Testicular thermoregulation, scrotal surface temperature patterns and semen quality of water buffalo bulls reared in a tropical climate

Effect of access to natural shade on scrotal thermoregulatory capacity, integrity of the testicular parenchyma and sperm morphology of Nelore (Bos indicus) and Canchim (Bos taurus x Bos indicus) bulls

The objective of this work was to evaluate the effect of using naturally shaded pastures on scrotal thermoregulatory capacity, testicular echotexture, and sperm morphology of Nelore (Bos indicus) and Canchim (5/8 Bos taurus x 3/8 Bos indicus) bulls in a tropical climate region. Sixty-four adult Nelore and Canchim bulls were used, equally allocated in Full Sun (FS, n = 32) or Crop-Livestock-Forestry (CLF, n = 32) pasture systems. During five consecutive climate seasons, the bulls underwent monthly breeding soundness evaluations and the biometeorological variables in the systems were continuously monitored. Microclimate was significantly different between systems. CLF system had lower BGHI than FS throughout the experimental period. No triple interaction (Season x Breed x Treatment, P > 0.05) was observed for any of the variables. Animals in CLF showed lower body temperature in Summer (FS:39.41 ± 0.05 vs. CLF:39.30 ± 0.05 °C; P = 0.005) and in Autumn (FS:39.54 ± 0.05 vs. CLF:39.35 ± 0.05 °C; P = 0.005). Access to shading did not determine differences in the evolution of scrotal biometry, temperatures, and scrotal thermal gradients (P > 0.05). Regardless of breed, animals in CLF showed greater right testicular volume (FS:247.5 ± 5.7 vs. CLF:259.0 ± 5.7 cm³; P < 0.05), more suitable parenchyma echotexture, and fewer microlithiasis spots in the Spring and Summer. Testosterone concentration was higher in FS (FS:2.6 ± 0.2 vs. CLF:2.1 ± 0.2 ng/mL; P = 0.035). Canchim bulls presented higher total sperm defects during the Autumn and Winter (P = 0.010), but the total defects levels for Canchim and Nelore bulls were in normal range for adult bulls. Thus, the natural shade in CLF system was effective in improving the microclimate of pastures and minimizing adverse environmental effects on some reproductive features of interest in beef cattle.

Selection of reference genes for normalizing gene expression data across seasons in spermatozoa of water buffalo (Bubalus bubalis)

Selection of the most stably expressed reference genes is key to monitoring accurate target gene expression across any tissue or cell type. The mRNA in spermatozoa stores valuable information related to changes in spermatogenesis due to variations in environmental conditions, especially during heat stress, which affects various sperm functions. Semen quality in buffalo bulls is significantly influenced by the seasons. In the study, a panel of nine genes was evaluated to identify the most stably expressed internal control gene (ICG) for the normalization of real-time gene expression data generated across various seasons for Murrah buffalo bulls' spermatozoa. Sperm cells were purified from the semen samples collected during different seasons, with temperature-humidity index (THI) ranging from 80.80 ± 1.47 (hot summer) to 55.88 ± 1.98 (winter), using the BoviPure™ gradient purification method. The RNA isolated from the purified spermatozoa fraction was quality checked prior to reverse transcription and subjected to qPCR (quantitative real-time PCR) based expression analysis. An automated 'endoGene' pipeline was employed to apply the geNorm, NormFinder, and BestKeeper algorithms for data analysis. The result indicated that GAPDH and PP1A were the most stably expressed among the gene panel, whereas ATPSF1 and ACTB were the two least stable expressed reference genes. Further, the most suitable ICGs identified were validated by normalization of real time expression data of heat stress and sperm quality genes, HSFY2 and AKAP4, respectively. The genes identified would help in generating the most reliable results for the expression profiling of the genes dictating sperm quality and heat stress cope-up mechanism in buffalo spermatozoa, collected during different seasons.

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.

Global warming and testis function: A challenging crosstalk in an equally challenging environmental scenario

Environmental pollution, accounting for both chemical and physical factors, is a major matter of concern due to its health consequences in both humans and animals. The release of greenhouse gases with the consequent increase in environmental temperature is acknowledged to have a major impact on the health of both animals and humans, in current and future generations. A large amount of evidence reports detrimental effects of acute heat stress on testis function, particularly on the spermatogenetic and steroidogenetic process, in both animal and human models, wich is largely related to the testis placement within the scrotal sac and outside the abdomen, warranting an overall scrotal temperature of 2°C-4°C lower than the core body temperature. This review will provide a thorough evaluation of environmental temperature's effect on testicular function. In particular, basic concepts of body thermoregulation will be discussed together with available data about the association between testis damage and heat stress exposure. In addition, the possible association between global warming and the secular decline of testis function will be critically evaluated in light of the available epidemiological studies.

