9
Tables of Nutrient Requirements

This seventh revised edition of Nutrient Requirements of Beef Cattle attempts to predict beef cattle requirements and performance under specific animal, environmental, and dietary conditions. Many variables (e.g., maintenance, growth, milk, microbial growth) are continuous and interact with the effects of feed composition. With this edition, the computer model described in Chapter 10 is provided on disk to calculate the effects of these variables. Because of all of the complex interactions accounted for in these models, the model tables differ from the tables of nutrient requirements in previous National Research Council (NRC) publications. Tables of nutrient requirements are, nevertheless, useful and instructive for some applications, so a computer program has been developed that uses model level 1 to compute and print nutrient requirement tables. This program allows determination of requirements for any body size and level of production of growing and finishing cattle, breeding bulls, bred heifers, and beef cows. No environmental stress is assumed. This chapter includes an example of each type of table for each of these classes of cattle, using the estimated U.S. average body size of finished steer and mature cow (533 kg). Simplified versions of these tables are provided at the end of the User’s Guide to be used as guidelines.

Two types of tables can be computed and printed. The first type, daily nutrient requirements, computes a table of daily nutrient requirements for the body size and production level specified. The second type, diet evaluator, allows the user to determine the concentration of protein, calcium (Ca), and phosphorus (P) required in a diet under specific conditions. The diet evaluator computes energy allowable production for specified diets, balances for DIP, UIP, and MP, and Ca and P needed in the diet to support the diet energy allowable production. The CP requirement is determined by adjusting diet CP and DIP until DIP and UIP requirements are met.

In addition to determining nutrient density requirements, the diet evaluator allows the user to see how well a particular diet meets requirements of cattle in a feeding group with the range of weights specified for growing cattle or at each of the 12 months of the reproductive cycle for beef cows. In most beef production situations, cattle are fed in groups that vary in stage of growth or reproduction. Each group is usually fed to appetite either available forage (stocker, backgrounding, cow-calf) or high-energy based diets (growing and finishing cattle) and are provided supplements as needed to support the energy allowable production. The objective in diet formulation for high-forage diets is to determine supplemental energy, protein, and minerals needed to meet target levels of production. The objective in high-energy diets is typically to determine the protein and minerals needed to support the energy allowable ADG. In all situations, the user attempts to develop a “best fit” diet, considering the variation of animals in a feeding group.

To use the diet evaluator, the user enters the diet TDN, CP, and percent of CP that is DIP. Diet CP and CP degradability must be entered because the relationships between CP, DIP, and UIP vary, depending on diet and animal interactions. Diet NEm, NEg, DMI, ADG, or energy balance, DIP, UIP, and MP balances (g/day) are predicted for each of the diets over a range of body weights for the body size specified for growing cattle or for each month of the reproductive cycle for breeding cattle. Next, the predicted DMI and diet NE values can be modified with adjusters until DMI and animal production level agree with observed values. Diet concentration of CP and DIP can then be altered until the requirement for the observed energy allowable production is met. The DIP balance can be increased by increasing diet CP percentage and/or increasing DIP as a percentage of CP. The UIP balance can be improved by increasing percent of CP and/or reducing DIP as a percentage of the CP.

