Feeding Strategies to Lower P in Manure

Dr. Mireille Chahine, Extension Dairy Specialist

Dr. Rick Norell, Extension Dairy Specialist

Measuring Nutrient Excretion

Source: Weiss, 2006

1. Formulate Rations to Meet the 2001 NRC Guidelines•Avoid the “safety margin” principle

•P fed in excess of a cow’s requirements

•Reduce or eliminate the supplemental P

•Free-choice P should not be used on dairies

Current Phosphorus RequirementsMilk (lbs) DMI (lbs) P intake (g) P (% DM)

44 41 55 0.31

66 48 73 0.33

88 56 91 0.36

110 63 110 0.38

132 70 128 0.40

Source: 2001 NRC

Example of Reductions in Phosphorus Intake and Excretion

Dietary P (%DM)

P Intake

(g/cow/day)

P Excretion

(g/cow/day)

0.5% 113.5 84.7

0.38% 86.3 69.5

Reduction 27.2 15.2

(Assumes average DMI = 50 lbs/cow/day)

Impact of Reducing Phosphorus

• 15.2 gram decrease on a 1000 cow dairy equates to an annual reduction of 12,220 pounds of phosphorus!

• Benefits▫ Reduced total number of

acres required for land application

▫ Higher manure application rates possible per acre

▫ Improved N:P ratio in manure

Feed Savings

•27 g reduction in P equates to 0.34 lbs of 17% P mineral per day at $0.10/cow/day

•Elevated P may be due to other high P feeds in the diet rather than solely due to the mineral supplement

Accuracy in Feeding Cows

Source: Dou, J Dairy Sci 86:3787

Source: J Dairy Science 88:3721

Source: J Dairy Sci. 99:3721)

2. Group and feed cows according to their stage of lactation and repro status•Avoid the one ration for all scenario

Cows eating approximately 7% more P than requirements

•Grouping cows according to milk production and repro status Decreased feeding costs and less nutrient excretions

3. Wisely use byproducts and concentrates in dairy cow rations•Nutritionists should be encouraged to

utilize ingredients with lower P concentrations

•General rule: Byproduct ingredients and oilseed meals higher in P relative to cereal grains and forages

Average protein and phosphorus content of common protein supplementsSource CP% P% Ratio CP:P

Blood meal 95.5 0.30 318:1

Soybean meal 49.9 0.71 70:1

Cottonseed meal 44.9 1.15 39:1

Canola meal 37.8 1.10 34:1

Fish meal 68.5 3.05 22:1

Source: 2001 Dairy NRC

Ethanol Production in the US

• Ethanol price availability of wet distillers grains with solubles (WDGS) and dried distillers grains with solubles (DDGS)

Corn: 1 bushel Ethanol: 2.7 gal

CO2+ +

DDGS: 18 lbs CO2: 18 lbs

Conversion from Corn to Distiller’s grains

NRC, 2001

4. Routinely analyze the ingredients used in the ration•The level of P in the feed ingredients used

in dairy cow rations is variable

•This variability needs to be addressed when formulating rations

Plant 1n=9

Plant 2n=11

Plant 3n=31

Entire Population

P 0.8 0.9 0.9 0.9

Min 0.5 0.6 0.6 0.5

Max 1.0 1.2 1.1 1.2

SD 0.2 0.2 0.1 0.2

Source: Robert M. Kaiser, 2005

Variation in composition of WDGS

5. Maximize the use of forages in the ration

•Maximizing the amount and quality of forages in dairy cow rations Improves cow health, reduces the need for imported feed, and reduces the need to use imported by-products

Wu and Ishler, 2002

Wu and Ishler, 2002

Source: Weiss, 2007

Feeding strategies to lower P in manure:•Formulate rations to meet the 2001 NRC

guidelines•Group and feed cows according to their

stage of lactation and reproduction status•Routinely analyze the ingredients used in

the ration•Wisely use byproducts and concentrates

in dairy cow rations•Maximize the use of forages in the ration