Nutrient Requirements of Beef Cattle

Theorem of the 7 PsPriorProperPreparationPreventsPoorProductionPerformance

The Unique Ruminant AnimalRuminants have a four compartment stomach and are able to digest fiber. This is an important consideration when attempting to convert fiber products into a usable food-source for humans.Four Compartments Include:1. Reticulum2. Rumen3. Omasum4. Abomasum

The RumenOne of the coolest places on earth

The Beef Cows AssignmentOur expectation of a productive cowMaintain her body weight / conditionDeliver a live calf without difficultyCome into heat promptlyConceive early in the breeding seasonNourish a developing fetusAdequately nurse the calf through to weaning

Cow Nutrient Requirements - Nutrients Supplied by Forage = Nutrients Needed in SupplementThe Basic, Complicated Nutritional Equation:

Defining the SituationWhat is the overall objective of the feeding / supplementation programExtend the forage baseMeet nutritional deficienciesAlter cow production

You have to know where you want to go before you can get there.

Basic Required NutrientsWaterProteinMineralsVitaminsFatsEnergy

WaterWater is the most critical nutrient in ALL livestock production:CleanFreshConsider semi-routine analysis:MicroorganismsChemicalsTo ensure availability and control contamination of waterways, it is best to provide cattle with water derived from a well.

EnergyEnergy is derived from digestion of feedstuffsFiberProteinStarchFatTDN is our common measure of feedstuff energy Net energy assigns the proportion of that feedstuff which meetsMaintenance, growth, lactation, gestationCommon sources of energy include:forage (hay)citrus pulpmolassesgrain byproductsfat

EnergyEnergy (TDN)Major nutrient required by cattleMain driver for productionGrowthReproductionLactationDirect relationship between TDN and quality of feedstuffLow quality feed = low energy and low intake

Feed% TDNBahiagrass Hay51Alfalfa Pellet59Soybean Hulls70Molasses72Soybean Meal84Corn88

Energy SupplementationMain driver of BCSReasons for use:Reduce forage consumptionMeet energy demandsDiet selection allows

Energy Supplementation ConsiderationsBegin feeding before it is too lateResponse improves with long term low level supplementationFeeding low levels of energy (w/out adequate diet protein) decreases overall energy intakeHigh starch supp. decreases fiber digestibility (Negative Associative Effects)

Energy Supplementation ConsiderationsUsually contain < 20% CPDo not feed energy when high CP supplement will improve performanceGrain is a substitute for forageHigh starch supp. work best with moderate to high quality forage

ProteinRuminant protein requirements are met by:DietRumen microbesRecycling of ureaRuminants are able to utilize microbial- protein, derived from microbes, which live in the rumen.Common protein sources include:Forage, Oilseed Meals, Grain By-products, Feather Meal

John Arthint5)

Protein SupplementationIncreases forage dry matter intake and digestibilityCritical level: forage CP < 7% or TDN:CP is >7 (51% TDN: 5% CP)Correct protein type is essentialNon-protein nitrogenNatural proteinRuminal Degradable Protein (DIP)Ruminal Undegradable Protein (UIP)

Natural ProteinSoybean, cottonseed, feather meal, distillers grains, other forages: ryegrass, perennial peanutAnimal performance: natural>NPNSupplies DIP, UIP, energy, and other nutrientsProportions of DIP and UIP vary and can affect use and performance in given situation

Natural Protein ConsiderationsUtilization: similar among classes of animalsUse with younger animals with increased requirementsFed as dry or additive in liquid feedsSupplies N to rumen for microbes and protein to animal

Non-Protein NitrogenSynthetic (Urea, Biuret) chemical compounds that contain a nitrogen source not associated with protein.Improvement in performance compared with no supplementation.Utilization rate may be reduced because of decreased forage digestibility potential.Lacks energy, vitamins, and minerals.Urea is a common NPN source used in cattle supplements.Rumen microbes are able to use NPN to synthesis microbial protein.

