Sulfur amino acid requirements and metabolism in cats

近40%的加拿大人拥有一只猫（2016年为880万），加拿大猫粮的销量也在增长。猫是专性食肉动物，动物蛋白被大量用于制造猫粮。随着人口的增长和发展中国家对动物蛋白的需求增加，未来动物蛋白的供应和价格可能会受到限制。虽然我们有足够的数据来精确喂养许多单胃农业动物，但我们目前对必需氨基酸（AA）需求和提供AA对猫的广泛影响的了解却非常缺乏。一般来说，生长或氮平衡的结果被用来衡量生长猫的AA需求，但没有对成年猫的估计。侵入性更小的碳氧化技术，特别是AA氧化指示器（IAAO）技术已被用于经验估计许多哺乳动物的AA需要量。我的实验室估计了猫体内苯丙氨酸的周转率，这些数据表明口服示踪剂是一种有效的方法，少食多餐支持伪同位素稳定状态。我们还验证了猫对空间限制进行呼吸气体收集和量化所需的行为适应，并将这些应用于测量猫消耗的能量代谢和不同食物的净能量。最后，我应用IAAO对猪和狗的AA需要量和蛋白质质量进行了估算。我的长期目标是确定成年猫对必需氨基酸的需求，并了解其他饮食因素（如膳食维生素）如何改变这些需求。这些数据将显著优化猫的蛋白质输送，减少猫粮中蛋白质和AA的过量供应。我的计划的短期中期目标是：1。使用直接AA氧化技术测量向成年绝育公猫和母猫提供过量酪氨酸时苯丙氨酸的需用量（研究1）2。使用IAAO测量成年阉割公猫和绝育母猫在提供最小囊肿(e)线时的蛋氨酸需求量（研究2）2。在半胱氨酸过量的情况下，使用IAAO测量成年阉割公猫和绝育母猫的蛋氨酸需求量（研究3）3。利用标记的蛋氨酸和半胱氨酸示踪剂了解饲粮蛋氨酸与半胱氨酸的比例如何改变成年去势公猫和绝育母猫的转甲基化、再甲基化和转硫化，并有助于控制牛磺酸和猫碱的合成（研究4）意义：拟开展的研究将为家猫硫AA需求以及其他营养物质如何影响硫AA需求提供基础知识。当应用于猫粮开发时，这些知识将导致更精确的AA输送，减少过量的膳食蛋白质供应，并支持猫的健康和福祉。

Close to 40% of the Canadian population owns a cat (8.8 million in 2016) and there has been growth in Canadian cat food sales. Cats are obligate carnivores and animal proteins are used in large amounts to manufacture cat food. The availability and price of animal proteins may become constrained in the future as the human population increases and developing countries demand more animal-based proteins. While we have sufficient data to precisely feed many mono-gastric agricultural animals, our current knowledge of the indispensable amino acid (AA) requirements and broader effects of provision of AA on cats is woefully lacking. In general, outcomes of either growth or nitrogen balance have been used to measure AA requirements in growing cats, but no estimates in adult cats exist. Much less invasive carbon oxidation techniques, and more specially, the indicator AA oxidation (IAAO) technique have been used to empirically estimate AA requirements in many mammals. My laboratory estimated phenylalanine turnover in cats and these data suggest that orally dosing a tracer is a valid approach and small, frequent meals support a pseudo isotopic steady state. We have also validated behavioural acclimation to space restriction required to conduct respiratory gas collection and quantification in cats and applied these to measure energy metabolism and the net energy of different foods consumed by cats. Finally, I have applied the IAAO to estimate AA requirements and protein quality in pigs and dogs. My long term goals are to determine the requirement for the indispensable AA requirements of adult cats and understand how other dietary factors, such as dietary vitamins, may alter these. These data will lead to significant optimization in the delivery of protein to cats and reduce over supply of protein and AA in feline diets. The short-medium term goals of my program are to: 1. Measure the phenylalanine requirements when tyrosine is provided in excess to adult neutered male and female cats using the direct AA oxidation technique (Study 1)  2. Measure the methionine requirement when minimal cyst(e)ine is provided in adult castrated male and spayed female cats using the IAAO (Study 2) 2. Measure the methionine requirement when cysteine is provided in excess in adult castrated male and spayed female cats using the IAAO (Study 3)  3. Understand how the ratio of dietary methionine to cysteine alter transmethylation, remethylation and transsulfuration and contribute to the control synthesis of taurine and felinine in adult castrated male and spayed female cats using labeled methionine and cysteine tracers (Study 4) SIGNIFICANCE: The proposed studies will provide fundamental knowledge of sulfur AA requirements and how other nutrients affect sulfur AA requirements in domestic cats. When applied to cat food development, this knowledge will lead to more precise AA delivery, reduce excess provision of dietary protein, and support the health and well-being of cats.