Effect of heat stress on reproductive performances of dairy cattle and buffaloes: A review

Effect of seven days heat stress on feed and water intake, milk characteristics, blood parameters, physiological indicators, and gene expression in Holstein dairy cows

This study examined the effects of 7 days of heat stress on eight early lactating Holstein cows in climate-controlled chambers. The early lactating Holstein cows (42 ± 2 days in milk, 29.27 ± 0.38 kg/day milk yield, 1.21 ± 0.05 parity) were subjected to two 14-day periods, each consisting of 7 days of adaptation and 7 days of heat stress. Conditions were set to 22 °C and 50% humidity during adaptation, followed by heat stress periods with low-temperature, low-humidity (LTLH, 71 THI) and high-temperature, high-humidity (HTHH, 86 THI) treatments. Data from the last 7 days were analyzed using a mixed procedure in SAS. In the study, the HTHH group displayed marked physiological and biochemical changes on 14 days of heat stress exposure compared to the LTLH group. Firstly, the HTHH group's dry matter intake decreased by approximately 12% while their water intake increased by about 23%. Secondly, both milk yield and milk protein production in the HTHH group decreased by 10% and 20%, respectively. Thirdly, there was a reduction in white blood cells, hemoglobin, mean corpuscular hemoglobin, and platelets in the HTHH group, with concurrent increases in glucose, non-esterified fatty acids, and albumin concentrations. Additionally, the HTHH group exhibited elevated plasma concentrations of cortisol and haptoglobin. Moreover, the gene expression of heat shock protein 70 and heat shock protein 90 was significantly upregulated in the HTHH group's peripheral blood mononuclear cells. Lastly, key physiological indicators such as rectal temperature, heart rate, and skin temperature showed substantial elevations in the HTHH group. Considering the enormous negative effects observed in the analyzed blood metabolites, milk yield and compositions, and heat shock protein gene expression, early lactating Holstein cows were found to be more vulnerable to HTHH than LTLH over a 7 days exposure to heat stress.

The effect of first-lactation calving season, milk production, and morphology on the survival of Simmental cows

Longevity in dairy and dual-purpose cattle is a complex trait which depends on many individual and managerial factors. The purpose of the present study was to investigate the survival (SURV) rate of Italian Simmental dual-purpose cows across different parities. Data of this study referred to 2 173 primiparous cows under official milk recording that calved between 2002 and 2020. Only cows linearly classified for type traits, including muscularity (MU) and body condition score (BCS) were kept. Survival analysis was carried out, through the Cox regression model, for different pairwise combinations of classes of milk productivity MU, BCS, and calving season. Herd-year of first calving was also considered in the model. SURV (0 = culled; 1 = survived) at each lactation up to the 6th were the dependent variables, so that, for example, SURV2 equal to 1 was attributed to cows that entered the 2nd lactation. Survival rates were 98, 71, 63, 56, and 53% for 2nd, 3rd, 4th, 5th, and 6th lactation, respectively. Results revealed that SURV2 was not dependent on milk yield, while in subsequent parities, low-producing cows were characterized by higher SURV compared to high-producing ones. Additionally, cows starting the lactation in autumn survived less (47.38%) than those starting in spring (53.49%), suggesting that facing the late gestation phase in summer could increase the culling risk. The present study indicates that SURV in Italian Simmental cows is influenced by various factors in addition to milk productivity. However, it is important to consider that in this study all first-calving cows culled before the linear evaluation - carried out between mid- and late lactation in this breed - were not accounted for. Finding can be transferred to other dual-purpose breeds, where the cows' body conformation and muscle development - i.e. meat-related features - are often considered as important as milk performance by farmers undertaking culling decisions.

Seasonal assessment of mastitis using thermogram analysis in murrah buffaloes

Mastitis is a global threat that challenges dairy farmers' economies worldwide. Sub-clinical mastitis (SCM) beholds the lion's share in it, as its visible clinical signs are not evident and are challenging to diagnose. The treatment of intramammary infection (IMI) demands antimicrobial therapy and subsequent milk withdrawal for a week or two. This context requires a non-invasive diagnostic tool like infrared thermography (IRT) to identify mastitis. It can form the basis of precision dairy farming. Therefore, the present study focuses on thermal imaging of the udder and teat quarters of Murrah buffaloes during different seasons to identify SCM and clinical mastitis (CM) cases using the Darvi DTL007 camera. A total of 30-45 lactating Murrah buffalo cows were screened out using IRT regularly throughout the year 2021-22. The IMI was further screened using the California mastitis test. The thermogram analysis revealed a significant difference (p < 0.01) in the mean values of the udder and teat skin surface temperature of Murrah buffaloes between healthy, SCM, and CM during different seasons. The mean values of udder skin surface temperature (USST) during different seasons ranged between 30.28 and 36.81 °C, 32.54 to 38.61 °C, and 34.32 to 40.02 °C among healthy, SCM, and CM-affected quarters. Correspondingly, the mean values of teat skin surface temperature (TSST) were 30.52 to 35.96 °C, 32.92 to 37.55 °C, and 34.51 to 39.05 °C, respectively. Further results revealed an increase (p < 0.01) in the mean values of USST during winter, summer, rainy, and autumn as 2.26, 4.04; 2.19, 3.35; 1.80, 3.21; and 1.45, 2.64 °C and TSST as 2.40, 3.99; 2.28, 3.26; 1.59, 3.09; and 1.68, 2.92 °C of SCM, CM-affected quarters to healthy quarters, respectively. The highest incidence of SCM was observed during autumn and CM during winter. Henceforth, irrespective of the seasons studied in the present study, IRT is an efficient, supportive tool for the early identification of SCM.

Equine chorionic gonadotropin treatment and timed artificial insemination for dairy cow production under heat stress

This study investigated the effects of timed artificial insemination (TAI) and equine chorionic gonadotropin (eCG) administration on lactating dairy cows under heat-stress conditions (average temperature-humidity index: 80). Timed artificial insemination was performed on the cows with (n = 57) or without (control, n = 41) supplementation with 500 IU of eCG at the day of PGF2α treatment using the CIDR-Ovsynch protocol. GnRH was administered, and a progesterone device (CIDR) was inserted on Day -10 of the treatment protocol. The CIDR was removed on Day -3, and the cows were treated with PGF2α. Two days later, a 2nd GnRH injection was administered. Subsequently, AI was performed on Day 0 (16-20 h after the 2nd GnRH injection), and pregnancy was diagnosed on Days 32 and 60. Plasma progesterone (P4) concentrations were measured after AI. Results showed that the eCG group had a higher pregnancy per AI (P/AI) than the control group (43.9 vs. 12.2%, P = 0.002), which was also accompanied by elevated P4 levels. Four cows in the eCG group had multiple calves, representing 7.0 and 16.0% of the group and pregnant cows, respectively. In conclusion, 500 IU of eCG combined with CIDR-Ovsynch in lactating dairy cows under severe heat stress conditions successfully improved fertility. However, the protocol may have a slight risk of multiple births.

Supplementation with long-acting injectable progesterone 3 days after TAI impaired luteal function in buffaloes

Three experiments were conducted to evaluate the effects of long-acting injectable progesterone (iP4) in buffalo cows. In Experiment 1, ovariectomized buffaloes received 300 mg (iP300) or 600 mg (iP600) of iP4, and serum P4 concentrations were evaluated. In experiment 2, three groups were compared: control or administration of 300 mg of iP4 3 (iP4-D3) or 6 days (iP4-D6) after timed artificial insemination (TAI). On day 16, reproductive tract was recovered for conceptus, endometrium, and corpus luteum (CL) analysis. In experiment 3, pregnancy per AI (P/TAI) and proportion of pregnancy losses were evaluated after administration of 300 mg of iP4 3 (iP4-D3) or 6 days (iP4-D6) after TAI in lactating buffaloes. In experiment 1, serum P4 concentrations remained over 1 ng/mL for ~ 3 days in both groups. The 300 mg dose was used in subsequent experiments. In experiment 2, CL weight and endometrial glands density were decreased, and conceptus length was increased in iP4-D3 compared to control and to iP4-D6 (P < 0.05). Transcript abundance of Prostaglandin F Receptor (FP) and ISG15 in CL and of ISG15 and MX1 in endometrium was greater in iP4-D3 when compared to control and to iP4-D6 (P < 0.05). In experiment 3, there was no difference among experimental groups for P/TAI at D30 and pregnancy losses (P > 0.1); however, iP4-D3 presented a lower P/TAI at day 60 (41.7%) when compared to control (56.8%) and iP4-D6 (57.7%; P = 0.07). In conclusion, administration iP4 at 3 days after TAI affects CL development and consequently decreases final pregnancy outcome in buffaloes.