NPN ConsiderationsManagement IssuesMature cows consuming forage of adequate quality can use NPN as an economic substitute to natural protein.Better performance in older cows than young/growing cows.Young and low body condition cattle will experience improved performance with the use of natural protein.Potentials for toxicityRequires a carrier that supplies energySuccess of utilization depends on adequate ruminal energy for microbesLiquid Feeds (Molasses)Provide carbohydrates for bacterial energy to utilize NPN.

Vitamin-Mineral SupplementationVitamin-Mineral deficiencies cause problems regardless of protein/energyDeficiencies in forageespecially low qualityfast-growing and/or winter annualsOther supplements may alter mineral availability in forageEfficacy of all other supplementation depends on vitamin/mineral adequacy

Mineral SupplementationMineralsForage most important contributorMacro-minerals > 1 gram/dayMicro-minerals< 1 gram/dayEssential for basic physiological processesMany forage sources are deficient in multiple minerals

MacroMicroPotassiumCopperMagnesiumIronSodiumManganeseSulfurZincPhosphorusCobaltCalciumIodineSelenium

Vitamin SupplementationVitaminsWater-solubleFat-solubleRuminants synthesize water soluble vitaminsFat-soluble vitamins often supplementedVitamin ALow quality, hay, or frosted forage when consumed for >2 months

WaterFatThiamine (B1)Vit. ARiboflavin (B2)Vit. DNiacinVit. EBiotinVit. KB6B12PantothenicAcidFolic Acid

What affects cow nutrient requirementsNutrient requirements differ:AgeLevel of productionCurrent and/or desired body conditionBreedPhysiologyLactationGestationPasture activityTerrainPest loadFeed AdditivesIonophoreEnvironmentTemperatureSeason

Effect of Time on Requirement Cycles in Beef CowsCalveWean

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Energy / Protein

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S. FL7892100958678715354576167

C. FL6778921009586787153545761

N. FL6167789210095867871535457

Energy/Protein Requirement Cycles in Beef Cows

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14.49552.26319.9991.42362

13.72382.0354410.29211.45754

10.86581.4495810.63811.50898

11.03781.4893811.0511.57165

11.3041.5611.61061.665

11.78271.67312.3741.8055

11.19221.6542213.31942.00265

13.82522.1598814.61562.30824

Cow TDN

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Heifer TDN

Heifer CP

Months Since Calving

Lbs of TDN

bs of CP

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Cow TDN15.731616.652216.358415.398814.495513.723810.865811.037811.30411.782711.192213.8252

Cow CP2.70682.971822.817282.53452.26312.035441.449581.489381.561.6731.654222.15988

Heifer TDN9.74659.99910.292110.638111.05111.610612.37413.319414.6156

Heifer CP1.391531.423621.457541.508981.571651.6651.80552.002652.30824

Comparison of Cow vs Heifer Energy Requirement

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Nutrient Requirement Cycles and Pasture CharacteristicsJanuary

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15.73162.7068116.51

16.65222.97182226.71.6

16.35842.817283310.52.4

15.39882.53459.74651.39153112.5

14.49552.26319.9991.42362142.8

13.72382.0354410.29211.45754142.7

10.86581.4495810.63811.50898142.2

11.03781.4893811.0511.57165132.2

11.3041.5611.61061.66511.71.9

11.78271.67312.3741.8055101.6

11.19221.6542213.31942.002658.51.4

13.82522.1598814.61562.3082471.5

Cow TDN

Cow CP

Heifer TDN

Heifer CP

Pasture TDN

Pasture CP

Months Since Calving

Lbs of TDN

Lbs of CP

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Cow TDN15.731616.652216.358415.398814.495513.723810.865811.037811.30411.782711.192213.8252

Cow CP2.70682.971822.817282.53452.26312.035441.449581.489381.561.6731.654222.15988

Heifer TDN9.74659.99910.292110.638111.05111.610612.37413.319414.6156

Heifer CP1.391531.423621.457541.508981.571651.6651.80552.002652.30824

Pasture TDN6.56.710.5111414141311.7108.57

Pasture CP11.62.42.52.82.72.22.21.91.61.41.5

Months Needing Energy/Protein Supplementation to Meet Requirements Grazing Bahiagrass

JanFebMarAprMayJunJulAugSepOctNovDecMaintenance XXLactation XXXXGestation XXXXXXX

Assessing Effectiveness of Nutrition

How to tell if cattle are getting adequate nutritionBody Condition ScoreEstimation of body fatGauge effectiveness of feeding programDecision tool to determine future feeding needsScale of 1 to 9Most Florida cows score from 3 to 7 BCS 3 = 7 to 9% fat. BCS 5 = 15 to 18% fat. BCS 7 = 25 to 27% fat.

