RESUMEN
For the development of efficient management and conservation strategies for wild rodent species, understanding the aspects related to their reproduction, including the interaction of this physiological function with the environment, is essential. This study aimed to evaluate the impacts of weather changes derived from a semiarid region's dry and rainy seasons on the epididymal sperm characteristics of red-rumped agouti (Dasyprocta leporina), a histricognath rodent, still little studied, which inhabits the Brazilian Caatinga. The sperm from the epididymal cauda of 14 agoutis were collected, seven individuals per season (dry and rainy). Samples were evaluated for kinetic parameters, membrane structural and functional integrity, mitochondrial activity, morphology, and morphometry. The environmental variables were measured: maximum air temperature, relative humidity, wind speed, solar radiation, and the total rainfall for dry and rainy seasons were, respectively, 36.2 and 34.1 °C, 66.8 and 80.1%, 4.0 and 1.9 m/s, 527.3 and 441.8 W/m2, and 0.2 and 517.7 mm. There were strong correlations between some sperm parameters and environmental variables, mainly those related to the acquisition of sperm mobility. Sperm concentration and the number of sperm collected were higher in the dry (1028.7 sperm/mL × 106 and 1361.2 × 106 sperm) than in the rainy season (758.9 sperm × 106/mL and 714.6 sperm × 106). During the rainy season, there were fewer sperm defects, higher sperm metrics, and higher membrane structural integrity with mitochondrial activity. Regarding motility patterns, the increases during the rainy season stand out in total and progressive motility, VAP, VSL, VCL, and subpopulations of rapid sperm. In summary, our results suggest that the adverse climatic conditions of the dry season in the semiarid region, mainly high solar radiation and temperature, considerably impair the epididymal sperm quality of red-rumped agoutis. On the contrary, the largest amount of sperm was obtained during this season, probably due to compensatory and adaptive mechanisms of the species to enable its reproduction throughout the year.
Asunto(s)
Estaciones del Año , Espermatozoides , Masculino , Animales , Brasil , Motilidad Espermática , DasyproctidaeRESUMEN
The aim of this study was to evaluate whether feeding propolis extract (PE) influences nutrient intake, milk production and composition, serum biochemistry, and physiological parameters of heat-stressed dairy cows. For this purpose, we used three primiparous Holstein cows with a lactation period of 94 ± 4 days and with 485 ± 13 kg body weight. The treatments were 0 mL/day, 32 mL/day, and 64 mL/day of PE randomly assigned in a 3x3 Latin square design, repeated over time. The experiment lasted a total of 102 days; each Latin square lasted 51 days divided into three 17-day periods (12 days for adaptation and five days for data collection). The PE supply did not influence (P > 0.05) the cows' intake of dry matter (18.96 kg/d), crude protein (2.83 kg/d), and neutral detergent-insoluble fiber (7.36 kg/d), but there was an increase in feeding time with the 64 ml/day PE supply (P < 0.05). Providing 64 ml/day of PE tended (P = 0.06) to increase milk production by 11.64% and improve gross feed efficiency of cows by 12.04%. The PE supply did not influence milk composition and blood parameters of cows (P > 0.05). Offering 32 mL/day of PE decreased (P < 0.05) the rectal temperature and respiratory rate of cows. We recommend a supply of 64 mL/day of PE for heat-stressed dairy cows.
Asunto(s)
Leche , Própolis , Femenino , Bovinos , Animales , Leche/química , Dieta/veterinaria , Própolis/análisis , Própolis/metabolismo , Própolis/farmacología , Calor , Alimentación Animal/análisis , Digestión , Lactancia/fisiología , Rumen/metabolismoRESUMEN
Heat stress is one of the main obstacles to achieving efficient cattle production systems, and it may have numerous adverse effects on cattle. As the planet undergoes climatic changes, which is predicted to raise the earth's average temperature by 1.5 °C between 2030 and 2052, its impact may trigger several stressful factors for livestock. Among these, an increase in core body temperature would trigger physiological imbalance, consequently affecting reproduction, animal health, and dry matter intake adversely. Core body temperature increase is commonly observed and poses challenges to livestock farmers. In cattle farming, thermal stress severely affects milk production and weight gain, and can compromise food security in the coming years. This review presents an updated approach to the physiological and thermoregulatory responses of cattle under various environmental conditions. Strategies for mitigating the harmful effects of heat stress on livestock are suggested as viable alternatives for the betterment of production systems.
