Desempeño cardiovascular de dos estirpes de Gallus gallus domesticus sometidas a estrés calórico agudo / Cardiovascular Performance of Two Lineages of Gallus gallus domesticus Subjected to Acute Heat Stress

La selección genética en aves de corral se ha basado en caracteres para crecimiento rápido y no para la adaptabilidad a condiciones estresantes. En esta investigación, se evaluaron variables ambientales y cardiovasculares de dos estirpes de Gallus gallus domesticus con diferentes niveles de domesticación, sometidas a condiciones de estrés calórico agudo. Para la realización del experimento, se utilizaron pollos de engorde comerciales con alto nivel de selección genética (n=40) y pollos criollos (n=40) con bajo nivel de selección. Todos los pollos se criaron bajo las mismas condiciones hasta el día 36 de edad, día en que se evaluó: temperatura ambiental, humedad relativa, temperatura corporal, frecuencia cardiaca, volumen sistólico y gasto cardiaco. El día 37, ambos grupos de animales fueron expuestos a una simulación de estrés calórico agudo (34°C), midiéndose las variables antes mencionadas. Los datos fueron analizados como medidas repetidas (PROC MIXED de SAS, 2005), bajo un diseño de bloques. El día 37, las temperaturas corporales de los pollos comerciales (46,1±0,2°C) fue significativamente mayor (P £ 0,01) que las de los criollos (43,5±0,9°C). El incremento en la frecuencia cardiaca (38±1 lat/min) de los pollos comerciales fue mayor (P ≤0,01), en contraste con la de los pollos criollos (23±0 lat/min), cuando comparamos con el día anterior. De igual modo, cuando se hace la comparación con respecto al día anterior (día 36), el volumen sistólico (0,33±0,03 mL/lat) y el gasto cardiaco (38,50±3,3 ml/min) y disminuyeron (P>0,05) en los pollos comerciales; en contraste, estas variables (volumen sistólico: 0,09±0,00 mL/lat; gasto cardiaco: 59,10±4,8 mL/ min) aumentaron en los criollos. La relación gasto cardiaco sobre peso vivo fue mayor (P≤0,01) en los pollos criollos (0,81±0,03 mL/min/g) con respecto a los comerciales (0,40±0,07 mL/min/g). Estos hallazgos sugieren que el desempeño cardiaco de la estirpe comercial fue menos eficiente, en relación al desempeño cardiaco de la estirpe criolla, frente al estrés calórico, en comparación con los pollos criollos y que estos últimos se encuentran mejor adaptados para hacer frente a situaciones de estrés calórico ambiental.

Genetic selection in poultry has been based on fast growth characters and not on stress adaptability. This investigation assessed cardiovascular variables in two lineages of Gallus gallus domesticus of different domestication levels, subjected to acute heat stress. To carry out the assay, broiler chickens (n=40) with a high-end level of genetic selection and creole chickens (n=40) with a low-end level of genetic selection were evaluated. All chickens were reared under the same conditions until day 36 of age, at which day, the following variables were measured: environmental temperature, relative humidity, body temperature, heart rate, systolic volumen, and cardiac output. On day 37, both flocks were exposed to an acute environmental heat stress simulation (34 ºC). Data were analyzed with repetitive measures test (PROC MIXED, SAS, 2005), with a two-way arrangement. During the heat stress simulation, body temperature of broilers (46.1±0.2°C) was higher (P≤0,01) than that of creole chickens (43.5±0.9°C); likewise, the increase in broilers heart rate (38±1 beats/min) was higher (P≤0,01), when compared to the increase in creole chickens (23±0 beats/min) from the day before. Similarly, a lower (P>0,05) systolic volume (0.33±0.03 mL/beats) and cardiac output (38.5±3.3 mL/min) was registered in broilers in contrast to an increment of these variables (systolic volume: 0.09±0.00 mL/beats; cardiac output: 59.10±4.8 mL/min) in creoles. Cardiac output to body weight ratio was higher (P≤0,01) in creole chickens (0.81±0.03 mL/min/g) in comparison to broilers (0.40 ± 0.07 mL/min/g). These results suggest that chickens from a commercial lineage (broilers) were less effective in terms of cardiac performance, under environmental heat stress, when compared to creole chickens, suggesting that creole chickens are better adapted to cope with environmental heat stress.

