Mahendran Sophie A, Blackie Nicola, Wathes D Claire, Booth Richard E
Pathobiology and Population Sciences, Royal Veterinary College, Hawkshead Lane, Hatfield, Hertfordshire, AL9 7TA United Kingdom.
Pathobiology and Population Sciences, Royal Veterinary College, Hawkshead Lane, Hatfield, Hertfordshire, AL9 7TA United Kingdom.
J Dairy Sci. 2023 Apr;106(4):2461-2474. doi: 10.3168/jds.2022-22613. Epub 2023 Feb 14.
Preweaning calves are kept in a range of housing types that offer variable protection against the weather and provide differing internal environments. This cross-sectional observational study assessed the effect of housing type (shed, polytunnel, or hutches) on internal environmental parameters, using 2 blocks of 8-wk measurements from 10 commercial dairy farms in the south of England, covering both summer and winter periods. Continuous measurements for internal and external temperature and humidity were recorded by data logger placed within the calf housing and used to calculate the temperature-humidity index (THI). Weekly point readings were also taken for temperature, humidity, light, air speed, ammonia level, and airborne particulate matter. Airborne bacterial levels were determined at wk 2, 5, and 8 by incubating air samples at 35°C for 24 h in aerobic conditions. Data were analyzed using linear mixed models. Housing type influenced THI significantly in both seasons. In summer, calves were exposed to heat stress conditions (THI ≥72) for 39, 31, and 14 of 46 d in polytunnel housing, hutches, and sheds, respectively. The maximum summer temperature (37.0°C) was recorded in both hutch and polytunnel housing, with sheds remaining consistently cooler (maximum 31.0°C). In winter, the lowest minimum internal temperature recorded was in hutches at -4.5°C, with both the sheds and polytunnel, but not hutches, providing a significant increase in temperature compared with the external environment. Hutches remained ≤ 10°C for 86% of the winter study period. Light levels were reduced in all housing types compared with the external environment. The particulate matter in air that is capable of reaching the lungs (particulate matter <10 μm) was highest in sheds, intermediate in hutches, and lowest in polytunnel housing (0.97 ± 3.75, 0.37 ± 0.44, and 0.20 ± 0.24 mg/m, respectively). This was mirrored by airborne bacterial numbers, which were also highest in sheds (8,017 ± 2,141 cfu/m), intermediate in hutches (6,870 ± 2,084 cfu/m), and lowest in the polytunnel (3,357 ± 2,572 cfu/m). Round, white, catalase-positive, and oxidase-negative colonies were most prevalent, likely indicating Staphylococcus species. This study demonstrated that UK calves are routinely exposed to either heat or cold stress, especially when housed in hutches or polytunnels. Sheds had the highest levels of particulate matter and airborne bacteria, both known contributory factors for respiratory disease. These findings demonstrate that all calf housing systems result in environmental compromises that could have long-term impacts on calf health and growth; therefore, further studies should identify husbandry and housing modifications to mitigate these factors.
断奶前的犊牛饲养在一系列不同类型的畜舍中，这些畜舍对天气的防护程度不同，内部环境也有所差异。这项横断面观察性研究评估了畜舍类型（棚舍、塑料大棚或犊牛栏）对内部环境参数的影响，研究使用了来自英格兰南部10个商业奶牛场的2组为期8周的测量数据，涵盖夏季和冬季。通过放置在犊牛舍内的数据记录器连续记录内部和外部的温度及湿度，并用于计算温湿度指数（THI）。每周还会对温度、湿度、光照、风速、氨气水平和空气中颗粒物进行定点读数。在第2周、第5周和第8周，通过在35°C有氧条件下将空气样本培养24小时来测定空气中的细菌水平。数据采用线性混合模型进行分析。畜舍类型在两个季节对THI均有显著影响。夏季，在塑料大棚畜舍、犊牛栏和棚舍中，犊牛分别在46天中有39天、31天和14天暴露于热应激条件（THI≥72）下。犊牛栏和塑料大棚畜舍记录到的夏季最高温度为37.0°C，棚舍温度则一直较低（最高31.0°C）。冬季，记录到的最低内部温度出现在犊牛栏，为-4.5°C，棚舍和塑料大棚畜舍相比外部环境温度均有显著升高，但犊牛栏没有。在冬季研究期间的86%时间里，犊牛栏温度保持在≤10°C。与外部环境相比，所有畜舍类型的光照水平均降低。能够进入肺部的空气中颗粒物（粒径<10μm的颗粒物）在棚舍中最高，犊牛栏中次之，塑料大棚畜舍中最低（分别为0.97±3.75、0.37±0.44和0.20±0.24mg/m）。空气中细菌数量的情况与之相似，在棚舍中最高（8,017±2,141cfu/m），犊牛栏中次之（6,870±2,084cfu/m），塑料大棚畜舍中最低（3,357±2,572cfu/m）。圆形、白色、过氧化氢酶阳性和氧化酶阴性的菌落最为普遍，可能表明是葡萄球菌属。这项研究表明，英国的犊牛经常面临热应激或冷应激，尤其是当饲养在犊牛栏或塑料大棚中时。棚舍中的颗粒物和空气中细菌水平最高，而这两者都是已知的导致呼吸道疾病的因素。这些发现表明，所有犊牛饲养系统都会导致环境方面的问题，可能对犊牛健康和生长产生长期影响；因此，进一步的研究应确定饲养管理和畜舍方面的改进措施，以减轻这些因素的影响。
