Ration Phosphorus Management Req by fjwuxn


									IN: Proc. Four-State Applied Nutrition and Management Conf. July 9-10, 2003. pp.145 - 151 .

  Ration Phosphorus Management: Requirements and Excretion
                                        Dave Beede
                                Department of Animal Science
                                 Michigan State Univeristy
                                    East Lansing 48824


        Dairy farms must be environmentally sustainable businesses.
Environmental sustainability means that the management objective of zero
phosphorus (P) balance is realized. Zero P balance is achieved when the amount
P imported into the farm equals the amount exported during some defined period
of time. Attainment of zero P balance typically occurs in a whole-farm system
composed of animals, crops, animal and manure handling facilities, plus access to
cropland to recycle manure P, or other means to export manure P out of the
        Legislation in the U.S. aims to reduce soil P build-up and losses from
livestock systems by controlling manure management (CAST, 2002; USDA-
NRCS, 2001). Additionally, the Environmental Protection Agency‟s recent final
rule (released December 15, 2002) for Concentrated Animal Feeding Operations
(CAFOs) emphasizes the need for meticulous on-farm P balancing and
management. This management starts with accurate input of P to cattle, largely
from feed supplements (Sutton and Beede, 2003; CAST, 2002). Typically,
imported feed P makes up the majority of imported P in dairy farms (Klausner,
1993); the other major input is P-containing fertilizer. Both sources should and
must be managed effectively to achieve whole-farm P balance.
        The emphasis on P in nutrient management additionally is underscored by
the fact that application of manure P to cropland generally is first limiting because
recommended or allowable maximum application rates of P are reached before
the maximum allowable application rates of nitrogen or potassium are met.
        This paper focuses on management of feed P inputs and the effects of
ration P on excretion of P by dairy cattle.

                                    Phosphorus Balancing

        Surveys in several states indicate that in many dairy cattle operations P
inputs often are greater than outputs. When inputs are greater than outputs, P
builds-up in soils over time and the potential for P runoff increases when soil P
builds up to excessive concentrations (CAST, 2002; NPMP, 2002). Phosphorus
in runoff causes oxygen debt killing aquatic life and excessive algae growth
reducing water quality of steams and lakes (CAST, 2002; NRC, 2001). This
series of event is not sustainable --- environmentally or legally. Total P inputs
(imports) must be less than or equal to total P outputs (exports) for a sustainable
IN: Proc. Four-State Applied Nutrition and Management Conf. July 9-10, 2003. pp.145 - 151 .

                                    Phosphorus Nutrition

         The National Research Council (2001) publication for dairy cattle reviews
and summarizes the fundamental biological roles of P for productive functions.
Also, explanation is given on the approach to estimate the dietary requirements of
cattle for various physiological functions --- growth, pregnancy, lactation, and
maintenance. The factorial approach is used to estimate the total dietary P
requirement. This is the summation of amounts of P needed for various
physiological functions divided by the absorption coefficient of P in the ration.
For dairy cattle, different absorption coefficients are specified for forages (0.64)
and concentrates (0.70) (NRC, 2001). And, the P in inorganic mineral sources
varies in absorbability [e.g., 0.75 for dicalcium phosphate; 0.80 for bone meal;
and, 0.90 for monosodium phosphate (NRC, 2001)]. Based on the NRC (2001)
model the absorption coefficient for P will vary from ration to ration depending
upon what specific set of feed ingredients that make-up that particular ration.

Optimizing Ration P

        How can dairy producers, nutritionists, or feed suppliers optimize ration P
in herd rations?
        Who’s in charge? Firstly in my opinion, dairy producers must understand
that they are the ultimate and supreme managers of their farm‟s P balance. They
must be in charge of and responsible for the P concentrations of their rations.
This responsibility can not and must not be “farmed-out” to nutritionists, feed
sales persons, or employees. Nutrition consultants, veterinarians, employees, and
other service-providers really only can help dairy producers manage P in rations
and the whole farm system.
        Match ration P content to requirements. Secondly, matching ration P
content (%) to the amount of milk produced by different management groups
within the herd or the whole herd is absolutely critical. To do this effectively
good knowledge about the rate of feed intake of the different management groups
within the herd is paramount. As reference, use the National Research Council‟s
(2001) feeding recommendations (examples are in Table 1). Note that the highest
concentration of P recommended for high producing cows is only 0.38%, dry

Table 1. Phosphorus feeding recommendations for lactating dairy cows a.
       Milk yield (lb/cow/day)                  Ration P(%, dry basis)
                   55                                    0.32
                   77                                    0.35
                   99                                    0.36
                  120                                    0.38
  Assumes feed intake rates of the NRC (2001) model.