Cow Body Condition ScoreBody condition score is the best measure of past nutritional status and a good indicator of future reproductive performance.5 is the magic number!

SupplementationFeeding the cow herd is the largest cost area in beef enterprises, approx 45-50% of annual maintenance costStored or supplemental feeds constitute the largest, most variable portionDesigning supplementation program correctly is a must

Final RemarksUnderfeeding the cow herd before or after calving really affects 2 calf crops, this years and next years.

THE MOST IMPORTANT NUTRIENT IS THE ONE THAT IS MISSING!

Questions

*The key to meeting any animals nutrient requirements is through proper nutrition. To make sure that we meet our cows nutrition needs we should subscribe to the theorm of the 7 Ps. It is that prior, proper preparation prevents poor productive performance. If we adopt the mindset of thinking ahead and planning for our cattles nutritional needs, then we should see better performance from our cows and a little heavier pocketbook.*When addressing the issue of beef cattle nutrition, we first should spend a little time on the unique aspect of the ruminant or cow that we are dealing with. Ruminants are unique in that they have a four compartment stomach compared to pigs, horses, or human which have a simple one compartment stomach. The unique design of the ruminant stomach allows beef cattle to effective and rather efficiently utilize feedstuffs that are composed of fiber. This is an important trait because we can utilize ruminants to convert fiber, a product that we can use, into meat, milk, or wool. The four compartments are: reticulum (honeycomb), rumen (paunch, where the majority of the action takes place), the omasum (manyplies), and the abomasum (true stomach).*This is a schematic of the rumen, one of the coolest places on earth. Feedstuffs enter the rumen every time an animal eats. The contents of the rumen get stratified based upon the density of the feedstuff. Gases, which are a product of the digestion of feed in the rumen rise to the top, gas is the least dense. Next is the new fiberous feed feeds (hay, grass) that the animal consumed today. The digestion process has not begun to any great extent yet, and thus the particles are still buoyant. This layer is also the fiberous mat. In the bottom of the rumen are the most dense particles. These particles are is more advance stages of digestion waiting to exit the rumen, or start as more dense particles such as grain. All of these layers function together to create a very functional fermentation system in the animal. The fermentation is performed by rumen microbes, the animal provides the perfect environment.**So like any employee on a beef cattle enterprise our cows have a job and certain responsibilities to fulfill if she wants to stick around. Our expectations of our bovine employees are to maintain herself, deliver a live calf, start the re-breeding process promptly, get pregnant, maintain her pregnancy, and nurse the calf that is already on her side until weaning. Thats quite a load of tasks for one cow to accomplish. In order to adequately perform her duties we need to give the cow the tools and resources to do her job. The main tool for her to accomplish her assignment is adequate nutrition. So lets address the nutritional equation. On the surface it is fairly simplistic, if we know what the cows nutrient requirements are and we know what the amount of nutrients that the base forage is supplying then we will know if the is a need for supplementation, and if so to what extent is the need for supplemental nutrients. The equation is complicated by the fact that cow nutrient requirements change depending upon a number of factors and further complicated by a forage base that is not static and has daily and seasonal changes. *So when we are talking about a feeding or supplementation program we have to outline some goals. We can not effectively and efficiently feed cattle if we go not have some specific goals in mind. We dont decide to supplement cattle just because we like to put feed in front of animals. Raisin cattle can be expensive enough, we need to use our dollars and our feedstuffs wisely. So what is the overall objective of the feeding/supplementation program? Do we need to extend the forage base through the use of supplements to get another month out of our forage resources. Are there specific nutritional deficiencies that we are aware that need to be met? Or do we want to alter animal production, having that cow make more milk, putting body weight and condition back on the cow? Ultimately, we have to set a goal of what we want to accomplish through a feeding program before we can start one.*There are six basic nutrients that cattle or any animal needs. Those nutrients are water, protein, minerals, vitamins, fats, and carbohydrates to generate energy. The subsequent slides briefly discuss all of the nutrients.*Water is the most critical nutrient of all. Without water nothing else happens in the body. Digestion doesnt occur, absorption of nutrient doesnt happen, blood doesnt flow, nothing. Cattles water needs to be clean and fresh. If you look at the water and decide that you wouldnt drink it then consider why do you make cattle drink it. We should consider having our water source tested on a semi-routine basis to check for the incidence of contamination by harmful microorganisms and or chemicals, additionally checking water levels for mineral and heavy metal contamination could be beneficial. To ensure availability and control potential contamination of surface water sources, well derived water is a the best option. Additionally, environmental issues may necessitate the restriction of cattle from surface water.