The Anti-Müllerian Hormone as Endocrine and Molecular Marker Associated with Reproductive Performance in Holstein Dairy Cows Exposed to Heat Stress

Anti-Müllerian hormone (AMH) is proposed as a biomarker for fertility in cattle, yet this associative relationship appears to be influenced by heat stress (HS). The objective was to test serum AMH and AMH-related single nucleotide polymorphisms (SNPs) as markers potentially predictive of reproductive traits in dairy cows experiencing HS. The study included 300 Holstein cows that were genotyped using BovineSNP50 (54,000 SNP). A genome-wide association study was then executed. Nine intragenic SNPs within the pathways that influence the AMH gene were found important with multiple comparisons adjustment tests (p < 1.09 × 10-6). A further validation study was performed in an independent Holstein cattle population, which was divided into moderate (MH; n = 152) and severe heat-stressed (SH; n = 128) groups and then subjected to a summer reproductive management program. Serum AMH was confirmed as a predictor of fertility measures (p < 0.05) in MH but not in the SH group. Cows were genotyped, which revealed four SNPs as predictive markers for serum AMH (p < 0.01), reproductive traits (p < 0.01), and additional physiological variables (p < 0.05). These SNPs were in the genes AMH, IGFBP1, LGR5, and TLR4. In conclusion, serum AMH concentrations and AMH polymorphisms are proposed as predictive markers that can be used in conjunction with genomic breeding value approaches to improve reproductive performance in Holstein cows exposed to summer HS conditions.

Seasonal assessment of mastitis using thermogram analysis in Sahiwal cows

"India is the world's leading producer of milk" and demands a non-invasive diagnostic tool like infrared thermography (IRT) to identify the costliest production disease, mastitis. It can form the basis of precision dairy farming. Therefore, the present study focuses on thermal imaging of the udder and teat quarters of Sahiwal cows during different seasons to identify subclinical (SCM) and clinical mastitis (CM) cases using the Darvi DTL007 camera. A total of 24-69 lactating Sahiwal cows were screened out using IRT regularly throughout the year. The intramammary infection status was further assessed using the CMT. The receiver operating characteristic analysis was carried out to develop the current study's cut-off for various thermographic parameters. The incidence for SCM and CM ranged from 26.47 to 38.75% and 17.83-22.79%, respectively during different seasons in Sahiwal udder quarters. The thermogram analysis revealed a significant difference (p < 0.01) in the mean values of the udder and teat surface temperature of Sahiwal cows between healthy, SCM, and CM during different seasons. The mean values of udder skin surface temperature (USST) during different seasons ranged between 29.07 and 36.91 °C, 31.51 to 37.88 °C and 32.42 to 38.79 °C among healthy, SCM, and CM-affected quarters, and correspondingly, the mean values of teat skin surface temperature (TSST) were 28.28 to 36.77 °C, 30.68 to 37.88 °C and 31.70 to 38.73 °C, respectively. Further results revealed an increase (p < 0.01) in the mean values of USST during winter, summer, rainy, and autumn as 2.44, 3.35; 0.97, 1.88; 1.06, 1.83; 1.29, 2.39 °C and TSST as 2.4, 3.42; 1.11, 1.96; 1.21, 2.19, 1.3, 2.4 °C of SCM, CM-affected quarters to healthy quarters, respectively, in Sahiwal cows. Thermograms showed a strong positive correlation with the CMT scores of SCM, CM cases, and healthy samples. Henceforth, irrespective of the seasons studied in the present work, IRT is an efficient, supportive tool for the early identification of subclinical mastitis.

Effects of Climatic Conditions and Supplementation with Palm Cake on the Thermoregulation of Crossbred Buffaloes Raised in a Rotational Grazing System and with Natural Shade in Humid Tropical Regions

In ruminants, diet composition has a positive correlation with heat production, which can influence thermoregulation, energy expenditure and, consequently, animal performance. The objective of this work was to evaluate the effects of climatic conditions and supplementation based on palm kernel cake, on the thermoregulation of crossbred buffaloes in the eastern Amazon. The research was carried out at Embrapa Amazônia Oriental (01°26' S and 48°24' W), Belém, Pará, and lasted 12 months (representing the entire year). Twenty-four buffaloes, females, with initial age and an average weight of 54 ± 7 months and 503.1 ± 23 kg, respectively, non-pregnant, non-lactating and clinically healthy were used, divided into four treatments based on the supplementation content of the palm cake (%DM) in relation to their body weight (%): 0, 0.25, 0.50 and 1.0. The animals were kept in paddocks with Brachiaria brizantha (cv. Marandu), in a rotating system, with water to drink and mineral salt ad libitum. Equipment was installed to record environmental data (temperature and relative humidity, dew point temperature, wet bulb and black globe) and physiological data: rectal temperature (RT); respiratory rate (RR); and body surface temperature (BST), recorded twice a day, always in the morning (6:00 a.m. to 7:00 a.m.) and afternoon (12:00 p.m. to 1:00 p.m.) shifts, and were used to calculate the Globe Temperature and Humidity Index (GTHI). Supplementation did not influence the physiological variables of thermoregulation (p > 0.05). However, there were differences in the GTHI between the shifts, with higher means in the afternoon shift, especially in the less rainy period of the year, where the GTHI reached 92.06 ± 2.74 (p < 0.05). In all periods of the year, the mean values of RT, RR and BST were higher in the afternoon shift (p > 0.05). The respiratory rate (RR) is associated with the annual seasonality of the thermal waters, with higher averages in the afternoons of the rainy season. The positive correlation for rectal temperature, respiratory rate and body surface temperature indicated that buffaloes respond to thermal elevations in the atmosphere (afternoon period) and, consequently, reflect on the GTHI. Supplementation does not influence thermoregulation; the changes observed occurred in response to the region's thermal and rainfall conditions (mainly in the afternoon shift), with higher GTHI values.

Understanding Knowledge and Attitude of Farmers towards Antibiotic Use and Antimicrobial Resistance in Jhunjhunu District, Rajasthan India

The misuse of antibiotics in veterinary practices by farmers is harming livestock production and food safety and leading to the rise of antibiotic resistance (AMR). This can also transfer resistant bacteria from animals to humans, posing a serious public health threat. However, we have not paid enough attention to understanding how farmers behave in this regard. Our study aims to explore farmers' behaviors and identify the factors that influence their choices. To conduct this study, we used a questionnaire with 40 questions and surveyed 208 farmers in Jhunjhunu district, Rajasthan. We analyzed the data using SPSS. Here are the key findings: About 58.3% of the farmers have some awareness of antibiotics, and 49.5% are aware of antimicrobial resistance (AMR). Notably, as the level of education increases, so does awareness of antibiotics. Unfortunately, 63.9% of the farmers are not aware of the withdrawal time, and 64% have no idea about the presence of antibiotic residues during this period. Around 75% of farmers vaccinate their animals, but approximately 56.9% of individuals have never undergone an antibiotic sensitivity test (ABST) for milk. Around 48.6% of farmers are unaware of government testing centers. Several factors hinder farmers from implementing proper animal management practices, such as the high fees of veterinarians. When their animals become sick, their first choice is home remedies, followed by using old prescriptions. Additionally, 63.9% stop treatment once the animal looks better. A significant portion (83.8%) of farmers rely on local pharmacists for medicine. It has been determined that there is no significant correlation between education, experience, age, and the level of awareness concerning withdrawal periods, the existence of government antibiotic sensitivity test (ABST) centers, and entities responsible for sending samples for ABST. In our qualitative analysis, focus groups identified significant barriers to following best farm practices and spreading awareness about AMR. These findings suggest that addressing AMR in livestock requires a comprehensive approach. This should include targeted education and awareness programs for farmers, as well as improved access to veterinary services.