       Thirdly, analyze feeds for P content. This includes concentrates,
especially byproduct feeds, as well as forages. Use a qualified laboratory to
IN: Proc. Four-State Applied Nutrition and Management Conf. July 9-10, 2003. pp.145 - 151 .

determine P contents of feeds and adjust inputs and rations as necessary. “Book
values” for P content of feeds will not give the needed management accuracy.
Many feed ingredients, especially byproducts resulting from wet- or dry-
processing or fermentation (e.g., distiller‟s grain), have variable P contents or
values different from the book. Also, to have reliable information for P
balancing, laboratory analysis must be done by the wet chemistry method, instead
of NIRS (near infrared reflectance spectroscopy). Analysis by NIRS gives
inaccurate estimates of actual P concentrations of most feeds. Re-analysis of
different lots of a specific type of purchased feed through time as well as home-
grown forages is highly recommended because of the variation associated with
different sources and processes used to produce concentrates (e.g., byproduct

Purchasing Byproducts and Supplements
         Typically feed byproducts are incorporated into dairy rations because of
their relatively high protein or energy contents at cost-attractive market prices.
But, some byproducts contain quite high concentrations of P. Table 2 gives
„ballpark‟ P and crude protein concentrations of some common protein sources
and byproduct feeds.

Table 2. Phosphorus (P) and crude protein (CP) contents of common protein
sources and byproduct feedsa.
Protein sources                                Phosphorus         protein      CP-to-P
and byproduct feedsb                           content (%) content (%)           ratio
Blood meal                                         0.30             95.5          318
Corn gluten meal                                   0.60             65.0          108
Soybean meal (44%CP; expellers)                    0.70             49.9           71
Brewer‟s grain (dried)                             0.67             29.2           44
Cottonseed, whole                                  0.60             23.5           39
Distiller‟s grain, corn (with solubles, dried)     0.83             29.7           36
Canola meal (mechanically extracted)               1.10             37.8           34
Corn gluten feed                                   1.00             23.8           24
Wheat middlings                                    1.00             18.5           19
Corn steep liquors                                 1.70             33.0           19
Wheat bran                                         1.18             17.3           15
Whey                                               1.04             14.6           14
Porcine meat and bone meal                         4.73             54.2           12
  Values from NRC (2001).
  Refer to Sidebar comment at end of this paper for additional discussion of the real
cost of byproduct feeds when whole-farm P balancing is an important consideration.

        Additionally, dairy producers and nutritionists must be vigilant to ensure
that unneeded supplements are not used in rations --- even as a „safety factor‟?
Rations should be carefully and routinely (e.g., monthly). It might be possible to
reduce ration costs by eliminating unneeded supplements. Is a supplement
IN: Proc. Four-State Applied Nutrition and Management Conf. July 9-10, 2003. pp.145 - 151 .

included that contributes to more total ration P than is necessary to meet animals'
requirements? In many dairy rations (including lactation rations), very little if
any, supplemental P is needed. In most cases, the primary objective of a
supplement is to provide protein, not P. Therefore, using protein sources with
higher crude protein-to-phosphorus ratios will provide more of the needed protein
with less P (e.g., blood meal, corn gluten meal, and soybean meal; Table 2).
Actually, using protein sources or byproduct feeds that supply more P than
needed in the ration (those with lower crude protein-to-phosphorus ratios; Table
2) may be even more costly than one might think ---- especially in the long-term
(see Sidebar comment following this main paper).

