There is a trend to reduce the space allowance per animal in cattle feedlot, despite its potential negative impact on animal welfare. Aiming to evaluate the effects of space allowance per animal in outdoor feedlots on beef cattle welfare, a total of 1350 Nellore bulls (450 pure and 900 crossbred) were confined for 12 weeks using three space allowances: 6 (SA6), 12 (SA12) and 24 (SA24) m2/animal (n = 450 per treatment). Bulls were housed in three pens per treatment (n = 150 per pen). The first 6 weeks in the feedlot were defined as ‘dry’ and the last as ‘rainy’ period, according to the accumulated precipitation. Animal-based (body cleanliness, health indicators and maintenance behaviour) and environmental-based indicators (mud depth and air dust concentration) were assessed weekly during the feedlot period. Most of the health indicators (nasal and ocular discharge, hoof and locomotion alterations, diarrhoea, bloated rumen and breathing difficulty) were assessed in a subset of 15 animals randomly selected from each pen. Coughs and sneezes were counted in each pen. Maintenance behaviours (number of animals lying and attending the feed bunk) were recorded with scan sampling and instantaneous recording at 20-min intervals. Postmortem assessments were carried out in all animals by recording the frequencies of macroscopic signs of bronchitis, pulmonary emphysema, nephritis and urinary cyst and by measuring the weight and cortical and medullar areas of adrenal glands (n = 30 per pen). Compared with SA12 and SA24, SA6 showed a greater number of sneezes per minute during the dry period and a greater percentage of animals with locomotion alterations during the rainy period. Coughing, diarrhoea and nasal discharge affected a larger number of animals in the SA6 relative to the other two groups. During the rainy period, there was a lower percentage of animals with nasal and ocular discharge, and a greater percentage of animals with abnormal hoof and lying. A lower percentage of animals in SA6 and SA12 (but not SA24) attended the feed bunk during the rainy relative to the dry period. A mud depth score of 0 (no mud) was most frequent in SA24 pens, followed by SA12 and then SA6. Adrenal gland weight and cortical area were lower in SA24 animals compared with those in SA6 and SA12. The results show that decreasing the space allowance for beef cattle in outdoor feedlots degrades the feedlot environment and impoverishes animal welfare.

尽管对牲畜饲养场有潜在的负面影响，但趋势是减少每只动物的饲养空间。为了评估室外饲养场中每头动物的空间配额对肉牛福利的影响，使用三种空间配额将总共1350头内洛尔公牛（450头纯种和900头杂种）限制在12周内：6（SA6），12（SA12）和24（SA24）m 2 /动物（每处理n = 450）。每次处理将公牛放在三支钢笔中（n=每支笔150。根据累积的降水量，饲养场的前6周被定义为“干燥”，最后一个被定义为“阴雨”。在饲养场期间，每周评估基于动物的（身体清洁度，健康指标和维护行为）和基于环境的指标（泥浆深度和空气尘埃浓度）。在从每支笔中随机选择的15只动物的子集中评估了大多数健康指标（鼻和眼分泌物，蹄和运动改变，腹泻，瘤胃肿胀和呼吸困难）。每支笔计数咳嗽和打喷嚏。通过扫描采样和间隔20分钟的瞬时记录来记录维护行为（躺下和进入饲料铺的动物数量）。验尸评估是通过记录的支气管炎，肺气肿，肾炎和尿囊肿的宏观体征的频率和通过测量重量和肾上腺皮质和髓质区（在所有动物中进行Ñ= 30（每支笔）。与SA12和SA24相比，SA6在干燥期间每分钟打喷嚏次数更多，在雨季中出现运动变化的动物百分比也更高。相对于其他两组，咳嗽，腹泻和鼻涕影响了SA6中的大量动物。在雨季，鼻和眼分泌物的动物比例较低，蹄和躺卧异常的动物比例较高。相对于干旱时期，SA6和SA12（而非SA24）中有较低百分比的动物在下雨天参加饲料铺。在SA24笔中，泥浆深度得分为0（无泥浆）最为频繁，其次是SA12，然后是SA6。与SA6和SA12相比，SA24动物的肾上腺重量和皮质面积较低。