing study was conducted from May – August in 2021, 2022, and 2023. Yearling beef heifers (n = 32, 36, 40 heifers yr-1, respectively) were blocked by body weight, hair coat score and color into 4 grazing blocks that were assigned to 1 of 2 treatments (2 blocks treatment-1): 1. conventional non-medicated loose mineral control (0%-RC), or 2. conventional loose mineral + 20% wt/wt red clover leaf (20%-RC). Mineral treatments were provided in ground, 3-compartment mineral feeders ad libitum. Each grazing block was assigned to four, 0.8- ha. pastures consisting of predominantly E+ TF and were rotationally managed over the course of the study. Each year estrus was synchronized suitable for fixed time AI in May and all heifers resynchronized in June. In addition, each heifer was fitted with an ear-tag sensor (CowManager SensOor, Agis Automatisering BV, Harmelen, the Netherlands) for continuous behavioral monitoring (including high activity and activity). The CRAI were analyzed with the GLIMMIX procedure of SAS using the binomial distribution link logit function (v.9.4., SAS Inst. Inc., Cary, NC). Total daily activity and high activity reported by CowManger during May and June were analyzed by the MIXED procedure with repeated measures of SAS. The CRAI were similar for 20%-RC (67.30 ± 9.80%) and 0%-RC (60.70 ± 9.80%) heifers following the first service of AI (P = 0.51) during a thermoneutral period in May. In contrast, CRAI was greater (P = 0.02) for 20%-RC heifers (48.67 ± 13.47%) than CM (15.10 ± 13.47%) in June when temperatures increased to potential heat stress levels. Overall, conception rate after two rounds of AI for 20%-RC (78.30 ± 9.30%) heifers tended to be greater (P = 0.08) than CM (62.20 ± 9.30 %). While high activity (associated with estrous behavior) reported by CowManager did not differ between treatments (20%-RC: 203.94; 0%-RC: 213.90; SEM: 8.65 min d-1; P = 0.25), normal daily activity of 20%-RC heifers (150.69 ± 10.40 min d-1) tended to be greater (P = 0.06) than CM (126.33 ± 8.65 min d-1). Results of this study suggest supplementing red-clover containing mineral may mitigate negative effects of consuming E+ TF including decreased conception rates during times of heat stress.

Relationships between gastrointestinal permeability, heat stress, and milk production in lactating dairy cows

Heat stress (HS) is a global issue that decreases farm profits and compromises animal welfare. To distinguish between the direct and indirect effects of HS, 16 multiparous Holstein cows approximately 100 d in milk were assigned to one of 2 treatments: pair fed to match HS cow intake, housed in thermoneutral conditions (PFTN, n = 8) or cyclical HS (n = 8). All cows were subjected to 2 experimental periods. P1 consisted of a 4 d thermoneutral period with ad libitum intake. During P2, the HS cows were housed in cyclical HS conditions with a temperature humidity index (THI) ranging from 76 to 80 and the PFTN cows were exposed to a constant THI of 64 for 4 d. DMI of the PFTN cow was intake matched to the HS cows. Milk yield, milk composition, rectal temperature, and respiration rate were recorded twice daily, blood was collected daily via a jugular catheter, and cows were fed twice daily. On d 3 of each period, Cr-EDTA and sucralose were orally administered and recovered via 24 h total urine collection to assess gastrointestinal permeability (GIP). All data were analyzed using the GLIMMIX procedure in SAS. The daily data collected in P1 was averaged and used as a covariate if deemed significant in the model. HS decreased voluntary intake by 35% and increased rectal temperature and respiration rate (38.4 vs 39.4°C and 40 vs 71 respirations/min, respectively). HS reduced dry matter intake (DMI) by 35% which accounted for 66% of the decrease in milk yield. The yield, and not concentration, of milk protein, fat, and other solids were lower in the HS cows on d 4 of P2. Milk urea nitrogen (MUN) was higher and plasma urea nitrogen (PUN) tended to be higher on d 3 and d 4 of HS. Glucose was 7% lower in the HS cows and insulin was 71% higher in the HS cows than the PFTN cows on d 4 of P2. No difference in lipopolysaccharide binding protein (LBP) was observed. HS cows produced 7 L/d more urine than PFTN cows. No differences were detected in the urine concentration or percentage of the oral dose recovered for Cr-EDTA or sucralose. In conclusion, HS was responsible for 34% of the reduction of milk yield. The elevated MUN and the tendency for elevated PUN indicate a whole-body shift in nitrogen metabolism. No differences in GIP or LBP were observed. These results indicate that, under conditions of this experiment, activation of the immune system by gut derived lipopolysaccharide was not responsible for the decreased milk yield observed during HS.

