Effect of temperature-humidity index on the evolution of trade-offs between fertility and production in dairy cattle.

BACKGROUND: In the current context of climate change, livestock production faces many challenges to improve the sustainability of systems. Dairy farming, in particular, must find ways to select animals that will be able to achieve sufficient overall production while maintaining their reproductive ability in environments with increasing temperatures. With future forecasted climate conditions in mind, this study used data from Holstein and Montbeliarde dairy cattle to: (1) estimate the genetic-by-temperature-humidity index (THI) interactions for female fertility, and (2) evaluate the production-fertility trade-off with increasing values of THI. RESULTS: Two-trait random regression models were fitted for conception rate (fertility) and test-day protein yield (production). For fertility, genetic correlations between different THI values were generally above 0.75, suggesting weak genotype-by-THI interactions for conception rate in both breeds. However, the genetic correlations between the conception rate breeding values at the current average THI (THI = 50, corresponding to a 24-h average temperature of 8 °C at 50% relative humidity) and their slopes (i.e., potential reranking) for heat stress scenarios (THI > 70), were different for each breed. For Montbeliarde, this correlation tended to be positive (i.e., overall the best reproducers are less affected by heat stress), whereas for Holstein it was approximately zero. Finally, our results indicated a weak antagonism between production and fertility, although for Montbeliarde this antagonism intensified with increasing THI. CONCLUSIONS: Within the range of weather conditions studied, increasing temperatures are not expected to exacerbate the fertility-production trade-off. However, our results indicated that the animals with the best breeding values for production today will be the most affected by temperature increases, both in terms of fertility and production. Nonetheless, these animals should remain among the most productive ones during heat waves. For Montbeliarde, the current selection program for fertility seems to be adequate for ensuring the adaptation of fertility traits to temperature increases, without adverse effects on production. Such a conclusion cannot be drawn for Holstein. In the future, the incorporation of a heat tolerance index into dairy cattle breeding programs would be valuable to promote the selection of animals adapted to future climate conditions.

Heat stress from current and predicted increases in temperature impairs lambing rates and birth weights in the Australian sheep flock.

Livestock heat stress threatens production, particularly in semi-arid, arid and tropical regions. Using established temperature thresholds for sheep, we modelled +1 °C and +3 °C temperature increases over the historical baseline, estimating that 2.1 million potential lambs are lost annually due to heat stress alone, increasing to 2.5 and 3.3 million, respectively, as temperatures rise. Heat stress poses risks at key periods of the reproductive cycle, with consequences across the Australian sheep flock.

The amino acid pattern and dynamics of body protein, body fat deposition in male and female broilers under different temperatures.

The present study was conducted 1) to investigate the effects of gender and temperature on growth performance in broiler chickens and 2) to establish body protein and fat deposition curves and amino acid patterns for broilers of both genders at different ambient temperatures. A total of 432 1-day-old (d) Arbor Acres chickens with a male/female ratio of 1:1 were randomly divided into the following 4 treatment groups: the male thermoneutral group, the female thermoneutral group, the male heat stress group, and the female heat stress group. The chickens in the thermoneutral groups were kept at a comfortable temperature from 1 to 42 d, while chickens in the heat stress groups were kept at a comfortable temperature from 1 to 28 d and at a high ambient temperature from d 29 to 42. The body composition retention data were obtained by comparative slaughter method, and the models were constructed by the Gompertz model. The results revealed significant variation in body protein content (BPC) and body fat deposition efficiency (BFE) between both genders and the 2 temperatures. Moreover, a noteworthy interaction between gender and temperature was observed in terms of the BPC and protein deposition efficiency (BPE). The following equations for body protein and body fat deposition in the thermoneutral groups were obtained: Body protein weight of male broilers: [Formula: see text] ; Body protein weight of female broilers: [Formula: see text] ; Body fat weight of male broilers: [Formula: see text] ; Body fat weight of female broilers: [Formula: see text] . Where t means age (d). The following equations for body protein and body fat deposition in the heat stress groups were obtained: Body protein weight of male broilers: [Formula: see text] ; Body protein weight of female broilers: [Formula: see text] ; Body fat weight of male broilers: [Formula: see text] ; Body fat weight of female broilers: [Formula: see text] . Where t means age (d). In addition, no significant difference in amino acid content was found between different genders and temperatures. The amino acid pattern could be divided into 2 stages: 0 to 14 d and 15 to 42 d. Our equations and patterns enable a deeper understanding of the nutritional requirements in broiler chickens under various temperature conditions. This enables researchers to develop more accurate feeding programs to fulfill the growth and health requirements of broiler chickens.

