Effect of dietary phosphorus on performance of lactating dairy cows: milk production and cow health.

H Lopez,F.D Kanitz,V.R Moreira,L.D Satter,M.C Wiltbank

doi:10.3168/jds.s0022-0302(04)73151-3

Abstract

The objective of this study was to measure cow response to feeding of two dietary concentrations of P, one of which was close to recent National Research Council requirements, and the other of which was well in excess of the requirement. Diets containing 0.37 or 0.57% P (dry basis) were fed to Holstein cows for the first 165 d of lactation, and occasionally longer until cows were confirmed pregnant approximately 60 d after insemination. At calving, cows were randomly assigned to experimental diets. The number of cows completing a minimum of 165 d of lactation was 123 for the 0.37 and 124 for the 0.57% P groups. Cows were housed in a stanchion barn and fed one of two transition diets, each formulated to contain one of the P treatments for the first 3 wk of lactation, and then cows were moved to a free-stall barn where the experimental diets were group fed. Milk production, milk fat, and milk protein averaged 35.1 kg/d, 3.92%, and 2.90% for the 0.37% P diet, and 34.9 kg/d, 3.98%, and 2.91% for the 0.57% P diet. None of these measures were different between treatments. Blood serum P concentrations on d 50 and 100 of lactation averaged 6.1 and 6.2 mg/dL for the 0.37% P diet, and 6.8 and 6.9 mg/dL for the 0.57% P diet. No treatment differences were detected in milk production, cow health, or body condition score.

Highlights

Overfeeding of P is costly and increases the risk of environmental damage through eutrophication of lakes and streams (Rotz et al, 2002)
Since fecal P excretion increases linearly as P intake is increased above the requirement, close monitoring of dietary P is required to minimize risk of environmental damage caused by excessive P excretion in the feces (Knowlton and Herbein, 2002; Wu et al, 2000, 2001)
This paper reports results pertaining to milk production and animal health, and an accompanying paper (Lopez et al, 2004) reports results related to reproductive performance

Summary

Introduction

Overfeeding of P is costly and increases the risk of environmental damage through eutrophication of lakes and streams (Rotz et al, 2002). Ments of the cow are met, most excess dietary P is excreted in the manure, primarily in the feces (Wu et al, 2000, 2001). This excess P may accumulate in the environment through recycling of manure to land as fertilizer for crop production. Since fecal P excretion increases linearly as P intake is increased above the requirement, close monitoring of dietary P is required to minimize risk of environmental damage caused by excessive P excretion in the feces (Knowlton and Herbein, 2002; Wu et al, 2000, 2001). Eliminating the excess supplemental P from dairy diets may result in as much as 25 to 30% reduction of P content of manure, and a savings of $10 to 15 per cow per year in P supplementation costs (Wu et al, 2000)

Objectives

Methods

Results