Influence of Heat Stress on Body Surface Temperature and Blood Metabolic, Endocrine, and Inflammatory Parameters and Their Correlation in Cows.

This study aimed to determine whether heat stress affected the values and correlations of metabolic, endocrinological, and inflammatory parameters as well as the rectal and body surface temperature of cows in the early and middle stages of lactation. This experiment was conducted in May (thermoneutral period), June (mild heat stress), and July (moderate to severe heat stress). In each period we included 15 cows in early lactation and 15 in mid-lactation. The increase in rectal and body surface temperatures (°C) in moderate to severe heat stress compared to the thermoneutral period in different regions was significant (p < 0.01) and the results are presented as mean and [95%CI]: rectal + 0.9 [0.81-1.02], eye + 6 [5.74-6.25], ear + 13 [11.9-14.0], nose + 3.5 [3.22-3.71], forehead + 6.6 [6.43-6.75], whole head + 7.5 [7.36-7.68], abdomen + 8.5 [8.25-8.77], udder + 7.5 [7.38-7.65], front limb + 6 [5.89-6.12], hind limb + 3.6 [3.46-3.72], and whole body + 9 [8.80-9.21]. During heat stress (in both mild and moderate to severe stress compared to a thermoneutral period), an increase in the values of extracellular heat shock protein 70 (eHsp70), tumor necrosis factor α (TNFα), cortisol (CORT), insulin (INS), revised quantitative insulin sensitivity check index (RQUICKI), urea, creatinine, total bilirubin, aspartate transpaminase (AST), gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), and creatin kinase (CK) occurred, as well as a decrease in the values of triiodothyronine (T3), thyroxine (T4), non-esterified fatty acids (NEFA), glucose (GLU), β-Hydroxybutyrate (BHB), calcium, phosphorus, total protein (TPROT), albumin (ALB), triglycerides (TGCs), and cholesterol (CHOL). In cows in early lactation compared to cows in mid-lactation, there was a significantly larger increase (p < 0.01) in the values of eHsp70, TNFα, GLU, RQUICKI, and GGT, while the INS increase was smaller during the three experimental periods. The decrease in the values of Ca, CHOL, and TGC was more pronounced in cows in early lactation compared to cows in mid-lactation during the three experimental periods. Rectal temperature was related to eHsp70 (r = 0.38, p < 0.001) and TNFα (r = 0.36, p < 0.01) and showed non-significant poor correlations with other blood parameters. Blood parameters correlate with body surface temperature, with the following most common results: eHsp70 and TNFα showed a moderately to strongly significant positive correlation (r = 0.79-0.96, p < 0.001); CORT, INS, and Creat showed fairly to moderately significant positive correlations; T3, T4, NEFA and GLU showed fairly to moderately significant negative correlations (r = 0.3-0.79; p < 0.01); RQUICKI, urea, AST, and GGT showed fairly and significantly positive correlations; and TGC, CHOL, TPROT, and ALB showed fairly and significantly negative correlations (r = 0.3-0.59; p < 0.01). Measuring the surface temperature of the whole body or head can be a useful tool in evaluating the metabolic response of cows because it has demonstrated an association with inflammation (TNFα, eHsp70), endocrine response (CORT, T3, T4), the increased use of glucose and decreased use of lipids for energy purposes (INS, NEFA, GLU, and RQUICKI), and protein catabolism (ALB, TPROT, urea, Creat), which underlies thermolysis and thermogenesis in cows under heat stress. In future research, it is necessary to examine the causality between body surface area and metabolic parameters.

