Most cattle maintained on pasture receive supplemental feed during some portion of the year. Supplements are commonly fed to grazing cattle when pasture forage quality and quantity are below animal requirements

Lory, John A. (John Albert)

Olson, KC, M. S., Ph. D.

Zumbrunnen, Chris

University of Missouri: MOspace

AGRICULTURALPUBLISHED BY MU EXTENSION, UNIVERSITY OF MISSOURI-COLUMBIA extension.missouri.edu$.50	 G	2083	 Printed	on	recycled	paperMost cattle maintained on pasture receive supple-mental feed during some portion of the year. Supple-ments are commonly fed to grazing cattle when pas-ture forage quality and quantity are below animal requirements. The availability of low-cost grain milling byproducts has encouraged some producers to expand the use of supplemental feeds. Examples of grain mill-ing byproducts that have become popular for use as supplements include condensed distillers solubles (CDS), dried distillers grain with solubles (DDGS), corn gluten feed, and soybean hulls.The value of grain milling byproducts as cattle feeds is well established (MU publication G2076, Alternative Feeds for Beef Cows and Stockers). An often-overlooked aspect of supplementing grazing cattle with hay and grain milling byproducts is the addi-tional mineral nutrients that pass through the animal to the pasture in the manure. The objective of this guide is to help calculate the value of supplemental feeds as a fertilizer for pastures.Table 1 provides estimates of the fertilizer value of the nutrients fed a cow for 100 days. Capturing the fer-tilizer value in supplemental feeds is particularly impor-tant with rising fertilizer prices and the need to protect water quality by using fertilizer nutrients efficiently. The fertilizer value of these materials also can offset some of the cost of purchasing supplemental feed.Well-managed, intensively grazed pastures already have lower fertilizer maintenance requirements than hay fields because so many of the nutrients in the forage are redeposited onto the pasture. Nutrients in supplemental feeds can reduce or eliminate the need for main-tenance fertilizer applications on pastures. Table 2 summarizes the annual phosphate and pot-ash removal rates for pasture and hay fields. These removal rates for pastures can frequently be met or exceeded with typical supplemental feeding strategies.Some typical nutrient concentrations in feedstuffs are reported in Table 3. Cattle do not use the nutrients in feed with 100 percent efficiency. The majority of the nutrients consumed by cattle are redeposited on pas-ture in the urine and feces. Table 4 summarizes the percentage of consumed nutrients excreted by cattle. Mature cattle use the nutrients in feed to maintain the tissues of their bodies; however, they usually excrete about as much protein and minerals as they consume.See MU publication G4570, Reducing Losses When Feeding Hay to Beef Cattle, for more information on feeding hay in pastures. MU GuideBeef feedingCalculating Fertilizer Value of Supplemental Feed for Cattle on PastureJohn	A.	Lory,	Division	of	Plant	Sciences,	Commercial	Agriculture	ProgramK.C.	Olson,	Division	of	Animal	Sciences,	Commercial	Agriculture	ProgramChris	Zumbrunnen,	Livestock	SpecialistSupplemental feeds can provide an important source of nutrients for pastures.Table 1. Estimated fertilizer value of selected supplemental feeds fed to one cow for 100 days. FeedstuffDaily intake1 (lb/day)Nitrogen2(lb/100 days)Phosphate(lb/100 days)Potash(lb/100 days)Fescue	hay 30 23 23 67Alfalfa	hay 30 30 20 95Dried	distillers	grain	with	solubles 8 14 7 2Condensed	distillers	solubles 6 4 7 4Wet	corn	gluten	feed 18 8 13 5Dry	corn	gluten	feed 8 8 13 5Soybean	hulls 8 5 3 11Wet	brewers	grain 24 12 9 <11		On	an	“as-fed”	basis.2		Assumes	availability	of	35	percent	for	nitrogen	excreted	by	the	animals.G	2083	 Page	2		 University	of	Missouri	ExtensionCalculating the fertilizer value of supplemental feedThere are three steps in determining fertilizer nutrient value of supplemental feeds. 