Heat tolerance in Brazilian hair sheep

Physiological responses of Munjal sheep to variations in temperature humidity index in subtropical climate

Understanding the relationship between physiological parameters of livestock and temperature humidity index (THI) is essential for developing effective management strategies aimed at mitigating heat stress, especially during periods of elevated temperatures. The present study examined the physiological parameters of rectal temperature (RT), respiration rate (RR), and pulse rate (PR) in Munjal sheep reared in a subtropical climate, focusing on their association with THI. Data were collected from 29 female Munjal sheep at 15-day intervals, during morning (8:00 a.m.-10:00 a.m.) and afternoon (2:00 p.m.-4:00 p.m.) over one year. Results showed that RT was significantly higher in the afternoon compared to the morning for both lambs and adults. Likewise, RR and PR were elevated in the afternoon across both groups. In young lambs, RT (r = 0.86) and RR (r = 0.71), and in adults, RR (r = 0.89) and PR (r = 0.91) demonstrated a significant positive correlation (P < 0.05) with THI. These findings indicate that higher physiological parameters during hotter periods necessitate additional care for young lambs. In conclusions, this study highlighted the critical need for targeted management practices to support the physiological well-being of Munjal sheep in subtropical climates, particularly during periods of high temperature humidity index, ensuring optimal health and productivity.

Effects of heat stress on reproduction and gene expression in sheep

Small ruminant farming plays a pivotal role in agriculture, especially in developing countries due to sheep's diverse functions and capacity to acclimate to varying temperatures. This review comprehensively explored the impact of rising temperatures on reproductive processes, reproductive function encoding gene expression, and sheep's ability to adapt to heat stress. Several mechanisms contribute to sheep's resilience to heat stress, encompassing morphological, behavioral, physiological, and genetic adaptations. It has been shown that heat stress compromises fertility by affecting follicular development, ovulation rate, estrous behavior, rates of conception, embryonic survival, and fetal development, while also disrupting sperm production and motility, and increasing the incidence of structurally abnormal sperm in males. Estimates suggested that heat stress may reduce conception rates from 20% to 27%. Essential genes encoding the Gonadotrophin-releasing hormone, Follicle-stimulating hormone receptor, Luteinizing hormone receptor, Estradiol receptor, progesterone receptor, and Inhibin play a critical role in elucidating how heat stress impacts the reproductive performance of sheep. Furthermore, the resilience of sheep in facing heat stress adversities is associated with a specific heat shock factor. When an animal is under heat stress, Heat shock factors get activated and stimulate the production of Heat Shock Proteins (HSPs). Emphasis should be given to identifying specific genes and candidate genes that confer protection against heat stress and conducting comprehensive research to unravel how sheep adapt to demanding local climatic conditions to enhance production and profitability, improve animal welfare, and for genetic conservation and breeding programs.

Characterizing the Phan Rang Sheep: A First Look at the Y Chromosome, Mitochondrial DNA, and Morphometrics

The Phan Rang sheep, considered the sole indigenous breed of Vietnam, are primarily concentrated in the two central provinces of Ninh Thuan and Binh Thuan, with Ninh Thuan accounting for more than 90% of the country's sheep population. These provinces are known for their high temperatures and frequent droughts. The long-standing presence of the Phan Rang sheep in these regions suggests their potential resilience to heat stress-a trait of increasing interest in the face of global climate change. Despite the breed's significance, a critical knowledge gap hinders conservation and breeding programs. To address this, our study employed a two-pronged approach. First, we collected body conformational data to aid in breed identification. Second, we analyzed mitochondrial DNA (D-loop) and Y chromosome markers (SRY and SRYM18) to elucidate the maternal and paternal lineages. Among the 68 Phan Rang sheep analyzed for their D-loop, 19 belonged to mitochondrial haplogroup A, while 49 belonged to haplogroup B. The haplogroups can be subdivided into 16 unique haplotypes. All 19 rams surveyed for their paternal lineages belonged to haplotypes H5 and H6. These findings strongly support the hypothesis of dual origins for the Phan Rang sheep. This study presents the first genetic data for the Phan Rang breed, providing crucial insights for future research and conservation efforts.

Effect of Heat Stress on Lactating and Non-Lactating Blackbelly Ewes under Tropical Conditions during Summer

Two groups of ewes (10 lactating and 10 non-lactating) were used to evaluate the effect of heat stress during summer under tropical conditions. In this study, a temperature and humidity index (THI) was found that ranged between 65 and 79 (morning and afternoon). Likewise, a heat tolerance coefficient (HTC) of 6 units was observed. The highest breathing frequency (BF; 115.46 ± 35.25 breaths per minute (bpm)) and rectal temperature (RT; 38.95 ± 0.51 °C) were found during the afternoon in the group of lactating ewes. The means were compared by group, time of the day, and interaction, and only significant differences were found between groups for RT and udder temperature (p < 0.001). In the case of time of day, all parameters were higher during the afternoon, regardless of the group of ewes (p < 0.001). Likewise, an interaction was found in the parameters RT, right paralumbar fossa (RPF), rump, leg, and udder (p < 0.001). In conclusion, Blackbelly ewes lactating during the summer in the tropics have higher skin temperatures, and also raise BF and RT to tolerate HS in tropical climates.

