Heat Stress In Dairy Cattle Research Articles

Energy-saving cooling strategies in tunnel-ventilated dairy buildings: Computational fluid dynamics (CFD) simulations and validation

Ventilation is a key strategy for addressing heat stress in dairy cattle. In this study, we developed computational fluid dynamics (CFD) models for a 252-head free stall tunnel-ventilated dairy building equipped with ridge openings and circulation fans. A detailed cow model was developed for a standard 625 kg Holstein cattle. Both tube and floor cooling were developed as supplemental cooling strategies using a ground source heat pump while the ventilation fans continued to operate at a reduced air speed (30 to 65 % reduction). The average air velocity within the stalls for the control (1.4 ± 0.32 m s-1) was significantly higher than the average velocity achieved with floor cooling (1.02±0.41 m s-1) and tube cooling (0.69±0.21 m s-1) (p = 0.043). Despite lower air velocities, CFD simulations showed that the average temperature at cow resting height for tube cooling (27.9 ± 0.21 °C) was significantly lower than that for the control (28.6 ± 0.36 °C) and floor cooling (28.3 ± 0.14 °C) (p = 0.021). For 252 cows, the total electricity consumption for the control was 40,590 kWh during summer, while for floor cooling, it varied between 30,683 and 36,181 kWh, and for tube cooling, it ranged from 15,879 to 21,378 kWh. Ventilation-related greenhouse gas (GHG) emissions from the tunnel-ventilated barn were 0.12 t of CO2 eq. per cow. Future studies could investigate the impact of reduced airflow rates on air quality inside the buildings.

Establishment and risk factor assessment of the abnormal body temperature probability prediction model (ABTP) for dairy cattle

The study aims to develop an abnormal body temperature probability (ABTP) model for dairy cattle, utilizing environmental and physiological data. This model is designed to enhance the management of heat stress impacts, providing an early warning system for farm managers to improve dairy cattle welfare and farm productivity in response to climate change. The study employs the Least Absolute Shrinkage and Selection Operator (LASSO) algorithm to analyze environmental and physiological data from 320 dairy cattle, identifying key factors influencing body temperature anomalies. This method supports the development of various models, including the Lyman Kutcher-Burman (LKB), Logistic, Schultheiss, and Poisson models, which are evaluated for their ability to predict abnormal body temperatures in dairy cattle effectively. The study successfully validated multiple models to predict abnormal body temperatures in dairy cattle, with a focus on the temperature-humidity index (THI) as a critical determinant. These models, including LKB, Logistic, Schultheiss, and Poisson, demonstrated high accuracy, as measured by the AUC and other performance metrics such as the Brier score and Hosmer–Lemeshow (HL) test. The results highlight the robustness of the models in capturing the nuances of heat stress impacts on dairy cattle. The research develops innovative models for managing heat stress in dairy cattle, effectively enhancing detection and intervention strategies. By integrating advanced technologies and novel predictive models, the study offers effective measures for early detection and management of abnormal body temperatures, improving cattle welfare and farm productivity in changing climatic conditions. This approach highlights the importance of using multiple models to accurately predict and address heat stress in livestock, making significant contributions to enhancing farm management practices.

Review of the Heat Stress-Induced Responses in Dairy Cattle.

In the dairy cattle sector, the evaluation of the effects induced by heat stress is still one of the most impactful and investigated aspects as it is strongly connected to both sustainability of the production and animal welfare. On the other hand, more recently, the possibility of collecting a large dataset made available by the increasing technology diffusion is paving the way for the application of advanced numerical techniques based on machine learning or big data approaches. In this scenario, driven by rapid change, there could be the risk of dispersing the relevant information represented by the physiological animal component, which should maintain the central role in the development of numerical models and tools. In light of this, the present literature review aims to consolidate and synthesize existing research on the physiological consequences of heat stress in dairy cattle. The present review provides, in a single document, an overview, as complete as possible, of the heat stress-induced responses in dairy cattle with the intent of filling the existing research gap for extracting the veterinary knowledge present in the literature and make it available for future applications also in different research fields.