1.  Determine the amount of supplemental feed consumed by grazing animals.2.  Determine the amount nutrients in the supple-mental feed available for use as fertilizer. 3.  Determine the effective nutrient application rate onto a pasture.Step 1: Determine the amount of supplemental feed consumed by animals.The most convenient way to estimate the amount of supplemental feed consumed by animals is to esti-mate the daily intake of the feed by the animals graz-ing the pasture and the number of days feed was pro-vided to the animals. The amount of supplemental feed (SF) consumed, in pounds, is equal to the number of animals fed (A) times the amount of feed each ani-mal receives per day (Fd) times the number of days (D) the animals are on feed:SF 5 A 3 Fd 3 DTable 5 includes typical values for the daily intake (on an “as-fed” or wet basis) of specific supplemental feeds. The number of days animals are fed over the course of a year typically ranges from 90 to 150 days. These values are provided as guidelines; use the actual numbers for your farm. Step 2: Determine the amount of nutrients available for use as fertilizer. The objective here is to estimate the amount of supplemental nutrients excreted onto pasture and, therefore, available for use as fertilizer.Nutrient availability in supplemental feed is affected by the concentration of nutrients in the feed, the percentage of those nutrients excreted by the ani-mals and the availability of the manure nutrients as a fertilizer source. For the amount of supplemental feed (SF) calculated in Step 1, use values in Tables 3 and 4 to calculate the amount of nitrogen, in pounds, available as fertilizer (Na) as follows:Na 5 (SF 3 protein concentration (%)/100)  (see Table 3) 	 3 excreted nitrogen (%)/100   (see Table 4)	 3 35% fertilizer availability/100 3 1 lb nitrogen fertilizer/6.25 lb protein Similarly, the amounts of available phosphate (Pa) and available potash (Ka) can be calculated as follows:Pa 5 (SF 3 phosphorus concentration (%)/100)  3	excreted phosphorus (%)/100  3	100% fertilizer availability/100  3	2.3 lb phosphate fertilizer/lb phosphorusKa 5	(SF 3 potassium concentration (%)/100) 3	excreted potassium (%)/100 3	100% fertilizer availability/100 3	1.2 lb potash fertilizer/lb potassiumUse Table 3 to estimate the nutrient concentration in the supplemental feed. Use Table 4 to estimate the percentage of nutrients excreted by the animal. Note that phosphate and potash in manure are 100 percent equal to fertilizer nutrients. However, nitrogen in manure is substantially less available than fertilizer nitrogen. An estimated 35 percent of the nitrogen in excreted urine and feces is available as fertilizer. The rest is lost to the atmosphere as ammonia or tied up in unavailable forms in the manure.Step 3: Determine the effective nutrient application rate for a pasture.The rate (Ra) at which nutrients are applied to a pasture is affected by the availability of nutrients in the manure (calculated in Step 2), the proportion of the supplemental feed fed in a particular pasture and the size of the pasture: available nutrients (lb) 3	% of feed fed on that pasture/100Ra 5 ____________________________________________ pasture size (acres)Table 2.  