Consequences of Fat-Feeding and Ca-to-P Ratio on Ration P Management

        When feeding supplemental fat, it is fairly routine practice to feed
supplemental Ca in excess of that needed to meet the cow‟s Ca requirement. It is
common to find 1.0 to 1.2% Ca (dry basis) in lactation rations. It apparently is
suspected that supplemental fat forms insoluble soaps (salts) with Ca (and Mg) in
the digestive tract rendering the Ca unavailable for absorption. Research results
to support this idea are far from conclusive. In research with lactating dairy cows
Palmquist and Conrad (1978) fed blended hydrolyzed fat at 5.9 and 10.8% of the
TMR dry matter. No effects (negative or positive) of supplemental fat on Ca
absorption were detected. Similarly, when supplemental yellow grease was fed to
Holstein steers in digestion trials no effects on total tract absorption of Ca were
detected (Zinn and Shen, 1996). When blended animal-vegetable fat (0, 2.5, and
5% of diet dry matter) was added to rations of lactating dairy cows total tract Ca
absorption was not affected (Rahnema et al., 1994). However, when wethers
were fed diets with high levels corn oil or soy oil (4 to 7.5% of diet dry matter)
and feed intake was restricted (1.5 to 2.6% of body weight) Ca digestibility was
reduced compared with wethers not fed the vegetable oils (Tillman and Brethour,
1958; Steele, 1983). Adequate study to determine optimal dietary concentrations
of Ca and Mg with supplemental fat feeding has not been done. Thus, the general
formulation strategy to increase dietary Ca when supplemental fat is included
must be questioned because of the complication caused in P nutrition described
        Two points are especially important when considering excess Ca in rations
for lactating dairy cows supplemented with fat. Firstly, the extra Ca is most likely
not needed and even though it may not be exceedingly expensive to add, it is an
expense and takes space in the ration. Secondly, and more importantly, if the
routine ration formulation strategy is to set a particular Ca-to-P ratio, then with
the increased Ca content of the ration the P concentration will increase too. For
example, if one formulates to a 2-to-1 ratio of Ca-to-P and if the Ca content of the
ration is increased to 1% then the P content will increase to 0.5%. This
concentration of ration P is well in excess of that needed to meet the dairy cow‟s
requirement, and the excess P will be excreted in manure. Furthermore, there is
no evidence in the dairy nutrition research literature that there is some optimal
ratio of Ca-to-P in rations of lactating dairy cows as long as the requirements
IN: Proc. Four-State Applied Nutrition and Management Conf. July 9-10, 2003. pp.145 - 151 .

(grams/day) for each mineral element are met (NRC, 2001). Milk yield and
persistency and reproduction were normal and not different among early lactation
cows when Ca-to-P ratios ranged from 1-to-1 to 8-to-1 (Smith et al., 1966) or
from 3-to-1 to 1.5-to-1 (Stevens et al., 1971). For reference, based on the Ca and
P requirements of lactating cows yielding between 55 and 120 lb/day the Ca-to-P
ratio is between 1.1-to-1 and 1.2-to-1 (NRC, 2001).

Managing P Excretion through Management of P in Ration

         Lower Ration P, Lowers Manure P, Lowers Acres Required. There is
little doubt that the first and foremost management strategy to control P excretion
in dairy farms is to never allow imported (feed or fertilizer) P onto the farm if it is
not needed to improve animal or crop performance, or to improve the margin of
revenue over expenses. Because importation of P in feed supplements represents
such a significant potential source of excess P, prudent management of ration P is
paramount. The maximum ration P concentration needed for the highest
producing cows in most dairy herds is 0.38%, dry basis. For many (most) herds
and management groups of cows within herds, less than 0.38% ration P is
necessary (Table 1). Lowering dietary P to recommended concentrations
automatically will lower manure P (Table 3). This will result in the need for
fewer acres of cropland on which to spread manure.

Table 3. Example of relationships among ration P, manure P, and
spreadable acres a.
                                                     Spreadable          Acres
Relative to             Ration P      Manure P          acres           needed
recommendations           (%)        (lb/cow/yr)    (per cow/yr)b     /100 cows
Exceeds NRC (2)           0.55            78              2.9             290
recommendations           0.48            65              2.4             240
Within NRC (2)            0.38            47              1.8             180
recommendations           0.35            42              1.6             160
  Adapted from: Understanding soil phosphorus: An overview of phosphorus,
water quality and agricultural management practices, 2002.
(http://ipcm.wisc.edu), Nutrient and Pest Management Program, Univeristy of
Wisconsin-Extension and USDA-ARS Dairy Forage Research Center.
  Spreadable acres required depends upon local estimates of crop removal rates,
soil types, etc.

       Without accurate management control of ration P concentrations, more
acreage will be required. For example using the information in Table 3, for a
100-cow dairy farm, if ration P was lowered from 0.55% to 0.38%, the amount of
land needed to spread manure would be reduced by 110 acres annually. If ration
P concentrations are not lowered to NRC (2001) recommendations and the
operation is subject to the new CAFO Final Rule, more acres will be needed to
spread manure. Even if a particular dairy farm does not fall under the new CAFO
IN: Proc. Four-State Applied Nutrition and Management Conf. July 9-10, 2003. pp.145 - 151 .

Rule, the land needed to follow local states‟ guidelines based on P balancing will
be much easier to achieve by feeding at NRC (2001) recommendations.