Short-milking-tube thermograms: An alternative to udder thermograms for mastitis detection in Sahiwal cows

Mastitis is a multi-etiological production disease that causes substantial financial loss to dairy farmers. In this context, early detection of mastitis using thermograms can aid the dairy sector in managing mastitis efficiently, and this technology could be a supportive tool in precision dairy farming. Infrared cameras can detect minor temperature changes on the udder surface by taking multiple images of the udder and teat. In the current study, a thermogram of the short milking tube (SMT) of the milking machine, as well as the udder and teat of lactating Sahiwal cow (n = 100 quarters of 25 Sahiwal cows), was captured using a hand-held digital infrared thermal camera (DarviDTL007) during morning milking to assess the mastitis status. CMT and SCC of milk samples were carried out for further confirmatory diagnosis of healthy, sub-clinical (SCM), and clinical mastitis (CM). Cut-offs for short milking tube temperature were developed using the receiver operating characteristics analysis. Results of thermal image analysis revealed that the pre-milking, milking, and post-milking parameters of the udder and the teat skin surface temperatures showed a significant difference in the healthy, SCM, and CM-affected quarters. The thermogram analysis showed a significant increase (p < 0.05) of 1.11 and 2.04°C in the mean values of SMT surface temperature among SCM and CM quarters compared to healthy quarters, respectively. In addition, the values of CMT and SCC revealed a significant increase (p < 0.05) in SCM and CM samples and a positive correlation to SMT surface temperatures. Short milking tube thermograms can be a useful assessment tool for detecting sub-clinical mastitis in dairy animals.

Heat stress adaptation in cows - Physiological responses and underlying molecular mechanisms

Heat stress is a key abiotic stressor for dairy production in the tropics which is further compounded by the ongoing climate change. Heat stress not only adversely impacts the production and welfare of dairy cows but severely impacts the economics of dairying due to production losses and increased cost of rearing. Over the years, selection has ensured development of high producing breeds, however, the thermotolerance ability of animals has been largely overlooked. In the past decade, the ill effects of climate change have made it pertinent to rethink the selection strategies to opt for climate resilient breeds, to ensure optimum production and reproduction. This has led to renewed interest in evaluation of the impacts of heat stress on cows and the underlying mechanisms that results in their acclimatization and adaptation to varied thermal ambience. The understanding of heat stress and associated responses at various level of animal is crucial to device amelioration strategies to secure optimum production and welfare of cows. With this review, an effort has been made to provide an overview on temperature humidity index as an important indicator of heat stress, general effect of heat stress in dairy cows, and impact of heat stress and subsequent response at physiological, haematological, molecular and genetic level of dairy cows.

N-3 Polyunsaturated Fatty Acids as a Nutritional Support of the Reproductive and Immune System of Cattle-A Review

This paper focuses on the role of n-3 fatty acids as a nutrient crucial to the proper functioning of reproductive and immune systems in cattle. Emphasis was placed on the connection between maternal and offspring immunity. The summarized results confirm the importance and beneficial effect of n-3 family fatty acids on ruminant organisms. Meanwhile, dietary n-3 fatty acids supplementation, especially during the critical first week for dairy cows experiencing their peripartum period, in general, is expected to enhance reproductive performance, and the impact of its supplementation appears to be dependent on body condition scores of cows during the drying period, the severity of the negative energy balance, and the amount of fat in the basic feed ration. An unbalanced, insufficient, or excessive fatty acid supplementation of cows' diets in the early stages of pregnancy (during fetus development) may affect both the metabolic and nutritional programming of the offspring. The presence of the polyunsaturated fatty acids of the n-3 family in the calves' ration affects not only the performance of calves but also the immune response, antioxidant status, and overall metabolism of the future adult cow.

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.

Molecular, enzymatic responses and in vitro embryonic developmental competency of heat-shocked buffalo embryos co-cultured with granulosa cells monolayer

The present study was designed to establish a suitable alternative approach to mitigate the adverse effect of high culture temperature on in vitro embryo development and the related molecular response in buffalo. Pre-cultured granulosa cells (GCs) were used as a monolayer during in vitro embryo culture until day 8 (day of fertilization = D0). Post fertilization, presumptive embryos were randomly assigned into two culture conditions: embryos cultured in the presence of GCs monolayer under normal culture temperature (N: 38.5 °C; GEN group) or heat shock (H: 40.5 °C; GEH group) and their counterpart groups of embryos cultured without GCs (EN and EH groups). Additionally, two groups of GCs monolayer were cultured without embryos up to day 8 under 38.5 °C (GN) or 40.5 °C (GH) for further spent culture media enzymatic analyses. Heat shock was administered for the first 2 h of culture then continued at 38.5 °C until day 8. The results indicated that under heat treatment, GCs enhanced (P ≤ 0.05) embryo cleavage and development (day 8) rates, which were comparable to the embryos cultured at 38.5 °C. On the molecular level, blastocysts of the GEH group showed similar expressions of metabolism-regulating genes (CPT2 and SlC2A1/GLUT1) and an antioxidant gene (SOD2) when compared to the blastocysts of the EN group. The relative expression of HSP90 was significantly up-regulated under heat shock and/or co-culture conditions. However, HSF1 expression was increased (P ≤ 0.05) in the GEH group. No statistical differences were observed among the study groups for the pluripotency gene NANOG, and stress resistance transcript NFE2L2. Regarding the enzymatic profile, the concentrations of SOD, total protein, and MDA were decreased (P ≤ 0.05) in the GEH group compared to the cultured GCs without embryos (GH group). In conclusion, GCs as a monolayer have a beneficial impact on alleviating heat stress at the zygote stage through the regulatory mechanisms of metabolic activity, defense system, and heat shock response genes.

Temporal variation and risk factors associated with reproductive disorders in Hardhenu (Bos taurus × Bos indicus) dairy cattle

This study aimed to investigate the incidence and effect of non-genetic factors on reproductive disorders in the Hardhenu cattle population over a period of 11 years (2010-2021). The study included a total of 1340 cattle for calculating the incidence of reproductive disorders and analysed the occurrence of different reproductive disorders. In the present study, retention of placenta had highest frequency, accounting for approximately 18.36% of the incidence, followed by repeater cows (11.19%), metritis (6.27%), dystocia (0.60%), anestrus (0.45%) and prolapse (0.37%). Chi-square analysis revealed a significant relationship between the year and the incidence of reproductive disorders (p < .05). Logistic regression analysis of temporal variability of reproductive disorders was also analysed, with an increase in the odds from 2014 to 2020, peaking in 2017-2018 and 2018-2019. Logistic regression analysis showed that season and parity did not significantly influence the incidence of reproductive disorders. However, period of calving had a significant impact. Cows calving between 2008 and 2014 had a significantly lower odds ratio (0.13, 95% CI: 0.06-0.30), indicating a decreased risk, while those calving between 2014 and 2017 had a higher odds ratio (0.59, 95% CI: 0.38-0.90), suggesting an increased risk of reproductive disorders. Compared to parity 3, parity 1 (1.344, 95% CI: 0.869-2.08) and parity 2 (1.193, 95% CI: 0.768-1.851) showed highest odds ratio. Similarly, the odds ratio for winter (1.64, 95% CI: 0.93-2.89), summer (1.71, 95% CI: 0.89-3.26) and rainy season (1.64, 95% CI: 0.92-2.91) was higher as compared to autumn. The present results provided valuable insights into the incidence of various reproductive disorders and associated risk factors in Hardhenu cattle. These results can be utilized for targeted interventions to enhance reproductive health and overall productivity in dairy cattle.

Effects of rumen-protective γ-aminobutyric acid additive on lactation performance and serum biochemistry in heat-stressed cows

In the context of global warming, heat stress has become one of the major stress factors limiting dairy cattle production. Although many methods have been explored to help cows mitigate the negative effects of heat stress during the hot summer months, maintaining the performance of high-yielding cows under heat stress is still a great challenge. The aim of this trial was to investigate the effect of RP-GABA in the diet on milk yield, milk composition and serum biochemical parameters in heat-stressed cows. Twenty Chinese Holstein cows in early lactation (51.00 ± 4.92 kg milk/d, 71 ± 10.94 d in milk and 2.68 ± 0.73 parities) were included in this experiment and randomly divided into four groups (n = 5/group). The four experimental groups consisted of one control group (0 g RP-GABA/d) and three treatment groups, given 5, 7.5 and 10 g RP-GABA/d of dry matter (DM) per cow, respectively. The results showed that supplementing high-yielding cows with 10 g/d of RP-GABA improved milk protein production but had no effect on the improvement of other production performance, the alleviation of heat stress in cows, or the improvement of immune function and antioxidant capacity. Ultimately, we conclude that the supplementation of 10 g/d RP-GABA to heat-stressed, high-yielding dairy cows can provide a degree of performance enhancement. Furthermore, our study provides some reference for nutritional improvement measures for summer heat stress in dairy cows, especially high-yielding cows.