Estimated annual phosphate and potash removal from cool-season pasture and hay fields.ForageYield goal (tons/A)Phosphate removal (lb/A)Potash removal (lb/A)Pasture 3 10 34Hay 3 27 	102Table 3. Nitrogen, phosphorus and potassium concentration of selected feedstuffs. All values are reported on an “as-fed” basis.Feedstuff Dry matter, % Protein1, % Phosphorus, % Potassium, %Fescue	hay 100 12.5 0.3 1.7Alfalfa	hay 100 18 0.3 2.6Dried	distillers	grain	with	solubles 90 32 0.4 0.2Condensed	distillers	solubles 35 12 0.5 0.6Wet	corn	gluten	feed 40 8 0.3 0.3Dry	corn	gluten	feed 90 18 0.7 0.6Soybean	hulls 90 11 0.2 1.1Wet	brewers	grain 30 9 0.2 0.031	To	convert	from	protein	to	nitrogen,	divide	by	6.25.G	2083	 Page	3		 University	of	Missouri	ExtensionExample 1:  Feeding fescue hayA	farmer	feeds	100	cows	(A)	30	pounds	fescue	hay	per	day	(Fd)	from	mid-December	to	early	April	(D = 110	days).	The	winter	pasture	is	100	acres.	What	is	the	fertilizer	value	of	the	imported	hay	to	this	pasture?Step 1:Amount	of	supplemental	feed	(SF)		5		100	cows	3	30	lb	hay/cow/day	3	110	days	5	330,000	lb	feedStep 2:Available	nitrogen	(Na)		 5		(330,000	lb	feed	3	12.5%	nitrogen/100)		3	100%	excreted/100		3	35%	available/100		3	1	lb	nitrogen	fertilizer/6.25	lb	protein		 5	2,310	lb	nitrogenAvailable	phosphate	(Pa) 5		(330,000	lb	feed	3	0.3%	phosphorus/100)		3	100%	excreted/100		3	100%	available/100		3	2.3	lb	phosphate	fertilizer/lb	phosphorus		5	2,280	lb	phosphateAvailable	potash	(Ka)	 5		(330,000	lb	feed	3	1.7%	potassium/100)		3	100%	excreted/100		3	100%	available/100		3	1.2	lb	potash	fertilizer/lb	potassium		 5	6,730	lb	potashStep 3:	 	 2,310	lb	nitrogen	3	100%	on	field/100	Nitrogen	application	rate	 5 ________________________________	 5	23	lb	nitrogen/acre  100	acres	 	 2,280	lb	phosphate	3	100%	on	field/100Phosphate	application	rate	5	 _________________________________	 5	23	lb	phosphorus/acre  100	acres	 	 6,730	lb	potash	3	100%	on	field/100	Potash	application	rate	 5 ________________________________	 5	67	lb	potash/acre  100	acresNote	that	the	phosphate	and	potash	application	rate	is	more	than	double	the	annual	removal	rate	for	most	pastures,	so	soil	test	levels	for	these	nutrients	will	increase	over	time	if	this	pasture	is	used	annually	for	winter	pasture.	The	available	nutrients	in	the	manure	are	worth	$2,967,	or	$29.50	per	acre	or	$18/ton	of	hay	if	one	assumes	fertilizer	value	of	$0.40/lb	nitrogen,	$0.30/lb	phosphate	and	$0.20/lb	potash.Table 5. Typical daily intake (on an “as-fed” basis) for selected supplemental feeds.FeedstuffTypical daily intake(lb/animal/day)Fescue	hay 30Alfalfa	hay 30Dried	distillers	grain	with	solubles 6–10Condensed	distillers	solubles 3–9Wet	corn	gluten	feed 13–23Dry	corn	gluten	feed 6–10Soybean	hulls 6–10Wet	brewers	grain 17–30Table 4. Percentage of consumed nutrients (nitrogen, phosphorus and potassium) excreted by cattle.Animal typeNitrogen(% excreted)Phosphorus(% excreted)Potassium(% excreted)Growing	cattle 50–70 65–75 65–85Mature	cattle 100 100 100Unrolling hay is one strategy for increasing the distribution of nutrients on pasture.■ Issued in furtherance of Cooperative Extension Work Acts of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. L. Jo Turner, Interim Director, Cooperative Extension, University of Missouri, Columbia, MO 65211. ■ University of Missouri Extension does not discriminate on the basis of race, color, national origin, sex, sexual orientation, religion, age, disability or status as a Vietnam era veteran in employment or programs. ■ If you have special needs as addressed by the Americans with Disabilities Act and need this publication in an alternative format, write ADA Officer, Extension and Agricultural Information, 1-98 Agriculture Building, Columbia, MO 65211, or call (573) 882-7216. Reasonable efforts will be made to accommodate your special needs.Barriers to using feed nutrients as a fertilizerWith manure nutrients, cattle are the fertilizer spreader. Urine typically contains more than 50 per-cent of the total nitrogen and potassium excreted by cattle. Conversely, feces contain 