Diet TDN is used to predict diet NEm and NEg. Diet



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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 9 Tables of Nutrient Requirements This seventh revised edition of Nutrient Requirements of Beef Cattle attempts to predict beef cattle requirements and performance under specific animal, environmental, and dietary conditions. Many variables (e.g., maintenance, growth, milk, microbial growth) are continuous and interact with the effects of feed composition. With this edition, the computer model described in Chapter 10 is provided on disk to calculate the effects of these variables. Because of all of the complex interactions accounted for in these models, the model tables differ from the tables of nutrient requirements in previous National Research Council (NRC) publications. Tables of nutrient requirements are, nevertheless, useful and instructive for some applications, so a computer program has been developed that uses model level 1 to compute and print nutrient requirement tables. This program allows determination of requirements for any body size and level of production of growing and finishing cattle, breeding bulls, bred heifers, and beef cows. No environmental stress is assumed. This chapter includes an example of each type of table for each of these classes of cattle, using the estimated U.S. average body size of finished steer and mature cow (533 kg). Simplified versions of these tables are provided at the end of the User’s Guide to be used as guidelines. Two types of tables can be computed and printed. The first type, daily nutrient requirements, computes a table of daily nutrient requirements for the body size and production level specified. The second type, diet evaluator, allows the user to determine the concentration of protein, calcium (Ca), and phosphorus (P) required in a diet under specific conditions. The diet evaluator computes energy allowable production for specified diets, balances for DIP, UIP, and MP, and Ca and P needed in the diet to support the diet energy allowable production. The CP requirement is determined by adjusting diet CP and DIP until DIP and UIP requirements are met. In addition to determining nutrient density requirements, the diet evaluator allows the user to see how well a particular diet meets requirements of cattle in a feeding group with the range of weights specified for growing cattle or at each of the 12 months of the reproductive cycle for beef cows. In most beef production situations, cattle are fed in groups that vary in stage of growth or reproduction. Each group is usually fed to appetite either available forage (stocker, backgrounding, cow-calf) or high-energy based diets (growing and finishing cattle) and are provided supplements as needed to support the energy allowable production. The objective in diet formulation for high-forage diets is to determine supplemental energy, protein, and minerals needed to meet target levels of production. The objective in high-energy diets is typically to determine the protein and minerals needed to support the energy allowable ADG. In all situations, the user attempts to develop a “best fit” diet, considering the variation of animals in a feeding group. To use the diet evaluator, the user enters the diet TDN, CP, and percent of CP that is DIP. Diet CP and CP degradability must be entered because the relationships between CP, DIP, and UIP vary, depending on diet and animal interactions. Diet NEm, NEg, DMI, ADG, or energy balance, DIP, UIP, and MP balances (g/day) are predicted for each of the diets over a range of body weights for the body size specified for growing cattle or for each month of the reproductive cycle for breeding cattle. Next, the predicted DMI and diet NE values can be modified with adjusters until DMI and animal production level agree with observed values. Diet concentration of CP and DIP can then be altered until the requirement for the observed energy allowable production is met. The DIP balance can be increased by increasing diet CP percentage and/or increasing DIP as a percentage of CP. The UIP balance can be improved by increasing percent of CP and/or reducing DIP as a percentage of the CP. Diet TDN is used to predict diet NEm and NEg. Diet