                                      Predicting P Excretion

        Various models (equations) have been developed and evaluated to predict
the amount of P excreted by lactating dairy cows (Beede and Davidson, 1999). It
would be valuable to have good estimates (predictions) of actual P excretion from
dairy herds especially to help in nutrient management planning. We evaluated
various published models using results from the dairy research literature. A
simple relationship for predicting P excretion in manure is the difference between
dietary P intake and P secreted in milk. Figure 1 shows the relationship between
actual P excretion measured in research trials and the difference between actual P
intake minus actual P secreted in milk. Not surprising, this difference calculation
explained 86% of the variation in actual measured P excretion in manure (Beede
and Davidson, 1999).

Excretion (g/d)

 Measured P

                            R2 = 0.86, P < 0.01
                        0          20         40             60            80           100
                              Measured Intake P - Milk P (g/d)
  Figure 1. Measured phosphorus excretion versus P intake minus milk P
  secretion from research results from the scientific literature (Beede and
  Davidson, 1999).
         Numeric values for the variables (pounds of ration dry matter intake and
known [analyzed] P content of the rations, and the amount of milk produced and
the average P content of milk [0.09%]) in this simple difference equation can be
obtained relatively easily on farm to predict P excretion. We believe this
approach gives dairy producers reasonable, useful information for nutrient
management planning.

Example: Excess Ration P, Impact on P Excretion, Need for More Cropland

              Rations balanced to meet P requirement. To emphasize the
importance of management of P in dairy rations consider the following example
IN: Proc. Four-State Applied Nutrition and Management Conf. July 9-10, 2003. pp.145 - 151 .

using the simple difference approach to compute the change in the amount of P
excreted by a herd of dairy cows when: 1) ration P concentrations are formulated
to just meet NRC (2001) requirements; or, 2) when higher (excess) ration P is
included in rations.
        A herd of 300 Holstein cows are in management groups (high, medium,
and low with average daily milk yield of 80, 70 and 60 lb/cow, respectively).
There are 100 cows in each group. Three rations (high, medium and low) are
balanced to meet the NRC (2001) energy and nutrient requirements (including P)
of cows in each management group based on the expected rates of daily feed
intake (NRC, 2001). The P contents of each group‟s ration (0.34, 0.33, 0.32% dry
basis, for high, medium, and low groups, respectively), the actual amount of feed
consumed by each group of cows, and the total P intake by each group is in Table
4. The total daily P intake for the entire herd of 300 cows is 49.7 lb.
        In the example, the average amount (lb) of milk produced by cows in each
group is multiplied by 0.0009 (milk contains 0.09% P on average) to determine
the amount of total P secreted daily. In the example, the total P secreted in milk
daily is 18.9 lb.
        From this information, the amount of manure P excreted by the whole
herd can be predicted by calculating the difference between total P intake and
total P produced in milk. The total predicted P excretion is 30.8 lb/day for the
whole herd fed ration P concentrations that are formulated to meet NRC (2001) P
requirements (Table 4).
        Situation with excess ration P. Now consider the case in which this same
herd of 300 cows produces the same amount of milk, but the concentrations of P
in the rations are 0.44, 0.43, 0.42%, dry basis. That is, just 0.1 percentage unit
higher P in each ration than is needed to meet the requirement. Having higher
ration P concentrations than needed to meet requirements is common in many
dairy herds. In this case, total daily P intake by the whole herd is 64.7 lb/day
(Table 4). Phosphorus secreted in milk is still 18.9 lb per day; milk production or
the concentration of P in the milk would not be expected to increase. No more P
is needed to meet requirements for milk production. Therefore, the excess dietary
P was consumed and simply excreted in manure. In this case, the amount of P
excreted daily in manure is 45.8 lb.
        In this case of excess feeding of P, 15 lb/day excess P was excreted
compared with the case when the herd was fed to requirements. Being just 0.1
percentage unit in excess of needed ration P content to meet requirements,
resulted in a 49% increase in P in manure. This is equivalent to 12,443 lb of
additional (excess) P2O5 that must be managed [(15 lb/day  0.44) x 365 days). If
one was to apply this excess manure P to cropland with the expectation of 50 lb
P2O5 annual crop removal rate, then the extra cropland needed to manage the extra
manure P and still maintain whole-farm P balance would be about 249 acres or an
additional 0.83 acre/cow per year in this example 300-cow Holstein herd! That is
a very significant amount of excess manure P and cropland requirement from
simply being 0.1 percentage unit of ration P concentration in excess of NRC
(2001) requirements in milking herd rations. This is not sustainable ----
environmentally or economically.
IN: Proc. Four-State Applied Nutrition and Management Conf. July 9-10, 2003. pp.145 - 151 .

