RESUMEN
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.
Asunto(s)
Regulación de la Temperatura Corporal , Escroto , Espermatozoides , Testículo , Masculino , Animales , Testículo/anatomía & histología , Testículo/fisiología , Bovinos/fisiología , Escroto/anatomía & histología , Escroto/fisiología , Espermatozoides/fisiología , Microclima , Estaciones del Año , Clima Tropical , Luz SolarRESUMEN
We aimed to analyze the seasonal acclimatization process of Nelore and Canchim cattle raised on two production systems (non-shaded, NS, and integrated crop-livestock-forest, ICLF), based on the dynamics of the morphological and functional attributes of the hair coat and skin during winter and summer. The study was conducted in Brazil, in a low-altitude tropical climate region. A completely randomized 2 × 2 factorial design was adopted as follows: two production systems (NS and ICLF), two breeds (Nelore and Canchim) in a longitudinal structure, with measurements repeated over time through two stations (winter and summer). The experimental animals consisted of 32 Nelore (Bos indicus) and 32 Canchim (5/8 Bos taurus × 3/8 Bos indicus) bulls. The animals were equally distributed between two intensive rotational grazing systems. In both breeds, the hair coat was significantly thicker in winter but longer in summer, which increased epidermal protection. The Nelore bulls had shorter, wider, and thicker hairs, which are attributes that promote heat loss via conduction. The Canchim bulls showed significantly lower hair density and higher epithelium distance to sweat glands, which resulted in higher core temperature and respiratory rate. In turn, Nelore bulls had higher serum concentrations of triiodothyronine and lower serum concentrations of cortisol. However, Canchim bulls more frequently and intensely activated their thermoregulatory system and markedly adjusted their hair coat and hair features to reduce heat gain, especially in summer. Therefore, the anatomical plasticity and functional integumentary characteristics of Nelore and Canchim bulls reflect their acclimatization to tropical conditions.
Asunto(s)
Estaciones del Año , Clima Tropical , Animales , Bovinos , Brasil , Aclimatación/fisiología , Masculino , Cabello/fisiología , Pelaje de AnimalRESUMEN
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⯱â¯0.12⯰C), ST (36.10⯱â¯0.07⯰C), OGT (37.40⯱â¯0.06⯰C) and RT (38.83⯱â¯0.03⯰C) differed significantly (PË0.05). There was positive correlation of RT with OGT (râ¯=â¯0.392), ET (râ¯=â¯0.264) and ST (râ¯=â¯0.236) (PË0.05). Considering the bioclimatic indicators, the highest magnitude correlations were observed between ET and THI (râ¯=â¯0.71), ET and BGHI (râ¯=â¯0.65), and ET and RHL (râ¯=â¯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.
Asunto(s)
Temperatura Corporal , Bovinos/fisiología , Termografía/métodos , Animales , Granjas , Femenino , Humedad , Rayos Infrarrojos , Monitoreo Ambulatorio/instrumentación , Monitoreo Ambulatorio/métodos , TemperaturaRESUMEN
Morada Nova breed sheep are without wool, tropicalized, small-sized animals, known for their high-quality meat and skin. Their body development naturally depends on the genetic potential and adequate nutritional support, which suggests that the offer of high-energy density diets positively influences their productive indicators. Thus, the present study investigated the effect of a high-energy diet for the Morada Nova lambs on body development and testicular function, considering their histomorphometric characteristics and seminal quality. Forty-two males (19.2 weeks, 20.7 ± 3.5 kg) were equally divided into two groups and fed with 2.05 Mcal (G7, n = 21) or 2.37 Mcal (G24, n = 21) of metabolizable energy/day, equivalent to 7% and 24% above the minimum for growing lambs. The animals were confined for 23 weeks (W0 to W23). Weight and body score differed significantly from the W1 (P < 0.05). From the W5, thoracic perimeter, body length, wither height, and rump attributes were higher in G24 (P < 0.05). The scrotal circumference and testicular volume were higher in G24 from the W3 (P < 0.05). Although testosterone levels were not affected (P = 0.05), the highest energy intake increased the diameter of the seminiferous tubules and the development of the epididymal epithelium (P < 0.05). This positively influenced the seminal quality and reduced the minor defects (21.87% vs. 17.13%) and the total spermatic defects (26.34% vs. 21.78%, P < 0.05). Thus, it is possible to employ higher levels of dietary energy for Morada Nova young males to express higher productive efficiency and earlier reproductive attributes of interest.