*Energy while not technically a nutrient, is one of the most important things that cattle require. Cattle generate energy from the digestion of feedstuffs. Energy is derived from the digestion of dietary carbohydrates including fiber and starch, dietary and microbial protein, and dietary fat. We measure energy content of feeds and talk about energy requirements of cattle in terms of TDN (total digestible nutrients). More advance energy discussion relate the energy content of feeds and the energy requirements of cattle in the Net energy system. The NE system assigns a proportion of the energy in the feedstuff to meet the cows requirement for maintenance, growth, lactation, and gestation. Common sources of energy include: forage or hay, citrus pulp, molasses, grain by-products, and fat.*Energy is the major nutrient required by cattle. Energy is the main driver of all of the productive process in cattle, growth, reproduction, and lactation. There is a direct relationship between TDN and the quality of the feedstuff. The lower the quality of the feed, the lower the energy content of the feed, and generally, the lower the intake of the feed will be. Low quality feeds have a lot of filler that takes up space in the rumen, is not digested and thus provides no energy for the animal. In this table are some examples of feedstuffs and there approximate TDN value.*So lets touch on energy supplementation. As was stated earlier, energy is the main driver for a lot of the productive measures in the cow herd, and body condition score is a prime example. Body condition score is measure of the relative fat content of the animal. Fat is deposited when there is an excess of energy, thus BCS is a reflection on the energy status of the animal. Likewsie, the reason for energy supplementation might include the need to reduce forage consumption to stretch a limited forage supply, the need for additional or supplementation energy to meet a deficiency of energy, or finally if there a limited amount of high-quality forage that an energy supplement could compliment. *These are some considerations to keep in mind when formulating and implementing an energy supplementation program. First of all begin feeding energy or any supplement for that matter before is too late. Because a the response to energy supplementation improves with long-term low levels of feeding compared to short-duration high levels of energy supplementation. If you have to pour a lot of feed to forage-fed cattle to get them to respond and reach the level of production that is desirable then likely supplementation should have been initiated earlier. Additionally, while energy supplementation may be what is needed, if the protein content of the diet is not sufficient then the energy will actually have a negative effect on the overall diet energy supply. Finally, high starch supplements (corn) will have a negative impact on fiber digestions, which leads to a decrease in forage intake, and ultimately a decrease in animal performance. We call this negative associative effects, they are bad, and we want to avoid them. But generally, in Florida we do not utilize starch base energy supplements very often.*Generally, when we describe energy supplements, we consider them to have less than 20% crude protein. Anything over 20% CP should likely be considered a protein supplement that provides energy. When choosing supplements, do not feed an energy supplement when a high crude protein supplement will actually improve performance. This situation occurs when there is adequate low-quality forage available. Remember the rumen microbes will digest the fiber and provide energy, but they need some protein substrates as part of the digestion process. Energy supplements just exasperate a situation where energy and protein are out of balance. Grain will directly substitute for forage, as simple as that. We can use that to our advantage if need be, but we need to be aware of how the situation works. Finally, if we utilize high-starch supplements, they work best with moderate to high quality forage. In this situation we are matching the protein supplied by the forage with the energy supplied by the supplement.*The protein requirements of beef cattle are met by three different sources. The first source is the diet, protein is derived from digestion of the forage that is consumed and any supplemental feeds that are offered. The next protein source is the digestion of the rumen microbes that grow in the rumen and then are passed to the lower GI tract for digestion. Microbial protein is the main source of protein for most grazing cattle. This protein is high quality and allows ruminants to flourish on high-forage diets. The final source of protein is actually the recycling of urea back into the rumen for the rumen microbes to utilize. Recycling of N is again and adaptation that allows cattle to consume low-quality forages and yet survive and grow.Common protein sources include forage, which is the primary source of protein and nitrogen for the animal and the rumen microbes. Supplemental sources included oilseeds and oilseed meals like soybean and cottonseed meal, grain by-products are sources of protein (distillers grains, corn gluten feed), finally approved animal by products like feather meal, fish meal, and porcine blood meal. *When considering protein supplementation to meet protein requirements there are several considerations to keep in mind. Generally, protein supplementation will increase forage dry matter intake and digestibility particularly low-quality forages. The supplemental protein provides the rumen microbes needed N or peptides to help with their growth and ability to digest fiber efficiently. The critical levels to consider when supplementing protein are what