Heat loss efficiency and HSPs gene expression of Nellore cows in tropical climate conditions

Characterization of the Temperament and Reactivity of Nelore Cattle (Bos indicus) Associated with Behavior Scores during Corral Management in the Humid Tropics

The evaluation of the reactivity and distress of cattle during corral management, by means of subjective scores, aims at the standardization of behavioral indicators, through non-invasive methods, in addition to enabling the development of more appropriate management practices, thus promoting the comfort and well-being of these animals. Therefore, in this study, we aimed to characterize the temperament and distress of cattle managed in a corral using behavioral indicators during the rainiest period. For this, the experiment was conducted on a property located in the municipality of Mojuí dos Campos, during the rainiest quarter (February-April). Thus, 30 male cattle, not castrated, approximately 29 months of age, clinically healthy, and weighing 310 + 20 kg, were divided into three rearing systems: silvopastoral (SP), traditional (SS), and integrated (SI) systems. There were 10 animals per system. Physiological parameters were collected to evaluate rectal temperature (RT) and respiratory rate (RR), as well as body surface temperature (BST), through thermal windows (head and flank infrared temperature and rump infrared temperature). To evaluate temperament and reactivity, scores indicative of corral behavior were used, namely escape speed (ES), tension score (SS_1), tension score (SS_2), reactivity scale (RS), movement score (MS), and temperament scale (TS). The results showed that there was a thermal amplitude of 5.9 °C on average and 8.6 °C at maximum when comparing the structure of the corral and the trees. In addition, the comparisons between the production systems for the behavioral variables did not differ at the 5% significance level, except for ES, where the traditional system differed from the integrated system and the silvopastoral system, showing intermediate average values for both. In addition, there was a positive correlation between the variables RT and RR (r = 0.72; p < 0.01), RR and SS_2 (r = 0.38; p = 0.04), flank infrared temperature and MS (r = 0.47; p = 0.01), rump infrared temperature and RS (r = 0.37; p = 0.04), SS_1 and RS (r = 0.41; p = 0.02), SS_1 and SS_2 (r = 0.39; p = 0.03), RS and SS_2 (r = 0.58; p = 0.00), RS and MS (r = 0.50; p = 0.01), RS and TS (r = 0.61; p = 0.00), SS_2 and MS (r = 0.51; p = 0.00), SS_2 and TS (r = 0.47; p = 0.01), and MS and TS (r = 0.44; p = 0.02), and a negative correlation between ES and TS (r = -0.42; p = 0.02). The rainy season had a major influence on the evaluation of temperature and distress levels during handling in the corral, as evidenced by the association between physiological and behavioral parameters.

Characterization of Thermal Patterns Using Infrared Thermography and Thermolytic Responses of Cattle Reared in Three Different Systems during the Transition Period in the Eastern Amazon, Brazil

In the Lower Amazon mesoregion, there are basically three types of production systems: the traditional (without shade and no bathing area), the silvopastoral (with shade and no bathing area), and the integrated (with shade and bathing area). It is considered that the type of production system influences the thermal comfort and productivity of cattle, so this research aims to evaluate the influence of these three types of production systems on the thermoregulation of Nellore cattle. The experiment was carried out on a rural property for raising cattle, located in Mojuí dos Campos, Pará, Brazil, during the transition period (June/July). Thirty bovine males (not castrated, aged between 18 and 20 months, average weight of 250 ± 36 kg, body condition score of 3.5, clinically healthy) were randomly divided into three groups: Silvopastoral System-SS (n = 10), Traditional System-TS (n = 10), and Integrated System-IS (n = 10). Climate variables were collected (air temperature (AT °C), relative humidity (RH %), wind speed (WS, m/s), solar radiation (SR), black globe temperature (BGT °C), and physiological parameters, such as respiratory rate (RR) and rectal temperature (RT)) at 6 a.m., 12 p.m., 6 p.m., and 12 a.m. to determine the thermal comfort situation of the animals. Thermographic images of the environment and animals were captured in order to obtain the body surface temperature (BST) through infrared thermography. The Benezra Thermal Comfort Index (BTCI), Environmental Stress Index (ESI), Equivalent Temperature Index (ETI), and Iberian Heat Tolerance Index (Iberian HTI) were used. The results showed that the silvopastoral system, with shading by chestnut trees and an ample vegetative area, presented better thermal conditions, with an average of 28.98 °C, in comparison with the traditional system (35.93 °C) and the integrated one (34.11 °C). It was observed that the body surface temperature of cattle did not differ significantly between the anatomical regions of the body and the studied systems (p > 0.05). As for the respiratory rate, the traditional system registered higher values, with an average of 41 movements per minute, indicating possible thermal stress (p < 0.05). The thermal comfort indices revealed that all systems presented moderate stress conditions during times of higher solar intensity. It is concluded that the silvopastoral system proved to be more favorable for cattle, providing shade and reducing thermal stress, which may have a positive impact on animal welfare and productivity in this region.