296 Short-Term Diurnal Heat Stress Modulation of Growing Gilt and Barrow Growth and Feed Intake

Abstract During summer months, the increase in temperature and humidity can lead to heat stress conditions that have negative impacts on the growth performance of pigs. The objective of this study was to characterize the effects of diurnal heat stress (dHS) on gilt and barrow growth, day-time and night-time feed intake. Twelve gilts and 12 barrows (46.5 ± 2.47 kg BW) were individually housed in metabolism crates over two experimental periods. For Period 1, all pigs were housed in thermoneutral (TN) conditions (20-21°C and 40-60% humidity). Following the TN period, period 2 consisted of four days of dHS (6 h at 32°C, 18 h at 27°C, 40-60% humidity). The conditions in the dHS period were designed to replicate summer, industry-applicable cyclical heat stress conditions. In each period lasting 4 days, pig BW and feed disappearance were recorded and ADG, ADFI and G:F calculated. Additionally, within each day, 0700 to 1700 h (day-time) and 1700 to 0700 h (night-time) feed intake was recorded. Changes in pig body temperatures (BT) and respiration rates (RR) were measured daily at 0800, 1200 and 1800 h. Pig was considered the experimental unit, and all data were analyzed for the fixed effects of period (TN vs. HS), sex, and period-by-sex interaction. There were no period-by-sex interactions observed for any analyzed variable (P &amp;gt; 0.05). As expected, dHS markedly increased pig 3-day average BT and RR compared with their TN values (P &amp;lt; 0.05). Compared with TN, dHS BT measurements at noon, PM, and overall were on average 1.0°C greater (P &amp;lt; 0.0001). The RR was also increased by 200 to 300% for AM, noon, PM, and overall, for the dHS period as compared with TN (P &amp;lt; 0.001). Within the dHS period, BT was highest at the noon and PM recordings, and RR was highest at the noon recording (P &amp;lt; 0.0001). Pigs tended to have reduced ADFI during dHS compared with TN period (1.54 vs 1.70 kg/d, P = 0.051). During the TN period, pigs consumed 61% (1.03 kg) of daily total feed consumption during day-time and 39% (0.67 kg) in the PM period (P &amp;lt; 0.0001). The opposite effect was found during dHS, in which pigs consumed 33.3% (0.52 kg) of their total daily feed during the peak heat conditions (day-time) and 66.7% (1.02 kg) consumed in the cooler night-time period (P &amp;lt; 0.0001). Compared with barrows, gilts tended to have greater overall ADFI (1.61 vs. 1.48 kg/d; P = 0.079). Within both the TN and dHS period, gilts had a lower average noon BT (P &amp;lt; 0.05), and lower morning RR (P &amp;lt; 0.05). Altogether, three days of dHS increased pig RR and BT, and decreased ADFI. However, day- and night-time feed intake patterns changed compared with the TN period. Diurnal heat stress has similar impacts to both gilts vs. barrows.

Influence of Heat Stress on Body Temperatures Measured by Infrared Thermography, Blood Metabolic Parameters and Its Correlation in Sheep.

The aim of this research is to examine the influence of heat stress (HS) on body temperature (BT) measured rectally (RT) or by infrared thermography (IRT) of the nose (NT), eye (ET), leg (LT) and abdominal (AT) regions in intensively and extensively breed sheep and to detect a correlation between body temperature and metabolic response in sheep. A total of 33 Wurttemberg × Sjenica Pramenka sheep breeds were examined, 17 ewes were from outdoors and 16 were from indoor housing systems during three experimental periods (thermoneutral period, severe HS and moderate HS). Sheep under HS have a higher BT, and the magnitude of BT measured by infrared thermography (IRT) was higher than RT. LT and AT showed positive linear correlations with the temperature-humidity index (THI), while other ways of measuring BT did not give statistically significant correlations. Sheep under HS showed higher cortisol, insulin, total protein, albumin, urea, creatinine, bilirubin, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, lactate dehydrogenase, creatine kinase and index of insulin resistance, with lower values of triiodothyronine (T3), thyroxine (T4), non-esterified fatty acids, beta-hydroxybutyrate (BHB), glucose, calcium, inorganic phosphates, magnesium and cholesterol. BT and metabolic response were different in the function of the housing method of sheep. LT and AT showed a significant correlation with almost all blood parameters, and the strongest connections were made with T3, T4, BHB and the revised quantitative insulin sensitivity check index of insulin resistance. The abdomen and legs are good thermal windows because LT and AT are good summative responses to external ambient THI and internal metabolic changes in sheep under heat stress.

Heat Stress: A Serious Disruptor of the Reproductive Physiology of Dairy Cows.

