Correlação entre variáveis ambientais e fisiológicas de novilhas leiteiras mestiças

<p>Devido às perdas produtivas e reprodutivas, têm sido propostos estudos para avaliar indivíduos mais adaptados ao estresse pelo calor<b>.</b> Assim, objetivou-se correlacionar medidas fisiológicas de termorregulação de novilhas leiteiras mestiças e variáveis do ambiente térmico em Uberlândia-MG, Brasil. Oito novilhas mestiças foram expostas ao sol das 09h às 13h. Após, os animais foram conduzidos para o tronco para quantificar frequência respiratória (FR), temperatura retal (TR) e temperatura corporal superficial (TCS). Simultaneamente, foram obtidas a temperatura de bulbo seco (T_A), a temperatura de bulbo úmido (T_U), a temperatura do globo negro (T_G) e a velocidade do vento (V). Realizou-se a estatística descritiva dos dados e a correlação simples de Pearson entre as variáveis fisiológicas e ambientais. As variáveis fisiológicas apresentaram média de FR 41,97 mov.min^-1, TR de 38,8ºC e TCS no flanco preto e no flanco branco foram, respectivamente de 35,82°C e 35,04°C. Referente às variáveis ambientais, a T_A média foi 29,96ºC, a T_G média, 41,73ºC, a V teve uma variação de 0 a 1,2 m.s^-1e a umidade relativa do ar (UR) variou de 39% a 80%. A TR não correlacionou com nenhuma das variáveis ambientais avaliadas. A FR teve as maiores correlações com a T_G e a V. Por fim, a TCS, seja no flanco branco ou no preto, teve as correlações mais expressivas com a T_A e com a T_G. A temperatura ambiente e do globo e velocidade do vento influenciam diretamente na frequência respiratória de novilhas leiteiras mestiças criadas em Uberlândia MG e estas são adaptadas às condições meteorológicas da região.</p

Ingestive behaviour of Nelore bulls fed with a GrowSafe system and its relation to the thermal environment

<p>The demand for food, especially of animal origin, is increasing every year. On the other hand, it is believed that climate changes will have impacts on livestock production, especially in tropical regions. Therefore, the development and improvement of livestock production systems is crucial. Thus, the objective of this study was to relate the ingestive behavior of Nellore cattle reared in confinement and fed with a GrowSafe System with measures of the thermal environment. Fifty Nelore bulls, with an average age of 21 months were distributed into two paddocks. The behavioural categories (resting while standing, resting while lying, ruminating while standing, ruminating while lying, eating at feedbunk and feedbunk intention) and meteorological variables (dry and wet bulb temperatures, wind speed [v] and black globe temperature [Tg] were evaluated. The Temperature and Humidity Index (THI), Equivalent Temperature Index (ETI), Black Globe humidity Index (BGHI) and Heat Load Index (HLI) were calculated. Observations were divided into two periods (morning and afternoon) and the study was divided into the following schedules: 1 = 07 hours to 08 hours; 2 = 08 hours: 30 minutes to 09 hours 30 minutes; 3 = 13 hours: 45 minutes to 14 hours: 45 minutes; 4 = 15 hours: 30 minutes to 16 hours: 30 minutes and 5 = 17 hours: 15 minutes to 18 hours: 15 minutes. Pearson's simple correlation between ingestive behavior and thermal environment measurements was performed. There was a positive and moderate correlation between animals eating at feedbunk and air temperature (Ta). Ruminating while standing showed moderate and negative correlation with Ta and Tg, being moderate and positive with relative humidity (Ur). Ruminating while lying correlated moderately and positively with HLI. There was a moderate and negative correlation between the resting while standing activity and the variables Tg, v, BGHI and HLI, while resting while lying had a moderate and positive correlation with Tg and HLI. It is concluded that the thermal environment can affect the ingestive behavior of confined Nellore bulls fed through a GrowSafe System during winter time at Uberlândia, MG.</p