Organic selenium supplementation on metabolic profile of dairy goats

The aim of this study was to evaluate the effect of organic selenium (SE) supplementation on blood constituents related to hematology and serum biochemistry of dairy goats in the productive phase. A total of 16 lactating Saanen × Toggenburg crossbred goats, aged between 2 and 3, lactating, nonpregnant, clinically healthy, and having a body weight (BW) of 40.75 ± 8.31 kg were selected for this study. Higher SE concentrations were observed on the 42^nd day of supplementation, and on the 63^rd day, the SE concentrations were similar ([Formula: see text]) to the 21^st and 42^nd days. There was no interaction for plasma constituents comparing treatment effects and days of supplementation ([Formula: see text]). SE supplementation reduced ([Formula: see text]) plasma proteins with a gradual increase in available SE. There was no difference ([Formula: see text]) for the blood count comparing the effects of treatment and days of supplementation. There was no interaction ([Formula: see text]) for serum biochemical constituents between treatments and periods, except for urea ([Formula: see text]). Animals that received SE supplementation had similar plasma urea concentrations before and after supplementation, while animals that did not receive SE in the diet had increased serum urea concentrations. The main action of selenium in metabolism occurred in the reduction of plasma proteins and urea levels, which leads us to conclude that it influenced protein metabolism. Finally, hematology, liver function, and energy metabolism are not affected by selenium supplementation in dairy goats reared in semiarid conditions.

Effects of the bovine SLICK1 mutation in PRLR on sweat gland area, FOXA1 abundance, and global gene expression in skin

The SLICK1 mutation in the prolactin receptor (PRLR) results in a short-hair coat and increased ability to regulate body temperature during heat stress. It is unclear whether the mutation affects capacity for sweating. The objective of this observational study was to evaluate whether the SLICK1 mutation in PRLR alters characteristics of skin related to sweat gland abundance or function. Skin biopsies from 31 Holstein heifers, including 14 wild-type (SL^-/-) and 17 heterozygous slick (SL^+/-), were subjected to histological analysis to determine the percent of the surface area of skin sections that are occupied by sweat glands. We detected no effect of genotype on this variable. Immunohistochemical analysis of the forkhead transcription factor A1 (FOXA1), a protein essential for sweating in mice, from 6 SL^-/- and 6 SL^+/- heifers indicated twice as much FOXA1 in sweat glandular epithelia of SL^+/- heifers as in SL^-/- heifers. Results from RNA sequencing of skin biopsies from 5 SL^-/- and 7 SL^+/- heifers revealed few genes that were differentially expressed and none that have been associated with sweat gland development or function. In conclusion, results do not support the idea that the SLICK1 mutation changes the abundance of sweat glands in skin, but do show that functional properties of sweat glands, as indicated by increased abundance of immunoreactive FOXA1, are modified by inheritance of the mutation in PRLR.