Determination of the change in variance components due to heat stress in dairy cattle using a random regression model

The aim of this study is to evaluate changes in variance components for dairy cows under heat stress conditions using a random regression model. The daily milk yield and pedigree records used in the research were obtained from a dairy farm in Sanliurfa, affiliated with The General Directorate of Agricultural Enterprises (TIGEM), a public institution. Records were from Holstein dairy cows registered between 2017 and 2019 in the farm. A total of 690 lactations from healthy dairy cows were used in the study. Among these lactations, 278, 130, 135, and 147 were the first, second, third, and fourth or higher lactations, respectively. In addition to this, the total number of cow-days was 207 003. In order to evaluate heat stress on animals meteorological data were used and collected from a public weather station in Sanliurfa, which is operated by the Turkish State Meteorological Service authorized by the Ministry of Environment, Urbanization, and Climate Change of the Republic of Türkiye. In the study, variance components were separately estimated for the comfort period (CP) and the heat stress period (HSP) using a random regression test-day model and six-knot linear spline function was used. In the study, it was observed that heat stress resulted in an increase in additive genetic, permanent environmental, and consequently, phenotypic variance. During the lactation period, the average heritability was determined to be 0.13±0.007 for CP, while it was found to be 18±0.010 for HSP. According to the findings obtained from the study, it was concluded that the time periods for selection should coincide with the peak milk yield under heat stress conditions, while for the period without heat stress, it should be around the 120th day of lactation. These results indicate that climatic factors such as temperature and humidity should be included in the models used for genetic parameter and breeding value estimation. Thus, it may be possible to identify dairy cattle that are genetically more tolerant to hot conditions. In this way, more successful outcomes can be achieved in selection studies.

Candidate genes associated with heat stress and breeding strategies to relieve its effects in dairy cattle: a deeper insight into the genetic architecture and immune response to heat stress.

The need for food products of animal origin is increasing worldwide. Satisfying these needs in a way that has minimal impact on the environment requires cutting-edge technologies and techniques to enhance the genetic quality of cattle. Heat stress (HS), in particular, is affecting dairy cattle with increasing frequency and severity. As future climatic challenges become more evident, identifying dairy cows that are more tolerant to HS will be important for breeding dairy herds that are better adapted to future environmental conditions and for supporting the sustainability of dairy farming. While research into the genetics of HS in the context of the effect of global warming on dairy cattle is gaining momentum, the specific genomic regions involved in heat tolerance are still not well documented. Advances in omics information, QTL mapping, transcriptome profiling and genome-wide association studies (GWAS) have identified genomic regions and variants associated with tolerance to HS. Such studies could provide deeper insights into the genetic basis for response to HS and make an important contribution to future breeding for heat tolerance, which will help to offset the adverse effects of HS in dairy cattle. Overall, there is a great interest in identifying candidate genes and the proportion of genetic variation associated with heat tolerance in dairy cattle, and this area of research is currently very active worldwide. This review provides comprehensive information pertaining to some of the notable recent studies on the genetic architecture of HS in dairy cattle, with particular emphasis on the identified candidate genes associated with heat tolerance in dairy cattle. Since effective breeding programs require optimal knowledge of the impaired immunity and associated health complications caused by HS, the underlying mechanisms by which HS modulates the immune response and renders animals susceptible to various health disorders are explained. In addition, future breeding strategies to relieve HS in dairy cattle and improve their welfare while maintaining milk production are discussed.

Assessment of Ruminating, Eating, and Locomotion Behavior during Heat Stress in Dairy Cattle by Using Advanced Technological Monitoring.

