Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 11/9/2000
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Dairy producers supplement 20 percent more phosphorus (P) than the National Research Council (NRC) recommends. Reasons for this can be attributed to the small and outdated database upon which NRC recommendations rest, a deeply rooted notion that high dietary P improves reproduction, and aggressive marketing of P supplements by the feed industry. Recent research has indicated need for revision of how the feeding recommendations are calculated. Current estimates of P availability in the gut are low, and need to be increased. The maintenance requirement for P is based on body weight, and this should be changed to units of P per kg dry matter intake. Also, current feeding recommendations do not acknowledge that a minimum of 500-600 g of P can be mobilized from bone in early lactation to help meet needs. Studies with high-producing dairy cows indicate that .30-.32 percent dietary P (dry basis) is the minimum amount required for 10,000 kg milk per 305 days. Currently, NRC recommends .38-.40 percent dietary P for this level of production, and dairy producers typically feed .45-.50 percent. Some margin of safety is required, and the NRC provides for more than enough. If producers reduce P content of dairy diets by 20 percent, a 25-30 percent reduction in manure P can be realized. This would reduce environmental risk, and save $100 million annually in P supplements in the U.S.