Polymorphism of the beta-casein gene and adaptability of Sindhi cows to semiarid conditions

This study aimed to investigate the effect of beta-casein genotypes (A1A2 and A2A2) in three different thermal comfort conditions on the adaptability of Sindhi cows and as a tool for selecting thermotolerant cattle. Twelve Sindhi cows were used in a completely randomized design in a 2 × 3 factorial arrangement, with six replicates, with two genotypes, and three thermal comfort conditions. The climatic variables were recorded, while black globe temperature, humidity index, and radiant heat load were calculated. We measured respiratory rate, surface temperature, and rectal temperature while the heat tolerance coefficient was calculated. Genotype had no significant effect (p > 0.05) on any of the parameters measured. However, there was a thermal comfort condition effect (p < 0.05) on rectal temperature, surface temperature, and thermal gradients. The respiratory rate and heat tolerance coefficient were not significantly affected (p > 0.05). Therefore, although the results indicate substantial adaptability of Sindhi cows under any thermal conditions, the tested genotypes should not be used as a tool for selecting thermotolerant Sindhi cows.

Identification and in silico characterization of structural and functional impacts of genetic variants in milk protein genes in the Zebu breeds Guzerat and Gyr

Whole genome sequencing of bovine breeds has allowed identification of genetic variants in milk protein genes. However, functional repercussion of such variants at a molecular level has seldom been investigated. Here, the results of a multistep Bioinformatic analysis for functional characterization of recently identified genetic variants in Brazilian Gyr and Guzerat breeds is described, including predicted effects on the following: (i) evolutionary conserved nucleotide positions/regions; (ii) protein function, stability, and interactions; (iii) splicing, branching, and miRNA binding sites; (iv) promoters and transcription factor binding sites; and (v) collocation with QTL. Seventy-one genetic variants were identified in the caseins (CSN1S1, CSN2, CSN1S2, and CSN3), LALBA, LGB, and LTF genes. Eleven potentially regulatory variants and two missense mutations were identified. LALBA Ile60Val was predicted to affect protein stability and flexibility, by reducing the number the disulfide bonds established. LTF Thr546Asn is predicted to generate steric clashes, which could mildly affect iron coordination. In addition, LALBA Ile60Val and LTF Thr546Asn affect exonic splicing enhancers and silencers. Consequently, both mutations have the potential of affecting immune response at individual level, not only in the mammary gland. Although laborious, this multistep procedure for classifying variants allowed the identification of potentially functional variants for milk protein genes.

Silvopastoral system is an alternative to improve animal welfare and productive performance in meat production systems

Climate change is a reality and global surface temperature is projected to rise substantially in the next 80 years. Agriculture practices will have to adapt to climate change, and also help to mitigate this effect using, among other strategies, forest conservation and management. Silvopastoral systems have been adopted in tropical climate livestock areas but their benefits on thermal comfort and reproductive performance of beef cows are not completely known. Therefore, our aims were to compare the microclimate of silvopastoral and intensive rotational unshaded grazing systems in different months and to evaluate physiological variables (Exp. 1 and 2), metabolism, and in vitro embryo production (Exp. 2) in crossbred beef females. Our hypothesis is that the silvopastoral system can improve the thermal comfort of beef heifers and cows and, consequently, also improve dry matter intake, body weight gain, and in vitro embryo production when compared to the unshaded rotational grazing system. In Exp 1, the silvopastoral system decreased body temperature and increased welfare and performance of heifers. In Exp. 2, the silvopastoral system enhanced the body weight but did not affect metabolism and the general reproductive performance, but increased the recovery rate of oocytes in primiparous cows.

The specific enthalpy of air as an indicator of heat stress in livestock animals

Along with recognition of environmental effects on the performance and welfare of livestock animals, studies have been proposing new methodologies and parameters to diagnose the heat stress of animals through the physical properties of air. This article aims to present the state-of-the-art on the use of the specific enthalpy of air as an indicator of heat stress in livestock animals. As a starting point, conceptual considerations were made about the connection between homoeothermic animals and the environment. Variables for heat stress evaluation based on psychrometric air properties are then described, including dry bulb temperature and relative humidity, which are often used microclimate variables, and the specific enthalpy of dry air, which acts as a thermal comfort index. Final considerations highlight the recent history of the use of specific enthalpy of air equations as indicators of heat stress in livestock animals, with the intention of better understanding the relationship between animals and the environment. As a conclusion, the specific enthalpy of air is recommended as an indicator in the assessment of livestock housing conditions as, unlike other indices, it is based on thermodynamic air properties and not on linear regressions.