Behavioural responses related to increasing core body temperature of grazing dairy cows experiencing moderate heat stress.

Exposure to direct solar radiation, high ambient temperature, lack of wind movement, coupled with own metabolic heat production, makes grazing dairy cows vulnerable to heat stress. In pastures, it would be beneficial to monitor heat stress by observable changes in behaviour. We hypothesised that grazing dairy cows exhibit behavioural changes due to increasing heat load in temperate climate. Over two consecutive summers, 38 full-time grazing Holstein dairy cows were investigated in 12 experimental periods of up to 3 consecutive days where the cows were repeatedly exposed to various levels of moderate heat load determined by the comprehensive climate index (CCI). The CCI defines the ambient climate conditions, combining air temperature, relative humidity, solar radiation and wind speed. Vaginal temperature (VT) was automatically measured as an indicator of heat stress. In addition, as a less invasive method, we investigated if reticular temperature (RET) can be indicative of heat stress on pastures. Walking activity, lying-, feeding, and ruminating durations were recorded continuously with sensors. Respiration rate (RR), proximity to and competition at the water trough, social licking, self-licking, inter-individual distance, and fly intensity were directly observed. Data were analysed in the morning (0900-1100 h) and during the hottest time of day when cows were on pasture (1230-1430 h). The VT and RET showed similar patterns in relation to the CCI, suggesting that RET can be suitable for continuous monitoring of heat stress on pastures. In the morning, the cow's VT and RET did not relevantly react to the CCI. During the period 1230-1430 h, the cow's mean VT (mean vaginal temperature (VTMEAN); range: 37.7-40.3 °C) and mean RET (mean reticular temperature; range: 37.0-41.1 °C) were positively related to the mean CCI (mean comprehensive climate index) in this period (mean ± SD: 25.9 ± 5.71 °C). For cows with greater VTMEAN, an increased mean RR and decreased durations of walking, lying, feeding, and ruminating were found. These cows were also more likely to be in proximity to the water trough and to have small inter-individual distances. Changes in these traits seem to reflect behavioural adaptations to heat stress in a temperate climate and could be used to detect the heat stress in individual dairy cows on pastures.

Effect of extended heat stress in dairy cows on productive and behavioral traits.

This study evaluates the response of dairy cows to short and extended heat stressing conditions (from 1 to 28 days), as expressed in changes in their behavior. Due to climate change, heat stress and strong heat waves are frequently affecting the productivity and behavior of dairy cows. In the five years under study from 2018 to 2022, two were characterized by extremely strong heat waves occurring in the region analyzed in this study (Northern Italy). The dairy cattle farm involved in this study is located in Northern Italy and includes about 1 600 Holstein Friesian lactating dairy cows. Phenotypic data were provided by the Afimilk system and compromised behavioral and productive traits. Behavioral traits analyzed were activity, rest time, rest bouts, rest ratio, rest per bout and restlessness. Production traits were daily milk yield, average milking time, somatic cell count, fat percentage, protein percentage and lactose percentage. Climate data came from the National Aeronautics and Space Administration/Prediction of Worldwide Energy Resources database. Heat stress was analyzed considering Temperature-Humidity Index (THI) averaged over 28 different time windows of continuous heat stress. Results showed that rest time and milk yield were the two traits most affected by the increased THI. Rest time was immediately affected by high THI, showing a marked decrease already from 1d window and maintaining this all over the other windows. Furthermore, results show that rest time and rest ratio were only slightly negatively correlated with milk yield (-0.14 and -0.15). In addition, heat stress has a different effect depending on parity and lactation stages on the studied traits. In conclusion, the results indicate that heat stress increases activity and compromises milk production, rest time and milk quality traits. Results further suggest that rest time can be a better parameter than activity to describe the effects of heat stress on dairy cattle. The novel approach used in this study is based on the use of different time windows (up to 28 days) before the emergence of undesired THI and allows to identify the traits that are immediately influenced by the undesirable THI values and those that are influenced only after a prolonged heat stress period.

Effect of three different insect larvae on growth performance and antioxidant activity of thigh, breast, and liver tissues of chickens reared under mild heat stress.

