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Snapshots of Feed & Manure Management

Mark Powell
Research Soil Scientist-Agroecology
USDA-Agricultural Research Service
US Dairy Forage Research Center, Madison, Wisconsin

Introduction
Escalations in feed and fertilizer cost, and ebbing milk prices are motivating many dairy farmers to find new ways to improve nutrient use on their farms. On many farms, it may be possible to put more feed nutrients into milk and more fertilizer and manure nutrients into crops and pasture. This would not only reduce farm input costs and enhance profits, but such improvements in nutrient use efficiency (NUE) also could reduce nutrient losses from dairy farms, which would allow farmers to comply more easily with environmental regulations. Over the past several years various procedures have been developed to provide ‘snapshot’ assessments of feed, fertilizer and manure use on a wide range of dairy farm types. 

Overall Approach
Questionnaires are used during initial face-to-face interviews to compile information on herd size and composition, livestock facilities, land use, management practices, and motivations and goals related to feed, fertilizer and manure management. The questionnaire is designed to provide a ‘snapshot’ of nutrient management for the period ‘yesterday-today-tomorrow’. Then, retrospective questions are posed to define broad, seasonal differences in nutrient management.  For example, timelines are established for when dairy cow diets may change, for when manure is spread, for crop rotations, etc. The information obtained during the first interview is used to establish benchmark NUE values and to develop additional survey tools for subsequent farm visits. Subsequent farm visits (usually monthly or quarterly) are set up to collect additional data, feed and manure samples, and to discuss survey results with farmers. 

Focus on Feed Management
During each farm visit, farmers are asked the number of lactating cows, dry cows and heifers they have. With the focus on the day of the visit, questions are asked related to feed management, such as whether the lactating herd is subdivided into different feeding groups, the basis for herd grouping, how often rations are balanced, the use of milk production technologies, milking frequencies, and average milk production per cow (usually the previous day’s bulk tank volume divided by cows milked). The types and amounts of feed being offered are recorded for each feeding group, and samples of each feed component and/or the total milked ration (TMR) are taken for analyses.

The information provided by the farmer on what feed they offer to their cows, milk production, and feed and milk nutrient analyses  are used to calculate feed nutrient use efficiencies (FNUE) as follows:
 

FNUE =     100 x               nutrients in milk (lbs/cow/d)
                                nutrient consumed in feed (lbs/cow/d)          
     
Our studies of FNUE have focused on nitrogen (N, or crude protein) and phosphorus (P) because putting more feed N and P into milk (and less into manure) has both cost reduction and environmental benefits. Excess feed N is a wasted cost. It is simply excreted as urea in urine, which is lost rapidly as ammonia gas or leached through the soil as nitrates in groundwater (and may be re-emitted as nitrous oxide, a greenhouse gas). Excess dietary P is also a wasted cost and is excreted in feces, which after land application, can runoff from fields and pastures into lakes and streams and promote algae growth and declines in water quality. Table 1 provides an example of snapshot estimates of feed N consumption, milk N secretion, and manure N excretion.
 
Table 1:  Milk production, feed N intake, manure N excretion and feed N use efficiency (FNUE) on Wisconsin dairy farms determined by snapshot methods.

 

Milk Production

Feed N Intake

Manure N excretion


FNUE

 

____________  lb/cow/day _________

percent

Average

65

1.44

 

24.9

Range
(low to high)


32 to 90


0.77 to 2.28

 


12.5 to 45.7

Focus on Manure Management
To determine the relative amount of manure that farmers collect (and available for application to cropland) the snapshot survey contains a series of questions related to herd management, barn cleaning and manure storage practices. To determine the amount of manure that goes uncollected (a wasted resource), the survey questionnaire is designed to determine where and for how long livestock spend outside. Time spent outside is delineated by animal type (e.g., lactating cows, dry cows, heifers), season (spring, summer, fall, and winter) and location. Information on relative time spent in outside areas is combined with manure nutrient excretions to determine loading rates in areas where manure is not collected. Table 2 provides the type of information obtained using snapshot assessment of manure collection practices.

Table 2: Snapshot assessment of manure collection on Wisconsin dairy farms




Category




Sub-category



Manure collection
(% of annual excretion)

Housing type

Stanchion

66 (±18.9)

 

Free-stall

89 (±16.5)

Herd size (cows/farm)

<50

57 (±12.6)

 

50-99

76 (±18.2)

 

100-199

95 (±5.1)

 

>200

100 (±0)

The survey part related to manure collection is followed by an exercise using farm maps and information on crop rotations to assess when, where and how collected manure is land-applied. This information can be used to calculate approximate manure application rates to cropland. The information also provides the basis for developing manure spreading logs which can be used by farmers to track actual spreading practices. Using these logs, farmers record information on the type of manure spread (semi-solid, liquid, bedded pack), the type of spreading equipment used, when and which fields receive manure, etc. Manufacturer information on manure spreader holding capacities and relative fullness of each load are used to estimate manure amounts (tons) spread. Manure samples taken by farmers are analyzed to estimate the amount of manure nutrients spread on a per field basis. 

Sharing Validation Data with Farmers
We have used various methods to validate the ‘snapshot’ estimates of feed intake, milk production, and manure nutrient excretion; and of the manure collection and manure spreading practices. For example, cow nutrient balances and associated feed requirements can be used to calculate the errors associated with data on apparent feed nutrient intake and calculated feed nutrient use efficiencies, and manure nutrient excretions can be compared published values of relationships between feed, milk, and manure.

Once a farm’s information has been compiled and analyzed, a report can be compiled to depict various NUEs for individual farms, how each farm’s NUEs compares to NUEs on other study farms, and where improvements in NUE can be made. We’ve found that this type of information provides for interesting discussion with producers (and dairy nutrition consultants) on how the farm’s FNUE compares to other farms, and what may be needed for the herd to attain the potential FNUE established under experimental conditions.

A sample questionnaire, manure spreading log, a final farmer report, and scientific articles related to the snapshot assessments are available on the U.S. Dairy Forage Research Center web site under the Products & Services tab. www.ars.usda.gov/mwa/madison/dfrc

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