One daunting task for writing about dietary

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1 Nutrition & Helth: Beef By G.C. DUFF One dunting tsk for writing bout dietry nutrient llownces for beef cttle is relted to the vst number of production systems used. Beef production vries widely from grzing systems utilizing ntive pstures or improved pstures to confinement feeding utilizing high-concentrte diets. Therefore, this rticle will present brod overview of beef cttle nutrition. Dr. T.W. Perry previously wrote this rticle with informtion bsed on Ntionl Reserch Council (NRC) 1996 recommendtions; severl sections remin unedited from the originl mnuscript by Dr. Perry. Digestive physiology There re severl unique spects of the digestive trct of beef cttle tht deserve ttention. Strting t the hed, in the mouth, beef cttle hve no upper incisors. When grzing, beef cttle will wrp their tongue round the forge prticles nd with the muscles in the bck of their hed, use the bottom incisors to sher off the plnt prticles. Another importnt spect is the copious quntities of sliv tht beef cttle produce. Besides iding in moistening the bolus for swllowing nd iding in tste, sliv is source of recycled nutrients for ruminnts, prticulrly nitrogen (ure) nd minerls (e.g., phosphorus, mgnesium, sodium, potssium nd chloride). Sliv is lso importnt in buffering the rumen. The mount of sliv produced cn be s much s 180 liters per dy nd is dependent on the diet consumed. The esophgus is hollow tube tht llows the bolus formed to be trnsported to the next section of the gstrointestinl trct (GIT). Peristltic ctions in the esophgus re importnt to llow ruminnts to regurgitte the feed bolus, remsticte nd reswllow undigested mteril (rumintion). The time spent ruminting is dependent on diet with grzing cttle ruminting more thn cttle consuming high-grin diets typicl in feedlot settings. It hs been estimted tht beef cttle cn ruminte up to 8 hours per dy. In ddition to regurgittion of undigested feedstuffs, the esophgus is importnt in eructtion of gses produced during fermenttion in the rumen. When eructtion is interfered with, blot cn occur, which, if gone undetected, cn result in deth. Two types of blot cn occur in ruminnts. One type is free-gs blot, which occurs secondry to fctors tht prevent eructtion. The second type of blot is frothy, where froth produced by fermenttion prevents eructtion of gses. Feeding the ionophore monensin hs been shown to reduce blot on whet psture nd my be effective in reducing feedlot blot either by reducing gs production or by ltering the feeding ptterns of the cttle. The reticulum (honeycomb) is the next section of the GIT, nd this section is responsible for regulting digest flow into nd out of the rumen. It is in this section where shrp objects (e.g., nils nd wires) tht my be consumed by the nimls cn ccumulte nd, over time, penetrte the reticulum lining, llowing rumen contents to lek into the peritonel cvity cusing hrdwre disese. Diry producers often plce mgnet in the rumen to ttrct the objects. The rumen of the niml is virtully fermenttion vt. Ruminl fluid contins nywhere from 30 billion to 50 billion microorgnisms (bcteri nd protozo) per milliliter of ruminl fluid. Just like rumintion, the microbil popultion present in the rumen is relted to diet consumed. The vrious types of bcteri present is beyond the scope of the rticle, but with forge diets, the primry bcteril species will be cellulolytic nd hemicellulolytic, wheres with grin-bsed diets, mylolytic bcteri will be in greter concentrtions. In ddition, proteolytic nd lipolytic bcteri re present in the rumen nd re responsible for digesting protein nd lipids, respectively. The omsum (mny folds) is responsible for regulting flow to the bomsum nd is site of wter bsorption. The next section of the beef cttle digestive trct is the true stomch, referred to s the bomsum. It is similr in function to the stomch of monogstric nimls such s the pig. The lower digestive trct is virtully identicl to other species; however, the duodenum is unique in tht it secretes greter quntities of nucleses nd less pncretic mylse thn other species of nimls. The greter mounts of 32 Feedstuffs, September 10, 2008