This study investigated the potential of insect-based diets to mitigate heat stress impact on broiler chickens, focusing on growth performance and antioxidant stability. Four dietary groups were examined, including a control and three treated groups with Tenebrio molitor (TM), Hermetia illucens (HI), and Zophobas morio (ZM) larvae, respectively, at a 5% replacement ratio. Temperature and relative humidity of the poultry house were monitored. Under heat stress conditions, the HI-fed group consistently exhibited the highest body weight, demonstrating their remarkable growth-promoting potential. TM-fed broilers also displayed commendable growth compared to the control. Insect larvae inclusion in the diet improved feed intake during early growth stages, indicating their positive influence on nutrient utilization. Regarding antioxidant stability, malondialdehyde (MDA) levels in the liver, an oxidative stress and lipid peroxidation marker, were significantly lower in the TM-fed group, suggesting reduced oxidative stress. While the specific insect-based diet did not significantly affect MDA levels in thigh and breast tissues, variations in the total phenolic content (TPC) were observed across tissues, with HI larvae significantly increasing it in the breast. However, the total antioxidant capacity (TAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) levels did not differ significantly among dietary groups in the examined tissues. Results suggest that insect-based diets enhance broiler growth and potentially reduce oxidative stress, particularly in the liver. Dietary presence of bioactive compounds may contribute to these benefits. Further research is required to fully elucidate the mechanisms underlying these findings. Insect-based diets seem to offer promise as feed additives in addressing the multifaceted challenges of oxidative stress and enhancing broiler health and resilience under heat stress conditions.

Strategies to alleviate heat stress on performance and physiological parameters in feedlot-finished cattle under heat stress conditions. A systematic review-meta-analysis.

Strategies to alleviate heat stress on live performance - dry matter intake (DMI), average daily gain (ADG), and feed conversion efficiency (FCE) - and on physiological parameters - respiratory rate (RR) and panting score (PS) - of feedlot-finished cattle were evaluated by systematic review-meta-analysis. Using the PICO framework were identified 3813 records, with 31 publications and 6729 cattle being considered in the meta-analysis (MA). The comparison most reported was sun vs. shade (n = 24 publications), followed by shade vs. shade (area per animal and effectivity in reduce solar load) (n = 7 publications) and sun vs. sprinkling (n = 4 publications). Cattle with access to shade with total reduction in solar load improved ADG (p = 0.008) and FCE (p = 0.024), and reduced RR (p < 0.001) compared to unshaded animals. Cattle with access to shade with a height between 3 and 4 m increased ADG (p < 0.001), tended to improve FCE (p = 0.054), and reduced RR (p < 0.001) compared to unshaded animals. An area of shade from 2 to 4 m2/animal increased ADG (p = 0.002), and higher than 4 m2/animal reduced RR (p < 0.001) compared to unshaded animals. Animals that received sprinkling volume below 1 L/animal/min improved ADG (p = 0.008) compared to unshaded animals. Cattle with access to shade with a high area per animal improved DMI (p = 0.023) and ADG (p < 0.001) compared to animals with a low area. In univariate meta-regression, it was observed that the variables significantly (P < 0.05) influencing DMI were THI category; influencing ADG were cattle gender, THI category, and coat color; influencing FCE were cattle age and hemisphere; and influencing RR were country, THI category and climate. Performance and physiological parameters of feedlot-finished cattle under heat stress depend on animal and environmental characteristics.

Effects of medical plants on alleviating the effects of heat stress on chickens.

Over the past decades, global climate change has led to a significant increase in the average ambient temperature causing heat stress (HS) waves. This increase has resulted in more frequent heat waves during the summer periods. HS can have detrimental effects on poultry, including growth retardation, imbalance in immune/antioxidant pathways, inflammation, intestinal dysfunction, and economic losses in the poultry industry. Therefore, it is crucial to find an effective, safe, applicable, and economically efficient method for reducing these negative influences. Medicinal plants (MPs) contain various bioactive compounds with antioxidant, antimicrobial, anti-inflammatory, and immunomodulatory effects. Due to the biological activities of MPs, it could be used as promising thermotolerance agents in poultry diets during HS conditions. Nutritional supplementation with MPs has been shown to improve growth performance, antioxidant status, immunity, and intestinal health in heat-exposed chickens. As a result, several types of herbs have been supplemented to mitigate the harmful effects of heat stress in chickens. Therefore, several types of herbs have been supplemented to mitigate the harmful effects of heat stress in chickens. This review aims to discuss the negative consequences of HS in poultry and explore the use of different traditional MPs to enhance the health status of chickens.