is the forage CP concentration, CP below 7% are considered low-quality and cattle would generally benefit from supplemental protein. Secondly, if the TDN to CP ration is greater than 7. In this situation, the forage is out of balance in regards to energy and protein; there is likely adequate energy but deficient protein in the forage to result in efficient use of the forage by the rumen microbes. Finally, the correct protein type to choose is essential. There are two basic types of protein: Non-protein nitrogen (NPN) or Natural protein. Within natural protein sources are two different types: Ruminal degradable protein or ruminal undegradable protein also know as bypass or escape protein. *First well turn our attention to Natural Protein. Common natural protein sources in Florida include soybean, cottonseed, and feather meals. Distillers grains, and potentially other forages including ryegrass and perennial peanut. Generally, animal performance is better when supplemented with natural protein compared to non-protein nitrogen. The increase in performance can be attributable to the fact that natural protein sources supply DUP, UIP, energy and other nutrients like vitamins and minerals, whereas NPN only supplies nitrogen. An important aspect to remember with natural protein is that the proportions of DIP and UIP varies among supplements and is not an all or nothing situation. Regardless the variation between DIP/UIP can be used to our advantage to meet and formulate protein requirements of cattle.*When we consider the supplementation of natural protein the utilization of natural protein is similar among different classes of cattle. I would suggest that younger cattle make the best use of natural proteins compared to older cattle. The improvement in younger cattle is because younger cattle have maintenance and growth requirements. The growth requirements require amino acids which natural protein with bypass characteristics can supply.Natural proteins can be utilized either as dry supplements in meal or pellets or incorporated into liquid feeds to create slurries. Finally, the use of natural protein supplies both nitrogen and protein to the rumen microbes for their metabolism, and also amino acids and peptides for the animal itself.*Feed Non-protein-nitrogen is are compounds, generally urea, that contains nitrogen attached to a carbon back-bone. Thus all NPN supplies is N only. When feeding NPN sources cattle performance improves compared to no supplemental nitrogen. NPN has some limitations, the utilization rate of urea may be decreased if the digestion potential and the resulting energy supplied by the forage is limiting. Additionally, urea does not supply any additional energy, vitamins, or minerals as a supplement. However, despite these stated limitations, urea is a common NPN source that is often included in many cattle supplements. The reason that urea works is that the rumen microbes can utilize the nitrogen provided by NPN sources, match it with energy substrates from fiber digestion to form microbial protein. The animal then utilizes the microbial protein as a protein source.*Some consideration for the use of NPN in supplementation programs. Mature cows consuming adequate amounts of digestible forage can utilize NPN as an economic source of nitrogen to support microbial protein production. Generally, we would expect better performance of mature cattle compared to younger cattle when utilizing NPN. This is related to two factors: first, that mature cows can consume more digestible forage than younger cattle and thus have a greater amount of fermentable fiber and thus energy to match the N in the rumen; secondly, young cattle still have growth requirements that require amino acids, vitamins, minerals, and additional energy that NPN does not provide. There is the potential for toxicity when using NPN sources, however, I believe that this threat is often overstated and wrongfully perpetuated. Most problems associated with urea toxicity occur with bad formulations of poorly manufactured supplements and/or the use of high urea supplements as the major source of nutrition rather than as a supplement to a forage diet. Urea (NPN) requires a carrier to deliver the product, often this carrier provides the energy to couple with the N in the rumen. Therefore, the success in utilizing urea is having adequate ruminal energy supply for the microbes. In Florida we have a great carrier for NPN in liquid molasses. Molasses provided the carbohydrate substrate to create energy for the rumen microbes, molasses acts as a great carrier, and comes with some amount of additional nutrients. *Meeting vitamins and minerals requirement are just as important to beef cattle production as meeting energy and protein requirements. That is because a deficiency in a vitamin or mineral will cause a loss in performance regardless of the amount of energy or protein content of the diet. In many cases our forage base may be deficient in one or more vitamins or minerals. These deficiencies may be particularly apparent in low quality/mature forages or fast-growing /winter annual forages. The interaction of all of the feedstuffs in the diet may alter the availability of vitamins and particularly minerals. Excess concentrations of certain minerals can have negative effects on the availability of other key minerals in the diet. Finally, the efficacy of the nutritional program is dependant on adequate vitamin/mineral status of the animal.