2 nucleses is relted to brekdown of bcteril protein nd less mylses is relted to decresed mounts of strch entering the smll intestine versus other species. The lrge intestine in beef cttle is proportionlly lrger thn omnivorous species nd proportionlly less thn nonruminnt herbivores such s horses nd rbbits. With high concentrte diets, fiber digestion my be shifted to the lrge intestine due to decresed fiber digestion in the rumen s result of decresed ruminl ph. However, it is not known whether the lrge intestine cn fully compenste for the incresed fiber lod. Ruminl fermenttion The first step in ruminl fermenttion occurs in the mouth with the nimls reducing the plnt prticle size with the molrs. In ddition, rumintion is responsible for further reduction in prticle size. These ctions serve to increse the surfce re of plnt prticle which llow the bcteri to ttch to plnt prticle. A symbiotic reltionship exists between the host niml nd the bcteril species. The host niml supplies wrm, moist environment with substrtes introduced nd removl of end products of ruminl fermenttion. This llows the microbes to brek down the fibrous mteril nd produce end products tht the niml cn utilize. The microbes will ferment the crbohydrte portion of plnts nd produce voltile ftty cids (VFAs). The primry 1. Nutrient requirements for growing nd finishing beef cttle,b,c Bodyweight, lb Mintennce requirement per dy NEm, Mcl Metbolizble protein, g Clcium, g Phosphorus, g Averge dily gin, lb Net energy for gin, Mcl per dy Metbolizble protein required for gin, lb. per dy Clcium required for gin, g per dy Phosphorus required for gin, g per dy Adpted from 7th rev. ed., Nutrient Requirements of Beef Cttle, 1996, Ntionl Reserch Council. b Crystlline vitmin A should be dded t level of 1,100 IU/lb. DM. c Weight of niml t smll mrbling, 1,172 lb.; ADG rnge, 1.1 to 5.5 lb. per dy; breed, Angus. Nutrition & Helth [ Dietry llownces for beef ] VFAs produced include cette, propionte nd butyrte. In ddition, gses re produced including crbon dioxide nd methne. The nimls cn utilize VFAs for energy with n estimted 70-80% of the cloric requirements met by VFAs. In ddition, other components re fermented in the rumen resulting in production of microbil protein nd B vitmins. Nutrients Although beef cttle require the sme nutrients s other species of nimls, dietry concentrtions my differ becuse of the unique bility of ruminnts to ferment dietry components. Wter Without doubt, wter is primry nutrient for ll species. Beef cttle should be provided with n dequte source of wter. If feed intke diminishes drsticlly for no pprent reson, the first thing producers should check is the wter source. Another fctor tht will ffect wter requirements is environmentl temperture. Crbohydrtes Crbohydrtes re importnt for ll spects of beef cttle nutrition. For grzing ruminnts, forges comprise the mjority of the diet. Depending on loction, for cttle grzing ntive rnges, forges consumed will included forbs, shrubs nd grsses, wheres cttle in other regions of the country will rely hevily on introduced forges including brome grss, timothy, ryegrss, etc. For finishing beef cttle, crbohydrtes re mjor portion of the diet. The microbil popultion produces the cellulses nd hemicellulses to brek down the structurl crbohydrtes in the plnts. Strches nd sugrs re lso extensively fermented by microbil popultion in the rumen. The primry VFAs produced re cette, propionte nd butyrte. Acette is produced in the highest proportions, followed by propionte nd butyrte. Adding cerel grins will increse the mount of propionte produced, lbeit cette will still be in the gretest proportion. Protein Bcteril protein synthesis my ccount for s much s 50% of the protein nd mino cids needed by cttle. Beef cttle cn metbolize dietry protein, s well s non-protein nitrogen sources such s ure. Ruminnts hve the bility to up-regulte low-qulity protein. Ruminnts cn tke nitrogen source such s ure nd turn it into moderte-qulity bcteril protein. Furthermore, it is generlly recognized tht ruminnts down-regulte high- September 10, 2008, Feedstuffs 33

