Webster A B
Department of Poultry Science, University of Georgia, Athens, Georgia 30602-4356, USA. bwebster.uga.edu
Poult Sci. 2003 Jun;82(6):992-1002. doi: 10.1093/ps/82.6.992.
Feed deprivation has been adopted by the commercial egg industry to induce molt because it is the easiest method to apply and produces the best results. Feed deprivation, however, raises concerns about animal welfare. Birds respond to long-term feed deprivation in three phases. The first phase lasts at most a few days, during which physiological and behavioral adjustments ultimately reduce protein catabolism and energy expenditure. A temporary increase in plasma corticosterone may be observed at this time. Corticosterone promotes gluconeogenesis, helping to maintain plasma glucose levels in the initial stage of the fast. The corticosterone increase may also be linked to increased activity in feed-deprived birds. Hens have been observed to manifest temporarily increased levels of alertness and activity during the first 48 h of feed deprivation. Aggressive behavior of hens also has been observed to increase briefly during the first day of feed deprivation. The second phase is the longest, during which proteins are spared and lipids are catabolized to provide energy. This phase may last several months in some species; in the chicken it can continue more than 20 d. Hens show increasing amounts of resting behavior during this phase. The third phase begins when protein catabolism accelerates. A pathological stage eventually is reached when the bird will cease activity and no longer eat. The phased response to feed deprivation optimizes a tradeoff between the need to maintain constant levels of plasma glucose to sustain activity and the need to preserve critical body structures such as muscles and organs. Hens are capable of vigorous activity throughout feed deprivation periods typical of induced molts, which do not appear to take birds beyond the second phase of fasting. Hens having undergone extended fasts may also have improved livability. Alternative induced molting methods are being sought to reduce animal welfare concerns. The methods of current interest involve alteration of feeding regimen and cause at least some body weight loss. These alternative methods should be evaluated to ensure that they do not actually make aspects of hen welfare worse compared to feed withdrawal, which might happen if hens perceive feed restriction without being allowed to progress fully into the second phase of adaptation to feed deprivation.
商业蛋鸡行业采用饥饿法来诱导换羽，因为这是最容易实施的方法且效果最佳。然而，饥饿法引发了对动物福利的担忧。鸟类对长期饥饿的反应分为三个阶段。第一阶段最多持续几天，在此期间，生理和行为调整最终会减少蛋白质分解代谢和能量消耗。此时可能会观察到血浆皮质酮暂时升高。皮质酮促进糖异生，有助于在禁食初期维持血浆葡萄糖水平。皮质酮升高也可能与饥饿鸟类的活动增加有关。据观察，母鸡在饥饿的前48小时内会表现出警觉性和活动水平暂时升高。母鸡的攻击性行为在饥饿的第一天也会短暂增加。第二阶段是最长的，在此期间蛋白质被节省下来，脂质被分解以提供能量。这个阶段在某些物种中可能持续数月；在鸡身上，它可以持续超过20天。在此阶段，母鸡的休息行为会增加。第三阶段开始于蛋白质分解代谢加速时。最终会达到一个病理阶段，此时鸟类将停止活动且不再进食。对饥饿的阶段性反应优化了维持血浆葡萄糖恒定水平以维持活动的需求与保护关键身体结构（如肌肉和器官）的需求之间的权衡。在诱导换羽的典型饥饿期内，母鸡能够保持旺盛的活动，而这些饥饿期似乎不会使鸟类进入禁食的第二阶段之后。经历过长时间禁食的母鸡的存活率也可能会提高。人们正在寻求替代的诱导换羽方法以减少对动物福利的担忧。目前感兴趣的方法涉及改变饲喂方案，并且会导致至少一些体重减轻。应该对这些替代方法进行评估，以确保与断料相比，它们不会实际上使母鸡福利的某些方面变得更糟，如果母鸡感觉到饲料受限但不被允许完全进入适应饥饿的第二阶段，这种情况可能会发生。
