Threonine incorporation in tissues of growing broiler chickens using L-[15 N] threonine.

Most amino acid requirement trials appear for whole-body responses, but there is little information concerning amino acid incorporation in individual tissues, which may vary according to the age. L-[15 N] threonine was used to evaluate its incorporation rate and distribution among broiler tissues in different ages. Seventy-two male broiler chickens were distributed into three different phases: starter (4 to 9 days old), grower (18 to 23 days old) and finisher phase (32 to 37 days old). L-[15 N] threonine was added on balanced diets, and birds were fed for five days in each phase. Enriched samples of breast muscle, feathers, liver, jejunum and plasma were collected at 0, 6, 12, 24, 48, 72, 96 and 120 hr after fed birds with the tracer in each phase. In the tissues were analysed dry matter, nitrogen and stable nitrogen. The 15 N isotope abundance according to the time was fitted into exponential or linear equations using a same intercept. The ratio of the steepness or slope coefficients was determined to compare the L-[15 N] threonine incorporation according to the age. In addition, L-[15 N] threonine mass balances were performed to assess the L-[15 N] threonine distribution among the evaluated tissues. Except for feathers, the L-[15 N] threonine incorporation rate decreased with ageing. Taking into account the L-[15 N] threonine distribution in the tissues, only in the jejunum was not observed an increase as the broiler grew. The L-[15 N] incorporation varied in each tissue and according to the age of the broiler chickens. These outcomes could be useful to comprehend changes in amino acid requirements tissue-specific according to age.

Physiological responses and thermal equilibrium of Jersey dairy cows in tropical environment.

Long-term assessments of thermal responses of housed Jersey cows raised in tropical conditions were performed to investigate the effect of climate environment on their physiological performance and thermal equilibrium. Twelve Jersey dairy cows with 326.28 ± 30 kg of body weight, 17.66 ± 1.8 of milk yield, and 165.5 ± 6.8 of days in milking were assigned in two 12 × 12 Latin square designs. Air temperature, relative humidity, partial vapor pressure, direct and diffuse short-wave solar radiation and black globe temperature under the shade, and direct sunlight were recorded. Physiological responses as respiratory rate (RR, breaths min-1), ventilation (VE, L s-1), proportion (%) of oxygen (O2) and carbon dioxide (CO2), saturation pressure (PS{TEXH}), and air temperature (TEXH, °C) of the exhaled air were assessed protected from solar radiation and rain. Rectal temperature (TR, °C), skin temperature (TEP, °C), and hair coat surface temperature (TS, °C) were also recorded. The thermal equilibrium was determined from biophysical equations according to the principles of the energy conservation law in a control volume. Exploratory and confirmatory analyses were performed from principal components and by the least square method, respectively. The cows were evaluated under range of ambient air temperature from 26 to 35 °C, relative humidity from 27 to 89%, and short-wave radiation from 0 to 729 W m-2. Exploratory and confirmatory analyses demonstrated that a similar level of nocturnal and diurnal air temperatures evoked distinct (P < 0.05) responses for rectal (TR, °C) and skin (TEP, °C) temperatures, ventilation (VE, L s-1), tidal volume (TV, L breaths-1), and oxygen consumption (∆O2, %) and carbon dioxide output (∆CO2, %), clearly revealing an endogenous rhythm dependence. In conclusion, these findings clarify how the circadian rhythmicity of the thermal environment and animal's biological clock dictate dynamics of heat generated by metabolism, dissipated to the environment and physiological parameters of the housed Jersey cows raised in tropical condition; therefore, it is fundamental to help us to understand how the Jersey dairy cows under tropics are affected by the climatic conditions, leading to better ways of the environmental management.

Thermal balance of Nellore cattle.