3 2. Nutrient requirements for growing bulls,b,c Bodyweight, lb ,100 1,320 1,540 1, Mintennce requirement per dy NE m, Mcl Metbolizble protein, g Clcium, g Phosphorus, g Averge dily gin, lb Net energy for gin, Mcl per dy Metbolizble protein required for gin, lb. per dy Clcium required for gin, g per dy Phosphorus required for gin, g per dy Adpted from 7th rev. ed., Nutrient Requirements of Beef Cttle, 1996, Ntionl Reserch Council. b Crystlline vitmin A should be dded t level of 1,100 IU/lb. DM. c Weight t mturity, 1,958 lb.; ADG rnge, lb. per dy; breed, Angus. qulity protein sources. Down-regultion would be tking high-qulity protein nd turning it into moderte-qulity bcteril protein. With the 1996 NRC, protein requirements for beef cttle were bsed on metbolizble protein rther thn formulting on crude protein requirements s with previous publictions. This method divides protein requirements into niml nd microbil components. Significnt progress ws mde in evluting protein requirements with the 1996 NRC publiction; however, complete implementtion of the publiction hs not been ccomplished. It is generlly recognized tht the metbolizble protein system better describes requirements of beef cttle; however, formultion on totl crude protein continues to be prcticed. Crude protein concentrtions used by consulting feedlot nutritionists rnges from 12.5 to 14.0 (men 13.34; mode 13.5 with ure concentrtions in the finishing diet of (men 1.01; mode 1.2; Vsconcelos nd Glyen, 2007; J. Anim Sci. first published on June 25, 2007 s doi: / js ). In ddition, only 9 (31.03%) out of 20 (68.97%) nutritionists responding to the questionnire reported formulting bsed on degrdble intke protein (DIP). Energy Although not nutrient per se, it is importnt to discuss energy requirement of beef cttle. Energy is term used to define the cpcity to do work. In the U.S., the clorie, kiloclorie (kcl) nd meg clories (mcl) re the common terms used in nutrition. Gross energy (GE) is the mount of het produced 34 Feedstuffs, September 10, 2008 when feedstuff is completely oxidized using bomb clorimeter. Digestible energy is obtined by subtrcting fecl energy from GE consumed nd is the mount of energy pprently bsorbed from feed. Metbolizble energy (ME) is determined by subtrcting urinry nd combustible gs loss from DE. Net energy is determined by subtrcting energy losses from rumen fermenttion nd tissue metbolism from ME. Net energy will predict the mount of energy vilble for mintennce nd production. The mintennce energy requirements of beef cttle hve been well estblished s 77 kcl/w 0.75 where weight (W) is bodyweight in kilogrms. Energy is considered first when blncing for beef cttle. Beef cttle will obtin mjority of their energy requirements from fermenttion of crbohydrtes. Lipids nd proteins cn lso supply energy to cttle. As mentioned previously, 70-80% of the niml s cloric requirements will be met by VFAs. Minerls Dr. Perry hd n excellent presenttion of vitmin nd minerl requirements for beef cttle, nd it remins unchnged except for comment on vitmin E for newly received beef clves. When formulting for newly received beef clves, trce minerl concentrtions should be incresed to ccount for decresed feed intke during the first few weeks fter rrivl. Tble 6 hs been included s reference to compre formultions from consulting nutritionists vs. NRC recommendtions. It ppers tht most mcro nd micro minerls re formulted slightly higher thn NRC recommendtions. Vsconcelos nd Glyen (2007) suggested tht over supplying nutrients my reflect the nutritionist s desire to err on the side of cution. The totl minerl or sh content of the niml body represents very smll percentge of the totl dry mtter content. One uthor hs expressed bovine on ft-free bsis, minus the contents of the gstrointestinl trct s pproximtely 73% wter, nerly 22% protein nd 5.3% sh, plus smll mounts of crbohydrtes. Reserch workers t the University of Missouri nlyzed the bodies of severl bred nimls nd found minerl vlues of 1.3% clcium, 0.74% phosphorus, 0.16% sodium, 0.19% potssium, 0.11% chloride, 0.04% mgnesium nd 0.15% sulfur. Nturlly, there ws whole host of other minerl elements in very minute quntities. The 1996 NRC bulletin sttes tht there re 17 minerl elements required by beef cttle. However, becuse of the nture of the diets of most beef nimls, it is rre tht more thn of such minerl elements re deficient. A brief discussion of those minerl elements tht might be expected to be deficient in typicl diets of cttle will follow. Clcium. Severl dietry ingredients supply ner optiml