*The forage base, pasture or hay, is the most important contributor of minerals for cattle just like it is for energy and protein. However, because of differences in forage type and quality the forage base also causes some of the major dietary deficiencies. There are two types of mineral classifications, Macro and Micro. Macro minerals are those minerals required in the diet in greater than 1 gram amounts, whereas micro minerals are those that are required in less than 1 gram amounts on a daily basis. In the table on the right are some of the important macro and micro minerals that need to be addressed when formulating mineral supplements to meet cattle nutrient requirements. The need for minerals is paramount because they are essential for many of the basis physiological process in the body (regulation of osmotic pressure, transmission of nervous impulses, antioxidants, bone growth, etc.). Generally, our forages are not just deficient in one mineral, thus mineral supplements to meet cattle requirements should be well-balanced to address all of the potential mineral concentration shortfalls in the forage.*Like minerals, vitamins are separated into two different classes, water soluble and fat soluble vitamins. The table on the right breaks down the vitamins according to their solubility. Ruminants do not normally need to be supplemented with B vitamins or any of the other water soluble vitamins to meet their nutritional requirements. The rumen microorganisms synthesize adequate levels of all of the B vitamins, niacin, pantothenic acid, and folic acid to satisfy cattle requirements. The fat soluble vitamins with the exception of vitamin K are often incorporated into well-formulated good quality vitamin/mineral supplements. Fat soluble vitamins can be stored in specific tissues of the body for limited time periods, but cattle benefit by having adequate levels of fat soluble vitamins supplemented to their diet. *Weve outlined the different nutrients that are needed by cattle, including water, protein, energy, vitamins, and minerals. The amounts of these nutrients that are required by cattle are affected by an number of different factors. The nutrient requirements differ for different ages, level of production, breed, and stage of physiology of cattle. Additionally, there is a whole list of other factors that can affect the level of nutrients required by cattle. **It is important to realize that cattle nutrient requirements change throughout the productive year. This graph presents the relative percent of the maximum energy or protein requirements on a monthly basis depending upon the calving and weaning date. It should be pointed out that maximal energy/protein requirements occur the 2nd month after calving when cows reach peak lactation. Minimal energy and protein requirements occur at weaning when the need for nutrients dedicated to lactation ceases. Obviously, this graph is generalized and specific needs will be dictated by many of the factors previously mentioned.This graph takes the previous graph one step further. This graph presents the pounds of energy and protein required by a cow and heifer relative to the calving cycle regardless of calendar month. Again peak requirement of the cow occurs the 2nd month after calving which account for maintenance, and lactation nutrient requirements. Nutrient requirements decline to weaning, and then increase again during gestation. The heifer in contrast demonstrates gradual increase in energy and protein requirement up to parturition. The requirements of the heifer are meeting the demands for maintenance, growth, and the products of conception. *The previous graph did not demonstrate a great difference between cow and heifer energy or protein requirements. However, the difference in nutrient requirements and feeding management between these two ages of cattle is readily apparent. This set of graph is a comparison of a 1200 lb cow and a 1000 lb heifer with a mature body weight of 1200 lb. On the left is the estimated dry matter intake of these two animals assuming a intake potential of 2.0% of BW. In that case a mature cow can consume 24 lbs of dry matter compared to 20 lbs by the heifer. On the right is the %TDN required in the diet one month prior to calving. The mature cow with her greater intake potential requires a diet that is 56% TDN compared with the heifer that requires a diet TDN of 60%. The heifer can not consume as much feed, but her total lb of TDN required is still similar to that of the cow, thus her diet needs to me more energy dense compared to the cow. This principle would similar for protein requirements. *This graph takes the energy and protein requirement cycles and superimposes on them a nominal bahiagrass content for TDN and CP. In this example we assume a nominal calving date of January 1. It should be obvious to see that during the first 4 months of a cows production cycle bahiagrass will not meet her energy requirement and her protein requirement will not be met during the first 3 months. After lactation demands decline bahiagrass pasture can meet the energy and protein requirements of the mature cow. However, when the quality of bahiagrass declines, and the demands of gestation increase, bahiagrass alone can not meet the energy and protein demands of a mature cow. Examining the heifer, bahiagrass is sufficient until the final three months prior to calving, which again at this time the heifer has nutritive demands to meet maintenance, her body growth, and fetal growth demands. * This table breaks down the need for supplementation to meet the various energy/protein requirements for a grazing cow. In January and February energy and protein supplementation is need to meet maintenance requirements. Supplemental energy and protein is required in January through April to meet lactation requirements. Gestational energy and protein needs require supplementation in March through June and October through December. The need for supplementation is indicating that forage alone is not providing enough energy.