This work aimed at characterizing the thermal balance of Nellore cattle from the system of indirect calorimetry using a facial mask. The study was conducted at the Animal Biometeorology Laboratory of the São Paulo State University, Jaboticabal, Brazil. Five male Nellore weighing 750 ± 62 kg, at similar ages and body conditions were distributed in four 5 × 5 Latin squares (5 days of records and five schedules) during 20 days. Physiological and environmental measurements were obtained from the indirect calorimetry system using a facial mask. Respiratory parameters, hair coat, skin, and rectal temperature were continuously recorded. From this, metabolic heat production, sensible and latent ways of heat transfer were calculated. Metabolic heat production had an average value of 146.7 ± 0.49 W m-2 and did not change (P > 0.05) over the range of air temperature (24 to 35 °C). Sensible heat flow reached 60.08 ± 0.81 W m-2 when air temperature ranged from 24 to 25 °C, being negligible in conditions of temperature above 33 °C. Most of the heat produced by metabolism was dissipated by cutaneous evaporation when air temperature was greater than 30 °C. Respiratory parameters like respiratory rate and ventilation remained stable (P > 0.05) in the range of temperature studied. Under shade conditions and air temperature range from 24 to 35 °C, metabolic heat production, respiratory rate, and ventilation of mature Nellore cattle remain stable, which is indicative of low energetic cost to the thermoregulation.

Models to predict both sensible and latent heat transfer in the respiratory tract of Morada Nova sheep under semiarid tropical environment.

The aim of this study was to build a prediction model both sensible and latent heat transfer by respiratory tract for Morada Nova sheep under field conditions in a semiarid tropical environment, using easily measured physiological and environmental parameters. Twelve dry Morada Nova ewes with an average of 3 ± 1.2 years old and average body weight of 32.76 ± 3.72 kg were used in a Latin square design 12 × 12 (12 days of records and 12 schedules). Tidal volume, respiratory rate, expired air temperature, and partial vapor pressure of the expired air were obtained from the respiratory facial mask and using a physiological measurement system. Ewes were evaluated from 0700 to 1900 h in each day under shade. A simple nonlinear model to estimate tidal volume as a function of respiratory rate was developed. Equation to estimate the expired air temperature was built, and the ambient air temperature was the best predictor together with relative humidity and ambient vapor pressure. In naturalized Morada Nova sheep, respiratory convection seems to be a mechanism of heat transfer of minor importance even under mild air temperature. Evaporation from the respiratory system increased together with ambient air temperature. At ambient air temperature, up to 35 °C respiratory evaporation accounted 90 % of the total heat lost by respiratory system, on average. Models presented here allow to estimate the heat flow from the respiratory tract for Morada Nova sheep bred in tropical region, using easily measured physiological and environmental traits as respiratory rate, ambient air temperature, and relative humidity.

Thermoregulatory responses of goats in hot environments.

Notwithstanding the solar radiation is recognized as a detrimental factor to the thermal balance and responses of animals on the range in tropical conditions, studies on the amount of thermal radiation absorbed by goats therein associated with data on their production and heat exchange are still lacking. Metabolic heat production and the heat exchange of goats in the sun and in the shade were measured simultaneously, aiming to observe its thermal equilibrium. The results showed that black goats absorb twice as much as the white goats under intense solar radiation (higher than 800 W m(-2)). This observation leads to a higher surface temperature of black goats, but it must not be seen as a disadvantage, because they increase their sensible heat flow in the coat-air interface, especially the convection heat flow at high wind speeds. In the shade, no difference between the coat colours was observed and both presented a lower absorption of heat and a lower sensible heat flow gain. When solar radiation levels increases from 300 to 1000 W m(-2), we observed an increase of the heat losses through latent flow in both respiratory and cutaneous surface. Cutaneous evaporation was responsible for almost 90 % of the latent heat losses, independently of the coat colour. Goats decrease the metabolic heat production under solar radiation levels up to 800 W m(-2), and increase in levels higher than this, because there is an increase of the respiratory rate and of the respiratory flow, but the fractions of consumed oxygen and produced carbon dioxide are maintained stable. The respiratory rate of black goats was higher than the white ones, under 300 W m(-2) (55 and 45 resp min(-1)) and 1000 W m(-2) (120 and 95 resp min(-1), respectively). It was concluded that shade or any protection against solar radiation levels above 800 Wm(-2) is critical to guarantee goat's thermal equilibrium. Strategies concerning the grazing period in accordance with the time of the day alone are not appropriate, because the levels of radiation depend on the latitude of the location.