Asunto(s)
Dieta/veterinaria , Ingestión de Energía , Ovinos/crecimiento & desarrollo , Alimentación Animal/análisis , Fenómenos Fisiológicos Nutricionales de los Animales , Animales , Peso Corporal , Metabolismo Energético , Masculino , Reproducción , Escroto/crecimiento & desarrollo , Testículo/crecimiento & desarrolloRESUMEN
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 (nâ¯=â¯11) or CLF (nâ¯=â¯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⯱â¯2.2 vs 36.6⯱â¯2.2â¯min) and shorter resting time (57.6⯱â¯2.7 vs 65.9⯱â¯2.8â¯min) during the morning. The grazing time and other activities did not differ between treatments (Pâ¯>â¯0.05) in the afternoon. Animals in CLF exhibited lower surface temperatures of the back (TBack: 31.9⯱â¯0.2 vs 32.8⯱â¯0.2⯰C, Pâ¯<â¯0.05) and of the trunk (TTrunk: 32.0⯱â¯0.1 vs 32.5⯱â¯0.1⯰C, Pâ¯<â¯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.
Asunto(s)
Crianza de Animales Domésticos , Temperatura Corporal , Bovinos/fisiología , Actividad Motora , Árboles , Crianza de Animales Domésticos/métodos , Animales , Brasil , Femenino , Árboles/crecimiento & desarrolloRESUMEN
Our aim was to evaluate the effects of three thermal environments over time on kinetics, functionality and in vitro fertility of cryopreserved bovine spermatozoa. Four ejaculates from five bulls (n = 20) were cryopreserved. After thawing, semen was evaluated (0 hr), incubated for 4 hr in T36.0 (36.0°C), T38.0 (38.0°C) and T39.5 (39.5°C), and analysed every hour (1 hr, 2 hr, 3 hr, 4 hr). In vitro production of embryos was performed at 0 hr and 4 hr. Sperm motility and cell kinetics (Computer-Assisted Sperm Analysis) were impaired after 2 hr at T38.0 and T39.5 (p < 0.05). Flow cytometry revealed an increase in the cells with injured plasma membrane to 39.5°C and a general reduction in the mitochondrial potential over time (p < 0.05). In vitro fertility was impaired in all temperatures after 4 hr, but there was no difference between 36.0°C and 38.0°C. Our results suggest that the ex situ resilience of semen at 36.0°C after thawing with no major damage to the quality is limited to 3 hr. In normothermia or in thermal stress, sperm cells present a gradual reduction of movement and functionality, which were more significant after 1 hr of incubation. The in vitro production of embryos is impaired when the semen is kept in a thermal environment ≥36.0°C for 4 hr.
Asunto(s)
Criopreservación/veterinaria , Fertilidad/fisiología , Calor/efectos adversos , Preservación de Semen/efectos adversos , Espermatozoides/fisiología , Animales , Bovinos , Femenino , Fertilización In Vitro/veterinaria , Inseminación Artificial/veterinaria , Masculino , Ovario , Preservación de Semen/veterinaria , Motilidad Espermática/fisiología , Factores de TiempoRESUMEN
For different ovine breeds to maximize their reproductive capacity in countries with tropical climate, it is important to evaluate their potential for thermal resilience and consequences on their reproductive traits. Therefore, the objective of this study was to evaluate the effect of thermal environment temperatures of climate seasons in a tropical climate region on the surface temperatures of the scrotum, testicular biometric characteristics, seminal quality and serum testosterone concentration of rams of different genotypes. Breeders of four different genotypes (Dorper, nâ¯=â¯8, Texel, nâ¯=â¯8, Santa Inês, nâ¯=â¯9 and Morada Nova, nâ¯=â¯8) were used throughout the four climate seasons. Higher thermal challenge was recorded in the spring and summer. In the summer increase in scrotal surface temperature was detected by infrared thermography (Pâ¯<â¯0.05), mainly in the regions of the distal testicular pole and tail of the epididymis. The animals of the Texel genotype had higher rectal temperature in the summer. In spring, this genotype also had the highest testicular pole (32.2⯱â¯0.5⯰C; Pâ¯<â¯0.05) and distal (29.9⯱â¯0.4⯰C; Pâ¯<â¯0.05) temperatures and a higher mean testicular temperature (31.7⯱â¯0.4⯰C; Pâ¯<â¯0.05). The Morada Nova genotype showed a higher surface temperature gradient between testicular poles (2.96⯱â¯0.1⯰C; Pâ¯<â¯0.05), especially in spring. Genotype-dependent thermal sensitivity was detected for the thermal gradient between the testicular poles, reflecting the seminal quality. There was a positive correlation of the thermal gradient between testicular poles with sperm membrane integrity and negative correlation with total sperm defects. The Texel genotype showed less progressive motility and higher percentage of sperm defects. There was no difference in testosterone concentration between genotypes and in the different seasons (Pâ¯>â¯0.05). Thus, the indigenous genotypes showed a greater capability to maintain the scrotum-testicular thermoregulation. Dorper animals resembled the indigenous sheep genotypes, in terms of seminal characteristics, unlike Texel animals, which showed lower adaptability and lower seminal quality.
Asunto(s)
Genotipo , Análisis de Semen/veterinaria , Semen/fisiología , Ovinos/genética , Ovinos/fisiología , Animales , Calor , Masculino , Clima TropicalRESUMEN
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.