Blood biochemical, hormonal, and hematological responses of native sheep submitted to different environmental conditions

The aim of this study was to evaluate the biochemical, hormonal, and hematological blood responses of native sheep subjected to five temperatures (20°, 24°, 28°, 32°, and 36 °C), using 24 sheep of the following breeds: Santa Inês (SI), Morada Nova (MN), Soinga (SO) and no defined racial pattern (NDRP), kept in collective pens inside the climatic chamber. The experimental design was completely randomized, in a 5 × 4 factorial scheme (5 temperatures and 4 breeds) with 6 animals of each breed at each temperature. There was interaction for urea (P < .0001), glucose (P < .0001), cholesterol (P < .0001), and magnesium (P < .0001) as a function of breed and air temperature. Urea (P = .001), glucose (P < .0001), triglycerides (P = .033), cholesterol (P = .004), and magnesium (P < .0001) showed differences according to breed. It was observed that T4 (P < .0001) and cortisol (P < .0001) showed an interaction between breed and temperature, while T4 (P = .001) and cortisol (P = .001) an effect of breed. The highest magnesium concentration was observed in MN, and the lowest was in NDRP, SO, and SI, which are statistically similar, and SI and NDRP are statistically similar. The hormones showed a significant effect (P < .0001) for temperature, where cortisol increased, and thyroid hormones decreased with increasing temperature. Temperatures of 32° and 36 °C contribute to changes in blood, hormone, and hematological biochemical responses of native sheep.

Environmental adaptability, morphometric features with reproductive and productive potentialities of indigenous sheep in Bangladesh

Indigenous sheep are highly adaptable and widely distributed in different regions of Bangladesh. They are famous for their tolerance to harsh environmental conditions, low demand for feed, and disease resistance with minimum or no housing and management facilities. Ample indiscriminate research reports and case studies on the native sheep of Bangladesh have been published. Nonetheless, a comprehensive review of reproductive and productive performances, as well as their various morphometric physiognomies and climate resilience capabilities, is lacking. This review was designed to explore and summarize the available research reports on indigenous sheep to highlight the gaps and provide an updated database for the future research plan for sustainable native sheep production in Bangladesh. It covers studies on sheep biodiversity, their adaptability to the local environment, morphometric features, feeding and nutrition, reproduction and production performances, diseases and health management, and the problems and prospects of sheep farming in Bangladesh. Due to the increased demand for animal protein, especially red meat, the scope of sheep farming increases along with that of other large and small ruminants. The vital constraints of sheep production in Bangladesh include insufficient feed and fodder supply with its high prices, higher disease occurrence with low or no management practices, kid mortality, and a poor marketing channel with the lower popularity of sheep meat than goat meat. Future research would be a prerequisite to measuring the impact of native sheep on household economies and food security during the year, evaluating the other challenges, and finding out the possible interventions in the fields of nutrition, reproduction, and health management.

The effect of tree shade on ambient conditions and heat stress indicator traits of new-born South African Mutton Merino and Dormer lambs: Preliminary results

This preliminary study investigated the provision of shade on heat stress indicators of South African Mutton Merino (SAMM) and Dormer lambs shortly after birth, during the autumn 2017 and 2018 lambing seasons. Newborn lambs were assessed to determine whether welfare, as assessed by respiratory response and rectal temperature as heat stress indicators, survival and early growth benefitted from the provision of shade. Groups consisting of 4-17 pregnant SAMM and Dormer ewes were randomly allocated to 5-10 paddocks with natural shade from trees and 5-9 paddocks that were directly in the sun with no shade available. The lambs were recorded within 24 h of birth at noon. Climate data were obtained from a nearby weather station. The lambs were also weighed at 12 (SD = 2) days of age at tail-docking. Tree shade had a moderating effect on temperature, resulting in lower maximum daytime and higher minimum night-time temperatures. There was an interaction between a temperature-humidity index (THI) and the treatments (access to shade or no access to shade) for respiration and rectal temperature (P < 0.01). Both traits were relatively unaffected by the THI at values below 77. Unshaded lambs exhibited a pronounced upwards trend following a THI-threshold of 77-78. Tailing weight tended to be higher while lamb survival of live-born lambs to tail-docking was lower in lambs born in shaded paddocks but these trends did not persist to weaning. Shade is needed to enhance animal welfare by alleviating the effect of high THI-values on hot days in an autumn lambing season.