Avaliação ecocardiográfica em bezerros da raça Holandesa / Echocardiographic evaluation in Holstein calves

Com o objetivo de estabelecer valores de medidas ecocardiográficas em bezerros da raça Holandesa, utilizaram-se 25 animais, com idade entre 8 e 28 dias e peso entre 27 e 57 kg. Procedeu-se o exame ecocardiográfico em modo-B e modo-M para a obtenção dos valores médios dos seguintes parâmetros, em diástole e sístole, respectivamente: diâmetros internos dos ventrículos direito (2,05±0,13cm e 1,59±0,13cm) e esquerdo (3,91±0,09cm e 2,52±0,13cm), espessuras do septo interventricular (1,24±0,04cm e 1,62±0,06cm) e da parede livre do ventrículo esquerdo (0,92±0,04cm e 1,50±0,05cm). Obtiveram-se ainda valores do diâmetro dos átrios direito e esquerdo em sístole (2,97±0,12cm e 4,11±0,21cm, respectivamente), dos volumes diastólico (67,90±3,65ml), sistólico (25,32±3,05ml) e de ejeção (42,58±2,46ml) do ventrículo esquerdo, do débito cardíaco (3857±339ml/min), do diâmetro aórtico (2,52±0,05cm), da distância entre o ponto de maior abertura do folheto anterior da valva atrioventricular esquerda até o septo interventricular (0,65±0,08cm) e tempo de ejeção (0,39±0,02s), das frações de encurtamento (36,27±2,40 por cento) e de ejeção do ventrículo esquerdo (64,67±3,22 por cento). Houve média correlação linear positiva (66,4 por cento, P<0,01) entre diâmetro aórtico e peso dos animais, média correlação linear negativa (P<0,01) entre tempo de ejeção do ventrículo esquerdo e freqüência cardíaca (69,1 por cento) e com o débito cardíaco (62,4 por cento). Observou-se uma tendência dos bezerros em apresentar menor diâmetro da câmara cardíaca esquerda, apesar de mantidas as relações de espessura de parede e índices funcionais do miocárdio.

With the purpose of establishing echocardiographic measurements in Holstein calves, 25 calves, 8 to 28 days of age and body weight ranging from 27 to 57 kg, were used. The echocardiographic examination was proceeded in B and M-modes to obtain the following parameters, in diastole and systole: right ventricle (2.05±0.13cm and 1.59±0.13cm) and left ventricle internal diameter (3.91±0.09cm and 2.52±0.13cm), and interventricular septum (1.24±0.04cm and 1.62±0.06cm) and left ventricle free wall thickness (0.92±0.04cm and 1.50±0.05cm). The values for both left and right atria in systole were 2.97±0.12cm and 4.110.21cm, respectively. The left diastolic (67.90±3.65ml), systolic (25.32±3.05ml) and ejection (42.58±2.46ml) volumes, cardiac output (3857±339ml/min), aortic root diameter (2.52±0.05cm), E-point septal separation (0.65±0.08cm), left ventricle ejection time (0.39±0.02s), fractional shortening (36.27±2.40 percent) and ejection fraction (64.67±3.22 percent) were also calculated. There was a mean positive linear correlation (66.4 percent, P<0.01) between the aortic root diameter and the bodyweight, mean negative linear correlation (P<0.01) heart rate (69.1 percent) and cardiac output (62.4 percent). There was a tendency of the calves in between the left ventricle ejection time and presenting a smaller left chamber diameter, although maintained the relationship between myocardial wall thickness and functional indexes.