Chronic heat stress inhibits glycogen synthesis through gga-miR-212-5p/GYS1 axis in the breast muscle of broilers.

Studies have demonstrated that chronic heat stress can accelerate glycolysis, decrease glycogen content in muscle, and affect muscle quality. However, the consequences of chronic heat stress on glycogen synthesis, miRNA expression in pectoralis major (PM) muscle, and its regulatory functions remain unknown. In this study, high-throughput sequencing and cell experiments were used to explore the effects of chronic heat stress on miRNA expression profiles and the regulatory mechanisms of miRNAs in glycogen synthesis under chronic heat stress. In total, 144 cocks were allocated into 3 groups: the normal control (NC) group, the heat stress (HS) group, and the pair-fed (PF) group. In total, 30 differently expressed (DE) miRNAs were screened after excluding the effect of feed intake, which were mainly related to metabolism, signal transduction, cell growth and death. Furthermore, the gga-miR-212-5p/GYS1 axis was predicted to participate in glycogen synthesis through the miRNA-mRNA analysis, and a dual-luciferase reporter test assay confirmed the target relationship. Mechanistically, chronic heat stress up-regulated gga-miR-212-5p, which could inhibit the expression of GYS1 in the PM muscle. Knocking down gga-miR-212-5p alleviates the reduction of glycogen content caused by chronic heat stress; overexpression of gga-miR-212-5p can reduce glycogen content. This study provided another important mechanism for the decreased glycogen contents within the PM muscle of broilers under heat stress, which might contribute to impaired meat quality.

Anti-oxidant effects of herbal residue from Shengxuebao mixture on heat-stressed New Zealand rabbits.

Heat stress can lead to hormonal imbalances, weakened immune system, increased metabolic pressure on the liver, and ultimately higher animal mortality rates. This not only seriously impairs the welfare status of animals, but also causes significant economic losses to the livestock industry. Due to its rich residual bioactive components and good safety characteristics, traditional Chinese medicine (TCM) residue is expected to become a high-quality feed additive with anti-oxidative stress alleviating function. This study focuses on the potential of Shengxuebao mixture herbal residue (SXBR) as an anti-heat stress feed additive. Through the UPLC (ultra performance liquid chromatography) technology, the average residue rate of main active ingredients from SXBR were found to be 25.39%. SXBR were then added into the basal diet of heat stressed New Zealand rabbits at the rates of 5% (SXBRl), 10% (SXBRm) and 20% (SXBRh). Heat stress significantly decreased the weight gain, as well as increased neck and ear temperature, drip loss in meat, inflammation and oxidative stress. Also, the hormone levels were disrupted, with a significant increase in serum levels of CA, COR and INS. After the consumption of SXBR in the basal diet for 3 weeks, the weight of New Zealand rabbits increased significantly, and the SXBRh group restored the redness value of the meat to a similar level as the control group. Furthermore, the serum levels T3 thyroid hormone in the SXBRh group and T4 thyroid hormone in the SXBRm group increased significantly, the SXBRh group showed a significant restoration in inflammation markers (IL-1ß, IL-6, and TNF-α) and oxidative stress markers (total antioxidant capacity, HSP-70, MDA, and ROS) levels. Moreover, the real-time fluorescence quantitative PCR analysis found that, the expression levels of antioxidant genes such as Nrf2, HO-1, NQO1, and GPX1 were significantly upregulated in the SXBRh group, and the expression level of the Keap1 gene was significantly downregulated. Additionally, the SXBRm group showed significant upregulation in the expression levels of HO-1 and NQO1 genes. Western blot experiments further confirmed the up-regulation of Nrf2, Ho-1 and NQO1 proteins. This study provides a strategy for the utilization of SXBR and is of great significance for the green recycling of the TCM residues, improving the development of animal husbandry and animal welfare.

Investigating intestinal mast cell dynamics during acute heat stress in growing pigs.

