Thompson S, Schaefer A L, Crow G H, Basarab J, Colyn J, Ominski K
Department of Animal Science & National Centre for Livestock and the Environment (NCLE), University of Manitoba, Winnipeg, MB, Canada R3T 2N2.
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5.
J Therm Biol. 2018 Dec;78:304-311. doi: 10.1016/j.jtherbio.2018.10.007. Epub 2018 Oct 19.
Residual feed intake (RFI) has been used to select metabolically efficient cattle in beef breeding programs, particularly for sire selection. Adoption of genetic selection using RFI has been limited due to the cost and difficulty of measuring individual feed intake. An alternative method of predicting RFI is to measure radiated heat loss using infrared thermography (IRT) as previous studies have shown promise using this technique to predict metabolic efficiency in mature cows, heifers, and growing bulls. The objective of this study was to explore use of IRT to predict RFI in growing beef bulls. Sixty bulls in each of two years were fed either a forage-based or a grain-based ration. Eye (Ey) and cheek (Ck) surface temperatures were measured using infrared images of the head collected on 16 and 14 sample days in Years 1 and 2, respectively, using a FLIR S60 camera. In Year 2, infrared images were collected continuously using a within-pen FLIR A310 camera system. Bulls were grouped into low, medium and high classes based on ± 0.5 standard deviations of backfat adjusted residual feed intake (RFI); RFI values ranged from - 2.27 to + 2.61 kg DM day (mean=0.0; SD=0.61). Sample day Ey and Ck temperatures were pooled and an average temperature was calculated for individual bulls. Average Ey and Ck temperatures measured using the FLIR S60 and the within-pen camera did not differ significantly across low, medium and high RFI groups (P > 0.05). Temperature deviations associated with extremes in ambient temperature (placing animals outside their thermoneutral zone) or underlying subclinical health problems could bias results in IRT measurements and RFI ranking. Standardization of IRT data and the conditions during measurement is necessary to more accurately assess its potential use to predict RFI.
剩余采食量（RFI）已被用于肉牛育种计划中选择代谢高效的牛，特别是用于种公牛的选择。由于测量个体采食量的成本和难度，采用RFI进行遗传选择受到了限制。预测RFI的另一种方法是使用红外热成像（IRT）测量辐射热损失，因为先前的研究表明，使用该技术预测成年母牛、小母牛和生长公牛的代谢效率具有前景。本研究的目的是探索使用IRT预测生长肉牛公牛的RFI。在两年中，每年60头公牛分别饲喂以粗饲料为主或谷物为主的日粮。分别在第1年和第2年的16天和14个采样日，使用FLIR S60相机通过采集头部的红外图像来测量眼睛（Ey）和脸颊（Ck）的表面温度。在第2年，使用围栏内的FLIR A310相机系统连续采集红外图像。根据背膘调整后的剩余采食量（RFI）的±0.5个标准差，将公牛分为低、中、高组；RFI值范围为-2.27至+2.61 kg DM/天（平均值=0.0；标准差=0.61）。将采样日的Ey和Ck温度合并，并计算每头公牛的平均温度。使用FLIR S60和围栏内相机测量的平均Ey和Ck温度在低、中、高RFI组之间没有显著差异（P>0.05）。与极端环境温度（使动物处于热中性区之外）或潜在的亚临床健康问题相关的温度偏差可能会使IRT测量结果和RFI排名产生偏差。为了更准确地评估IRT预测RFI的潜在用途，需要对IRT数据和测量期间的条件进行标准化。
