Abstract：
Environmental conditions and available forage on pastures greatly differ between different farming systems, which can affect the behaviour of grazing cattle. The interplay between environment-, forage-, and animal-related variables may affect the use of feed and water resources in grazing-based systems. Hence, our objectives were (i) to study the differences between grazing-based systems and seasons in environment- and pasture-related variables as well as the behaviour, feed intake, performance, and water productivity of Nellore heifers, and (ii) to understand the interrelationships between these variables. The measurements were performed in a conventional grazing system (CON), an integrated crop-livestock (ICL), and a crop-livestock-forestry (ICLF) systems in the Brazilian Cerrado during the rainy and dry seasons. Ambient temperature and relative air humidity were hourly measured in both seasons. Forage biomass and sward height were determined every month. Forage samples were taken to determine the proportions of alive leaves, alive stems, and dead plant material and to analyse their nutritive value. Forage intake, drinking water intake, and liveweight changes were quantified in 12 Nellore heifers per system and season. Feeding behaviour was recorded by chewing sensors on nine continuous days in each season. Drinking water intake was measured by water meters attached to drinking water troughs, whereby trial cameras at the troughs recorded the frequency of drinking events of individual animals. Feed conversion efficiency and water productivity were estimated. The ICLF reduced the exposure time to high ambient temperatures so that heifers even grazed during the hottest hours. Forage biomass in ICL and CON had greater proportions of stem and dead plant material than in ICLF. Forage intake rate was greater and grazing events were longer for animals in ICLF than those in CON, whereas the daily number of grazing events was greater in CON. Feed conversion efficiency and water productivity were greater in integrated systems than in CON. Amongst studied variables, thermal environment and forage canopy structure with its proportions of dead plant material are the main driving factors for animal behaviour, forage intake rate, and animal performance. These variables reduce feed conversion efficiency and water productivity in grazing cattle. Further research should analyse strategies for promoting thermal comfort for the animals, increasing the proportions of alive biomass, and enhancing the nutritional value of pastures for more efficient use of forage and water resources in grazing-based systems.
摘要：
不同的耕作系统之间的环境条件和牧场上的可用牧草有很大差异，会影响放牧牛的行为。环境之间的相互作用-，觅食-,与动物相关的变量可能会影响放牧系统中饲料和水资源的使用。因此，我们的目标是（i）研究基于放牧的系统和季节在环境和牧场相关变量以及行为之间的差异，饲料摄入量，性能，和内洛尔小母牛的水生产力，和（ii）了解这些变量之间的相互关系。测量在常规放牧系统(CON)中进行，综合作物-牲畜(ICL)，在雨季和旱季，巴西Cerrado的农作物-畜牧业-林业（ICLF）系统。在两个季节中每小时测量环境温度和相对空气湿度。每个月测定牧草生物量和草皮高度。采集牧草样本以确定活叶的比例，活着的茎，和死亡的植物材料，并分析其营养价值。饲草摄入量，饮用水摄入量，每个系统和季节对12只Nellore母牛的体重变化进行了量化。在每个季节连续9天通过咀嚼传感器记录喂养行为。饮用水摄入量是通过连接到饮用水槽的水表测量的，在槽的试验摄像机记录了个体动物饮酒事件的频率。估计了饲料转化效率和水生产率。ICLF减少了暴露在高环境温度下的时间，因此母牛甚至在最热的时间里放牧。ICL和CON中的牧草生物量比ICLF中的茎和死植物材料所占比例更大。与CON相比，ICLF中的动物的牧草摄入量更高，放牧事件更长，而CON中每天放牧事件的数量更多。集成系统的进料转化效率和水生产率高于CON。在研究的变量中，热环境和牧草冠层结构及其死亡植物材料的比例是动物行为的主要驱动因素，牧草的采食率，和动物表演。这些变量降低了放牧牛的饲料转化效率和水分生产率。进一步的研究应该分析促进动物热舒适的策略，增加活生物量的比例，并提高牧场的营养价值，以便在放牧系统中更有效地利用牧草和水资源。