Global warming is a significant threat to the sustainability and profitability of the dairy sector, not only in tropical or subtropical regions but also in temperate zones where extreme summer temperatures have become a new and challenging reality. Prolonged exposure of dairy cows to high temperatures compromises animal welfare, increases morbidity, and suppresses fertility, resulting in devastating economic losses for farmers. To counteract the deleterious effects of heat stress, cattl e employ various adaptive thermoregulatory mechanisms including molecular, endocrine, physiological, and behavioral responses. These adaptations involve the immediate secretion of heat shock proteins and cortisol, followed by a complex network of disrupted secretion of metabolic and reproductive hormones such as prolactin, ghrelin, ovarian steroid, and pituitary gonadotrophins. While the strategic heat stress mitigation measures can restore milk production through modifications of the microclimate and nutritional interventions, the summer fertility records remain at low levels compared to those of the thermoneutral periods of the year. This is because sustainment of high fertility is a multifaceted process that requires appropriate energy balance, undisrupted mode of various hormones secretion to sustain the maturation and fertilizing competence of the oocyte, the normal development of the early embryo and unhampered maternal-embryo crosstalk. In this review, we summarize the major molecular and endocrine responses to elevated temperatures in dairy cows, as well as the impacts on maturing oocytes and early embryos, and discuss the consequences that heat stress brings about in dairy cattle fertility.

Influence of high temperatures on the behavior, productivity and bioenergetic characteristics of goats

Abstract. The research was carried out in IE «Babyni kozy» of Kyiv region at a goat farm where a stable-pasture system of goats is used. In winter, goats are kept at free-stall housing on a deep litter and during the grazing period, on a forage area. Goats are milked on a milking parlor into the milk line. The article presents the results of researches of the influence of ambient temperature during the thermo neutral period and during the period of high temperatures on the productivity, daily behavior and bioenergetic characteristics of Saanen goats. A group of goats of the Saanen breed of the 3rd lactation was formed during the period of the milk yield increasing. The research was performed in thermo neutral period (average daily air temperature was up to + 22.3 °C) and during the period of temperature load at an average daily air temperature of + 27.6 °C. Each period lasted 12 days. It has been found that goats responded to the change in temperature by reducing of productivity by 10.70 % (0.35 kg). Hereby, the mass fraction of fat in goat's milk during this period increased by 0.09 %. During the period of high temperatures, goats spent a little less time eating food, watering and walking, but rested more in a supine position compared to the thermo neutral period. In general, in both temperature periods, the duration of the main acts of behavior in goats corresponded to physiological norms. The decrease in the duration of feed consumption during the temperature load caused a decrease in the number of feed reactions and the duration of chewing the cuddy in goats. The energy index, i.e. the amount of net energy consumption of feed, which transfers into milk energy during the temperature load decreased by 1.42 MJ %. Net energy consumption per 1 MJ of milk energy during the period of high temperatures has increased by 0.62 MJ. Key words: goats, temperature, productivity, metabolic energy, behavior, bio-energy.

Modeling the effects of heat stress in animal performance and enteric methane emissions in lactating dairy cows