Scrotal thermoregulation and sequential sperm abnormalities in buffalo bulls (Bubalus bubalis) under short-term heat stress

Heat stress reduces the reproductive capacity of bulls raised in tropical climate. However, the reestablishment of scrotal thermoregulation and the dynamics of sperm defects emergence after stress are not completely known in buffaloes. Thus, the study aimed to evaluate the effect of short-term heat stress over scrotal thermoregulation and sperm attributes, relating them to spermatogenesis stages. Five buffalo bulls went through scrotal insulation during 48 h (from day 0 to day 2). Semen samples were collected every 7 days (from day -7 to day 49) and analyzed about the progressive motility, viability, and sperm morphology. Heat stress significantly destabilized scrotal thermoregulation (P < 0.001). Scrotal temperature was from 4.2 to 6.3 °C lower than the core body temperature, except on insulation days (P < 0.001), and returned to the basal condition five days after the removal of the stressing stimulus. More significant deleterious effects were observed in sperm morphology than in cell concentration, motility, and viability. The chronology of morphologic defects expression demonstrated tail defects (days 7-14), cytoplasmic droplets (days 14-28), and head defects (day 28), returning to pre-insulation condition 35 days after the thermal challenge. Thus, hyperthermia harmed more intensely spermatozoa in epididymal transit, elongated spermatids, and secondary spermatocytes. It is concluded that water buffalo bulls present a peculiar manifestation of sperm morphology after short-term stress, indicating an important difference related to the bovine species. Therefore, during the andrological evaluation of buffalo bulls, it is necessary to avoid the allometric extrapolation between these species.

Effect of fans and showers on the physiological measures and reproductive performance of Holstein Friesian bulls during subtropical summer

The objective of the current study was to determine the effect of fans and showers on the physiological measures and reproductive performance of Holstein Friesian bulls during subtropical summer in Pakistan. Thirty-six bulls with an average body weight of 898.0 ± 135.2 kg (mean ± SD) and an average age (4 to 6 years) were randomly divided into three treatment groups: (1) CTL, bulls kept under shade only; (2) FN, bulls provided with fans under shade; and (3) FNS, bulls provided showers in addition to fans under shade. The trial was carried out for 6 months from April to September 2016 and was categorized into two seasons (dry summer and humid summer). Ambient temperature, relative humidity, temperature-humidity index, dry matter intake (DMI), water intake, rectal temperature (RT), pulse rate (PR) and respiration rate (RR) were recorded daily. Semen characteristics and selected blood metabolites were measured every 2 weeks. The results indicated that the DMI of the bulls was similar between the treatment groups. Water intake, RT, PR and RR were significantly lower in the FNS group than in the CTL and FN groups (P < 0.001). Semen characteristics, including semen concentration, post-thaw semen motility, progressive motility, amplitude of lateral head displacement, straightness, live-to-dead ratio, plasma membrane integrity, normal acrosomal ridge and DNA integrity, were not different between the treatment groups (P > 0.05). The FNS group tended to have a higher semen volume than that of the FN and CTL groups (P = 0.10). Blood glucose levels were significantly lower in the FNS group than in the FN and CTL groups (P < 0.05). Blood urea nitrogen and testosterone were not different among the treatment groups (P > 0.05). The current results indicated that showers with fans improved the welfare of Holstein Friesian bulls by lowering physiological measures in addition to increasing trends in semen volume during subtropical summer.

Behavior and body surface temperature of beef cattle in integrated crop-livestock systems with or without tree shading

Pasture-based livestock production is largely centered on monoculture systems that degrade grasslands. In integrated crop-livestock-forestry systems a synergy is supposed to occur between its components, contributing to global food production. Thus, this study aimed to evaluate the effects of the microclimate on integrated crop-livestock-forestry (CLF) and crop-livestock (CL) systems on the behavior and body surface temperatures of beef cattle in a tropical climate. The experiment was carried from December/2016 to June/2017. Adult beef cows were maintained in CL (n = 11) or CLF (n = 12) systems, permanently monitored by automatic weather stations. The microclimatic conditions indicated that CLF was more effective in mitigating the environmental heat load. Animals maintained in CLF showed favorable behavior, longer rumination (42.9 ± 2.2 vs 36.6 ± 2.2 min) and shorter resting time (57.6 ± 2.7 vs 65.9 ± 2.8 min) during the morning. The grazing time and other activities did not differ between treatments (P > 0.05) in the afternoon. Animals in CLF exhibited lower surface temperatures of the back (TBack: 31.9 ± 0.2 vs 32.8 ± 0.2 °C, P < 0.05) and of the trunk (TTrunk: 32.0 ± 0.1 vs 32.5 ± 0.1 °C, P < 0.05) measured by infrared thermography. Animals maintained in CLF showed a significant preferential use of shade and a 23% reduction in the frequency of the animals searching for water troughs. It is evident from the study that integrated crop-livestock-forestry systems can be used to provide a more favorable microclimate within grasslands. Thus, beef cattle benefits from the milder environment and exhibits a higher thermal comfort, which favors food production and the rational use of natural resources.