Objectives were to examine the temporal pattern of intestinal mast cell dynamics and the effects of a mast cell stabilizer (ketotifen [Ket]) during acute heat stress (HS) in growing pigs. Crossbred barrows (n = 42; 32.3 ±â€…1.9 kg body weight [BW]) were randomly assigned to 1 of 7 environmental-therapeutic treatments: (1) thermoneutral (TN) control (TNCon; n = 6), (2) 2 h HS control (2 h HSCon; n = 6), (3) 2 h HS + Ket (2 h HSKet; n = 6); (4) 6 h HSCon (n = 6), (5) 6 h HSKet (n = 6), (6) 12 h HSCon (n = 6), or (7) 12 h HSKet (n = 6). Following 5 d of acclimation to individual pens, pigs were enrolled in two experimental periods (P). During P1 (3 d), pigs were housed in TN conditions (21.5 ±â€…0.8 °C) for the collection of baseline measurements. During P2, TNCon pigs remained in TN conditions for 12 h, while HS pigs were exposed to constant HS (38.1 ±â€…0.2 °C) for either 2, 6, or 12 h. Pigs were euthanized at the end of P2, and blood and tissue samples were collected. Regardless of time or therapeutic treatment, pigs exposed to HS had increased rectal temperature, skin temperature, and respiration rate compared to their TNCon counterparts (1.9 °C, 6.9° C, and 119 breaths/min; P < 0.01). As expected, feed intake and BW gain markedly decreased in HS pigs relative to their TNCon counterparts (P < 0.01). Irrespective of therapeutic treatment, circulating corticotropin-releasing factor decreased from 2 to 12 h of HS relative to TNCon pigs (P < 0.01). Blood cortisol increased at 2 h of HS (2-fold; P = 0.04) and returned to baseline by 6 h. Plasma histamine (a proxy of mast cell activation) remained similar across thermal treatments and was not affected by Ket administration (P > 0.54). Independent of Ket or time, HS increased mast cell numbers in the jejunum (94%; P < 0.01); however, no effects of HS on mast cell numbers were detected in the ileum or colon. Jejunum and ileum myeloperoxidase area remained similar among treatments (P > 0.58) but it tended to increase (12%; P = 0.08) in the colon in HSCon relative to TNCon pigs. Circulating lymphocytes and basophils decreased in HSKet relative to TN and HSCon pigs (P ≤ 0.06). Blood monocytes and eosinophils were reduced in HS pigs relative to their TNCon counterparts (P < 0.01). In summary, HS increased jejunum mast cell numbers and altered leukocyte dynamics and proinflammatory biomarkers. However, Ket administration had no effects on mast cell dynamics measured herein.

Heat stress (HS) affects various physiological, metabolic, and endocrine parameters, ostensibly due to reduced intestinal barrier integrity and the ensuing immune response. Evidence indicates that generalized "stress" may be a critical component of HS-induced leaky gut, a mechanism likely mediated by mast cells. Mast cell activation has been extensively associated with various stress-related intestinal inflammatory conditions; however, its contribution to intestinal barrier dysfunction during HS remains unclear. Thus, this study was designed to evaluate mast cell dynamics during an acute HS challenge and to assess the effects a mast cell stabilizer on biomarkers of intestinal inflammation. Herein, HS induced a rapid increase in circulating cortisol, increased jejunum mast cell numbers, and altered metabolism, leukocyte dynamics, and proinflammatory biomarkers. Contrary to our hypothesis, HS did not alter circulating histamine (a biomarker of mast cell activation), and mast cell stabilization did not affect mast cell numbers nor altered histamine concentrations. Altogether, our observations support a connection between HS and intestinal mast cell infiltration that may contribute to the pathophysiology of intestinal dysfunction during a heat load.

Genistein alleviates chronic heat stress-induced lipid metabolism disorder and mitochondrial energetic dysfunction by activating the GPR30-AMPK-PGC-1α signaling pathways in the livers of broiler chickens.