Heat Stress as a Barrier to Successful Reproduction and Potential Alleviation Strategies in Cattle

In recent decades, the adverse effects of global warming on all living beings have been unanimously recognized across the world. A high environmental temperature that increases the respiration and rectal temperature of cattle is called heat stress (HS), and it can affect both male and female reproductive functions. For successful reproduction and fertilization, mature and healthy oocytes are crucial; however, HS reduces the developmental competence of oocytes, which compromises reproduction. HS disturbs the hormonal balance that plays a crucial role in successful reproduction, particularly in reducing the luteinizing hormone and progesterone levels, which leads to severe problems such as poor follicle development with a poor-quality oocyte and problems related to maturity, silent estrus, abnormal or weak embryo development, and pregnancy loss, resulting in a declining reproduction rate and losses for the cattle industry. Lactating cattle are particularly susceptible to HS and, hence, their reproduction rate is substantially reduced. Additionally, bulls are also affected by HS; during summer, semen quality and sperm motility decline, leading to compromised reproduction. In summer, the conception rate is reduced by 20-30% worldwide. Although various techniques, such as the provision of water sprinklers, shade, and air conditioning, are used during summer, these methods are insufficient to recover the normal reproduction rate and, therefore, special attention is needed to improve reproductive efficiency and minimize the detrimental effect of HS on cattle during summer. The application of advanced reproductive technologies such as the production of embryos in vitro, cryopreservation during the hot season, embryo transfer, and timed artificial insemination may minimize the detrimental effects of HS on livestock reproduction and recover the losses in the cattle industry.

A Summer Heat Wave Reduced Activity, Heart Rate, and Autumn Body Mass in a Cold-Adapted Ungulate

AbstractHeat waves are becoming more frequent across the globe and may impose severe thermoregulatory challenges for endotherms. Heat stress can induce both behavioral and physiological responses, which may result in energy deficits with potential fitness consequences. We studied the responses of reindeer (Rangifer tarandus tarandus), a cold-adapted ungulate, to a record-breaking heat wave in northern Finland. Activity, heart rate, subcutaneous body temperature, and body mass data were collected for 14 adult females. The post-heat wave autumn body masses were then analyzed against longitudinal body mass records for the herd from 1990 to 2021. With increasing air temperature during the day, reindeer became less active and had reduced heart rate and increased body temperature, reflecting both behavioral and physiological responses to heat stress. Although they increased activity in the late afternoon, they failed to compensate for lost foraging time on the hottest days (daily mean temperature ≥20°C), and total time active was reduced by 9%. After the heat wave, the mean September body mass of herd females (69.7±6.6 kg, n=52) was on average 16.4% ± 4.8% lower than predicted (83.4±6.0 kg). Among focal females, individuals with the lowest levels of activity during the heat wave had the greatest mass loss during summer. We show how heat waves impose a thermoregulatory challenge on endotherms, resulting in mass loss, potentially as a result of the loss of foraging time. While it is well known that environmental conditions affect large herbivore fitness indirectly through decreased forage quality and limited water supply, direct effects of heat may be increasingly common in a warming climate.

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.

Administration of melatonin prior to modified synchronization protocol improves the productive and reproductive efficiency of Chinese crossbred buffaloes in low breeding season

Introduction

Melatonin is a neurohormone involving various biological processes, including restoration of cyclicity in animals with seasonal breeding patterns. The use of melatonin in different forms has gained broader acceptance in different species, particularly in summer anestrous buffaloes.

Objectives

The objective of the current study was to evaluate the melatonin effect on the reproductive and productive performance of crossbred buffaloes during the low breeding season.

Methods

Sixty-five cyclic and reproductively sound crossbred buffaloes were randomly allocated to three groups: the G1 (n = 20) served as the control group and received no single melatonin, G2 received melatonin (n = 22; 18 mg/50 kg, body weight) once prior to synchronization and G3 group was administered multiple melatonin injections (n = 23; 6 mg/50 kg body weight) for three consecutive days before the start of the synchronization protocol. The reproductive performance, milk yield traits, and serum immunoglobulin M (IgM) and melatonin levels were evaluated in treated and untreated crossbred buffaloes.

Results

The results revealed that a single dose of melatonin administration has (p < 0.05) improved estrus response, ovulation occurrence and follicular growth in crossbred buffaloes compared to control groups. Higher pregnancy rates were observed in both melatonin-treated buffalo groups compared to the control. Following the administration of melatonin, serum IgM level increased in G2 and G3; however, an increment in melatonin level (p < 0.05) was detected in the G2 group only as compared to the control group subsequent day of melatonin administration. The milk compositions were not affected by melatonin administration except for milk urea nitrogen and somatic cell count (SCC). The melatonin administration (p < 0.05) decreased the somatic cell count in buffalo milk compared to untreated.

Conclusion

In conclusion, single or multiple doses of melatonin before initiating the synchronization protocol improved the ovulation, ovulatory follicle diameter and pregnancy rates in crossbred buffaloes during the low breeding season. Moreover, the administration of melatonin enhanced the IgM values along milk traits in terms of milk protein, MUN and somatic cell count in treated buffaloes.

Responses of Dairy Buffalo to Heat Stress Conditions and Mitigation Strategies: A Review

Increases in temperature and the greater incidence of extreme events are the consequences of the climate change that is taking place on planet Earth. High temperatures create severe discomfort to animal farms as they are unable to efficiently dissipate their body heat, and for this, they implement mechanisms to reduce the production of endogenous heat (reducing feed intake and production). In tropical and subtropical countries, where buffalo breeding is more widespread, there are strong negative consequences of heat stress (HS) on the production and quality of milk, reproduction, and health. The increase in ambient temperature is also affecting temperate countries in which buffalo farms are starting to highlight problems due to HS. To counteract HS, it is possible to improve buffalo thermotolerance by using a genetic approach, but even if it is essential, it is a long process. Two other mitigation approaches are nutritional strategies, such as the use of vitamins, minerals, and antioxidants and cooling strategies such as shade, fans, sprinklers, and pools. Among the cooling systems that have been evaluated, wallowing or a combination of fans and sprinklers, when wallowing is not available, are good strategies, even if wallowing was the best because it improved the production and reproduction performance and the level of general well-being of the animals.

Animal welfare and effects of per-female stress on male and cattle reproduction—A review

Thermal stress causes severe effects on the wellbeing and reproduction of cattle, including changes in oogenesis and spermatogenesis, generating great concerns, which last for decades. In cattle, the occurrence of thermal stress is associated with a reduction in the production of spermatozoids and ovarian follicles, in addition to the increase of major and minor defects in gametes or in their intermediate stages. In bovine females able to reproduce, a reduction in the rate of estrus manifestation and an increase in embryonic mortality has been observed. Therefore, keeping animals on good welfare conditions, with water supply and in shaded areas can favor the improvement of different reproductive parameters. For all this, the present study aimed to gather, synthesize and argue recent studies related to animal welfare, focusing on the effects of thermal stress on the reproduction of cattle, aiming to support possible strategies to mitigate the harmful effects of thermal stress in this species.

Effect of Temperature and Humidity on Milk Urea Nitrogen Concentration

This study investigated the effect of ambient temperature and humidity on milk urea nitrogen (MUN) concentration in Holstein cows. Meteorological data corresponding to the dates of milk sampling were collected over six years. A linear mixed-effects model including a random effect term for cow identification was used to assess whether temperature and humidity were predictive of MUN concentration. Age, days in milk, temperature humidity index (THI), ration, milk yield, parity and somatic cell count were also evaluated as main effects in the model. A general linear model including all variables as random effects was then fitted to assess the contribution of each variable towards the variability in MUN concentration. Maximum daily temperature and humidity on the sampling day were positively associated with MUN concentration, but their interaction term was negatively associated, indicating that their effects were not independent and additive. Variables that contributed the most to the variability of MUN concentration were dietary crude protein (21%), temperature (18%) and other factors (24%) that were not assessed in the model (error term). Temperature has a significant influence on urea nitrogen concentration and should therefore always be considered when urea nitrogen concentration data are used to make inferences about the dietary management of dairy cows.