Ocorrência de ondas de calor no Triângulo Mineiro e Alto Paranaíba e seu efeito na produção leiteira e consumo alimentar em bovinos / Occurrence of heat waves in Triangulo Mineiro and Alto Paranaíba and their effect on milk yield and feed intake in cattle

Objetivou-se estimar a produção leiteira e o consumo alimentar a partir da ocorrência de ondas de calor no Triângulo Mineiro e Alto Paranaíba, MG por meio de um zoneamento bioclimático baseado no Índice de Temperatura e Umidade (ITU). Para tanto foi elaborado um histórico de ocorrências de ondas de calor entre os anos de 2000 a 2010. O declínio na produção de leite (DPL) e a redução do consumo alimentar (RCA) foram simulados nas cidades em que foram identificados períodos de ondas de calor. Ituiutaba e Frutal apresentaram o maior número de ocorrência de ondas de calor por ano. Os DPLs e RCAs mostraram diferenças bioclimáticas entre as cidades de Uberaba, Ituiutaba e Frutal. As cidades com melhores condições bioclimáticas foram Sacramento e Patrocínio, pois apresentaram ITU fora da classificação de emergência, ITU noturno abaixo de 76 e ausência de ondas de calor. Portanto, a ocorrência de ondas de calor pode prejudicar a ingestão de alimentos e diminuir a produção leiteira demonstrando de forma mais efetiva o efeito do estresse térmico em vacas leiteiras na mesorregião do Triângulo Mineiro e Alto Paranaíba.

The aim of this study was to estimate milk production and food consumption during the occurrence of heat waves in the Triângulo Mineiro and Alto Paranaíba, MG by means of bioclimatic zoning based on the Temperature and Humidity Index (THI). Therefore a history of heat wave occurrence between the years 2000-2010 was compiled. The decline in milk production (DMP) and reduced food consumption (RFC) were simulated in cities where periods of heat waves were identified. Frutal and Ituiutaba had the highest rate of heat wave occurrence per year. The DMP and RFC showed bioclimatic differences between the cities of Uberaba, Ituiutaba and Frutal. The cities with the best bioclimatic conditions were Sacramento and Patrocinio, as they presented a THI classified outside of the emergency range, with a night THI of below 76 and without heat waves. Therefore, the occurrence of heat waves can impair food intake and decrease milk production, thereby most effectively demonstrating the effects of thermal stress on dairy cows in the Triângulo Mineiro and Alto Paranaíba, MG region.

Ocorrência de anticorpos anti-leptospira spp. em diferentes sistemas de criação de suínos / Occurrence of leptospira spp. antibodies in pigs from different housing systems

A leptospirose é uma zoonose de grande importância sócio-econômica para a suinocultura. Neste estudo, objetivou-se determinar a ocorrência de anticorpos anti-Leptospira em 132 amostras de soro sangüíneo de suínos procedentes de três diferentes sistemas de produção: granja não tecnificada, granja tecnificada e granja que utiliza o sistema intensivo de suínos criados ao ar livre (SISCAL). As amostras foram processadas através da técnica de Soroaglutinação Microscópica (SAM) em campo escuro, utilizando os seguintes sorovares: Bratislava, Canicola, Grippotyphosa, Hardjo, Icterohaemorrhagiae e Wolffi. A ocorrência de anticorpos anti-Leptospira nas três granjas foi de 47,1%, sendo que identificou-se 20%, 56% e 44,4% nas granjas não tecnificada, tecnificada e o SISCAL, respectivamente. Sessenta e duas amostras foram positivas para um ou mais sorovar, sendo mais freqüentes o Icterohaemorrhagiae, Hardjo e Wolffi com ocorrência de 67,1%, 55,7% e 24%, respectivamente.

Leptospirosis is a zoonosis and an important social-economic aspect to the pig farming. In this study, aiming at the objective to determinate the occurrence of antibodies anti-Leptospira from 132 swine serum sample preceded from three differents housing systems: intensive swine farm (high technology), intensive swine farm (low technology) and free range conditions. The samples were processed through the Microscopic Aglutination Test (MAT) in dark field, using differents serovars: Bratislava, Canicola, Grippotyphosa, Hardjo, Icterohaemorrhagiae and Wolffi. The occurrence of antibodies anti-Leptospira from three differents housing systems was 47,1%, being identified 20%, 56% e 44,4% in the intensive swine farm (high technology), intensive swine farm (low technology) and free range conditions, respectively. Sixty-two serum samples were positive for one or more serovar, being more frequent Icterohaemorrhagiae, Hardjo and Wolffi, with occurrence of 67,1%, 55,7% e 24%, respectively.