80 percent of the total phosphorus excreted by cattle. The nutrients in supplemental feed are only valu-able as a fertilizer if you take steps to ensure that they are spread evenly around the whole field. Ani-mals typically do a poor job of distributing nutrients around a pasture; nutrients tend to concentrate near feeders, water and shade areas. The bulk of the pasture often gets only limited benefits from manure nutrients unless steps are taken to improve manure distribution by grazing animals. Through management farmers can improve nutri-ent distribution in pastures. Managing animals so they do a better job of distributing manure in a pasture makes their manure more valuable as a fertilizer. Rec-ommended steps include:•	 Regularly move feeders and feeding areas around the pasture.•	 Increase the stocking density of animals but move animals from area to area more frequently to pre-vent over use of areas in the pasture.•	 Do not use the same pasture for supplemental feeding every year. Instead move the supplemen-tal feeding area to distribute the nutrient benefits around the farm.•	 Maintain a setback area of at least 100 feet between supplemental feeding areas and streams. Avoid placing feeding areas where runoff will easily move into surface waters, particularly in win-ter when frozen and saturated soil promotes the movement of manure nutrients in runoff.Missouri research shows that moving the hay feed-ing area every two days resulted in higher pasture yield and higher phosphorus and potassium soil test levels in the field. Feeding hay in one spot resulted in similar yields in most of the pasture as importing no hay. These results emphasize that capturing the fertil-izer benefit of nutrients in supplemental feed requires moving feeding areas on a regular basis. You cannot fertilize a field with a manure spreader by just running the spreader in a corner of the field. Similarly, you can-not benefit from the fertilizer nutrients in your feed supplements if you always put the feeder in the same spot in a pasture. Example 2:  Feeding dried distillers grain with solublesA	farmer	feeds	40	cows	(A)	8	pounds	of	dried	distillers	grain	with	solubles	(DDGS)	per	day	(Fd)	from	January	to	early	March	(D = 60	days)	in	a	25-acre	pasture.	What	is	the	fertilizer	value	of	the	imported	feed	to	this	pasture.Step 1:	 Amount	of	supplemental	feed	(SF)	5	40	cows	3	8	lb	DDGS/cow/day	3	60	days	5	19,200	lb	feedStep 2:Available	nitrogen	(Na)		 5		(19,200	lb	feed	3	32%	protein/100)		3	100%	excreted/100	3	35%	available/100	3	1	lb	nitrogen	fertilizer/6.25	lb	protein		 5	344	lb	nitrogenAvailable	phosphate	(Pa)		 5		(19,200	lb	feed	3	0.4%	phosphorus/100)		3	100%	excreted/100		3	100%	available/100		3	2.3	lb	phosphate	fertilizer/lb	phosphorus		 5	176	lb	phosphateAvailable	potash	(Ka)		 5		(19,200	lb	feed	3	0.2%	potassium/100)		3	100%	excreted/100		3	100%	available/100		3	1.2	lb	phosphate	fertilizer/lb	phosphorus		 5	46	lb	potashStep 3:Nitrogen	application	rate		 5	(344	lb	nitrogen	3	100%	on	field/100)	4	25	acres		 5	14	lb	nitrogen/acrePhosphate	application	rate		 5	(176	lb	phosphate	3	100%	on	field/100)	4	25	acres		5	7	lb	phosphorus/acrePotash	application	rate		 5	(46	lb	potash	3	100%	on	field/100)	4	25	acres		 5	2	lb	potash/acreNote	that	the	nitrogen	application	rate	is	close	the	spring	nitrogen	needs	of	many	pastures	and	the	phosphate	application	rate	is	nearly	the	annual	removal	rate	for	most	pastures.	The	available	nutrients	in	the	manure	are	worth	$194,	or	$7.75	per	acre	or	$20/ton	of	DDGS	if	one	assumes	fertilizer	value	of	$0.40/lb	nitrogen,	$0.30/lb	phosphate	and	$0.20/lb	potash.G	2083	 Page	4	 New	4/06/3M

Calculating fertilizer value of supplemental feed for cattle on pasture (2006)

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