Influence of season and external morphology on thermal comfort and physiological responses in bulls from two breeds adapted to a subtropical climate

ABSTRACT Animals in subtropical regions can be exposed to periods of thermal stress. Locally adapted breeds are especially important in this context, but these have little information available in their natural environments. The aim of this study was to assess whether season affects thermal comfort and physiological responses to increased temperatures of two breeds of bulls in a subtropical climate. Four Angus and four Crioulo Lageano bulls were used in this study. Body and testicles measurements, skin pigmentation and thickness, hair number, length and pigmentation, respiratory rate, panting score, rectal temperature and haematological profile were recorded on three occasions in summer and winter, morning and afternoon. The surface temperature of the flank, eye and scrotum were obtained by infrared thermography. Hair coat colour was determined by CIELAB method. Thermal comfort indexes were calculated from meteorological data. Statistical analysis included analyses of variance, correlations and a partial least squares regression in determining which traits were the most important in thermal adaptability. External morphology of the bulls was important for explaining physiological changes in both seasons, but their contribution was greater in summer. Bulls experienced moderate heat stress in summer, which led to significant physiological responses, which were more pronounced in Angus bulls. The main differences in thermal adaptation found between breeds were the hair coat characteristics and respiratory rate. Despite using different mechanisms to cope with environmental challenges, all bulls were able to maintain optimal testicular thermoregulation as well as systemic normothermia throughout the seasons, showing good adaptation to the climate conditions.

Heat stress effects on sheep: Are hair sheep more heat resistant?

Climatic variables can trigger physiological, biochemical, haematological and hormonal alterations that influence the maintenance of homeothermy and can affect production and productivity in sheep. Different mechanisms are responsible for tolerance to heat stress (HS) including coat and skin colour, body size, fat distribution, physiological reactions and not just coat type (hair/wool). This review looks at physical, physiological, molecular and genetic aspects of heat tolerance in sheep and how they affect hair and wool sheep. We propose that it is the adaptation to hot environments and not the type of coat (wool/hair) itself that determines the capacity of the resistance of the animal to HS, due to modifications in essential pathways such as energy metabolism, physiological responses and body size. When studied in similar environments, commercial wool breeds tend to show higher heat stress, but hair breeds tend not to differ from wool breeds that are adapted to hot environments.

Adaptation Mechanisms of Small Ruminants to Environmental Heat Stress

Simple Summary

Heat stress is an intriguing factor that negatively influences livestock production and reproduction performance. Sheep and goat are among the livestock that can adapt to environmental heat stress via a combination of physiological, morphological, behavioral, and genetic bases. Sheep and goat are able to minimize adverse effect of high thermal stress by invoking behavioral responses such as feeding, water intake, shade seeking, and increased frequency of drinking. Their morphological mechanisms are comprised of body shape and size, light hair color, lightly pigmented skin, and less subcutaneous fat, and the physiological means are that of increased respiration rate (RR), increased sweating rate (SW), reduced metabolic rate, and change in endocrine function. Adaptation in terms of genetics is the heritable trait of animal characteristics which favor the survival of populations. For instance, genes like heat shock proteins 70 (HSP70) and ENOX2 are commonly expressed proteins which protect animals against heat stress.

Abstract

Small ruminants are the critical source of livelihood for rural people to the development of sustainable and environmentally sound production systems. They provided a source of meat, milk, skin, and fiber. The several contributions of small ruminants to the economy of millions of rural people are however being challenged by extreme heat stress difficulties. Heat stress is one of the most detrimental factors contributing to reduced growth, production, reproduction performance, milk quantity and quality, as well as natural immunity, making animals more vulnerable to diseases and even death. However, small ruminants have successfully adapted to this extreme environment and possess some unique adaptive traits due to behavioral, morphological, physiological, and largely genetic bases. This review paper, therefore, aims to provide an integrative explanation of small ruminant adaptation to heat stress and address some responsible candidate genes in adapting to thermal-stressed environments.

Effects of transport stress on physiological responses and milk production in lactating dairy cows

Objective

This study was conducted to investigate the effect of transport stress on physiological and hematological responses and milk performance in lactating dairy cows.

Methods

Ten lactating dairy cows were randomly divided into 2 groups. The treatment group (TG) was transported 200 km for 4 h by truck, and the control group (NTG) was restrained by stanchion for 4 h in Konkuk University farm. Blood and milk samples were collected at 24 h pre-transport; 1, 2, and 4 h during transport; and 2, 24, and 48 h post-transport. Milk yields were measured at 24 h pre-transport, 0 h during transport, and 24, 48, and 72 h post-transport.

Results

Leukocyte, neutrophil, and monocyte numbers in the TG were significantly higher than those of the NTG at each experimental time point. Lymphocyte numbers in the TG were significantly (p<0.05) higher than those of the NTG at 48 h post-transport. Additionally, the neutrophil:lymphocyte ratio of the TG was 45% and 46% higher than that of the NTG at 4 h during transport and 2 h post-transport, respectively. There were no significant differences in erythrocyte numbers, hemoglobin concentrations, platelet numbers, and hematocrit percentages between two groups. Cortisol levels in the TG were significantly (p<0.05) higher than those in the NTG. Milk yields in the TG were lower than those in the NTG. The somatic cell count (SCC) of the TG was significantly (p<0.05) higher than that of the NTG at 1 and 2 h during transport; that of the TG increased dramatically at 1 h during transport and gradually decreased subsequently.

Conclusion

Transport stress increased blood parameters including leucocyte, neutrophil, and monocyte numbers by increased cortisol levels, but did not affect erythrocytes, hemoglobin and hematocrit levels. Additionally, transport resulted in a decrease in milk yield and reduced milk quality owing to an increase in milk SCC.