4 levels of clcium, including the fmily of legume forges, plus severl other types of forges especilly young, fstgrowing plnts. The cerel grins re quite low in clcium. Thus, forging cttle might be expected to obtin nerly dequte clcium from their grzing, wheres feedlot cttle on very high-energy diets cn be expected to obtin insufficient clcium from their diets. Clcium cn be supplied so very economiclly from ground limestone tht there is no reson for clcium deficiency except lck of ttention to the cttle-feeding enterprise. Phosphorus. Most grins re pretty good source of phosphorus (0.25+%), with legume hys somewht less (0.20%) nd grss hys t 0.20%. Supplementl feed-grde phosphorus is more expensive thn sources of clcium. However, it is foolish to limit the intke of phosphorus below tht recommended by the NRC, becuse such prctice cn decrese rte of gin, even though ll the other nutrient requirements hve been met. Supplementl phosphorus s well s supplementl clcium cn be supplied by either diclcium phosphte or stemed bone mel. Nturlly, there re mny other sources of dietry phosphorus, including phosphoric cid (utilized in liquid-supplements production) nd defluorinted rock phosphte. It should be pointed out tht there is no known benefit in feeding levels of phosphorus greter thn those recommended by the NRC. Furthermore, it is criticl tht phosphorus is not supplied to beef cttle in excessive quntities becuse unused phosphorus will be excreted from the body nd eventully it my find its wy to surfce wter, nd thus represent potentil wste hzrd to the environment. 3. Nutrient requirements for pregnnt replcement heifers,b,c Months since conception NE m, Mcl per dy Mintennce Growth Pregnncy Totl Metbolizble protein, g per dy Mintennce Growth Pregnncy Totl Clcium requirement, g per dy Mintennce Growth Pregnncy Totl Phosphorus requirement, g per dy Mintennce Growth Pregnncy Totl Averge dily gin, lb. per dy Growth Pregnncy Totl Bodyweight, lb. Shrunk body Grvid uterus mss Totl ,010 1,078 Adpted from 7th rev. ed., Nutrient Requirements of Beef Cttle, 1996, Ntionl Reserch Council. b Crystlline vitmin A should be dded t level of 1,100 IU/lb. DM. c Mture weight, 1,172 lb.; clf birth weight, 88 lb.; ge t breeding, 15 months; breed, Angus. Nutrition & Helth [ Dietry llownces for beef ] Slt. Mny people force-feed slt in totl mixed rtion, wheres others my feed it on n d libitum bsis, lone or mixed with sources of clcium nd phosphorus. Often, slt, s trce-minerlized slt, is utilized s crrier for most of the so-clled trce minerls. Becuse the feeding of selenium is controlled by the Food & Drug Administrtion, it would not fit too well into free-choice slt sitution. There is no point in overfeeding slt. Furthermore, becuse of the ese of feeding slt, nd becuse slt is not expensive, there is no cuse for slt deficiency except poor mngement. Potssium. The legumes re exceptionlly good sources of potssium (lflf hy contins 1.5%); corn silge contins potssium t bout the requirement for cttle (0.8%), nd the cerel grins re deficient in potssium (0.3%). Therefore, cttle fed on very high-grin diets should hve their totl dietry potssium checked, probbly requiring considerble supplementtion. Optiml potssium level is relted directly to optiml rtes of gin so it is expensive to not feed dequte potssium. Iodine. Supplementl iodine is needed by reproducing cttle, but there is little rtionle to feeding iodine to growing nd finishing cttle. A possible exception to this is tht iodine compounds re utilized in lleviting the symptoms of footrot. Selenium. In beef cttle, the supplementtion of diets with selenium is restricted lrgely to reproducing nimls, since the use of supplementl selenium for growing nd finishing cttle, lrgely, hs not shown positive response. As indicted bove, the ddition of selenium to beef cttle diets is under the control of FDA nd so is hndled by feed mnufcturers who hve been given permission to mke such dditions. However, new spect of selenium supplementtion hs risen. It hs been demonstrted tht lctting cttle given supplementl selenium in the form of selenium-yest compound utilized selenium more efficiently thn those whose supplementl selenium ws in either the selenite or selente form. Since the rnge between optiml nd toxic levels of selenium is nrrow, possibly less of the selenium yest source would be required. Coblt nd copper. In certin res of the U.S., especilly prts of Florid nd Michign, the soil is so deficient in coblt nd copper tht crops grown on such soils reflect the deficiencies. Both of these elements re identified with the production of red blood, nd deficiency of either will be reflected in nemic conditions. Both re supplied redily in mnufctured feed nd in trce-minerlized slt. Mgnesium. Grss tetny is the nme given to mldy tht seems to occur most often in cttle grzing lush psture in erly spring when the wether is especilly cool. However, there hve been reported clinicl observtions under other conditions. The feeding of 1-2 oz. of mgnesium oxide per hed, dily, seems to prevent grss tetny. September 10, 2008, Feedstuffs 35