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 NEm and NEg can only be changed by adjusting diet TDN because the relationship between these energy values must be kept consistent. Diet TDN is used to predict microbial growth, which must be consistent with the energy value used to predict NEm available to meet maintenance, pregnancy, and lactation requirements and the energy value used to predict NEg allowable ADG. To get the diet NE value desired, the user adjusts TDN until the desired NE value is predicted. The subcommittee recognizes that the relationship between TDN, ME, NEm, and NEg may vary because of differences in amount of intake, rates of digestion and passage, and end products of digestion in the ME and their metabolizability. However, the relationships between them, as described in the preceding edition of this volume published in 1984, have also been used here for the reasons discussed in Chapters 1 and 10. The concentration of nutrients needed for a given level of production depends on the actual DMI of the diet being fed to support the observed level of performance in a particular production setting. The DMI predictions are from equations developed from experimental feeding period averages as reported in published feeding trials involving wide variations in cattle type and stage of growth, as discussed in Chapter 7. Thus, predicted and observed values often differ in a specific production setting. Cattle fed feedlot finishing rations will typically consume 0 to 25 percent more early in the feeding period than predicted by these equations, which is compensated for by DMI of 0 to 25 percent less late in the feeding period. Further, as discussed in Chapter 7, concerning feed intake, most DMI prediction equations account for only 50 to 60 percent of the variation, leaving 40 to 50 percent to be accounted for by variations in local conditions such as feeding management, cattle type, and environment. The DMI adjusters allow the user to change the predicted DMI until it agrees with observed DMI; then the NE adjuster can be changed until predicted and observed performance agree. Many factors can influence the NE derived from a diet for production, including variation in maintenance requirements, rates of digestion and passage, and metabolizability. If only DMI is adjusted, predicted and observed performance may not agree. For example, unrealistically high rates and efficiencies of gain may be predicted for calves consuming high-energy rations. Conversely, when these animals approach choice grade at the end of the finishing period, unrealistically low ADG may be predicted if only DMI is adjusted. Given these problems of prediction early and late in growth, limits were set on the weight ranges in the diet density tables at 55 percent of finished weight for the lightest weight and 80 percent of finished weight for the heaviest weight. The primary use of these tables is intended to be for teaching the interactions of body size, stage of growth, diet energy density, and energy and protein requirements. The diet densities for CP and DIP may not be practical because the CP may have to be overfed to meet both DIP and UIP requirements. The user is encouraged to use the model with actual feed ingredients available for computing requirements for specific conditions. Despite their limitations as discussed in this section, simple guideline tables with diet nutrient concentration requirements for different classes of cattle are all that are needed in many situations and are provided at the end of the User’s Guide. EXAMPLE TABLES FOR GROWING AND FINISHING CATTLE Tables 9–1 and 9–2 show daily requirements (Table 9–1) and diet evaluations (Table 9–2) for growing and finishing cattle. Inputs for Table 9–1 are for a 533-kg finished weight at 28 percent fat, a weight range of 200 to 450 kg, an ADG range of 0.50 to 2.50 kg, and breed code 1. Table 9–1 shows NEm, NEg, MP, Ca, and P required daily for maintenance and gain at six shrunk body weights, which represent six different stages of growth. All these requirements can be used directly to formulate dietary requirements for the specified level of performance, except the diet CP, DIP, and UIP required to meet the MP requirement. The CP intake needed can be estimated by dividing the total MP requirement in this table by 0.67, which is based on 80 percent of the MP from MCP and 20 percent from UIP. This approach was used in developing the guideline tables at the end of the User’s Guide. However, this assumes that the nitrogen difference between the diet CP and MP requirement will meet microbial requirements for DIP and tissue requirements for UIP. This approach, which was used in the preceding edition of this volume to compute CP requirements, has major limitations. For this edition, the dietary CP intake needed is computed in the model level 1 as a sum of the DIP needed for microbial growth plus the UIP needed above the MP required for maintenance plus gain not met by microbial protein. These variables are not directly accounted for when the CP required is determined as MP/0.67. Table 9–2 shows the evaluation of five diets (rations A through E) with the diet evaluator for the same animal used in Table 9–1 between 55 and 80 percent of final weight. The diet concentration of eNDF, TDN, and CP and DIP as a percentage of CP were entered for each of the five diets, and all DMI and NE adjusters were set at 100 percent. The eNDF values are used to adjust microbial protein yield and are affected only when diet eNDF drops below 20 percent of diet DM. The feed eNDF values in Appendix Table 1 (the feed library) can be used to determine eNDF in the diet. The program first computed diet NEm and NEg values, DMI, energy allowable ADG, MP, Ca, and P required for that ADG, MCP from the TDN