Fertility of Holstein cows and heifers submitted to timed artificial insemination and receiving one or two doses (12 h apart) of semen

The objective of this retrospective study was to assess the effect of receiving a single (n = 50,285) or double (n = 4392) artificial insemination (AI), 12 h apart, within a timed artificial insemination protocol on pregnancy per AI (P/AI) in nulliparous heifers (inseminated with either sex-sorted or conventional semen) and pluriparous Holstein cows in a commercial dairy herd. Also, this study aimed to investigate the relationship between temperature-humidity index (THI) and time of the first AI and fertility. Fertility of cows receiving two AI with normothermia (THI <68) was higher (p < .05) than cows receiving a single AI (42.9% vs. 36.4%). P/AI of cows receiving two AI with severe heat stress (THI >85) was higher (p < .05) than cows receiving a single AI (21.0% vs. 12.6%). Regardless of heat stress conditions, applying the first AI in the morning increased (p < .05) P/AI in cows with double AI than in cows whose first AI occurred in the afternoon (38.4 vs. 33.3%). With moderate heat stress, and sexed-sorted semen, P/AI to timed AI was higher (65.0 vs. 51.9%; p < .05) in heifers receiving double AI than those serviced once. It was concluded that double AI, 12 h apart, enhanced fertility at timed AI than herd mates with a single AI, particularly with heat stress at breeding.

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.

Assessment of Seasonal Variation in Methane Emissions of Mediterranean Buffaloes Using a Laser Methane Detector

A direct assessment of the methane (CH4) emission level and its variability factors is needed in each animal species in order to target the best mitigation strategy for the livestock sector. Therefore, the present study aimed to (1) test a laser methane detector (LMD) for the first time in Italian Mediterranean buffaloes (IMB), a non-invasive tool to quantify CH4 emissions; (2) test the effect of season on the emissions; and (3) compare the results measured directly with the ones estimated with the existing equations. CH4 emissions of twenty non-productive IMB, under the same feeding regimen, were monitored for 12 days in summer and winter. Significantly higher THI (74.46 ± 1.88 vs. 49.62 ± 4.87; p < 0.001), lower DMI (2.24 ± 0.04 vs. 2.51 ± 0.03% DMI/kg live weight; p < 0.001) and lower emission intensities (0.61 ± 0.15 vs. 0.75 ± 0.13; p < 0.001) were found during the summer period when compared with winter. LMD was found to be a versatile tool to be used in buffaloes, and it was clear that a summer increase in THI could act as a stressor for the animals, influencing their emissions. In addition, measured emissions were significantly higher than when estimated with the existing equations (p < 0.001), suggesting the need for further research in this area.

Influence of Heat Stress on Intestinal Epithelial Barrier Function, Tight Junction Protein, and Immune and Reproductive Physiology

The potential threat of global warming in the 21^st century is on the ecosystem through many aspects, including the negative impact of rising global temperature on the health of humans and animals, especially domestic animals. The damage caused by heat stress to animals has been more and more significant as the worldwide climate continues to rise, along with the breeding industry's expanding scale and stocking density, and it has become the most important stress-causing factor in southern China. In this review, we described the effects of heat stress on animal immune organs and immune system. The much-debated topic is how hyperthermia affects the tight junction barrier. Heat stress also induces inflammation in the body of animals causing low body weight and loss of appetite. This review also discussed that heat stress leads to hepatic disorder, and it also damages the intestine. The small intestine experiences ischemia, and the permeability of the intestine increases. Furthermore, the oxidative stress and mitogen-activated protein kinase (MAPK) pathways have a significant role in stress-induced cellular and organ injury. The study has shown that MAPK activity in the small intestine was increased by heat stress. Heat stress caused extreme small intestine damage, enhanced oxidative stress, and activated MAPK signaling pathways.

Histological and hemodynamic characterization of corpus luteum throughout the luteal phase in pregnant and non-pregnant buffalos in relation to nitric oxide levels based on its anatomical determination

This study aims to compare the complete growth and development of corpus luteum (CL) in domestic buffalos from day 5 until day 40 after ovulation either in pregnant or non-pregnant animals and whether luteal vascularity (LV) with progesterone (P4) and nitric oxide (NO) could determine luteal functionality or not. Pluriparous buffalos (Bubalus bubalis) were categorized as pregnant (n = 6) or non-pregnant (n = 9) after pregnancy check at day 25. Animals were subjected to ultrasound analysis to determine the CL area (cm²) and LV. Blood sampling was performed following the Doppler examination. Ovarian tissue samples from non-pregnant buffalo genitalia (n = 18) and early pregnant buffalo genitalia (n = 3) were collected from great abattoirs. Luteal Doppler indices were lower in the pregnant group, while peak systolic velocity (PSV) was increased (p < 0.05) in the same pregnant females. Both P4 and NOMs were elevated (p < 0.05) in the pregnant group. There was a positive correlation (p < 0.01) between P4 and CL PSV. Based on our macroscopical examination, the CL of non-pregnant buffalos was classified into four stages. Histologically, stage I showed that CL was covered by a highly vascularized connective tissue (CT) capsule. It consisted of small and large lutein cells, whereas stage II was similar to stage I except for the presence of numerous fibroblast cells and vacuolated cells. Stage III was characterized by increasing the number of collagen fibers and the thickness of the blood vessels. Stage IV revealed thickening of the CT capsule and septae, regressed capillaries and arterioles, in addition to shrunken degenerated lutein cells. CL of pregnant buffalos revealed the same structure as CL at stage II. CL area was increased in the pregnant group. The collective data suggested that evaluation of the luteal artery could be extremely helpful to determine the potential benefits of colored and pulsed Doppler in CL vascularization assessment in both luteal and early pregnancy phases.

Rectifying cow infertility under heat stress by immunization against inhibin and supplementation of progesterone

This study was undertaken for the development of novel techniques that are based on immunoneutralization of inhibin bioactivity to improve Holstein cow fertility. A series of 4 experiments were carried out on 2 farms that were located in subtropical or temperate regions, to test the effects of immunization against inhibin alpha subunit on cow fertility under varying degrees of heat stress conditions. Though immunization against inhibin alone improved conception rate (CR) after TAI moderately in cows under mild heat stress conditions, the treatment plus progesterone supplementation substantially enhanced CR in the range of 25 to 35 percentages from severe heat stress to comfortable weather conditions. There existed an additive effect between immunization against inhibin and progesterone supplementation that maximally enhanced CR. Further, immunization against inhibin increased both FSH and activin A concentrations in blood during both follicular and luteal phases. It also significantly increased blood concentrations of E2 in the follicular phase but decreased P4 concentrations during the early pregnancy. However, interferon-tau concentrations in blood around the time of pregnancy recognition were doubled in the inhibin immunized cows. In conclusion, immunization against inhibin plus P4 treatment enhances ovarian follicle and the subsequent early embryo developments that help to greatly improve the fertility of Holstein dairy cows.

Impact of Environmental Pollution on Female Reproduction

The increased pollution in the world atmosphere is a global concern. Water, air, and soil are polluted by various sources, such as farm fertilizer, sewage industrial waste products, fumes, and plastics, which in turn impact human health. Plastics and other mixtures of waste affect live in the water. Moreover, the ecosystem is disrupted by the use of heavy metal-containing chemicals in agriculture, and those are eventually consumed by humans. The consequences are a significant negative impact on health including reproductive health, which impairs fertility in the human population. Reproductive functions are severely affected by different chemicals which may interfere with hormonal functions. Greater consequences are faced by the women as the number of germ cells present in the ovary is fixed during fetal life, and which are nonrenewable. From the production of ovum to fertilization, to implantation, and finally continuation of pregnancy, all are affected by the heavy metals and endocrine disruptors. Lifestyle modifications such as consumption of organic foods, plastic product avoidance, separation of residential areas from industrial/agricultural areas, proper waste disposal, and so on, may help to improve the situation.

Influence of PMSG on Superstimulation and Embryo Development Following Somatic Cell Nuclear Transfer in Holstein Cows in the United Arab Emirates

The present study investigated the effect of superstimulation to improve in vitro embryo production in the Gulf area, where the temperature is high. Holstein cows were classified into the control and superstimulation groups. Superstimulation was induced with a single intramuscular injection of pregnant mare serum gonadotropin (PMSG; 2500 IU) on day 14 of the estrus cycle (day 0; estrus). The development of follicles was evaluated by ultrasonography of the ovaries daily. At 40 h after the PMSG injection, oocytes were collected by the ovum pick-up (OPU) technique. OPU was performed at the same stage of the estrus cycle in the control group as in the superstimulation group. The number of follicles with a diameter of more than 6 mm and the number of retrieved cumulus-oocyte complexes were significantly higher in the superstimulation group than in the control group. Furthermore, the maturation rate was higher in the superstimulation group than in the control group. Cloned embryos were produced by somatic cell nuclear transfer using matured oocytes. The cleavage and blastocyst formation rates were significantly higher in the superstimulation group than in the control group. In conclusion, a single injection of PMSG can facilitate the efficient production of cloned cow embryos.