Heat stress (HS) negatively affects dry matter intake (DMI), milk yield (MY), feed efficiency (FE), and free water intake (FWI) in dairy cows, with detrimental consequences to animal welfare, health, and profitability of dairy farms. Absolute enteric methane (CH4) emission, yield (CH4/DMI), and intensity (CH4/MY) may also be affected. Therefore, the goal of this study was to model the changes in dairy cow productivity, water intake, and absolute CH4 emissions, yield, and intensity with the progression (days of exposure) of a cyclical HS period in lactating dairy cows. Heat stress was induced by increasing the average temperature by 15°C (from 19°C in the thermoneutral period to 34°C) while keeping relative humidity constant at 20% (temperature-humidity index peaks of approximately 83) in climate-controlled chambers for up to 20 d. A database composed of individual records (n = 1,675) of DMI and MY from 82 heat-stressed lactating dairy cows housed in environmental chambers from 6 studies was used. Free water intake was also estimated based on DMI, dry matter, crude protein, sodium, and potassium content of the diets, and ambient temperature. Absolute CH4 emissions was estimated based on DMI, fatty acids, and dietary digestible neutral detergent fiber content of the diets. Generalized additive mixed-effects models were used to describe the relationships of DMI, MY, FE, and absolute CH4 emissions, yield, and intensity with HS. Dry matter intake and absolute CH4 emissions and yield reduced with the progression of HS up to 9 d, when it started to increase again up to 20 d. Milk yield and FE reduced with the progression of HS up to 20 d. Free water intake (kg/d) decreased during the exposure to HS mainly because of a reduction in DMI; however, when expressed in kg/kg of DMI it increased modestly. Methane intensity also reduced initially up to d 5 during HS exposure but then started to increase again following the DMI and MY pattern up to d 20. However, the reductions in CH4 emissions (absolute, yield, and intensity) occurred at the expense of decreases in DMI, MY, and FE, which are not desirable. This study provides quantitative predictions of the changes in animal performance (DMI, MY, FE, FWI) and CH4 emissions (absolute, yield, and intensity) with the progression of HS in lactating dairy cows. The models developed in this study could be used as a tool to help dairy nutritionists to decide when and how to adopt strategies to mitigate the negative effects of HS on animal health and performance and related environmental costs. Thus, more precise and accurate on-farm management decisions could be taken with the use of these models. However, application of the developed models outside of the ranges of temperature-humidity index and period of HS exposure included in this study is not recommended. Also, validation of predictive capacity of the models to predict CH4 emissions and FWI using data from in vivo studies where these variables are measured in heat-stressed lactating dairy cows is required before these models can be used.

Interactions between animal temperament and exposure to endophytic tall fescue: Effects on cell-mediated and humoral immunity in beef heifers

Two experiments (n=12 Angus heifers/experiment) investigated influences of animal temperament, as indicated by exit velocity (EV; determined at weaning) and consumption of toxic endophyte-infected tall fescue seed on peripheral lymphocyte production of interferon-γ. Heifers were selected from calves born on the University of Kentucky’s C. Oran Little Research Center. In experiment 1, calves were randomly selected from 50 heifers within a single calf crop. In experiment 2, calves with the 6 fastest and 6 slowest EV in the subsequent year’s calf crop were selected. In both experiments, heifers were assigned to either high or low EV treatments based on relative ranking, and endophyte treatments (toxic endophyte-infected, E+, or endophyte-free, E-, fescue seed) were balanced by body weight. Rations were restricted to 1.8 x NEm and common diet was top-dressed with fescue seed each morning. Experiment 1 had four phases (pre-endophyte treatment/thermoneutral, increased room temperature, increased room temperature/endophyte treatment, and post-endophyte/thermoneutral) and experiment 2 had two phases (increased room temperature/endophyte treatment and thermoneutral). During endophyte treatment phases, heifers were fed their respective treatment seed. During all other phases, all heifers received E- seed. In experiment 1, proportions of lymphocytes producing interferon-γ were decreased in E+ heifers during the heat/endophyte phase (P=0.03) whereas during the subsequent thermoneutral period this response was greater in high, compared with low, EV heifers on E- treatment, with no difference observed among E+ heifers (interaction P=0.08). Also during the recovery phase, average lymphocyte production of interferon-γ was higher in E+ heifers (P=0.01). Consistent with experiment 1 findings, during the recovery period of experiment 2, endophyte exposure increased the per cell production of interferon-γ (P&amp;lt;0.01). In this experiment, the difference was of sufficient magnitude to result in a concomitant increase (P=0.03) in total interferon-γ production during that period. These results indicate peripheral lymphocyte production of interferon-γ can be influenced by both EV and endophyte exposure following periods of increased ambient temperature humidity indices, though there was minimal indication of interactions between temperament and alkaloid exposure. This may imply that cattle with high exit velocities and those previously exposed to toxic endophyte-infected tall fescue are better poised against cell-mediated challenges.