Heat stress (HS) significantly impacts dairy farming, prompting interest in precision dairy farming (PDF) for gauging its effects on cow health. This study assessed the influence of the Temperature-Humidity Index (THI) on rumination, eating, and locomotor activity. Various parameters, like rumination time, drinking gulps, chews per minute, and others were analyzed. The hypothesis was that precision dairy farming technology could help detect HS. Nine healthy Lithuanian Black-and-White cows were randomly selected for the trial. RumiWatch noseband sensors recorded behaviors, while SmaXtec climate sensors monitored THI. The data collection spanned from 14 June to 30 June. Cows in the THI class ≥ 72 exhibited reduced drinking time (51.16% decrease, p < 0.01), fewer chews per minute (12.9% decrease, p < 0.01), and higher activity levels (16.99% increase, p < 0.01). THI showed an inverse correlation with drinking time (r = -0.191, p < 0.05) and chews per bolus (r = -0.172, p < 0.01). Innovative technologies like RumiWatch are effective in detecting HS effects on behaviors. Future studies should explore the impact of HS on RWS biomarkers, considering factors such as lactation stage, number, yield, and pregnancy.

Heat stress effects on milk yield traits and metabolites and mitigation strategies for dairy cattle breeds reared in tropical and sub-tropical countries.

Heat stress is an important problem for dairy industry in many parts of the world owing to its adverse effects on productivity and profitability. Heat stress in dairy cattle is caused by an increase in core body temperature, which affects the fat production in the mammary gland. It reduces milk yield, dry matter intake, and alters the milk composition, such as fat, protein, lactose, and solids-not-fats percentages among others. Understanding the biological mechanisms of climatic adaptation, identifying and exploring signatures of selection, genomic diversity and identification of candidate genes for heat tolerance within indicine and taurine dairy breeds is an important progression toward breeding better dairy cattle adapted to changing climatic conditions of the tropics. Identifying breeds that are heat tolerant and their use in genetic improvement programs is crucial for improving dairy cattle productivity and profitability in the tropics. Genetic improvement for heat tolerance requires availability of genetic parameters, but these genetic parameters are currently missing in many tropical countries. In this article, we reviewed the HS effects on dairy cattle with regard to (1) physiological parameters; (2) milk yield and composition traits; and (3) milk and blood metabolites for dairy cattle reared in tropical countries. In addition, mitigation strategies such as physical modification of environment, nutritional, and genetic development of heat tolerant dairy cattle to prevent the adverse effects of HS on dairy cattle are discussed. In tropical climates, a more and cost-effective strategy to overcome HS effects is to genetically select more adaptable and heat tolerant breeds, use of crossbred animals for milk production, i.e., crosses between indicine breeds such as Gir, white fulani, N'Dama, Sahiwal or Boran to taurine breeds such as Holstein-Friesian, Jersey or Brown Swiss. The results of this review will contribute to policy formulations with regard to strategies for mitigating the effects of HS on dairy cattle in tropical countries.

Impact of heat stress on dairy cattle and selection strategies for thermotolerance: a review.

Climate change is a problem that causes many environmental issues that impact the productivity of livestock species. One of the major issues associated with climate change is an increase of the frequency of hot days and heat waves, which increases the risk of heat stress for livestock species. Dairy cattle have been identified as being susceptible to heat stress due to their high metabolic heat load. Studies have shown heat stress impacts several biological processes that can result in large economic consequences. When heat stress occurs, dairy cattle employ several physiological and cellular mechanisms in order to dissipate heat and protect cells from damage. These mechanisms require an increase and diversion in energy toward protection and away from other biological processes. Therefore, in turn heat stress in dairy cattle can lead numerous issues including reductions in milk production and reproduction as well as increased risk for disease and mortality. This indicates a need to select dairy cattle that would be thermotolerant. Various selection strategies to confer thermotolerance have been discussed in the literature, including selecting for reduced milk production, crossbreeding with thermotolerant breeds, selecting based on physiological traits and most recently selecting for enhanced immune response. This review discusses the various issues associated with heat stress in dairy cattle and the pros and cons to the various selection strategies that have been proposed to select for thermotolerance in dairy cattle.