*The best way to asses the effectiveness and adequacy of a nutritional management program is to body condition score the cow herd. Body condition scoring is an estimation of the amount of body fat a cow has. Fat requires there to be a surplus of energy before it is deposited, therefore the amount of fat cover on cows is a good indicator of their energy status. Body condition scoring can be utilized as a decision making tool for future feeding needs, it can indicate either additional feed is required or a decrease in the energy supplied could be realized. Body condition score is ranked on a scale of 1 which is severely emaciated to 9 which is severely obese. Most cows fall in the range of 3 to 7.*Body condition score is an indicator to the past energy status and coupled with current feeding situation can be utilized to determine the appropriate feeding program. Body condition score is also a good indicator of future reproductive performance. Reproduction responds positively to adequate body condition score. A body condition score of 5 is the magic number. A BCS of 5 has been shown to optimize reproductive performance in terms of the return to estrus, days to conception, calving interval, pregnancy rate, and weaning percentage.*Why are we so concerned about meeting nutrient requirements and their relationship to supplementation? Feeding the cow herd represents the largest single cost in beef enterprises approximating 45-50% of the annual maintenance cost of keeping a cow. In that regard the use and of stored or supplemental feeds is the largest and most variable portion of that cost. Therefore, correctly designing a supplementation program to meet nutritional deficiencies and optimize cow herd performance is critical to the overall profitability of the beef cattle enterprise.*Ultimately, underfeeding the cow herd and not meeting nutritional requirements for any class of nutrient affects two calf crops, the one that the cow has at her side by limiting her nutritional environment and her ability to produce adequate milk, and next years calf crop by limiting her nutritional environment and thus her ability to express her reproductive potential.

Finally, the most important nutrient is the one that is missing in the diet.**