Table 4. Example: comparison of manure phosphorus excretion in a herd of
300 Holstein cows fed ration phosphorus to requirements (NRC, 2001) or fed
rations with excess phosphorus.
                                                     P                         Milk P     Predicted
Management            DMI,        Ration P,       intake,     Milk yield,      yield,      manure
Group                 lb/d           %              lb/d         lb/d          lb/d a      P, lb/d b

1. Herd fed to NRC (2001) phosphorus requirements:
High (80 lb)    5610       0.34     19.1     8,000                               7.2          11.9
Med (70 lb)     4884       0.33     16.1     7,000                               6.3           9.8
Low (60 lb)     4532       0.32     14.5     6,000                               5.4           9.1
Total                               49.7                                        18.9          30.8

2. Herd fed in excess of NRC (2001) phosphorus requirements:
High (80 lb)     5610       0.44      24.7     8,000      7.2                                 17.5
Med (70 lb)      4884       0.43      21.0     7,000      6.3                                 14.7
Low (60 lb)      4532       0.42      19.0     6,000      5.4                                 13.6
Total                                 64.7               18.9                                 45.8

Daily excess manure P (lb/day per 300 cows) from excess ration-P
(2.) compared with ration-P fed to meet NRC requirements (1.) in                              15.0
  Average P content of milk equals 0.09% (NRC, 2001).
  Predicted as the difference between P intake minus milk P, lb/day.


        Managing P inputs and outputs to achieve zero whole-farm P balance
should be a primary goal of dairy operations to control costs, achieve
environmental sustainability, and to be in compliance under the new CAFO rule
and states‟ guidelines. Balancing for P is achievable when dairy producers
effectively manage P inputs through accurate feeding and if sufficient land base is
available to spread manure P. Ration P concentrations in excess of those needed
to meet animals‟ needs result in excess manure P. Using imported feeds
(supplements) with lower P concentrations will help reduce P in manure.
Phosphorus balancing is achievable if feed P inputs are controlled and managed
carefully, and if adequate cropland is accessible.


Beede, D. K., and J. A. Davidson. 1999. Phosphorus: Nutritional Management for
       Y2K and beyond. Proc. Tri-State Dairy Nutr. Conf. p. 51-99.
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Council for Agricultural Science and Technology (CAST). 2002. Animal diet
      modifications to decrease the potential for nitrogen and phosphorus
      pollution. Issue Paper 21:1-16.

Klausner, S. D. 1993. Mass nutrient balances of dairy farms. Proc. Cornell Nutr.
      Conf. Ithaca, NY. p. 126.

NRC (National Research Council). 2001. Nutrient Requirements for Dairy Cattle.
      7th Revised Ed., National Academy Press, Washington, DC.

NPMP (Nutrient and Pest Management Program), Univeristy of Wisconsin-
     Extension and USDA-ARS Dairy Forage Research Center. Understanding
     soil phosphorus: An overview of phosphorus, water quality and
     agricultural management practices, 2002. (http://ipcm.wisc.edu).

Palmquist, D. L., and H. R. Conrad. 1978. High fat rations for dairy cows. Effects
      on feed intake, milk and fat production, and plasma metabolites. J. Dairy
      Sci. 61:890-901.

Rahnema, S. Z., Wu, O. A. Ohajuruka, W. P. Weiss, and D. L. Palmquist. 1994.
      Site of mineral absorption in lactating cows fed high-fat diets. J. Anim.
      Sci. 72:229-235.

Smith, A. M., G. L. Holck, and H. B. Spafford. 1966. Re-evaluation of nutrient
       allowances for high-producing cows. Calcium, phosphorus and vitamin D.
       J. Dairy Sci. 49:239-246.

Steele, W. 1983. Intestinal absorption of fatty acids, and blood lipid composition
        in sheep. J. Dairy Sci. 66:520-527.

Stevens, J. B., L. J. Bush, J. D. Stout, and E. I. Williams. 1971. Effects of varying
       amounts of calcium and phosphorus in rations for dairy cows. J. Dairy Sci.

Sutton, A., and D. K. Beede. 2003. Feeding strategies to lower nitrogen and
        phosphorus in manure. IN: Best Environmental Management Practices –
        Farm Animal Production. Extension Bulletins ID-304 (Purdue University)
        or E-2822 (Michigan State University Extension).