Scrotal infrared thermography and testicular biometry: Indicator of semen quality in Murrah buffalo bulls

This aim of this study was to assess the relationship, if any, of scrotal surface temperature gradient (SSTG), scrotal circumference (SC) and testicular covering thickness (TCT) with semen quality in Murrah buffalo breeding bulls. For this, buffalo breeding bulls (n = 130) were selected from four different semen centres. The ejaculates of each bull were evaluated for ejaculate volume (EV), mass motility (MM); concentration (SPC), motility (SM), viability and abnormalities (SA). The SSTG, SC and TCT of individual bulls were quantified using digital infrared thermography, measuring tape and ultrasonography, respectively. The bulls were divided into three groups on the basis of SSTG (≤ 4 °C, 4.1 to 6.4 °C and ≥ 6.5 °C), and SC (<31, 31 to 35 and> 35 cm) and into two groups on the basis of TCT (5 to 7.2 and 7.4 to 10.4 mm). Results indicated the bulls with a larger temperature gradient and larger SC produced greater quality semen than those with a lesser temperature gradient. The MM (P < 0.01) and SPC (P < 0.05) varied among the groups along with SSTG. Among the SC groups the EV, MM, SPC and SM (P < 0.01), and viability (P < 0.05) varied as did the SC. The bulls with a lesser TCT had a lesser SA (P < 0.05) as compared to the group with the greater TCT. Buffalo bulls having a greater SSTG, SC and lesser TCT produced semen of greater quality and these variables may be used as criteria for breeding soundness evaluation.

Application of microchip and infrared thermography for monitoring body temperature of beef cattle kept on pasture

The monitoring of body temperature is important for the diagnosis of the physiological state of the animal, being dependent on available methods and their applicability within production systems. This work evaluated techniques to monitor the body temperature of beef cattle kept on pasture and their ability to predict internal temperature. Twenty-three adult bovine females were monitored for six months, and collection data carried out in eleven campaigns (D0-D10) twelve days apart. During collections, the surface temperatures of ear base (ET, ^oC) and ocular globe (OGT, ^oC) were measured by infrared thermography, and the subcutaneous temperature (ST, ^oC) was measured with the use of transponder containing an implantable microchip. Rectal temperature (RT, ^oC) was considered as a reference for body temperature. Temperature and Humidity Index (THI), Black Globe Temperature and Humidity Index (BGHI) and Radiant Heat Load (RHL, W/m²) were calculated. ET (33.32 ± 0.12 °C), ST (36.10 ± 0.07 °C), OGT (37.40 ± 0.06 °C) and RT (38.83 ± 0.03 °C) differed significantly (P˂0.05). There was positive correlation of RT with OGT (r = 0.392), ET (r = 0.264) and ST (r = 0.236) (P˂0.05). Considering the bioclimatic indicators, the highest magnitude correlations were observed between ET and THI (r = 0.71), ET and BGHI (r = 0.65), and ET and RHL (r = 0.48). The use of microchip represented a practical method, but with limited predictability. On the other hand, infrared thermography proved to be safe and non-invasive, presenting greater precision for inference of internal body temperature. ET was more influenced by meteorological conditions.

Thermoregulatory responses and reproductive traits in composite beef bulls raised in a tropical climate

It is believed that increased livestock production is limited by tropical climate. Thermal imbalance in bulls can lead to hyperthermia and alter testicular metabolism, causing subfertility or infertility. Therefore, the thermoregulation of composite Canchim bulls (5/8 Charolais × 3/8 Zebu) raised in tropical climate as well as their consequences in the physiological, hematological, hormonal, and andrological parameters were evaluated monthly. The bulls (n = 18; 30.0 ± 1.5 months; 503.8 ± 23.0 kg) were kept on pasture, in a single group, from August 2015 to March 2016, comprising the winter, spring, and summer seasons. Biometeorological variables were continuously monitored, and the Temperature and Humidity Index (THI) was calculated. A greater thermal challenge occurred in spring and summer (THI ≥ 72.0). Nevertheless, the bulls exhibited normothermia (38.6 to 38.9 °C) in these seasons. The cortisol did not vary between seasons (7.0 vs. 8.7 vs. 6.8 ng/mL; P > 0.05) and remained within the physiological patterns. Independent of the seasons, stress leukogram was also not observed, refuting the incidence of acute or chronic thermal stress. It is noteworthy that T3 and testosterone increased (P < 0.0001, P < 0.05) in spring and summer, the time that coincides with the breeding season, when there is increased metabolic requirement from the bulls. The progressive thermal challenge increase did not affect the scrotal thermoregulatory capacity, and in general, scrotal temperature remained at 5.2 °C below the internal body temperature. In summer, there was a 5% reduction in the minor sperm defects (P < 0.05) and DNA fragmentation in 2.4% of spermatozoa, a compatible value for high fertility bulls. The results show that the studied composite bulls can be considered as climatically adapted and constitute a viable alternative to be used in production systems in a tropical climate, even if the breeding seasons occur during the most critical thermal condition periods of the year.