An Appropriate Genetic Approach for Improving Reproductive Traits in Crossbred Thai-Holstein Cattle under Heat Stress Conditions

Thailand is a tropical country affected by global climate change and has high temperatures and humidity that cause heat stress in livestock. A temperature−humidity index (THI) is required to assess and evaluate heat stress levels in livestock. One of the livestock types in Thailand experiencing heat stress due to extreme climate change is crossbred dairy cattle. Genetic evaluations of heat tolerance in dairy cattle have been carried out for reproductive traits. Heritability values for reproductive traits are generally low (<0.10) because environmental factors heavily influence them. Consequently, genetic improvement for these traits would be slow compared to production traits. Positive and negative genetic correlations were found between reproductive traits and reproductive traits and yield traits. Several selection methods for reproductive traits have been introduced, i.e., the traditional method, marker-assisted selection (MAS), and genomic selection (GS). GS is the most promising technique and provides accurate results with a high genetic gain. Single-step genomic BLUP (ssGBLUP) has higher accuracy than the multi-step equivalent for fertility traits or low-heritability traits.

The effect of high temperature and humidity on milk yield in Ankole and crossbred cows

Tropical regions are characterized by high temperature and humidity across the year. At high values of temperature humidity index (THI), there is a risk of heat stress leading to lower milk yield. The objective of this study was to describe the effect of season and the effect of maximum daily THI on milk yield of that day in purebred Ankole and Ankole-Friesian, Ankole-Jersey and Ankole-Sahiwal crosses in a tropical climate. In total, 53,730 records of daily milk yield from 183 cows in Rwanda were analyzed. The results showed that THI had a negative effect on daily milk yield above a threshold, but the effect was small (− 0.11 kg milk/THI unit at most). Purebred Ankole cows had the lowest daily milk yield and the lowest threshold (THI mean 66), as compared to the crossbreds (THI mean 68–69). Ankole-Friesian had a steeper decline in daily milk yield above the threshold than Ankole. The crossbreds, especially Ankole-Friesian, had higher daily milk yield than purebred Ankole also at very high THI. The results indicate some differences between breed groups in the way of coping with a hot and humid climate and raise questions about dairy cows’ adaptation to such a climate.

Evaluation of environmental parameters in a microregion in southern Amazonas State, Brazil, and their relationship with heat stress in dairy cattle

Abstract Environmental thermal comfort provides higher efficiency in the exploitation of dairy farming, as the responses of animals to the environment are decisive in the activity’s success. This study aimed to evaluate heat stress in dairy cows in the municipality of Humaitá, located in the south of theAmazonas State (AM), Brazil.Air temperature (TA) and relative humidity (RH) data were used to calculate the temperature humidity index (THI) in the dry (August 2020) and rainy seasons (January 2021). The August data were collected at the automatic weather station belonging to the National Institute of Meteorology. The January data were collected by a Hobo® U23-001 thermo-hygrometer installed at Fazenda Nossa Senhora Aparecida. The hourly and monthly means of the data were calculated and, subsequently, boxplots were plotted. TA and RH were 0.65 °C and 0.64% below the provisional climatological normal (PCN), respectively, for August, while January presented 0.77 °C and 3.61% above the PCN, respectively. THI values ranged from 56.25 (comfortable) to 84.68 (emergency) in August and 74.15 (comfortable) to 84.07 (emergency) in January. The maximum THI was observed in August, as well as the largest range. The results allow inferring that heat stress in dairy cows in the municipality of Humaitá-AM presents a state of alert even for cross-breed animals. Thus, the use of shading in pastures is suggested to minimize the effect of heat stress on the productive performance of the animals.

Avaliação de parâmetros ambientais em uma microrregião no sul do estado do Amazonas e suas relações com estresse térmico de bovinos leiteiros

Resumo O conforto térmico ambiental proporciona uma maior eficiência na exploração da pecuária leiteira, pois as respostas do animal ao ambiente são determinantes no sucesso da atividade. O objetivo deste trabalho foi avaliar o estresse térmico em vacas leiteiras no município de Humaitá, localizado no sul do estado do Amazonas (AM), Brasil. Foram utilizados dados de temperatura do ar (TA) e umidade relativa do ar (UR) para cálculo do Índice de Temperatura e Umidade (ITU) na estação seca (agosto de 2020) e na estação chuvosa (janeiro de 2021). Para o mês de agosto os dados foram coletados na estação meteorológica automática pertencente ao Instituto Nacional de Meteorologia. Em janeiro os dados foram coletados com o Termo-higrômetro (Hobo®, modelo U23-001) instalado na Fazenda Nossa Senhora Aparecida. As médias horárias e mensais dos dados foram feitas e, posteriormente, plotados gráficos boxplots. Os dados coletados para os meses do estudo apresentaram a TAe UR para o mês de agosto 0,65ºC e 0,64% abaixo da Normal Climatológica Provisória (NCP), respectivamente. Por outro lado, janeiro apresentou 0,77ºC e 3,61% acima da NCP, respectivamente. Os ITUs variaram entre 56,25 (confortável) e 84,68 (emergência), em agosto e de 74,15 (confortável) a 84,07 (emergência) em janeiro. O máximo ITU foi observado em agosto, bem como a maior amplitude. Baseados nos resultados encontrados pode-se aferir que o estresse térmico em vacas leiteiras no município de Humaitá-AM apresenta estado de alerta, mesmo para animais de raças cruzadas. Assim, sugere-se o uso de sombreamento nas pastagens para minimizar o efeito do estresse térmico no desempenho produtivo destes animais.

Systems biology under heat stress in Indian cattle

Transcriptome profiling of Vrindavani and Tharparkar cattle (n = 5 each) revealed that more numbers of genes were dysregulated in Vrindavani than in Tharparkar. A contrast in gene expression was observed with 18.9 % of upregulated genes in Vrindavani downregulated in Tharparkar and 17.8% upregulated genes in Tharparkar downregulated in Vrindavani. Functional annotation of genes differentially expressed in Tharparkar and Vrindavani revealed that the systems biology in Tharparkar is moving towards counteracting the effects due to heat stress. Unlike Vrindavani, Tharparkar is not only endowed with higher expression of the scavengers (UBE2G1, UBE2S, and UBE2H) of misfolded proteins but also with protectors (VCP, Serp1, and CALR) of naïve unfolded proteins. Further, higher expression of the antioxidants in Tharparkar enables it to cope up with higher levels of free radicals generated as a result of heat stress. In this study, we found relevant genes dysregulated in Tharparkar in the direction that can counter heat stress.

Genetics of tolerance to heat stress in milk yield of dairy buffaloes assessed by a reaction norm model

The objectives of this study were to assess the effects of heat stress on the milk yield and investigate the presence of genotype × environment interaction (G × E) in Brazilian Murrah buffaloes reared under tropical conditions. With this, 58,070 test-day (TD) records for milk yield from 3,459 first lactations of buffaloes collected between 1987 and 2018 were evaluated. A mixed model considering days in milk (DIM) and temperature-humidity index (THI) was applied to quantify milk yield losses due to heat stress. The most detrimental effect of THI on TD milk yield was observed in the mid-stages of lactation, after lactation peak, in DIM 105-154 and 155-204 days (-0.020 and -0.015 kg/day per THI, respectively). The least-squares means of TD milk yield were used to identify a heat stress threshold using a piecewise linear regression model. A substantial reduction in TD milk yield due to heat stress was observed for THI values above 77.8 (-0.251 kg/day per increase of 1 THI unit). An analysis using a single-trait random regression animal model was carried out to estimate variance components and genetic parameters for TD milk yield over THI and DIM values. Increased additive genetic variance and heritability estimates were observed for extreme THI values (THI = 60 and 80) combined with mid-lactation stages. The lowest genetic correlation (0.50) was observed between TD records at opposite extremes of the THI scale (THI = 60 vs. THI = 80). The genetic trends observed for the regression coefficients related to the general level of production (0.02) and specific ability to respond to heat stress (-0.002) indicated that selection to increase milk yield did not affect the specific ability to respond to heat stress until the present moment. These trends reflect the low genetic correlation between these components (0.05 ± 0.14). In this sense, monitoring trends of genetic components related to response to heat stress is recommended.