Tillman, A. D., and J. R. Brethour. 1958. The effect of corn oil upon the
       metabolism of calcium and phosphorus by sheep. J. Anim. Sci. 17:782-

USDA-NRCS. 2001. USDA Natural Resource Conservation Service.
     Conservation Practice Standard, Nutrient Management. CODE 590, Part
     402. NRCS, Washington, DC.
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Zinn, R. A., and Y. Shen. 1996. Interaction of dietary calcium and supplemental
       fat on digestive function and growth performance of feedlot steers. J.
       Anim. Sci. 74:2303-2309.
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    Feed for Thought:
    Hidden Costs, Real Costs of Byproduct Feeds in Dairy
                                        Dave Beede
                                 Department of Animal Science
                                  Michigan State University

        Dairy farmers have long been primary users of byproduct feeds resulting
 from wet- and dry-milling processes, corn syrup production, and distillery and
 brewery fermentations. Increased ethanol production from corn and other
 fermentable substrates in many states doubtless will make even more distiller‟s
 byproduct feed available. These byproduct feeds currently have few other uses
 except as livestock feed. Traditionally, we have considered byproduct feeds
 valuable sources for ration protein and energy --- especially in relation to their
 usual market prices. Ration formulation programs (least-cost or best-cost
 formulations) often call for byproducts to be used in rations.
     However, it is time to re-think how we use some byproduct feeds in cattle
 rations. There are hidden costs of feeding byproducts that must be considered
 and accounted for. As indicated in the preceding main article, many of these
 byproduct feeds contribute significant amounts of P to rations, sometimes in
 excess of dairy animals‟ requirements. Often dairy rations with significant
 amounts of byproduct feeds yet with no supplemental P from mineral premixes
 or other supplements, have P concentrations well in excess of the animals‟
 requirements. Excess ration P results in excess manure P. There are costs
 associated with this excess manure P --- mGholamore land required to spread
 extra manure P at agronomic rates, more processing to sequester and remove
 excess manure P, or other costs associated with processing and exporting excess
 P from dairy farms.
     For sound economics and environmental management, these additional costs,
 which are real costs of extra (excess) manure P should be reflected in feed prices
 in ration formulation – the extra costs of handling and disposal associated with
 high-P byproduct feeds. Doing so would better reflect the real cost of byproduct
 feeds in rations, including the true cost of achieving whole-farm P balancing.
 What that real price should be in ration formulation is a difficult question to
 answer. Doubtless, the real extra cost of excess manure P likely is very different
 from farm to farm. For example, if more land has to be purchased to spread
 excess manure P associated with feeding byproducts, then the extra cost
 associated with the excess P somehow should be computed considering cost of
 that land to deal with the excess P. Another approach if land is not available
 might be to determine the actual costs associated with export (disposal) of excess
 manure P and appropriately increase the price of the byproduct feed in ration
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 formulation. Then one would know when it is not cost-effective to include a
 particular byproduct feed in the ration; or, at least one would know and
 understand that there is extra cost associated with disposing of the excess manure
 P directly linked with use of that byproduct to maintain P balance in the whole
 farm system.
     For many years, dairy operations have been the “dumping ground” for excess
 P produced by the food, beverage, and fermentation industries through their
 byproducts. In effect, the dairy farmers have been given the responsibility
 (environmental and financial) of managing someone else‟s excess P. One way to
 help see that this is done equitably in the future is to put an appropriate price on
 each ton of high-P feed byproduct used in a farm‟s rations. When there are extra
 costs associated with managing the excess P, it should be reflected in the price of
 that feed ingredient in ration formulation. Ultimately, cattle producers should set
 the real demand for each particular high-P feed byproduct based on its real cost
 in their dairy operation. This is a shift in mindset for some --- from simply
 taking the best-value ingredients (lowest market price for a specified set of
 desired nutrients) to considering the real total cost of using those byproduct
 ingredients in a ration.
     If ration P is in excess of that absolutely needed to meet dairy animals‟
 requirements, manure P increases and extra costs will be incurred. To use high-
 P byproducts in many cattle rations ultimately increases costs. The real costs of
 high-P byproducts are greater than we have considered traditionally. There are
 additional hidden costs beyond the market price of many “good value” feed
 byproducts. Sound economic and environmental management of byproduct
 feeds is essential for sustainability of dairy farm systems.
         Feed for thought and action?!

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