Magnesium in the water of Japanese quails kept under comfort zone and under thermal stress / Magnésio na água de codornas japonesas mantidas em zona de conforto e sob estresse térmico

The objective was to evaluate the increasing levels of magnesium in the water supplied to laying quails (Coturnix coturnix japonica), kept in climatic chambers under thermoneutral temperature and thermal stress, on their performance and morphometry of their organs. The birds were distributed in a completely randomized design, 2x4 factorial arrangement, 2 temperatures (24 and 32 ºC) and 4 levels of magnesium in the water (50, 150, 250 and 350 mg L-1), with six replicates and eight birds per experimental unit. The data were subjected to analysis of variance and the means compared by the Tukey test at 5% probability level. The magnesium levels in the water did not affect (P > 0.05) the production performance and morphometry of the organs, with less water consumption at the magnesium level of 150 mg L-1, and birds kept at 32 °C had a reduction in feed consumption and feed conversion, but without affecting organ morphometry. Japanese quails in the production phase can consume water with magnesium levels up to 350 mg L-1 without having their production performance and morphometry of organs affected and raised in an environment with temperatures of up to 32 °C.(AU)

O objetivo foi avaliar os níveis crescentes de magnésio na água fornecida a codornas (Coturnix coturnix japonica) em postura, mantidas em câmaras climáticas sob temperatura termoneutra e estresse térmico, sobre o desempenho e morfometria dos órgãos das aves. As aves foram distribuídas em delineamento inteiramente casualizado, arranjo fatorial 2x4, 2 temperaturas (24 e 32 ºC) e 4 níveis de magnésio na água (50, 150, 250 e 350 mg L-1), com seis repetições e oito aves por unidade experimental e os dados submetidos à análise de variância e as médias comparadas pelo teste de Tukey a 5% de probabilidade. Os níveis de magnésio na água não afetaram (P > 0,05) o desempenho produtivo e a morfometria dos órgãos, com menor consumo de água ao nível de 150 mg L-1 de magnésio e, as aves mantidas a 32 °C tiveram uma redução no consumo de ração e conversão alimentar, mas sem afetar a morfometria dos órgãos. Codornas japonesas em fase de produção podem consumir água com níveis de magnésio de até 350 mg L-1 sem ter o desempenho produtivo e a morfometria dos órgãos afetados e criados em ambiente com temperatura de até 32 °C.(AU)

Thermoregulatory responses and adaptability of Anglo-nubian goats maintained in thermoneutral temperature and under heat stress

This study aimed to evaluate the physiological responses and adaptability of Anglo-Nubian goat breeds by Ibéria and Benezra tests, maintained in bioclimatic chamber under different temperatures: 20, 24, 28 and 32oC, where temperature and air relative humidity and black globe humidity index (BGHI) were measured. The design was completely randomized with four treatments and six replicates. With the increase of temperature and the BGHI, increased the surface temperature, the cardiac and respiratory frequency, and the thermal gradient, the rectal temperature remained within normal limits. The adaptability tests indicated that animals in the temperatures of 28 and 32°C had the physiological parameters altered to maintain the warm-blooded, which BGHI values corresponding were 78.21 and 82.55 respectively, characterizing a warning and danger situation.(AU)

Thermoregulatory responses and adaptability of Anglo-nubian goats maintained in thermoneutral temperature and under heat stress

This study aimed to evaluate the physiological responses and adaptability of Anglo-Nubian goat breeds by Ibéria and Benezra tests, maintained in bioclimatic chamber under different temperatures: 20, 24, 28 and 32oC, where temperature and air relative humidity and black globe humidity index (BGHI) were measured. The design was completely randomized with four treatments and six replicates. With the increase of temperature and the BGHI, increased the surface temperature, the cardiac and respiratory frequency, and the thermal gradient, the rectal temperature remained within normal limits. The adaptability tests indicated that animals in the temperatures of 28 and 32°C had the physiological parameters altered to maintain the warm-blooded, which BGHI values corresponding were 78.21 and 82.55 respectively, characterizing a warning and danger situation.

Thermoregulatory responses of Holstein cows exposed to experimentally induced heat stress.

Heat stress (HS) adversely influences productivity and welfare of dairy cattle. We hypothesized that the thermoregulatory mechanisms vary depending on the exposure time to HS, with a cumulative effect on the adaptive responses and thermal strain of the cow. To identify the effect of HS on adaptive thermoregulatory mechanisms and predictors of caloric balance, Holstein cows were housed in climate chambers and randomly distributed into thermoneutral (TN; n=12) or HS (n=12) treatments for 16 days. Vaginal temperature (VT), rectal temperature (Tre), respiratory rate (RR), heart rate (HR), and dry matter intake (DMI) were measured. The temperature and humidity under TN were 25.9±0.2°C and 73.0±0.8%, respectively, and under HS were 36.3±0.3°C and 60.9±0.9%, respectively. The RR of the HS cows increased immediately after exposure to heat and was higher (76.02±1.70bpm, p<0.001) than in the TN (39.70±0.71bpm). An increase in Tre (39.87±0.07°C in the HS vs. 38.56±0.03°C in the TN, p<0.001) and in VT (39.82±0.10°C in the HS vs. 38.26±0.03°C in the TN, p<0.001) followed the increase in RR. A decrease (p<0.05) in HR occurred in the HS (62.13±0.99bpm) compared with the TN (66.23±0.79bpm); however, the magnitude of the differences was not the same over time. The DMI was lower in HS cows from the third day (8.27±0.33kgd-1 in the HS vs. 14.03±0.29kgd-1 in the TN, p<0.001), and the reduction of DMI was strongly affected (r=-0.65) by changes in the temperature humidity index. The effect of environmental variables from the previous day on physiological parameters and DMI was more important than the immediate effect, and ambient temperature represented the most determinant factor for heat exchange. The difference in the responses to acute and chronic exposure to HS suggests an adaptive response. Thus, intense thermal stress strongly influence thermoregulatory mechanisms and the acclimation process depend critically on heat exposure time.