Feeding low crude protein diets to improve efficiency of nitrogen use
Sustainable production of adequate quantities of food to support the human population is a world-wide goal.Under current feeding conditions in the US,dairy cattle convert dietary nitrogen to milk nitrogen with 25% efficiency.The remaining 75% is excreted which contributes to air and water quality problems and reduces economic performance of the industry.Efficiency could be improved to 29% if protein was fed to just meet current NRC requirements.Additional improvements are achievable given improvements in our knowledge of amino acid requirements.The current metabolizable requirement model overestimate true requirements due to lack of knowledge of the absolute amino acid requirements and due to the assumption that the partial efficiency of use of metabolizable protein for lactation is a constant 65%.Numerous data indicate the efficiency of lactational use is variable and maximally 45%.Current models also assume that responses to individual nutrients are not additive,and thus production is limited to that nutrient most deficient with respect to requirements.Several pieces of evidence also indicate this assumption is incorrect.Protein synthesis is highly regulated and the regulatory pathways independently and additively respond to the supply of energy and individual amino acids and circulating concentrations of hormones.Thus protein synthesis can respond to nutrients other than the one identified as most limiting under current theory.Addressing these deficiencies should allow formulation of diets that will achieve 35% nitrogen efficiency or greater.However,we can utilize milk urea nitrogen to establish a lower protein feeding level and monitor feeding programs today to achieve improved nitrogen efficiency.Because of genetic variation in milk urea nitrogen concentrations,one should establish a herd specific milk urea nitrogen target by systematically reducing dietary protein until a loss in production is observed.
lactation nutrient requirements metabolizable protein amino acids milk urea nitrogen
M.D.Hanigan S.I.Arriola Apelo M.Aguilar
Dept.of Dairy Science Virginia Tech
国际会议
3rd International Symposium on Dairy Cow Nutrition and Milk Quality(第三届“奶牛营养与牛奶质量国际研讨会)
北京
英文
9-19
2013-05-11（万方平台首次上网日期，不代表论文的发表时间）