Genome-wide expression analysis reveals different heat shock responses in indigenous (Bos indicus) and crossbred (Bos indicus X Bos taurus) cattle

Environmental heat stress in dairy cattle leads to poor health, reduced milk production and decreased reproductive efficiency. Multiple genes interact and coordinate the response to overcome the impact of heat stress. The present study identified heat shock regulated genes in the peripheral blood mononuclear cells (PBMC). Genome-wide expression patterns for cellular stress response were compared between two genetically distinct groups of cattle viz., Hariana (B. indicus) and Vrindavani (B. indicus X B. taurus). In addition to major heat shock response genes, oxidative stress and immune response genes were also found to be affected by heat stress. Heat shock proteins such as HSPH1, HSPB8, FKB4, DNAJ4 and SERPINH1 were up-regulated at higher fold change in Vrindavani compared to Hariana cattle. The oxidative stress response genes (HMOX1, BNIP3, RHOB and VEGFA) and immune response genes (FSOB, GADD45B and JUN) were up-regulated in Vrindavani whereas the same were down-regulated in Hariana cattle. The enrichment analysis of dysregulated genes revealed the biological functions and signaling pathways that were affected by heat stress. Overall, these results show distinct cellular responses to heat stress in two different genetic groups of cattle. This also highlight the long-term adaptation of B. indicus (Hariana) to tropical climate as compared to the crossbred (Vrindavani) with mixed genetic makeup (B. indicus X B. taurus).

Extraction and Elevation of Cell-Free DNA under Mastitis and Heat Stress in Dairy Cattle.

In this study, four methods (phenol-chloroform protocol, sodium iodide kit, QIAamp DNA Blood Mini Kit, and TIANamp Micro DNA Kit) were used to extract cell-free DNA (cfDNA) from cattle blood, and the yield and purity of cfDNA varied in four different methods from 0.36 to 0.84 ng/mL for yield and 0.67 to 1.80 (A260/A280) for purity. Compared with other methods, the TIANamp Micro DNA kit performed better in both cfDNA amount and purity (p < 0.05); furthermore, blood cfDNA levels were significantly increased in Holstein dairy cows under the influence of heat stress (p < 0.01) and mastitis (p < 0.0001), which showed a potential power to discriminate mastitis (AUC = 0.99, 95% CI = 0.97 to 1.00) or heat stress (AUC = 0.86, 95% CI = 0.73 to 0.98) in cows. In brief, we established a complete experimental system for the extraction of cfDNA from cattle blood based on the high-yielding method of the TIANamp Micro DNA Kit and showed the effect of mastitis and heat stress on cfDNA levels in cattle blood for the first time. Our findings suggested that cfDNA in cattle blood may be a useful marker to measure mastitis and heat stress in dairy cattle.

Physiological and Pyhsical Responses of Dairy Cattle to Heat Stress

Herd management and nutrition strategies against increasing negative effects of global warming on farm animals have been the subject of significant debates in recent years. The fact that the changes in the environmental conditions are directly related to the habitats of the animals and the conditions inside the barn can affect the farm animals negatively. Although effects of heat stress differ according to species, especially high-yielding dairy cattle exposed to heat stress, respond with various interactive mechanism such as physiological, biochemical, immunological, anatomical and behavioral. Therefore, with the selection practices that have been going on for many years to improve the yield characteristics of the animals significantly increased. In this respect, the increased heat load in the body of dairy cattle due to the high productivity decreases their tolerance to environmental conditions. This situation adversely affects the productivity of cows with high breeding value. Yield losses, varying according to some factors about heat stress, can be partially explained by decreasing feed intake as a result of a series of hormonal responses affecting appetite center. However, the physiological requirements of cattle must be defined in order to develop appropriate strategies to reduce or eliminate the negative effects of heat stress. In this review, the variations in physiological, biochemical and behavioral mechanisms originating from heat stress in dairy cattle and the care, nutrition and herd management strategies that can be applied to eliminate or reduce the negative effects were discussed.