Asunto(s)
Trastornos de Estrés por Calor , Calor , Animales , Regulación de la Temperatura Corporal , Bovinos , Trastornos de Estrés por Calor/veterinaria , Respuesta al Choque Térmico , Ganado , Estrés FisiológicoRESUMEN
Heat stress is one of the main factors affecting egg production. One way to improve egg production is physical processing of the feed ingredients, allowing for better utilization of nutrients. In this study, the relationship between the corn particle size, measured as the geometric mean diameter (GMD), and thermoregulation was evaluated by determining the effect of the GMD on performance, egg quality, and physiological responses. Feed intake, eggshell quality (weight and thickness), rectal temperature (T R), respiratory rate (R R), and surface temperature (T S) were recorded in sixty 20-week-old naked neck laying hens that were fed corn of different particle sizes. Ambient temperature (T A) was also recorded during the trial. The GMD of corn particles was determined using a screens granulometer, resulting in sizes of 605, 1,030, and 2,280 µm. The analysis of variance (ANOVA) of a completely randomized design showed a significant effect (P < 0.05) of GMD on feed intake, shell weight, and shell thickness. The ANOVA performed by the least squares method showed a highly significant effect (P < 0.01) of GMD on T R and R R. T A, categorized into three classes (24.0-26, 26.1-28.9, and 29.0-31.0 °C), had a significant effect (P < 0.01) on T R and T S. The interaction between the GMD of corn particles and the T A classes was not statistically significant. Coarser corn particles cause an increase in the rectal temperature of naked neck hens, and these birds increase their respiratory rate to dissipate excess metabolic heat. This increase in the respiratory rate causes a decrease in the eggshell quality.
Asunto(s)
Alimentación Animal , Regulación de la Temperatura Corporal , Pollos/fisiología , Zea mays , Animales , Temperatura Corporal , Brasil , Ingestión de Alimentos , Ambiente , Femenino , Óvulo/crecimiento & desarrollo , Tamaño de la Partícula , Frecuencia RespiratoriaRESUMEN
This paper presents a new thermal stress index for dairy cows in inter-tropical regions, with special mention to the semi-arid ones. Holstein cows were measured for rectal temperature (T R), respiratory rate (F R) and rates of heat exchange by convection (C), radiation (R), skin surface evaporation (E S) and respiratory evaporation (E R) in the north eastern region of Brazil, after exposure to sun for several hours. Average environmental measurements during the observations were air temperature (T A) 32.4 °C (24.4-38.9°), wind speed (U) 1.8 m.s(-1) (0.01-11.0), relative humidity 63.6 % (36.8-81.5) and short-wave solar radiation 701.3 W m(-2) (116-1,295). The effective radiant heat load (ERHL) was 838.5 ± 4.9 W m(-2). Values for the atmospheric transmittance (τ) were also determined for tropical regions, in order to permit adequate estimates of the solar radiation. The average value was τ = 0.611 ± 0.004 for clear days with some small moving clouds, with a range of 0.32 to 0.91 in the day period from 1000 to 1300 hours. Observed τ values were higher (0.62-0.66) for locations near the seacoast and in those regions well-provided with green fields. Effects of month, location and time of the day were all statistically significant (P < 0.01). A total of 1,092 data were obtained for cows exposed for 1 to 8 h to sun during the day; in 7 months (February, March, April, July, August, September and November), 4 days per month on the average. A principal component analysis summarised the T R, F R, C, R, E S and E R measurements into just one synthetic variable (y 1); several indexes were then obtained by multiple regression of y 1 on the four environmental variables and its combinations, by using Origin 8.1 software (OriginLab Corp.). The chosen equation was the index of thermal stress for cows, ITSC = 77.1747 + 4.8327 T A - 34.8189 U + 1.111 U (2) + 118.6981 P V - 14.7956 P V (2) - 0.1059 ERHL with r (2) = 0.812. The correlations of ITSC with T R, F R, C, E S, R and E R were 0.275, 0.255, -0.493, -0.647, -0.818 and 0.075, respectively. Correlations of the index with the physiological variables are presented, and ITSC is compared to three other indexes.
