The aim of this study was to identify detailed changes in behavior, and in salivary serum amyloid A (SAA), associated with subclinical mastitis. This included standard sickness behaviors (which form part of an adaptive response to conserve energy, minimize heat loss and facilitate recovery following infection and inflammation) and lesser-studied behaviors, that are biologically predicted to change at low-level infection, and therefore particularly relevant for detecting subclinical mastitis (here labelled ‘luxury’ behaviors). SAA is a physiological marker of systemic inflammation, with levels in milk and serum already known to increase during subclinical mastitis. We investigated whether the same was true for SAA in cow saliva. Data were collected for n = 34 commercial barn-housed dairy cows, tested in 17 matched-pairs. Each pair comprised a cow with subclinical mastitis (SCM) and a healthy control (CTRL), identified using somatic cell count (SCC) (SCM: SCC >200 x1000 cells/ml; CTRL: SCC <100 x1000 cells/ml). SCM cows were selected for study ad-hoc, at which point they were paired with a CTRL cow, based upon parity and calving date; consequently, the full data set was accrued over several months. Data were collected for each pair over 3 days: SCC (l4:00-l5:00h) Day 1; behavior (24h from 00:00h) Day 2; salivary serum amyloid-A (SAA) Day 3. We report, for the first time, that an increase in salivary SAA occurs during subclinical mastitis; SAA was higher in SCM cows and demonstrated a positive (weak) correlation with SCC. The behavioral comparisons revealed that SCM cows had reductions in activity (behavioral transitions and distance moved), social exploration, social reactivity (here: likelihood to move away/be displaced following receipt of agonism), performance of social grooming and head butts, and the receipt of agonistic non-contact challenges. In addition, SCM cows received more head swipes, and spent a greater proportion of time lying with their head on their flank than CTRL cows. SCM cows also displayed an altered feeding pattern; they spent a greater proportion of feeding time in direct contact with two conspecifics, and a lower proportion of feeding time at self-locking feed barriers, than CTRL cows. Behavioral measures were found to correlate, albeit loosely, with serum SAA in a direction consistent with predictions for sickness behavior. These included positive correlations with both lying duration and the receipt of all agonistic behavior, and negative correlations with feeding, drinking, the performance of all social and all agonistic behavior, and social reactivity. We conclude that changes in salivary SAA, social behavior, and activity offer potential in the detection of subclinical mastitis and recommend further investigation to substantiate and refine our findings.

中文翻译：

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亚临床乳腺炎奶牛行为和唾液血清淀粉样蛋白A的变化

本研究的目的是确定行为的详细变化，以及唾液血清淀粉样蛋白 A（SAA)，与亚临床乳腺炎有关。这包括标准的疾病行为（这是一种适应性反应的一部分，以节省能量、减少热量损失并促进感染和炎症后的恢复）和研究较少的行为，这些行为在生物学上被预测在低水平感染时会发生变化，因此特别相关用于检测亚临床乳腺炎（此处标记为“奢侈”行为）。SAA 是全身炎症的生理标志物，已知在亚临床乳腺炎期间，牛奶和血清中的水平会增加。我们调查了奶牛唾液中的 SAA 是否也是如此。收集了 n = 34 头商业谷仓饲养的奶牛的数据，在 17 对配对中进行测试。每对包括一头患有亚临床乳腺炎 ( SCM)的奶牛和一个健康对照 (CTRL），使用体细胞计数（SCC）（SCM：SCC >200 x1000 细胞/ml；CTRL：SCC <100 x1000 细胞/ml）。选择 SCM 奶牛进行临时研究，此时根据胎次和产犊日期将它们与 CTRL 奶牛配对；因此，完整的数据集是在几个月内积累起来的。在 3 天内为每对收集数据：SCC (l4:00-l5:00h) 第 1 天；行为（从 00:00 开始的 24 小时）第 2 天；唾液血清淀粉样蛋白-A (SAA) 第 3 天。我们首次报告说，在亚临床乳腺炎期间唾液 SAA 增加；SCM 奶牛的 SAA 较高，并且与 SCC 呈正（弱）相关。行为比较显示，SCM 奶牛的活动（行为转变和移动距离）、社会探索、社会反应（此处：在接受激动后离开/流离失所的可能性）减少，社交修饰和头撞的表现，以及接受非接触式的对抗性挑战。此外，与 CTRL 奶牛相比，SCM 奶牛接受了更多的头部滑动，并且头部侧卧的时间比例更大。SCM 奶牛也表现出改变的喂养模式；与 CTRL 奶牛相比，它们与两个同种动物直接接触的喂养时间比例更大，而在自锁饲料屏障处的喂养时间比例更低。发现行为测量与血清 SAA 相关，尽管与疾病行为的预测一致。这些包括与躺着持续时间和接受所有激动行为的正相关，以及与进食、饮水、所有社交和所有激动行为的表现以及社交反应性的负相关。