The objective of this study was to investigate the preventive effects and mechanisms of genistein (GEN) on production performance and metabolic disorders in broilers under chronic heat stress (HS). A total of 120 male 3-wk-old Ross broilers were randomly assigned to 5 groups: a thermoneutral zone (TN) group maintained at normal temperature (21°C ± 1°C daily), an HS group subjected to cyclic high temperature (32°C ± 1°C for 8 h daily), and 3 groups exposed to HS with varying doses of GEN (50, 100, or 150 mg/kg diet). The experimental period lasted for 3 wk. Here, HS led to a decline in growth performance parameters and hormone secretion disorders (P < 0.05), which were improved by 100 and 150 mg/kg GEN treatment (P < 0.05). Moreover, the HS-induced increases in the liver index (P < 0.01) and abdominal fat rate (P < 0.05) were attenuated by 150 mg/kg GEN (P < 0.05). The HS-induced excessive lipid accumulation in the liver and serum (P < 0.01) was ameliorated after 100 and 150 mg/kg GEN treatment (P < 0.05). Furthermore, the HS-induced decreases in lipolysis-related mRNA levels and increases in lipid synthesis-related mRNA levels in the liver (P < 0.01) were effectively blunted after 100 and 150 mg/kg GEN treatment (P < 0.05). Importantly, the HS-stimulated hepatic mitochondrial energetic dysfunction and decreases in the mRNA or protein levels of peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α), nuclear respiratory factor 1, and mitochondrial transcription factor A in the liver were ameliorated by 150 mg/kg GEN (P < 0.05). Moreover, 50 to 150 mg/kg GEN treatment resulted in a significant increase in the mRNA or protein levels of G protein-coupled estrogen receptor (GPR30), AMP-activated protein kinase (AMPK) α1, phosphorylated AMPKα, and phosphorylated acetyl-CoA carboxylase α. Collectively, GEN alleviated metabolic disorders and hepatic mitochondrial energetic dysfunction under HS, possibly through the activation of GPR30-AMPM-PGC-1α pathways. These data provide a sufficient basis for GEN as an additive to alleviate HS in broilers.

Psychrometry in the thermal comfort diagnosis of production animals: a combination of the systematic review and methodological proposal.

Animal welfare and productive performance are compromised when animals are housed in environments which place them outside their thermal comfort zone. However, the identification of thermal stress, when based on air properties, suggests the use of outdated and generic indices. The objective of this work was to develop and validate a methodology for classifying and diagnosing heat stress in production animals based on psychrometric air relations. The model was created for broilers, pigs, dairy cattle, and laying birds, categorized into a total of 21 breeding phases. For each phase, a bibliographic search was carried out for the psychrometric parameters of the air-dry bulb temperature (AT) and relative humidity (RH)-that satisfied the animals' critical and ideal thermoneutral zones. Adding the local atmospheric pressure (AP), the parameters were used to calculate the enthalpy (h), resulting in five comfort ranges. Based on this, a decision tree was elaborated, consisting of three attributes (AT, RH, and h) and seven diagnostic classes, based on the psychrometric principles of air. The proposed methodology was used in a case study, with a database extracted from an individual shelter for calves. For the evaluation of the decision tree, two induction algorithms, ID3 and c4.5, were compared, both of which presented high accuracy and proposed simpler tree models than the one theoretically developed for the methodology. In conclusion, the methodology represents a great potential to characterize the thermal comfort of the animals, diagnose the causes of stress, and recommend possible corrective actions. The study revealed that decision trees can be adapted and simplified for each creation phase.

The autumn low milk yield syndrome in Brown Swiss cows in continental climates: hypotheses and facts.

Extensive research has been conducted globally on the impact of heat stress (HS) on animal health and milk production in dairy cows. In this article, we examine the possible reasons for the decrease in milk production in Brown Swiss (BS) cows during the autumn season, known as the autumn low milk yield syndrome (ALMYS). This condition has been extensively studied in high-yielding Holstein Friesian (HF) cattle and has also been observed in BS cows with a daily milk yield of around 30 kg. Our hypothesis is that the drop in milk yield and the increased prevalence of mastitis in autumn, as found in our recent studies, may be a long-term consequence of summer HS. We re-evaluate our previous findings in light of the possible manifestation of an HS-related form of ALMYS in BS cows. As milk yield, mastitis spread, and reproductive function of cows are interrelated and have seasonal dependence, we examine the consistency of our hypothesis with existing data. The significant drop in milk yield in BS cows in autumn (by 2.0-3.2 kg), as well as the threshold of milk yield decrease (temperature-humidity index of 70.7), may point in favour of the manifestation of ALMYS in BS cows, similar to HF cows. Only the percentage effect of seasonal factor (59.4%; p < 0.05) on milk yield of BS cows was significant. HS-related ALMYS provides a robust conceptual framework for diverse sets of productive and animal health data in BS cows, similar to observations in high-yielding HF cattle. However, the limitations associated with the lack of additional data (e.g. immunological indicators) suggest the need for further research to confirm ALMYS in BS breed.

Effect of transgenerational environmental condition on genetics parameters of Italian Brown Swiss.

