Macromineral digestion by lactating dairy cows: estimating phosphorus excretion via manure.
Data from 8 experiments involving 39 diverse dietary treatments and 162 Holstein cows were used to derive equations that estimate manure excretion of P by lactating dairy cows. Within an experiment, diets were formulated to have similar P concentrations and to meet or slightly exceed standard recommendations for P. The data were generated from total collection digestion trials. The only sources of supplemental P used were dicalcium phosphate and monosodium phosphate. The concentration of dietary P ranged from 0.34 to 0.45% of dry matter (DM). Cows varied in milk production (8 to 59 kg/d), DM intake (12.4 to 30.5 kg/d), and P intake (45 to 133 g/d). Apparent digestibility of P averaged 40.4%, fecal output of P averaged 47 g/d, and apparent P retention averaged 4 g/d. Two equations were derived to estimate excretion of P via manure (g/d): 1) Manure P = -2.5 + 0.64 x P intake, and 2) Manure P = 7.5 + 0.78 x P intake - 0.702 x Milk; where P intake is in g/d and milk is kg/d. Both equations were evaluated using literature data, and both equations had acceptable accuracy for field use. The requirements for P of lactating dairy cows from the National Research Council (NRC) were also evaluated, and for most diets, those requirements were adequate based on retention of P.
Weiss
W P
WP
Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster 44691, USA. weiss.6@osu.edu
Wyatt
D J
DJ
D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004032:Diet; D004063:Digestion; D005260:Female; D007774:Lactation; D008372:Manure / Q000032:analysis*; D008433:Mathematics; D008903:Minerals / Q000378:metabolism*; D010758:Phosphorus / Q000032:analysis* / Q000493:pharmacokinetics; D016226:Phosphorus, Dietary / Q000008:administration & dosage; D012820:Silage; D013025:Glycine max; D003313:Zea mays
D008372:Manure; D008903:Minerals; D016226:Phosphorus, Dietary; D010758:Phosphorus