Influence of successive heat waves on the thermoregulatory responses of pregnant and non-pregnant ewes

The frequency of heat waves has increased over the last years, with an impact on animal production and health, including the death of animals. Therefore, the aim of this study was to evaluate the dynamics of thermoregulation and hormonal responses in non-pregnant and pregnant ewes exposed to successive heat waves. Twenty-four non-pregnant and 18 pregnant Santa Ines ewes with black coat color (live weight: 55 ± 9.03 kg; age: 60 months) were used. Weather variables such air temperature, relative humidity, and solar radiation were continuously recorded. The rectal and tympanic temperatures and respiratory rate were measured daily. Serum triiodothyronine (T3) and prolactin were evaluated during the heat wave and thermoneutral periods. The physiological variables were higher under the heat wave conditions and were related to the activation of the thermoregulatory system for maintaining homeothermy (P < 0.05). The core body temperature was higher during successive heat waves (P < 0.05), as was the tympanic temperature, which are both affected by changes in air temperature (P < 0.05). T3 and prolactin levels were not influenced by successive heat waves (P < 0.05) and rectal temperature and respiratory rate were highest in non-pregnant ewes (P < 0.05). Prolactin was not affected by temperature. The results indicate that the Santa Ines breed overcomes the thermal challenge during a heat wave without showing severe signs of thermal stress regardless of being pregnant or not.

Effect of live yeast supplementation and feeding frequency in male finishing pigs subjected to heat stress.

In growing pigs, reduced growth during heat stress (HS) is mainly related to decreased feed intake. The study aimed to determine whether the reported positive effects of live yeast (LY) supplementation in HS pigs were due to a modified feeding behaviour or energy metabolism, and if these can be replicated by imposing an increased meal frequency. The effect of LY supplementation [0 (NS) vs. 100 (LY) g/ton of feed], and of feeding window (FW) [unlimited or Unli, 2FW of 1 h each, and 8FW of 15 min each] were measured in entire male finishing pigs (n=36). Ambient temperature was at 22°C during the thermoneutral period (TN; 5 d) and at 28°C during the HS period (5 d). Heat exposure decreased dry matter intake (DMI) and retained energy (RE) (-627 and -460 kJ∙kg BW-0.60∙d-1, respectively; P<0.01). During HS, LY-supplementation in Unli pigs decreased inter-meal intervals (P=0.02) attenuating HS effect on DMI which tended to improve RE (P=0.09). NS-8FW had higher DMI and RE than NS-2FW (P<0.05) but protein deposition (PD) were similar. Supplemented pigs had higher PD during HS regardless of FW (+18 g∙d-1; P=0.03). Comparing the 2FW groups, improved heat tolerance of LY-supplemented pigs were due to improved insulin sensitivity (P<0.05) and latent heat loss capacity after a meal (P<0.05) allowing them to increase their DMI (via an increased number of meals) and thus their energy efficiency. Imposing an increased meal frequency improved DMI in HS pigs but did not replicate positive effects of LY on protein deposition.

​Heat Stress-induced Changes in Milk Composition and Physiological Responses of Lactating Kankrej Cow during Summer Season as Compared to Thermo-neutral Period

Background: The Kankrej cattle is the heaviest and most priced of the Indian breeds of cattle. It is adapted to the geo-climatic conditions of North Gujarat and Kutch, which is normally hot and dry. It is reared in the district of Banaskantha in the state of Gujarat and also distributed in other parts of India and abroad. The experiment was carried out to study the effect of the summer season on the milk composition and physiological responses in lactating Kankrej cow compared to the thermoneutral period. Methods: For the experiment, total number of 16 clinically healthy Kankrej cows were randomly selected from Livestock Research Station (LRS), Sardar Krushinagar Dantiwada Agricultural University, Banaskantha, Gujarat and categorized into two different groups according to seasons. Physiological responses i.e. respiration rate and rectal temperature were recorded and milk samples were collected from each animal during the summer and thermoneutral period at fortnight intervals. The milk samples were analyzed by using an automated milk analyzer. Result: The results demonstrate that fat, SNF and density were significantly higher in the summer season. The physiological responses include respiration rate and rectal temperature were found significantly higher during summer than thermoneutral period. Milk protein was significantly higher during the thermo-neutral period as compared to summer.

Potential Biomarkers for Chronic Seasonal Heat Stress in Kagoshima Berkshire Pigs Reared in the Subtropical Region.

