Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Tham khảo tài liệu 'encyclopedia of animal science - n', nông - lâm - ngư, nông nghiệp phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Nutrient Management Diet Modification Terry J. Klopfenstein University of Nebraska Lincoln Nebraska U.S.A. INTRODUCTION Animal feeding operations are becoming more concentrated and the U.S. EPA Environmental Protection Agency has proposed more restrictive requirements. Great progress has been made in diet modifications designed to reduce animal excretion of nutrients. The nutrients of primary concern are nitrogen and phosphorus. PHOSPHORUS UTILIZATION Phosphorus P is an essential mineral nutrient required for bone growth and maintenance and for most body metabolic functions such as energy utilization. Phosphorus has been supplemented to animal diets in mineral form such as dicalcium phosphate produced from mined mineral deposits. Typically phosphorus was fed above the requirement of the animals as a safety factor due to lack of confidence in the precise P requirements and supplies. P in manure can build up in soils and subsequently contaminate ground water if not properly managed. P requirements are quite different for ruminants cattle and sheep and nonruminants pigs and chickens and P is metabolized differently by ruminants. Poultry and swine grow rapidly and therefore require high levels of P in their diets up to .6 of diet 11 31 . Much of the P in feed ingredients such as corn and soybean meal is in the form of phytate P. Swine and poultry lack the enzyme phytase necessary to utilize the phytate P so it appears in the manure. Inorganic P must be supplemented to meet the animal s requirements. This makes P use very inefficient 10 to 20 and most of the P ends up in the manure. There are four technologies that producers can use to reduce P excretion. 1. Feeding to requirements. Ongoing research is helping to more precisely define P requirements for each type of production and for animal ages within each type of production. With modern technology it is possible to formulate diets quite precisely so that P is not overfed.111 2. Phytase. This enzyme is produced .