5 However, mgnesium oxide ppers to not be pltble to cttle, so methods of msking its flvor, such s mixing it with pound or two of corn, my be helpful. Mgnesium cn be suspended in free-choice liquid supplements, nd grzing cttle seem to consume sufficient mounts of the mixture to prevent grss tetny. Vitmins Cttle out-of-doors, consuming green grss, were thought to be obtining ll the vitmins their bodies needed. It ws proposed they could convert sufficient mounts of the bet-crotene contined in their green forge to meet their vitmin A requirement dequtely nd; tht the ultrviolet rys of the sun would convert ftty substnces just under their hide to meet their vitmin D requirements dequtely; tht the mrvelous microbes of the rumen should synthesize dequte levels of the B vitmins, plus vitmin K; nd finlly, there should be sufficient vitmin E in their diet to meet tht requirement. There re exceptions to this supposition. Thimin (vitmin B1). Although cttle should be ble to mnufcture sufficient mounts of this vitmin by their rumen microbes, there re times especilly under feedlot conditions when reltive B1 deficiency my exist. Under such condition, mldy known s polio-encepholmlci my occur, but only in firly limited numbers of the pen of cttle. This condition lso is known s circling disese, becuse fflicted cttle tend to wlk imlessly in circles. The condition seems to occur most on corn silge diets nd is cused by n enzyme clled thiminse, mening it is n 4. Nutrient requirements for beef cows,b,c Month since clving NE m required, Mcl per dy d Mintennce Lcttion Pregnncy Totl Metbolizble protein required, lb. per dy d Mintennce Lcttion Pregnncy Totl Clcium required, g per dy d Mintennce Lcttion Pregnncy Totl Phosphorus required, g per dy d Mintennce Lcttion Pregnncy Totl Gin in weight from pregnncy, lb. per dy d Milk, lb. per dy Bodyweight, lb. per dy Shrunk weight 1,172 1,172 1,172 1,172 1,172 1,172 1,172 1,172 1,172 1,172 1,172 1,172 Conceptus Totl 1,172 1,172 1,174 1,174 1,179 1,181 1,187 1,198 1,214 1,236 1,269 1,313 Adpted from 7th rev. ed., Nutrient Requirements of Beef Cttle, 1996, Ntionl Reserch Council. b Crystlline vitmin A should be dded t level of 1,100 IU/lb. DM. c Mture weight, 1,173 lb.; clf birth weight, 88 lb.; ge t clving, 5 yers; ge t wening, 30 weeks; pek milk, 17.6 lb.; breed, Angus; milk ft, 4%; milk protein, 3.4%; clving intervl, 12 months. d No llownces mde for gin since this mture cow. 36 Feedstuffs, September 10, 2008 orgnism tht blocks the norml functioning of thimin. A sudden fll to the ground, followed by scissoring ction with the legs, then deth, chrcterize this condition. An intrmusculr injection of vitmin B1 will give lmost instntneous relief, nd clf will jump to its feet nd strt cting like the rest of the clves in the pen very shortly. As mentioned previously with coproducts, high concentrtions of sulfur in the feed or wter cn cuse this disese with production of hydrogen sulfide in the rumen nd bsorption in the bloodstrem. This condition does not occur very often nd should not discourge feeders from utilizing corn silge or co-products in their feeding progrms. Vitmin B12. Vitmin B12 should be synthesized in dequte quntities in the bovine rumen. Mny reserch studies hve demonstrted performnce improvement in cttle especilly those on high-energy diets. Perhps the bility of the rumen to synthesize vitmin B12 is borderline, t best. Vitmin A. Green nd yellow feeds usully contin betcrotene, which is the precursor of vitmin A. In other words, mny nimls possess the cpbility to convert bet crotene to meet their vitmin A needs. However, it is now known tht, under certin conditions, the beef niml is not cpble of converting sufficient bet-crotene to meet its vitmin A needs. It is sfe recommendtion to supply the mjority of the vitmin A needs