Relationship of the Temperature-Humidity Index (THI) with Ovarian Responses and Embryo Production in Superovulated Thai-Holstein Crossbreds under Tropical Climate Conditions

Heat stress strongly negatively affects reproductive traits in dairy cattle. The purpose of the present study was to investigate the effect of heat stress in superstimulated Thai-Holstein crossbreds under tropical climate conditions. Data included 75 records from 12 superovulated Thai-Holstein crossbreds between 2018 and 2020. Cows were superstimulated with conventional treatment. The mean temperature-humidity index (THI) was evaluated for three data collection periods: during the 9, 21 and 42-day periods before the insemination day to determine the period in which THI mostly affected superstimulation responses. The THI levels/thresholds were determined and interpreted together with the superovulatory response. A significantly negative correlation was obtained for the THI during the period 9 days before insemination. Negative effects on the number of large follicles and corpora lutea began at a THI of 72 and were apparently severe after a THI of 77, similar to the ovulation rate, fertilized ova and transferable embryos (p < 0.05). Meanwhile, more degenerated embryos were found with THI values (p < 0.05). The superovulatory response in Thai-Holstein crossbreds under tropical climate conditions is highly affected by heat stress starting at a THI of 72 and becomes more severe at a THI higher than 77.

Influence of Days after Calving and Thermal Stress on the Efficacy of a Progesterone-Based Treatment in Acyclic Italian Mediterranean Buffalo

Simple Summary

“Mozzarella di Bufala Campana DOP” (mozzarella cheese) is mainly produced and marketed during the spring and summer months. The buffalo is a seasonal species that increases its reproductive activity when daylight hours decrease. Therefore, to increase milk production in the favourable period, the so-called “Out of Breeding Season Mating” technique is applied. It consists of the interruption of sexual promiscuity during the naturally occurring breeding season and concentrating calving and milk production during periods of increasing daylight length. However, the application of this technique increases the incidence of anoestrus, as animals are forced to breed outside of their natural and favoured period of the year, although other factors can also increase the incidence of anoestrus, such as climate. A reduction of seasonal anoestrus can be achieved by using some hormonal treatments. In this study, primiparous acyclic buffaloes were selected and divided into three classes according to their days in milk. Animals were synchronized using P₄ vaginal implants, and artificial insemination (AI) was performed according to protocol. The temperature–humidity index (THI) was recorded to evaluate its influence on anoestrus. Statistical analysis showed that the implemented P₄-based treatments were highly effective in removing the anoestrus condition in buffaloes. On the contrary, no influence of the THI on the efficacy of the P₄ synchronization treatment was observed.

Abstract

The aim of this study was to evaluate the efficacy of a progesterone-based treatment on anoestrus in buffaloes. Primiparous acyclic buffaloes (n = 276), were divided into three classes according to their days in milk (DIM): from 50 to 90 (Class I; n = 86), from 91 to 150 (Class II; n = 102) and from 150 to 200 (Class III; n = 88). Animals were synchronized using P₄ vaginal implants, followed by timed artificial insemination (TAI). They were then allowed to enter into a larger group of buffaloes for natural mating 15 days after AI was performed, and pregnancy status was monitored from then on at 15-day intervals. Finally, the temperature–humidity index (THI) was calculated. Statistical analysis was performed by ANOVA by means and both multiple and linear regression. The total pregnancy rate (PR) was 87.7%, with no differences among DIM classes (88.0, 92.4, and 80.0% in Classes I, II, and III, respectively). However, the PR at TAI tended to be higher (p = 0.07) in buffaloes in Class II. The follicle (FL) area in Class II buffaloes was larger (p < 0.01) than that of the other classes. No influence of the THI on the total PR was recorded. The pregnancy outcome at TAI was affected by the FL area (odds ratio = 2.237; p < 0.05) and body condition score (BCS) (odds ratio = 1.256; p < 0.05). In conclusion, treatment with vaginal P₄ optimizes pregnancy rates in anoestrus buffaloes, particularly when the animals are in mid-lactation and show an optimal BCS. Furthermore, the THI does not seem to affect the efficiency of the progesterone treatment.

Physiological, oxidative and metabolic responses of lactating water buffaloes to tropical climate of South China

BACKGROUND

Heat stress in tropics is generally associated with significant economic losses resulting from reduced performance, morbidity, and mortality of livestock. To avoid serious consequences of heat stress, it is imperative to better understand the physiological responses and biochemical changes under the state of altered body homeostasis during different seasons of the year.

OBJECTIVES

This study aimed to evaluate the seasonal dynamics of physiological, oxidative and metabolic responses of lactating Nili-Ravi buffaloes to the tropical climate of South China.

METHODS

Physiological responses including rectal temperature (RT), body surface temperature (BST) and respiratory rate (RR) along with serum biochemical and antioxidant parameters of 20 lactating Nili-Ravi buffaloes were evaluated during different seasons of the year.

RESULTS

Higher temperature-humidity Index (THI) during the summer season (>80) resulted in a significant increases in RR and BST as compared to the winter season. Higher oxidative stress was observed in the summer season as revealed by significantly higher MDA while lower serum antioxidant enzyme (TAC, GSH-Px, SOD and CAT) contents. Moreover, serum cortisol was also significantly higher in summer and autumn. The levels of growth hormone and ACTH were also significantly (P < 0.05) lower in summer and autumn as compared to other seasons. The negative association of THI with physiological and antioxidant parameters was observed while it was positively associated with serum MDA and cortisol levels.

CONCLUSIONS

Our study revealed moderate heat stress in lactating buffaloes in the summer season which calls for attention to avoid economic losses and animal welfare issues.

Delineation of temperature-humidity index (THI) as indicator of heat stress in riverine buffaloes (Bubalus bubalis) of a sub-tropical Indian region

The erstwhile developed temperature-humidity index (THI) has been popularly used to indicate heat stress in dairy cattle and often in buffaloes. However, scientific literature suggests differences in thermotolerance and physiological responses to heat stress between cattle and buffalo. Therefore, THI range used to indicate degree of heat stress (mild, moderate, and severe) in cattle should be recalibrated for indicating heat stress in buffaloes. The present study was carried out to delineate THI range to indicate onset and severity of heat stress in buffaloes based on physiological, biochemical, and expression profiling of heat shock response (HSR) genes in animals at different THI. The result indicated early onset of heat stress in buffaloes as compared to cattle. Physiological and biochemical parameters indicated onset of mild signs of heat stress in buffaloes at THI 68-69. Significant deviation in these parameters was again observed at THI range 73-76. At THI 77-80, the physiological and biochemical responses of animals were further intensified indicating extreme alteration in homeostasis. The in vivo expression profiling of HSR genes indicated that members of Hsp70 gene family are expressed in a temporal pattern over different THIs, whereas expressions of Hsf genes were evident during intense heat stress. Overall, the study established that amplitude of heat shock response and THI range for indicating severity of thermal stress for buffaloes are not in unison to cattle. The study also suggests skin temperature of the poll region could be used as non-invasive tool for monitoring heat stress in dairy buffaloes.