The aim of this study was to infer the effects of heat stress (HS) of dams during late gestation on direct and maternal genetic parameters for traits related to milk production and milk quality parameters (90,558 records) in Italian Brown Swiss cattle (12,072 cows in 617 herds). Daily average temperature-humidity indices (THI) during the last 56 d of pregnancy were calculated, using the climate data from the nearest public weather station for each herd. Heat load effects were considered as the average across the entire periods considering a thermoneutrality condition for data below the THI 60. For parameter estimation a random regression model using the second-order Legendre polynomial regression coefficient for THI considering both animal and maternal effect for heat load. Direct heritability increased sharply from THI 60 to 65, then decreased gradually up to THI ∼72, and sharply thereafter. Maternal heritability showed a different trend, with values close to 0 up until to THI 65 and slightly increasing toward extreme THI values. The study suggests a lower threshold of THI 60 for the onset of HS. Higher heritability values indicate greater selective efficiency in the THI range of 65 to 70, even if a higher standard deviation value have been detected. The effects of high THI during intrauterine life varied among traits with different heritability levels. Genetic correlations for milk, fat, and protein content at 60 THI with increasing value of environmental variable, remained constant (∼0.90) until THI >75, where they slightly decreased (∼0.85). Fat and protein yields, as well as milk and energy-corrected milk, showed correlations dropping to 0.80 around THI 67 to 68 and stabilizing between 0.75 and 0.85 at extreme THI values. Maternal component correlations dropped close to zero, with negative values for protein content at THI 65 to 70. Antagonism between direct and maternal components was stronger for intermediate THI values but less divergent for extremes. Genotype by environment interaction was observed, indicating the selection of resilient animals would be theoretically possible. In the future, the application of climate variables in selection schemes first should take into account the dimensions of the genetic correlations to be able to decide between the simple inclusion of the environmental effect in the statistical models, rather than a real parallel genetic evaluation.

Thermal characterization and ventilation assessment of a battery-caged laying hen housing in the humid tropic climate.

The indoor climate to which livestock are exposed is a critical factor influencing their performance and productivity. Elevated air temperature and relative humidity could result in heat stress for laying hens. This situation results in severe adverse effects such as weight loss and mortality. Egg fertility and hatchability are also impacted. Consequently, a study was carried out in a naturally ventilated battery-caged laying hen house to measure climatic variables (air temperature, relative humidity and air velocity). The degree of heat stress was assessed using the temperature-humidity index (THI), and the index of temperature and air velocity (ITV) was also evaluated. According to the results obtained, birds reared within the study building would spend most of their productive life under stressful thermal conditions, which could significantly hamper their performance. The air velocity was below 1.0 ms-1 for most of the internal part of the housing, meaning natural air movement at the location was insufficient to provide a suitable environment for the birds. A high THI was recorded for nearly the entire study period. This high THI could indicate high relative humidity about air temperature. The observed ITV values (ITV > 25) suggest that birds throughout the building could be perpetually uncomfortable. The thermal and velocity profile within the structure could further be assessed numerically using computational fluid dynamics. This would enable engineers to make modifications to improve living conditions within the building.

Comparison of models for the relationship between respiration rate or rectal temperature and increased heat load in farm animals.

Heat stress is an increasing challenge for production animals, particularly in warmer regions of the world. The aim of this study was to compare the fit of three different relationships when modelling respiration rate (RR) and rectal temperature (RT) in animals exposed to increased load. Data from three published studies on finishing pigs, gestating sows and dairy cows were analysed. RR and RT are characterized by being unaffected by increased heat load as long as it is kept below a certain level, and in warmer conditions they increase with increased heat load. As an expression of heat load either the air temperature or the ET (Effective Temperature) was used. The ET unites the effect of air temperature, air humidity and velocity on the animal perception of increased heat load. The relationship between RR and RT and the temperature or the ET was analysed by multiple change point regression and the cubic relationships were modelled. In general, the models provided better fits for RR compared to RT. Relationships with an unaffected piece followed by a quadratic relationship and the cubic relationships performed nearly equally well. Using ET resulted in better correlations than using temperature alone for gestating sows and dairy cows.

Effects of heat stress on feed intake, milk yield, milk composition, and feed efficiency in dairy cows: A meta-analysis.