IntroductionPotential biomarkers for chronic seasonal heat stress in Kagoshima Berkshire pigs reared in the subtropical region were investigated by comparing the biomarker changes in the summer (a period of chronic heat stress) and winter (a thermoneutral period) seasons.Material and MethodsPigs were allocated to summer- and winter-finishing cohorts, 12 each. The evaluations included assessment of carcass traits and internal organs’ normality carried out at the time of slaughter, and measurement of biomarkers in whole blood: derivatives of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential as markers of oxidative stress, and serum amyloid A and albumin/globulin (A/G) ratio as markers of acute and chronic inflammation, respectively.ResultsThe summer-finished pigs reared under subtropical field conditions showed lower carcass quality than the winter-finished pigs, indicating a potential adverse effect of summer temperatures on the swine industry. Marginal changes were observed in d-ROMs and the A/G ratio between the summer- and winter-finishing cohorts.ConclusionThe results demonstrate that d-ROMs and the A/G ratio could be used as sensitive markers for heat stress under field conditions.

Oviductal epithelial cells transcriptome and extracellular vesicles characterization during thermoneutral and heat stress conditions in dairy cows

In this study, the transcriptome of oviductal epithelial cells and certain characteristics of their extracellular vesicles of dairy cows were described under thermoneutral and heat stress conditions. Twenty cows were compared in springtime at THI = 65.6 ± 0.90 and in summertime at THI = 78.36 ± 2.73. During each season, the estrous cycles of the cows were synchronized, and on day 3 of the ensuing cycle, a blood sample was collected for progesterone determination, while their oviducts were collected after slaughter. Epithelial cells and oviductal fluid were collected from the oviduct ipsilateral and contralateral to the corpus, respectively. For the gene expression study, a comparative transcriptomic approach, using RNASeq, was performed on cells collected from the ipsilateral and the contralateral oviducts. The size and the concentration of extracellular vesicles (EVs) at both seasons were analyzed using Transmission Electron Microscopy and Nanoparticle tracking analysis and specific proteins were detected by Western blotting. Progesterone concentration was higher during the thermoneutral period. Between seasons, divergent expression of genes related to immune system, contractility, gamete protection and lncRNAs was found. The size and the concentration of the EVs did not differ between seasons, however, the concentration in the ipsilateral oviduct tended to be lower (p = 0.09) from the contralateral one in the summer, but not in the spring. Our results show for the first time that HS could be involved with alterations in the oviductal cells’ gene expression and in the changes in concentration of EVs in the oviductal lumen. Our results imply that the altered oviductal environment during HS could be associated with the suppressed summer fertility in dairy cows.

PRODUCTIVITY AND COMFORT OF KEEPING COWS AT LOW ENVIRONMENTAL TEMPERATURES

The aim of this work was to study the effect of low temperatures on productivity, microclimate parameters and comfort of keeping cows in different variants of prefabricated premises. The research was conducted in the central part of Ukraine (Kyiv region, Bila Tserkva district) in three farms where animals are kept loose at different sizes of prefabricated premises. The first option is a prefabricated room without insulation elements; the second prefabricated room with elements of warming of side walls by polycarbonate glass; the third in an easy-to-assemble room on a deep, long-lasting straw litter. The average annual number of dairy cows in all farms is 400. The studies were performed in the thermoneutral period, when the average daily ambient temperature did not fall below -5.0 ° C (17 days) and the period of high-temperature load, when the value of the average daily ambient temperature was -15 °C and below (11 days). It was found that prolonged low-temperature load significantly affects the comfort of cows in the options for keeping in easily assembled rooms of different types. The average daily air temperature in all variants of easily assembled rooms was negative. At the same time, during boxing without insulation elements, the temperature was -5.3 ° С, which is slightly lower than the permissible values ​​recommended for dairy cattle. The best values ​​among prefabricated premises in terms of microclimate indicators, bioclimatic indices, resting place temperatures and energy costs for heat production were for the use of polycarbonate glass insulation systems during the winter period. The use of elements of insulation of easily assembled premises provided the lowest among the studied options of premises reduction of productivity in the period of low-temperature load.

Direct heat stress-induced effects on rumen fermentation characteristics and nutrients degradability in sheep pair-fed alfalfa hay