Application of udder surface temperature by infrared thermography for diagnosis of subclinical mastitis in Holstein cows located in tropical highlands

Several reports have indicated that udder surface temperature (UST) can be a useful indicator of subclinical mastitis (SCM). The objective was to evaluate UST by infrared thermography (IRT) as a diagnostic tool for SCM and intramammary infection (IMI), and to assess the influence of environmental conditions in the potential diagnosis of this disease in dairy cows located at high-altitude tropical regions. A total of 105 cows (397 quarters) from 3 dairy farms with mechanical and manual milking methods were enrolled in the study. Subclinical mastitis was diagnosed when quarter samples had a somatic cell count (SCC) ≥200 × 10³ cells/mL, microbial growth (MG) was defined when a major pathogen (≥1 cfu/plate) or Corynebacterium spp. (≥10 cfu/plate) was isolated, and IMI was defined as the presence of MG and SCC ≥100 × 10³ cells/mL. Infrared images were taken with a thermal camera placed 1 m away from the udder, and shots of the rear and left and right lateral view were made during the morning milking, before any manipulation of the udder and employing dark cardboard on the contralateral side to avoid artifacts in the background. A multilevel mixed effects linear regression model clustered within cows and herd was performed to evaluate the associations with UST. Clinical performance was evaluated using the Youden index to establish the optimum UST thresholds, which were set at 32.6°C for any case definition when milking was by hand, at 33.7°C for MG, and at 34°C for SCM and IMI in machine-milked quarters. Sensitivity (Se), specificity (Sp), area under curve (AUC), and positive likelihood ratio (+LR) were also assessed. Test agreement was assessed by kappa coefficient (κ). The UST of healthy quarters ranged between (95% CI) 32.4 and 32.6°C, lower than SCM quarters (n = 88) at 32.9°C (95% CI: 32.7-33.1 °C), MG quarters (n = 56) at 33.5°C (95% CI: 33.3-33.7°C), and IMI quarters (n = 50) at 33.5°C (95% CI: 33.2-33.7 °C). The UST was also related to the milking method: higher temperatures were observed for hand milking (n = 90) compared with machine milking (n = 185). No relation between environmental conditions such as wind speed, atmospheric temperature, relative humidity, and temperature-humidity index and UST were observed during this study. For hand milking, the optimal UST threshold was 32.6°C; for SCM, Se = 0.53, Sp = 0.89, AUC = 0.71, κ = 0.4; for MG, Se = 0.83, Sp = 0.93, AUC = 0.88, κ = 0.77; and for IMI, Se = 0.82, Sp = 0.92, AUC = 0.87, κ = 0.74. The machine milking threshold for SCM resulted in Se = 0.42, Sp = 0.97, AUC = 0.70, κ = 0.47; for MG, Se = 0.82, Sp = 0.89, AUC = 0.85, κ = 0.60; and for IMI, Se = 0.82, Sp = 0.98, AUC = 0.90, κ = 0.79. These findings suggest that UST determined by IRT is higher in machine-milked cows and in quarters with MG and IMI than in healthy quarters; therefore, UST by IRT is a reliable, clinically useful method for MG and IMI diagnosis.

Heat shock during in vitro maturation of bovine oocytes disturbs bta-miR-19b and DROSHA transcripts abundance after in vitro fertilization

While microRNAs (miRNAs) are a class of non-coding RNAs important for embryo development, the relationship between them and heat stress during oocyte maturation has not yet been established. This study investigated the effect of heat shock during in vitro maturation (IVM) on the abundance of bta-miR-20a, -27b, -103, -21-5p, -19b, -1246 miRNAs and DROSHA and DICER1 mRNAs, previously reported for being involved in oocyte maturation, response to heat stress and miRNA biogenesis. Oocytes were exposed for 12h to heat shock during IVM, fertilized in vitro and the presumptive zygotes cultured for eight days. The relative quantification of miRNAs and mRNAs was performed by real-time PCR in vitro-matured oocytes and 8-cell stage embryos. Progression of meiosis, embryonic development and apoptotic indices was also evaluated. Heat shock compromised (p < .05) oocyte nuclear maturation, cleavage and embryo development, with a higher (p < .05) embryonic apoptotic index than the control group. The abundance of bta-miR-19b increased (p < .05) whereas the abundance of DROSHA transcripts decreased (p < .05) in embryos derived from heat-shocked oocytes. In conclusion, heat shock during IVM influences the abundance of bta-miR-19b and DROSHA in pre-implantation embryos, indicating a persistent effect of heat shock that can be associated with impaired embryo development.

Antioxidant Resveratrol Increases Lipolytic and Reduces Lipogenic Gene Expression under In Vitro Heat Stress Conditions in Dedifferentiated Adipocyte-Derived Progeny Cells from Dairy Cows

Heat stress (HS) induces oxidative stress by increasing reactive oxygen species (ROS), and the polyphenol resveratrol (RSV) has been shown to have antioxidant properties by reducing ROS. Hence, we aimed to examine the effects of RSV, HS and their interaction on bovine adipocytes. We generated bovine dedifferentiated adipocyte-derived progeny (DFAT) cells from subcutaneous adipose tissue and examined the effects of RSV (100 µM), heat conditions: isothermal (ISO-37 °C), short heat (SH-41.2 °C for 1 h) and long HS (LH-41.2 °C for 16 h), and their interaction on gene expression in DFAT-cells. In medium of DFAT-cells treated with RSV, malondialdehyde levels were reduced and oxygen-radical absorbance-capacity levels were increased compared to control. Treating DFAT-cells with RSV increased the relative mRNA expression of stress-induced-phosphoprotein-1 (STIP1) and the expression of hormone-sensitive-lipase (LIPE) and perilipin-1 (PLIN1), whereas it reduced the expressions of fatty-acid-synthase (FASN) and of pro-inflammatory chemotactic-C-C-motif-chemokine-ligand-2 (CCL2) also under HS. Moreover, reduced protein abundance of FASN was found in RSV-treated DFAT-cells compared to controls. Molecular docking of RSV with FASN confirmed its possible binding to FASN active site. This work demonstrates that RSV has an antioxidant effect on bovine DFAT cells and may induce adipose lipolysis and reduce lipogenesis also under in vitro HS conditions.

Physiological, Biochemical, and Growth Parameters of Fogera Cattle Calves to Heat Stress during Different Seasons in Sub-Humid Part of Ethiopia

Simple Summary

Evaluation of Fogera cattle breed during the different seasons would help to determine their response to heat stress. This would assist in designing intervention strategies for the anticipated climate change. Therefore, this study aimed to determine physiological, hematological, biochemical, and growth parameters of Fogera cattle calves to heat stress in different seasons. We observed that the heart rate and respiration rate were increased by six beats per minute and four breaths per minute when the temperature-humidity index increased from 66 to 78, respectively. The positive relationship between the temperature–humidity index and physiological parameters further confirms that calves were good at thermoregulation at a temperature–humidity index value of 66. Thus, the temperature-humidity index value of 66 can be considered as optimum for high weight gain and normal physiological response to heat stress in Fogera cattle calves under their current production system. However, some more amelioration strategies such as better nutrition, availability of shade, and routine health management practice will further strengthen the resilience of the breed to heat stress in the future.

Abstract

Fogera cattle are among indigenous breeds of cattle in the northern part of Ethiopia. However, their response to heat stress (HS) under different seasonal variations has not been well investigated. This study was aimed to determine physiological, hematological, biochemical, and growth parameters of Fogera cattle calves to HS during dry season, short rainy, and long rainy. A total of 72 calves (24 for each season) that were 6 months of age with an equal number of males and females were evaluated for physiological, hematological, biochemical, and growth parameters. Daily ambient temperature (AT) and relative humidity (RH) were recorded two times per day during the study periods from which the daily average temperature–humidity index (THI) was calculated. The study revealed higher AT and THI during dry and short seasons while higher RH was observed during the long rainy season. Physiological parameters except rectal temperature were affected by the seasons. Hematological parameters were also affected by season except for packed cell volume. Biochemical and growth parameters were also significantly affected by the seasons. THI was positively related with physiological but negatively with growth parameters. Thus, the THI value of 66 can be considered as optimum for high weight gain and normal physiological response to HS in Fogera cattle calves under their current production system.

Sperm Global DNA Methylation (SGDM) in Semen of Healthy Dogs

Male infertility is an emerging problem in both humans and animals, and the knowledge of its causes is the first step to identifying new diagnostic and therapeutic strategies. In humans, alteration of sperm DNA methylation have been related to poor quality semen, impaired seminal parameters, azoospermia and reduced fertility. Although semen analysis is routinely used to evaluate the male reproductive potential in the canine species, no authors have attempted to relate semen characteristics to the sperm global DNA methylation (SGDM). The aim of this study was to evaluate the SGDM level in healthy dogs and to correlate it with semen parameters that are currently used in dog semen analyses. Conventional and unconventional (sperm DNA fragmentation and SGDM) seminal parameters of thirty dogs from different breeds were evaluated. A positive correlation was found between SGDM and sperm concentration (r = 0.41; p < 0.05), and total sperm count (r = 0.61; p < 0.001); SGDM was significantly lower in oligozoospermic vs non-oligozoospermic dogs (4.3% vs. 8.7%; p < 0.005). Our findings suggest that SGDM levels are related to conventional seminal parameters, and could be used as a marker of testis function and spermatogenesis in dogs.