Asunto(s)
Regulación de la Temperatura Corporal/fisiología , Bovinos/fisiología , Respuesta al Choque Térmico/fisiología , Respuesta al Choque Térmico/efectos de la radiación , Energía Solar , Clima Tropical , Animales , Regulación de la Temperatura Corporal/efectos de la radiación , Brasil , Clima , Ecosistema , Dosis de Radiación , Frecuencia Respiratoria/fisiología , Frecuencia Respiratoria/efectos de la radiaciónRESUMEN
The aim of this study was to evaluate the daily variations in the thermoregulatory behavior of 4- to 6-week-old naked neck broilers (Label Rouge) in an equatorial semi-arid environment. A total of 220 birds were monitored for 5 days starting at 0600 hours and ending at 1800 hours. The period of observation was divided into classes of hours (C H). The observed behaviors were as follows: feed and water intake, wing-spreading, sitting or lying, and beak-opening. A total of 14,300 behavioral data values were registered. In C H 2 (0900 hours to 1100 hours) and 3 (1200 hours to 1500 hours), the greatest average body surface temperature was recorded (34.67 ± 0.25 °C and 35.12 ± 0.22 °C, respectively). The C H had an effect on the exhibition of all behaviors with the exception of the water intake behavior. Feed intake was more frequent in C H 1 (0600 hours to 0800 hours) and 4 (1600 hours to 1800 hours). In C H 2 and 3, the highest frequency of sitting or lying behavior was observed. Beak-opening and wing-spreading behaviors occurred more frequently in C H 3 where the body surface temperature (35.12 ± 0.22 °C), radiant heat load (519.38 ± 2.22 W m(-2)), and enthalpy (82.74 ± 0.36 kJ kg(-1) of dry air) reached maximum recorded averages. Thus, it can be concluded that naked neck broilers adjust their behavior in response to daily variations in the thermal environment. Wing-spreading and beak-opening behaviors are important adaptive responses to the thermal challenges posed by the equatorial semi-arid environment.
Asunto(s)
Conducta Animal , Regulación de la Temperatura Corporal , Pollos/fisiología , Animales , Pico/fisiología , Brasil , Clima , Ingestión de Alimentos , Femenino , Masculino , Alas de Animales/fisiologíaRESUMEN
The aim of this study was to evaluate the regional differences in the surface temperature of Naked Neck hens that were subjected to different temperatures in a semi-arid environment. The surface temperature was measured in four body regions (face, neck, legs and feathered area) of 60 Naked Neck hens. The following environmental variables were measured at the center of the shed: the black globe temperature (T G ), air temperature (T A ), wind speed (U) and relative humidity (R H ). The T A was divided into three classes: 1 (24.0-26.0 °C), 2 (26.1-28.9 °C) and 3 (29.0-31.0 °C). An analysis of variance was performed by the least squares method and a comparison of the means by the Tukey-Kramer test. The results showed a significant effect of T A class, the body region and the interaction between these two effects on the surface temperature. There was no significant difference between the T A classes for the face and neck. The legs and feathered area showed significant differences between the T A classes. Regarding the effect of body regions within each T A class, there was a significant difference among all regions in the three T A classes. In all T A classes the neck had the highest average followed by the face and legs. The feathered area showed the lowest average of the different T A classes. In conclusion, this study showed that there are regional differences in the surface temperature of Naked Neck hens, with the legs acting as thermal windows.
Asunto(s)
Pollos/fisiología , Temperatura Cutánea , Animales , Regulación de la Temperatura Corporal , Brasil , Clima , Extremidades , Cara , Plumas , Femenino , Cuello , Termografía , Tiempo (Meteorología)RESUMEN
The present study aimed to evaluate evaporative heat transfer of dairy cows bred in a hot semi-arid environment. Cutaneous (E(S)) and respiratory (E(R)) evaporation were measured (810 observations) in 177 purebred and crossbred Holstein cows from five herds located in the equatorial semi-arid region, and one herd in the subtropical region of Brazil. Rectal temperature (T(R)), hair coat surface temperature (T(S)) and respiratory rate (F(R)) were also measured. Observations were made in the subtropical region from August to December, and in the semi-arid region from April to July. Measurements were done from 1100 to 1600 hours, after cows remained in a pen exposed to the sun. Environmental variables measured in the same locations as the animals were black globe temperature (T(G)), air temperature (T(A)), wind speed (U), and partial air vapour pressure (P(V)). Data were analysed by mixed models, using the least squares method. Results showed that average E(S) and E(R) were higher in the semi-arid region (117.2 W m(-2) and 44.0 W m(-2), respectively) than in the subtropical region (85.2 W m(-2) and 30.2 W m(-2), respectively). Herds and individual cows were significant effects (P < 0.01) for all traits in the semi-arid region. Body parts did not affect T(S) and E(S) in the subtropical region, but was a significant effect (P < 0.01) in the semi-arid region. The average flank T(S) (42.8°C) was higher than that of the neck and hindquarters (39.8°C and 41.6°C, respectively). Average E(S) was higher in the neck (133.3 W m(-2)) than in the flank (116.2 W m(-2)) and hindquarters (98.6 W m(-2)). Coat colour affected significantly both T(S) and E(S) (P < 0.01). Black coats had higher T(S) and E(S) in the semi-arid region (41.7°C and 117.2 W m(-2), respectively) than white coats (37.2°C and 106.7 W m(-2), respectively). Rectal temperatures were almost the same in both subtropical and semi-arid regions. The results highlight the need for improved management methods specific for semi-arid regions.