of beef cttle in the crystlline form. Fortuntely, vitmin A is not very expensive. Vitmin E. Sometimes, condition occurs in clves clled white muscle disese. This condition is ttributed to deficiency of vitmin E, selenium or both. Mny cttle producers mke it prctice to inject young clves with combintion of vitmin E nd selenium. Most feeds consumed by cttle except in erly clfhood re dequte in vitmin E. However, some interesting ppers hve been presented t scientific meetings, which indicte tht utiliztion of supplementl vitmin E with slughter cttle will increse the shelf-life of crcss beef in the grocery met cse. In ddition, reserch hs shown tht incresing concentrtions of vitmin E during the receiving period for newly received beef clves my decrese the incidence of bovine respirtory disese. Commodities Grins. Increses in fuel ethnol production nd high fuel prices hve drmticlly incresed the costs of commodities used in cttle feeding. The primry grins used for ethnol production

6 5. Minerl requirements nd mximum tolerble levels for beef cttle,b Requirement Mximum Growth nd Erly tolerble Minerl finishing Gesttion lcttion level Chlorine, % Chromium, ppm Coblt, ppm Copper, ppm Iodine, ppm Iron, ppm Mgnesium, % Mngnese, ppm ,000 Molybdenum, ppm 5 Nickel, ppm 50 Potssium, % Selenium, ppm Sodium, % Sulfur, % Zinc, ppm Adpted from 7th rev. ed., Nutrient Requirements of Beef Cttle, 1996, Ntionl Reserch Council. b Requirements for clcium nd phosphorus re not included since they re listed in ech of the nutrient requirement tbles. re corn nd sorghum. Albeit prices hve incresed, corn continues to be the primry cerel grin used by consulting feedlot nutritionists (Vsconcelos nd Glyen, 2007). In this survey, whet ws used most often by nutritionists tht used secondry grins, followed by sorghum nd brley. Six nutritionists did not use secondry grin sources. Grin co-products. As result of incresed fuel ethnol production, grin co-products hve become common ingredients in beef cttle diets. This is, however, gretly dependent on loction of the milling fcility nd feedlot, prticulrly wet milling fcilities. Of the feedlot consulting nutritionists surveyed by Vsconcelos nd Glyen, 82.76% reported using grin coproducts with wet distiller s grins most common, followed by dry distiller s grins with solubles (corn nd/or sorghum), wet corn gluten feed nd dry corn gluten feed. Level of inclusion in finishing diets rnged from 5 to 50% (verge 16.5; mode = 20%). It should be pointed out, however, tht concentrtions of sulfur in these coproducts should be monitored. One debte tht remins is the level of inclusion nd crcss merit. Roeber et l. (2005; J. Anim. Sci. 83: ) reported tht feeding up to 50% distiller s grins did not ffect tenderness or sensory trits of strip loins from Holstein steers. Liquid feeds. Ft is dded to finishing diets from 0 to 4.5%; (men = 3.1; mode = 3.0; Vsconcelos nd Glyen, 2007). Common ft sources included tllow, yellow grese, choice white grese nd blend of sources. In ddition, 32.4% of clients dded non-ft liquids to the diet. The non-ft liquids identified in the survey included corn distiller s solubles used most often, followed by molsses, molsses blends nd corn distiller s solubles in combintion with blends (Vsconcelos nd Glyen, 2007). Roughge source nd level. Roughge is commonly dded to finishing diets in smll mounts (0-13.5%; DM bsis) nd my vry with seson (Vsconcelos nd Glyen, 2007). Just s with other commodities, roughge sources vry with locle. In one survey (Glyen nd Gleghorn, 2001 vilble t www. sft.ttu.edu/burnett_center/progress_reports/bc12.pdf)), the primry roughge source used ws lflf hy (68%), but the more recent survey by Vsconcelos nd Glyen (2007) indicted tht corn silge ws the most common roughge source. The lter uthors suggested tht perhps the more recent survey included broder geogrphicl re nd more consultnts were from the midwestern cttle feeding res. Other common roughge ingredients include grss hys, other silges (whet, nd grsses) nd byproducts (cottonseed hulls, cotton burrs, etc.). Supplementtion During certin times of the yer, supplementtion of grzing cttle my be necessry. Supplements re normlly clssified s either protein or energy bsed on crude protein concentrtion. Protein supplements contin higher concentrtion of protein (normlly more thn 25%) nd energy supplements contin