Heat shock protein 90 alpha family class B member 1 (HSP90AB1) gene polymorphism and its effect on milk production traits in friesian holstein cattle

Increasing temperature caused by climate change is main contributor of heat stress in dairy cattle. Heat stress has a major impact on the milk production efficiency in dairy cattle. The HSP90AB1 gene is involved in overcoming heat stress response in cattle. The purpose of this study is to find single-nucleotide polymorphism (SNP) of HSP90AB1 gene and its relationship to milk production traits in Friesian Holstein (FH) cattle. In this study, 50 FH blood samples were used. Allele Specific Polymerase Chain Reaction (AS-PCR) method was used to successfully identify three genotypes: CC, CT, and TT. The CT genotype is the most common in the sample population. When compared to the C-allele, the T-allele is more common. Hardy-Weinberg (HW) analysis using Chi-Square method revealed that the population was not equilibrium (P&lt;0.05). Association study between genotypes and milk production trait was not significant (P&gt;0.05), but the CC genotype had a trend of higher mean milk yield in the first and second lactation. It was determined that the HSP90AB1 gene could be used as molecular marker for FH cattle heat stress response, in order to increase milk production capacity.

The Impact of Heat Stress on Immune Status of Dairy Cattle and Strategies to Ameliorate the Negative Effects

Heat stress (HS) is well known to influence animal health and livestock productivity negatively. Heat stress is a multi-billion-dollar global problem. It impairs animal performance during summer when animals are exposed to high ambient temperatures, direct and indirect solar radiations, and humidity. While significant developments have been achieved over the last few decades to mitigate the negative impact of HS, such as physical modification of the environment to protect the animals from direct heat, HS remains a significant challenge for the dairy industry compromising dairy cattle health and welfare. In such a scenario, it is essential to have a thorough understanding of how the immune system of dairy cattle responds to HS and identify the variable responses among the animals. This understanding could help to identify heat-resilient dairy animals for breeding and may lead to the development of climate resilient breeds in the future to support sustainable dairy cattle production. There are sufficient data demonstrating the impact of increased temperature and humidity on endocrine responses to HS in dairy cattle, especially changes in concentration of hormones like prolactin and cortisol, which also provide an indication of the likely im-pact on the immune system. In this paper, we review the recent research on the impact of HS on immunity of calves during early life to adult lactating and dry cows. Additionally, different strategies for amelioration of negative effects of HS have been presented.

Development of a heat load index for grazing dairy cattle

ABSTRACT Many indices have been developed to predict heat stress in dairy cattle, but no indices exist specifically for extensively grazed dairy cattle where wind and solar radiation modify heat stress responses. Using a large database of respiration rates and matching weather data, we developed a Grazing Heat Load Index (HLI) to predict respiration rates in extensively grazed dairy cattle. The Grazing HLI includes ambient temperature, solar radiation, and wind speed for the hour immediately preceding the respiration rate measure and was more accurate at predicting respiration rates than existing temperature humidity indices. On average, we observed an increase of 4.21 breaths per minute per 1°C increase in ambient temperature, an increase of 5.89 breaths per minute per 1 megajoule/m2 increase in solar radiation and a reduction of 1.70 breaths per minute per 1 km/hr increase in wind speed. We observed marked changes in panting score and percentage of drooling animals at Grazing HLI of greater than 70. This maybe a threshold when dairy cattle welfare is seriously compromised due to heat, however, noting that respiration rate starts to increase more steeply before this threshold.

Cooling temperature humidity index-days as a heat load indicator for milk production traits

Well-defined and accurate climatic indicators are important for evaluating heat stress in dairy cattle. This is imperative for sound management decisions for mitigating production losses. The most popular indicator for heat stress is the temperature humidity index (THI). Other heat stress indicators have been developed but remain largely unexploited. There is, therefore, possibly room to improve the THI and explore new indicators suitable for predicting production losses due to heat stress in dairy cattle. In this study, we apply the degree-day concept to develop temperature humidity index-day (THI-day). We defined the cooling THI-day as the hourly cumulative THI units above the heat stress threshold for milk production traits over the entire day. We then modeled reaction norms for cooling THI-day to analyze the effect of cumulative heat load expressed by THI-day on milk production traits. Milk performance records were from 16,216,145 monthly test-day records for the Fleckvieh breed for the period 2010 to 2019 in southern Bavaria, Germany. Individual cow records were averaged by herd and test-day resulting in 797,455 herd test-day records from 9,726 herds. Weather data for the same period were provided by the German Meteorological Service. Results indicated that cooling THI-day provided significant (p &amp;lt; 0.001) additional information to the conventional THI models. We found out that reaction norm models of average herd milk yield that do not account for the cumulative heat load tend to underestimate the effects of heat stress on milk production traits. Reaction norms modeled with cooling THI-day were more plausible for milk production traits that have a defined heat stress threshold including milk yield, protein yield, and milk urea.