Locally adapted goats efficiently gain and lose heat in an equatorial semi-arid environment

The aim of this study was to gain insights in respect to how locally adapted goats exhibit dynamic body heat in an equatorial semi-arid environment. Ten Canindé goats were used in the study (22.90 ± 2.70 kg). Respiratory rate (R_R; min breaths^-1), rectal temperature (R_T; °C) and sweating rate (S_R; g m^-2 h^-1) were measured for 8 days, once a week, for 8 consecutive weeks in each animal, with collection intervals of 1 h throughout the day (24 h), together with the meteorological variables. Air temperature (A_T, °C) and relative humidity (R_H, %) were measured, and then, the temperature humidity index (T_HI) was calculated. First, we determined 2 days with stressful climatic conditions and similar environmental characteristics (day 1 and 2) among the 8 experimental days. The R_T was evaluated on these 2 days using the means of each hour as the cut-off point, and determining whether the animals are efficient (EF) or inefficient (INEF) in heat loss (β₁) and gain (β₂). The R_T was separated in β₁ and β₂ for 24 h, setting times to obtain the angular coefficients (β) for both. The days with stressful climatic conditions and similar environmental characteristics were day 1 and 2. The hours in which the Canindé goats gained and lost heat were respectively 11 a.m. to 3 p.m. and from 4 p.m. to 10 a.m. The animals classified as EF lost more or equal the amount of heat represented for R_T. When the mean of all animals was evaluated for efficiency in heat control, the flock was classified as EF. Differences (P < 0.05) were observed for R_R and S_R between periods. The efficiency in dynamic body heat of the locally adapted goats in this study was determined and showed that the flock as a whole possesses an excellent heat dynamic in an equatorial semi-arid environment.

Sensitivity, Impact and Consequences of Changes in Respiratory Rate During Thermoregulation in Livestock – A Review

This review discusses the thermal conservative and heat dissipating roles of one of the most sensitive thermoregulatory variables (respiratory rate) with the aim of enhancing its application in evaluating both cold and heat adaptation. During cold exposure, livestock enhance the economy of body heat through reduction in respiratory rate with the extent of reduction being greater and commencing at relatively higher ambient temperature in poorly adapted phenotypes. This is accompanied by an increase in tidal volume and alveolar oxygen uptake, but a decrease in partial pressure of oxygen. On the other hand, heat stress induces increase in respiratory rate to enhance evaporative heat loss with the magnitude of such increase being greater and commencing at relatively lower ambient temperature in phenotypes that are poorly-adapted to heat. This is accompanied by a decrease in tidal volume and the development of hypocapnia. The increase in respiratory rate is observed to be greater, moderate and lesser in livestock that are mainly (pigs, rabbits and poultry), moderately (sheep, goats and Bos taurus) and less (Zebu cattle) dependent on respiratory evaporative heat loss, respectively. The changes during chronic heat stress may cause acid-base crisis in all livestock, in addition to reduction in eggshell quality in birds; due to marked decrease in partial pressure of carbon dioxide and a compensatory increase in elimination of bicarbonate. Within and between breed variations in sensitivity of respiratory rhythm to both cold and heat stress has shown high applicability in identifying phenotypes that are more susceptible to thermal stress; with some cellular and metabolic changes occurring to protect the animal from the consequences of hypo- or hyper-thermia. The information in this review may provide basis for identification of genes that support or suppress thermoregulation and may also be of great use in animal breeding, genomics and selective thermal stress mitigation to provide maximum protection and comfort to poorly-adapted phenotypes.