normlly less thn 18% crude protein. It is generlly recommended tht cttle grzing dormnt mture forges be supplemented. Protein supplements re generlly fed to these cttle. When the crude protein concentrtion of the forge is less thn 6-7%, protein supplementtion cn be used to increse forge intke. The microbes will brek down the protein into mino cids nd mmoni nd then utilize the mmoni for use in microbil synthesis nd fiber digestion will be improved. Pssge rte is then incresed nd intke cn be incresed. Supplementtion with nonstructurl crbohydrtes often decrese fiber digestion nd forge intke. Severl fctors hs been proposed for the decresed digestion including decrese in ph s result of incresed VFA production Source of live (vible) nturlly-occurring microbil cultures Box 77 Clrksdle, MO Fx: September 10, 2008, Feedstuffs 37

7 6. Formultion informtion for finishing diets (DM bsis) used by the consulting nutritionists surveyed by Vsconcelos nd Glyen (2007) Mjor minerls, % Men n Minimum Mximum Mode Clcium Phosphorus Is phosphorus dded? 24 (82.8%) = No 5 (17.2%) = Yes Mgnesium Potssium Sulfur Slt Trce minerls, mg/kg Copper Zinc Mngnese Iron Selenium Iodine Coblt Vitmins, IU/kg A 5, , , ,409.2 E D , Reproduced from Vsonelos nd Glyen: Nutritionl recommendtions of feedlot consulting nutritionists: The 2007 Texs Tech University survey. J. Anim Sci. first published on June 25, 2007 s doi: /js s growth of fibrolytic bcteri re sensitive to ruminl ph, competition between bcteri for the strch nd/or preferentil use of the nonstructurl crbohydrtes by fibrolytic bcteri nd the ssocited increse in lg time. Use of byproduct feedstuffs is n lterntive to using cerel grins. Products such s soyben hulls, whet middlings, corn gluten feed, etc., hve more fiber nd less strch thn the unprocessed feed. In ddition, the fiber components re generlly highly digestible nd higher in digestibility thn forge fiber. Therefore, use of byproduct feedstuffs hs incresed forge intke nd digestibility. Breed multiplier for mintennce requirements. Tbles 1, 2, 3 nd 4 present the nutrient requirements for production nd mintennce for vrious beef production situtions. Nturlly, mintennce requirements re tied to severl situtions, including body size nd hir cot thickness. Those requirements set forth in the tbles were intended for the Angus breed of cttle. The NRC committee tht prepred the recommendtions published in the 1996 requirements mde recommendtions for djustments tht need to be mde for vrious breeds. These re presented in Tble 7. As my be noted, these djustments represent chnges in mintennce requirements, since requirements for gin nd production re not ffected by body size. As n exmple, NEm for Holstein cttle (Code No. 12, Tble 7) would be 1.20 times s gret s for Angus (Code No. 1), wheres NEg would be the sme for either breed. Tble 7 lso contins nticipted birth weights nd pek milk yields for the vrious breeds of cttle. Feed Anlysis Tbles. A specil section in this Reference Issue contins tbles of feed nlyses tht represents verge vlues for ll the feedstuffs used commonly in feed formultion. However, cution must be exercised in formulting lestcost rtions in which proposed requirements represent miniml levels. A recent study conducted simultneously over three-yer period t 15 stte experiment sttions compred the chemicl nlyses for corn nd soyben mel (J. Anim. Sci : ). Among the corn sources, the rnge in protein nlysis ws from 7.31 to 9.06 (ir-dry bsis), representing 24% increse from low to high. Similrly, over two-yer period, for nine stte sources for soyben mel there ws rnge of 42.8 to 44.6% protein (ir-dry), representing n increse just greter thn 4% from lowest to highest. Finlly, to demonstrte tht ll corn is not like, some of the newer geneticlly engineered vrieties re quite different. One of the newer such high-oil corns contins 6.5% more crude protein (9.83 versus 9.23%, dry mtter bsis), 82.6% more oil, 5.1% more totl digestible nutrients for beef nd 58% more tocopherols thn typicl dent corn. Formulting rtions It is recommended tht the reder refer to the Feed Ingredient Anlysis Tble in this issue for nlyses of potentil feedstuff inclusion in beef cttle rtions. Duff is ssocite professor of niml nutrition, The University of Arizon. 38 Feedstuffs, September 10, 2008

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