Thermodynamic assessment of heat stress in dairy cattle: lessons from human biometeorology

A versatile meteorological index for predicting heat stress in dairy cattle remains elusive. Despite numerous attempts at developing such indices and widespread use of some, there is growing skepticism about the accuracy and adequacy of the existing indices as well as the general statistical approach used to develop them. At the same time, precision farming of high-yielding animals in a drastically changing climate calls for more effective prediction and alleviation of heat stress. The present paper revisits classical work on human biometeorology, particularly the apparent temperature scale, to draw inspiration for advancing research on heat stress in dairy cattle. The importance of a detailed, mechanistic understanding of heat transfer and thermoregulation is demonstrated and reiterated. A model from the literature is used to construct a framework for identifying and characterizing conditions of potential heat stress. New parameters are proposed to translate the heat flux calculations based on heat-balance models into more tangible and more useful meteorological indices, including an apparent temperature for cattle and a thermoregulatory exhaustion index. A validation gap in the literature is identified as the main hindrance to the further development and deployment of heat-balance models. Recommendations are presented for systematically addressing this gap in particular and continuing research within the proposed framework in general.

A meta-analysis of heat stress in dairy cattle: The increase in temperature humidity index affects both milk yield and some physiological parameters

In this study, the relationships of temperature humidity index (THI) with milk yield and some physiological responses in dairy cattle were investigated. Our goal in the meta-analysis was to find the parameter(s) primarily affected under heat stress. A total of 16 studies with the temperature humidity index value higher than 72, which is an important factor in determining the effect of heat stress, were included in the meta-analysis. The variables of interest in the meta-analysis included: milk yield (kg/day), respiratory rate (breaths/min), rectal temperature (°C). In addition to the meta-analysis, principal component analysis (PCA) was also performed. In the meta-analysis, high variation or heterogeneity (I&lt;sup&gt;2&lt;/sup&gt; &amp;gt; 99%) was determined between the results of the studies. This may depend on many factors (climate, region, number of samples and management etc.). Heterogeneity is desirable in the meta-analysis, because it provides accurate and reliable interpretations of the variances of parameters. Due to high heterogeneity, the results of the studies were combined according to the mixed model. According to the mixed model and PCA results, a linear relationship was determined between the temperature humidity index and these physiological parameters. According to the meta-analysis, at THI &amp;gt; 72, the mean effect size of milk yield was 50%, and the effect sizes of respiratory rate and rectal temperature were approximately 65% and 38%. All three parameters have a significant effect under heat stress (P &amp;lt; 0.000 1). As a result, there is a linear relationship between temperature humidity index, milk yield and physiological parameters. According to the other characteristics, the respiratory rate was determined as the primary response parameter in parallel with the increase in temperature humidity index.

Comparison of high resolution observational and grid-interpolated weather data and application to thermal stress on herd average milk production traits in a temperate environment

To study the effects of heat stress in dairy cattle, animal performance records are merged with weather data from nearby meteorological stations. However, the stations location and distribution may render them less reliable. Alternatively, weather information from several meteorological stations can be interpolated using empirical algorithms to produce gridded estimates of weather parameters at desired spatio-temporal resolutions. The objective of this study was to compare and apply observational weather station data (WSD) and gridded numerical weather prediction (NWP) model data with high spatio-temporal resolution to identify thermal stress thresholds for milk production traits. Weather data were from the German meteorological service and reanalysis was based on the COnsortium for Small-Scale MOdelling (COSMO)-REA6 model. Milk performance data were from over 16 million monthly test-day records for the period 2010 to 2019 in southern Bavaria, Germany. Individual cow records were transformed to herd averages resulting to 797,455 herd test-days from 9,726 herds. These were merged with temperature and temperature humidity index (THI) data from 53 weather stations and corresponding gridded data. There was good agreement between WSD and NWP model data with correlation coefficients of 0.97 for both daily average temperature and THI and 0.84 for relative humidity. However, positive and negative biases were observed in the pre-Alpine regions. The average herd reaction norms were in good agreement and followed similar trends when estimated from WSD and NWP. The heat stress threshold at which milk yield and protein yield started to decline was 16.0 °C for temperature and 60 units for THI. The responses of fat yield, protein and fat contents were generally linear decline with no definite thresholds. Milk urea increased in a non-linear accelerating pattern and there was no undesired effects on SCS. The thresholds obtained in this study may be applied to implement necessary management strategies to mitigate losses.