Heat stress compromises dairy production by decreasing feed intake and milk yield, and it may also alter milk composition and feed efficiency. However, little information is available for evaluating such effects across different levels of heat stress and cows enrolled in heat stress studies. The objectives of this study were to evaluate the effects of heat stress on dry matter intake (DMI), energy-corrected milk (ECM), milk composition, and feed efficiency (kg ECM/kg DMI) and to investigate the relationship between such effects and heat stress intervention and animal characteristics by using meta-analytical approaches. Data from 31 studies (34 trials) fulfilled the inclusion criteria and were used for analysis. Results showed that heat stress decreased DMI, ECM, and milk protein concentration, but did not alter milk fat concentration or feed efficiency. Meta-regression confirmed that such reductions in DMI and ECM were significantly associated with increasing temperature-humidity index (THI). Over the period of heat stress, for each unit increase in THI, DMI and ECM decreased by 4.13% and 3.25%, respectively, in mid-lactation cows. Regression models further revealed the existence of a strong interaction between THI and lactation stage, which partially explained the large heterogeneity in effect sizes of DMI and ECM. The results indicated a need for more research on the relationship between the effect of heat stress and animal characteristics. This study calls for the implementation of mitigation strategies in heat-stressed herds due to the substantial decrease in productivity.

A system dynamics approach to model heat stress accumulation in dairy cows during a heatwave event.

Climate change is expected to increase the number of heat wave events, leading to prolonged exposures to severe heat stress (HS) and the corresponding adverse effects on dairy cattle productivity. Modelling dairy cattle productivity under HS conditions is complicated because it requires comprehending the complexity, non-linearity, dynamicity, and delays in animal response. In this paper, we applied the System Dynamics methodology to understand the dynamics of animal response and system delays of observed milk yield (MY) in dairy cows under HS. Data on MY and temperature-humidity index were collected from a dairy cattle farm. Model development involved: (i) articulation of the problem, identification of the feedback mechanisms, and development of the dynamic hypothesis through a causal loop diagram; (ii) formulation of the quantitative model through a stock-and-flow structure; (iii) calibration of the model parameters; and (iv) analysis of results for individual cows. The model was successively evaluated with 20 cows in the case study farm, and the relevant parameters of their HS response were quantified with calibration. According to the evaluation of the results, the proposed model structure was able to capture the effect of HS for 11 cows with high accuracy with mean absolute percent error <5%, concordance correlation coefficient >0.6, and R2 > 0.6, except for two cows (ID #13 and #20) with R2 less than 0.6, implying that the rest of the nine animals do not exhibit heat-sensitive behaviour for the defined parameter space. The presented HS model considered non-linear feedback mechanisms as an attempt to help farmers and decision makers quantify the animal response to HS, predict MY under HS conditions, and distinguish the heat-sensitive cows from heat-tolerant cows at the farm level.

Effect of sustained release bolus oral administration on body condition change, blood parameters, and uterine health in primiparous cows under heat stress.

The transition period is very stressful for primiparous cows due to their first calving experience and will be more challenging if it occurs under heat stress conditions. Heat stress reduces the feed intake of dairy cows. Therefore, it reduces the consumption of minerals and vitamins. Oral administration of boluses through the provision of mineral-vitamin compounds can reduce metabolic abnormalities after calving. The present study aimed to evaluate effect of sustained-release bolus on body condition score (BCS) change, serum metabolites, uterine health, and reproductive status in primiparous cows. Heifers were selected at the beginning of the close-up period (n = 60, BCS = 3.35 ± 0.12). There were 2 experimental treatments at the time of calving: (1) heifers without bolus oral administration (H - Bo, n = 30); (2) heifers with bolus oral administration (H + Bo, n = 30). The results showed that although the rate of BCS loss was lower in the group receiving bolus, the effect of bolus was not significant. The effect of bolus on blood level of glucose, non-esterified fatty acids (NEFA), and beta-hydroxybutyrate (BHBA) was not significant; however, the highest concentration of albumin (P = 0.05) was observed in the H + Bo group on day 42 after calving. The concentration of aspartate transaminase (AST) tended to increase (P = 0.06) on day 14 after calving and entire the study. Total antioxidant capacity (TAC) was affected (P < 0.05) by bolus throughout the period of study, and the highest (P < 0.05) concentration of glutathione peroxidase (GPX) and superoxide dismutase (SOD) was observed in H + Bo group on day 42 after calving. The H + Bo group had the lowest (P < 0.05) vaginal discharge score (VDS). In general, oral administration of the sustained-release bolus in heifers significantly affected the antioxidant factors and uterine health, as well as had positive effects on liver function, body condition, and reproduction status.