Ruminal microorganisms play a pivotal role in cattle nutrition. The discovery of the main microbes or of a microbial community responsible for enhancing the gain of weight in beef cattle might be used in therapeutic approaches to increase animal performance and cause less environmental damages. Here, we examined the differences in bacterial and fungal composition of rumen samples of Braford heifers raised in natural grassland of the Pampa Biome in Brazil. We aimed to detect microbial patterns in the rumen that could be correlated with the gain of weight. We hypothesized that microorganisms important to digestion process are increased in animals with a higher gain of weight. The gain of weight of seventeen healthy animals was monitored for 60 days. Ruminal samples were obtained and the 16S and ITS1 genes were amplified and sequenced to identify the closest microbial relatives within the microbial communities. A predictive model based on microbes responsible for the gain of weight was build and further tested using the entire dataset., The main differential abundant microbes between groups included the bacterial taxa RFN20, Prevotella, Anaeroplasma and RF16 and the fungal taxa Aureobasidium, Cryptococcus, Sarocladium, Pleosporales and Tremellales. The predictive model detected some of these taxa associated with animals with the high gain of weight group, most of them being organisms that have been correlated to the production of substances that improve the ruminal digestion process. These findings provide new insights about cattle nutrition and suggest the use of these microbes to improve beef cattle breeding.

瘤胃微生物在牛的营养中起关键作用。发现主要微生物或负责增加肉牛增重的微生物群落可用于治疗方法，以提高动物的生产性能并减少对环境的损害。在这里，我们研究了巴西Pampa Biome天然草原上饲养的Braford小母牛瘤胃样品的细菌和真菌组成的差异。我们旨在检测瘤胃中可能与体重增加相关的微生物模式。我们假设对动物来说，对于消化过程重要的微生物会以更高的体重增加。监测60天中17只健康动物的体重增加。获得了瘤胃样品，并对16S和ITS1基因进行了扩增和测序，以鉴定微生物群落中最接近的微生物亲戚。建立了一个基于微生物导致体重增加的预测模型，并使用整个数据集对其进行了进一步测试。各组之间的主要差异丰富的微生物包括细菌分类群RFN20，普雷沃氏菌，厌氧菌和RF16，以及真菌类群金黄色葡萄球菌，隐球菌，沙门氏菌，伞形目和银耳。预测模型检测到其中一些与体重增加高的动物相关的类群，其中大多数是与改善瘤胃消化过程的物质产生相关的生物。这些发现提供了有关牛营养的新见解，并建议使用这些微生物来改善肉牛育种。