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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #89699

Title: PHOSPHORUS BALANCE OF DAIRY COWS IN EARLY LACTATION AT THREE LEVELS OF DIETARY PHOSPHORUS

Author
item WU, ZHIGUO - UNIV OF WISCONSIN-MADISON
item Satter, Larry
item SOJO, RICARDO - STUDENT INTERN-ARGENTINA
item Blohowiak, Alex

Submitted to: Journal Dairy Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/31/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Phosphorus balances during the first 8 wk of lactation were determined. Twenty-six multiparous Holsteins were assigned at parturition to treatments with .32, .42, or .52% dietary P (DM basis), obtained by addition of NaH2PO4 to the .32% P diet. Blood samples were taken on d 5 after calving. Milk and fecal samples, along with additional blood samples, were taken every other week during the first 8 wk of lactation. The biweekly fecal samples were composites from 8 consecutive morning and afternoon samples. Percentages of P apparently digested were determined using Yb as a marker. No differences in DMI, milk yield, blood serum P concentration, or apparent digestibilities of D or P were detected over the entire 8 weeks of observation. Fecal P excretion increased as dietary P was increased. Ignoring urinary P excretion (usually negligible), P balance was calculated (P intake - fecal P - milk P) and was negative for the .32% P group but positive for the .42% and.52% P groups. Dietary P at .42% was sufficient t support a positive P balance. Feeding a higher amount of P for early lactation (.48% as suggested by NRC, 1989) appeared unnecessary. Feeding more P will result in more excretion in the feces. Reducing P to .32% did not affect animal performance but caused a negative P balance. Some negative P balance can probably be tolerated in view of mobilization of bone P that occurs in early lactation.