Aim of the study: To investigate the direct effect of heat stress on rumen fermentation characteristics and nutrients degradability of pair-fed rams to subsequently eliminate the confounding effects of dissimilar feed intake induced by heat stress exposure.Area of study: Saudi Arabia.Material and methods: Five rumen-cannulated desert rams (45 ± 1.63 kg body weight; 2–3 years of age) were placed individually in controlled climatic-chambers to be exposed to two successive periods. The 1st period was a control thermoneutral period (TN; 23.64 ± 0.14 °C; extended for 21 days) followed by a 2nd period of heat stress (HS; 44.26 ± 1.70 °C, for another 21 days). Each period was consisted of a temperature acclimation phase (7 days) and a data collection phase (14 days). Alfalfa hay was offered twice daily during both periods in a pair-fed manner (800 g DM per head and day).Main results: Exposing pair-fed desert rams to elevated ambient temperature had (p&lt;0.05) elevated their respiration rate and skin temperature, without noticeable (p&gt;0.05) changes in their rectal temperature. Most of the rumen fermentation characteristics and nutrients degradability were not affected by HS (p&gt;0.05). However, exposure to HS increased (p&lt;0.05) pre-feeding rumen total volatile fatty acids concentrations, pre-feeding molar proportion of acetate, and post-feeding rumen osmolality.Research highlights: HS had no direct effect on post-feeding rumen fermentation characteristics and nutrients degradability in desert sheep. This implies that strategic approaches to mitigate the adverse effects of HS have to be directed towards promoting feed intake and nutrients utilization under such conditions.

Transcriptome analysis identifies genes and co-expression networks underlying heat tolerance in pigs

BackgroundHeat stress adversely affects pig growth and reproduction performance by reducing feed intake, weight gain, farrowing rate, and litter size. Heat tolerance is an important characteristic in pigs, allowing them to mitigate the negative effects of heat stress on their physiological activities. Yet, genetic variation and signaling pathways associated with the biological processes of heat-tolerant pigs are currently not fully understood. This study examined differentially expressed genes and constructed gene co-expression networks on mRNAs of pigs under different heat-stress conditions using whole transcriptomic RNA-seq analyses. Semen parameters, including total sperm number per ejaculate, motility, normal morphology rate, droplets, and rejected ejaculate rate, were measured weekly on 12 boars for two time periods: thermoneutral (January to May), and heat stress (July to October). Boars were classified into heat-tolerant (n = 6) and heat-susceptible (n = 6) groups based on the variation of their ejaculate parameters across the two periods. RNA was isolated from the blood samples collected from the thermoneutral and heat stress periods for gene expression analysis.ResultsUnder heat stress, a total of 66 differentially expressed genes (25 down-regulated, 41 up-regulated) were identified in heat-tolerant pigs compared to themselves during the thermoneutral period. A total of 1041 differentially expressed genes (282 down-regulated, 759 up-regulated) were identified in the comparison between heat-tolerant pigs and heat-susceptible pigs under heat stress. Weighted gene co-expression network analysis detected 4 and 7 modules with genes highly associated (r > 0.50, p < 0.05) with semen quality parameters in heat-tolerant and heat-susceptible pigs under the effects of heat stress, respectively.ConclusionThis study utilized the sensitivity of semen to heat stress to discriminate the heat-tolerance ability of pigs. The gene expression profiles under the thermoneutral and heat stress conditions were documented in heat-tolerant and heat-susceptible boars. Findings contribute to the understanding of genes and biological mechanisms related to heat stress response in pigs and provide potential biomarkers for future investigations on the reproductive performance of pigs.

Establishing the genetic variation in physiological response in response to heat stress in semi-arid region in Jamunapari goats

ABSTRACTThe genetic variation in physiological response was analysed at population level in Jamunapari goats. The temperature humidity index (THI) range varied from 82.00 to 92.08 during hot period, 49.96 to 59.68 during cold period and 65.32 to 74.00 during thermo-neutral period. Physiological responses were recorded for 695, 617 and 291 animals during the hot, cold and thermo-neutral period, respectively. The sire mean of heat stress-susceptible (HSS) and heat stress-tolerant (HST) families differed by 19.737 in respiration rate (RR) and 31.438 in heart rate (HR). RR and HR were significantly different (P < 0.01) between HSS and HST phenotype. However, rectal temperature (RT) did not differ significantly (P < 0.01) between HSS and HST phenotype. The heritability of RT, RR and HR were 0.180 ± 0.058, 0.077 ± 0.044 and 0.307 ± 0.076, respectively. Genetic correlation between RT and HR was high during hot and cold period. The genetic correlation between RT and HR was high and positive during hot and cold period. The phenotypic correlation between RT and HR ranged from 0.132 to 0.190. The genetic correlation between RT with other traits was low and negative. Our finding indicates that phenotypic difference can be heritable.

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

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.