Department of Animal Sciences & Industry, Kansas State University, Manhattan 66506.
Department of Animal Science, Michigan State University, East Lansing 48824.
J Dairy Sci. 2021 Sep;104(9):9418-9436. doi: 10.3168/jds.2021-20217. Epub 2021 Jun 5.
Suppression of appetite, or hypophagia, is among the most recognizable effects of disease in livestock, with the potential to impair growth, reproduction, and lactation. The continued evolution of the field of immunology has led to a greater understanding of the immune and endocrine signaling networks underlying this conserved response to disease. Inflammatory mediators, especially including the cytokines tumor necrosis factor-α and interleukin-1β, are likely pivotal to disease-induced hypophagia, based on findings in both rodents and cattle. However, the specific mechanisms linking a cytokine surge to decreased feeding behavior are more difficult to pin down and likely include direct effects on appetite centers in the brain, alteration of gastric motility, and modulation of other endocrine factors that influence appetite and satiety. These insights into the mechanisms for disease-induced hypophagia have great relevance for management of neonatal calves, mature cows transitioning to lactation, and cows experiencing mastitis; however, it is not necessarily the case that increasing feed intake by any means possible will improve health outcomes for diseased cattle. We explore conflicting effects of hypophagia on immune responses, which may be impaired by the lack of specific substrates, versus apparent benefits for controlling the growth of some pathogens. Anti-inflammatory strategies have shown promise for promoting recovery of feed intake following some conditions but not others. Finally, we explore the potential for early disease detection through automated monitoring of feeding behavior and consider which strategies may be implemented to respond to early hypophagia.
抑制食欲，又称食欲减退，是家畜疾病中最易被识别的特征之一，可能会损害生长、繁殖和泌乳。免疫学领域的持续发展，使人们对这种针对疾病的保守反应的免疫和内分泌信号网络有了更深入的了解。炎症介质，尤其是肿瘤坏死因子-α和白细胞介素-1β等细胞因子，可能是疾病引起的食欲减退的关键因素，这一结论基于啮齿动物和牛的研究结果。然而，将细胞因子激增与降低进食行为联系起来的具体机制更难确定，可能包括对大脑食欲中枢的直接影响、胃动力的改变，以及对影响食欲和饱腹感的其他内分泌因素的调节。这些对疾病引起的食欲减退机制的深入了解，对于管理新生牛犊、进入泌乳期的成年奶牛和患有乳腺炎的奶牛具有重要意义；然而，通过任何可能的手段增加采食量并不一定能改善患病牛的健康状况。我们探讨了食欲减退对免疫反应的矛盾影响，这种影响可能是由于缺乏特定的底物而导致免疫反应受损，而对控制某些病原体的生长则有明显的益处。抗炎策略已显示出在某些情况下促进采食量恢复的潜力，但在其他情况下则不然。最后，我们探讨了通过自动监测进食行为进行早期疾病检测的潜力，并考虑了可以实施哪些策略来应对早期的食欲减退。