Public perceptions of potential adaptations for mitigating heat stress on Australian dairy farms

Temperature variability resulting from climate change poses challenges around the world for livestock production and the welfare of the animals in these systems. As animal industries attempt to combat these challenges, it is vital to understand how potential changes implemented by farmers resonate with societal values. The aims of this study were to determine how different proposed changes to mitigate heat stress in dairy cattle influence public perceptions toward Australian dairy farm systems, including perceptions of (1) cow welfare, (2) confidence in the industry, and (3) trust in farmers. Participants were presented with 1 of 4 treatments representing a potential solution to mitigate heat stress in dairy cattle: (1) indoor system (a fully indoor barn), (2) choice system (cows have agency to choose to be indoors or outdoors), (3) gene edition + pasture (cows are genetically modified to become more resilient to heat stress), and (4) pasture (outdoor system that is currently used in Australia, but the farmer plants more trees). Participants were then asked to respond to questions on a 7-point Likert scale. Questions were about cow welfare (3 questions), confidence in dairy industry (4 questions), and trust in farmers (9 questions), with each section followed by an open-ended question for participants to explain their answers. Participants perceived cow welfare to be the lowest in the indoor system (2.80 ± 0.10), followed by gene edition + pasture (4.48 ± 0.11), with choice and pasture systems being the highest but not different from each other (5.41 ± 0.11 and 5.32 ± 0.11, respectively). Confidence in the dairy industry was lower among participants in the indoor (4.78 ± 0.08) compared with participants assigned to the choice (5.28 ± 0.08) or pasture (5.25 ± 0.08) systems. Confidence was also lower among participants in the gene edition (4.95 ± 0.08) compared with the choice system. Trust in farmers was similar across all treatments. Our results provide the first evidence that the Australian public may be reluctant to accept heat stress mitigation strategies that either do not allow cows to have access to pasture or those that include gene-editing technologies.

Relationship among production traits, somatic cell score and temperature–humidity index in the Italian Mediterranean Buffalo

The temperature–humidity index (THI) has been commonly used to analyse heat stress in dairy cattle, but little is known about its effects on buffaloes. In this study, daily milk yield (MY), fat percentage (FP), protein percentage (PP) and somatic cell count (SCC) data from 808 buffalo cows plus environmental temperature and relative humidity were used to investigate the consequence of heat stress. Two mixed models were used to evaluate the impact of THI on MY, FP, PP and log transformed SCC (SCS). The effect of THI was significant for PP, FP and SCS, whereas its interaction with parity was statistically significant for PP and SCS. The relationship between PP and FP and THI was positive but of different magnitude according to the parity. When THI was below 62, an unfavourable effect was observed, especially in primiparous buffalo cows. A significant interaction between SCS and THI across parities was also observed. The effect of THI on MY across parities was not definite but overall a favourable relationship was observed. Our findings depict a susceptibility of buffaloes to low values of THI, suggesting an optimal THI range for water buffaloes between 59 and 63, although some deleterious effects were observed in primiparous buffaloes at THI values lower than 62. Additional investigations are needed to better elucidate the influence of THI on buffalo species. HIGHLIGHTS The overall effect of THI on buffalo diverges from what commonly observed in dairy cattle Cold stress affects milk and udder health in buffaloes The effect of THI on buffaloes’ performance depends on parity, with a larger susceptibility in primiparous than pluriparous buffalo cows Udder health in buffaloes, evaluated using somatic cell count, is also affected by THI