title: Phosphorus feeding levels and critical control points on dairy farms.
abstract: A viable and cost-effective approach to managing P on dairy farms is to minimize excess P in diets, which in turn leads to less excretion of P in manure without impairing animal performance. A questionnaire survey was conducted, coupled with on-site feed and fecal sample collection and analysis on dairy farms in New York, Pennsylvania, Delaware, Maryland, and Virginia. The purpose was to assess dietary P levels and to identify critical control points pertaining to P feeding management. Survey responses, 612 out of 2500 randomly selected farms, revealed a wide range of dietary P concentrations for lactating cows, from 3.6 to 7.0 g/kg of feed DM. The mean was 4.4 g/kg, which was 34% above the level recommended by the NRC for 27.9 kg milk/d, the mean milk yield in the survey. Higher P concentrations in diets were not associated with higher milk yields (n = 98, R2 = 0.057 for the survey farms; n = 92, R2 = 0.043 for farms selected for on-site sampling). However, higher dietary P led to higher P excretion in feces (n = 75, R2 = 0.429), with much of the increased fecal P being water soluble. Phosphorus concentrations in diet samples matched closely with P concentrations in formulated rations, with 67% of the feed samples deviating <10% from the formulations. On 84% of the survey farms, ration formulation was provided by professionals rather than producers themselves. Most producers were feeding more P than cows needed because it was recommended in the rations by these consultants. In conclusion, P fed to lactating cows averaged 34% above NRC recommendations; to reduce excess dietary P, ration formulation is the critical control point.
authors.affiliation: Center for Animal Health and Productivity, School of Veterinary Medicine, University of Pennsylvania, Kennett Square 19348, USA. dou@cahp.vet.upenn.edu
authors.forename: Z
authors.initials: Z
authors.lastname: Dou
authors.forename: J D
authors.initials: JD
authors.lastname: Ferguson
authors.forename: J
authors.initials: J
authors.lastname: Fiorini
authors.forename: J D
authors.initials: JD
authors.lastname: Toth
authors.forename: S M
authors.initials: SM
authors.lastname: Alexander
authors.forename: L E
authors.initials: LE
authors.lastname: Chase
authors.forename: C M
authors.initials: CM
authors.lastname: Ryan
authors.forename: K F
authors.initials: KF
authors.lastname: Knowlton
authors.forename: R A
authors.initials: RA
authors.lastname: Kohn
authors.forename: A B
authors.initials: AB
authors.lastname: Peterson
authors.forename: J T
authors.initials: JT
authors.lastname: Sims
authors.forename: Z
authors.initials: Z
authors.lastname: Wu
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000822:Animal Husbandry / Q000379:methods; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle; D003612:Dairying; D004032:Diet; D004787:Environmental Pollution / Q000517:prevention & control*; D005243:Feces / Q000737:chemistry*; D008372:Manure; D009751:Nutritional Requirements; D010758:Phosphorus / Q000032:analysis*; D016226:Phosphorus, Dietary / Q000008:administration & dosage*; D012989:Soil Pollutants / Q000032:analysis; D011795:Surveys and Questionnaires; D014877:Water Pollution, Chemical / Q000517:prevention & control
chemical_list: D008372:Manure; D016226:Phosphorus, Dietary; D012989:Soil Pollutants; D010758:Phosphorus