RESUMEN
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
The amount of short-wave solar radiation willingly tolerated by lactating Holstein cows on pasture was determined in an equatorial semi-arid environment. The study was carried out on a dairy farm located in Limoeiro do Norte, CE, northeastern Brazil. The observed behaviours were as follows: grazing, under the sun, under the shade, standing, lying, ruminating, idling and wallowing in the water. The behaviours were recorded using instantaneous scan sampling at regular intervals of 15 min from 0600 to 1800 hours over 5 days. On all sampling days, the meteorological variables, including local short-wave solar radiation (R S-W, W m(-2)), were recorded. The R S-W data were divided into five levels. The sun exposure was more frequent under low (100 %) and moderately low (97 %) levels, when R S-W remained below 500 W m(-2). The grazing was more intense under low (100 %) and moderately low (93 %) levels. Above 500 W m(-2), the grazing time significantly decreased (11 %). The cows avoided grazing under high (0 %) and very high (0 %) levels, when R S-W exceeded 700 W m(-2). The ruminating behaviour was more frequent under high (33 %) and very high (37 %) levels, in which the highest averages of R S-W were recorded (815 and 958 W m(-2), respectively). The standing posture was more frequent under low (100 %) and moderately low (97 %) levels. Therefore, the critical R S-W level that motivates cows to stop grazing and seek shade was in the interval between 500 and 700 W m(-2).
Asunto(s)
Conducta Animal/fisiología , Bovinos/fisiología , Lactancia/fisiología , Luz Solar , Animales , Brasil , Ambiente , FemeninoRESUMEN
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.