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 TABLE 9–1 Nutrient Requirements for Growing and Finishing Cattle Wt @ Small marbling 533 kg   Weight range 200–450 kg ADG range 0.50–2.50 kg Breed Code 1 Angus Body Weight, kg 200 250 300 350 400 450 Maintenance Requirements NEm Mcal/d 4.1 4.84 5.55 6.23 6.89 7.52 MP g/d 202 239 274 307 340 371 Ca g/d 6 8 9 11 12 14 P g/d 5 6 7 8 10 11 Growth Requirements (ADG)   NEg required for gain, Mcal/d 0.5 kg/d 1.27 1.50 1.72 1.93 2.14 2.33 1.0 kg/d 2.72 3.21 3.68 4.13 4.57 4.99 1.5 kg/d 4.24 5.01 5.74 6.45 7.13 7.79 2.0 kg/d 5.81 6.87 7.88 8.84 9.77 10.68 2.5 kg/d 7.42 8.78 10.06 11.29 12.48 13.64 MP required for gain, g/d 0.5 kg/d 154 155 158 157 145 133 1.0 kg/d 299 300 303 298 272 246 1.5 kg/d 441 440 442 432 391 352 2.0 kg/d 580 577 577 561 505 451 2.5 kg/d 718 712 710 687 616 547 Calcium required for gain, g/d 0.5 kg/d 14 13 12 11 10 9 1.0 kg/d 27 25 23 21 19 17 1.5 kg/d 39 36 33 30 27 25 2.0 kg/d 52 47 43 39 35 32 2.5 kg/d 64 59 53 48 43 38 Phosphorus required for gain, g/d 0.5 kg/d 6 5 5 4 4 4 1.0 kg/d 11 10 9 8 8 7 1.5 kg/d 16 15 13 12 11 10 2.0 kg/d 21 19 18 16 14 13 2.5 kg/d 26 24 22 19 17 15 intake, and DIP required for the MCP produced and UIP required with the equations presented in Chapter 10 for level 1. All five diets were then balanced for UIP and DIP for the 300-kg body weight category by changing both CP and DIP until both UIP and DIP were balanced. The DIP is balanced for all other weights for each diet because MCP yield stays constant at 13 percent of TDN. The UIP would be deficient at lighter weights because the animal tissue requirement for protein at the energy allowable ADG exceeds the MCP and UIP provided by the diet. At weights less than 300 kg, the UIP deficiency would increase with the high-energy diets compared to low-energy diets because their lower eNDF results in a lower rumen pH, which reduces microbial growth as described in Chapter 2. This deficiency can be overcome by increasing the CP and lowering the DIP, but not to exceed that needed to balance DIP, until the UIP requirement is met. In practical diets, this means substituting sources of DIP in the supplement with sources of UIP. At weights more than 300 kg, the diet UIP provided exceeds the MP required because of less protein in the ADG as the cattle increase in weight. The UIP excess can be decreased by lowering the CP while increasing the DIP as needed to keep the DIP balanced. The only practical way to accomplish this in the diet formula is to replace sources of UIP with sources of DIP until the CP and DIP reach a level provided by the grain and forage plus urea. If actual data were available, predicted DMI would have been adjusted until it agreed with observed DMI, then the NE adjusters would have been used to adjust feed NE values until predicted and observed performance agree.

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 TABLE 9–2 Diet Evaluation for Growing and Finishing Cattle Wt @ Small Marbling 533 kg   Breed Code 1 Angus Ration eNDF % DM TDN % DM NEm Mcal/kg NEg Mcal/kg CP % DM DIP % CP Weight Class NE Adjuster A 57 50 1.00 0.45 7.4 88 325 100% B 43 60 1.35 0.77 10.0 78 350 100% C 30 70 1.67 1.06 12.6 72.4 375 100% D 5 80 1.99 1.33 14.4 48.5 400 100% E 3 90 2.29 1.59 16.6 44.2 425 100% Body Weight, kg DMI Adjuster DMI kg/d ADG kg/d DIP UIP MP Ca P balances, g/d requirements, % of DM 300—A 100% 7.9 0.32 1 0 0 0.22% 0.13% —B 100% 8.4 0.89 0 0 0 0.35% 0.18% —C 100% 8.2 1.36 2 0 0 0.48% 0.24% —D 100% 7.7 1.69 1 2 1 0.60% 0.29% —E 100% 7.1 1.90 1 2 1 0.71% 0.34% 325—A 100% 8.4 0.32 1 14 11 0.21% 0.13% —B 100% 8.9 0.89 0 38 30 0.33% 0.18% —C 100% 8.7 1.36 2 57 46 0.45% 0.22% —D 100% 8.2 1.69 1 73 58 0.55% 0.27% —E 100% 7.6 1.90 1 82 66 0.65% 0.31% 350—A 100% 8.9 0.32 1 27 22 0.20% 0.13% —B 100% 9.4 0.89 0 75 60 0.31% 0.17% —C 100% 9.2 1.36 2 114 91 0.42% 0.21% —D 100% 8.7 1.69 1 143 114 0.51% 0.25% —E 100% 8.0 1.90 1 160 128 0.60% 0.29% 375—A 100% 9.4 0.32 1 40 32 0.20% 0.13% —B 100% 9.9 0.89 0 111 89 0.30% 0.16% —C 100% 9.7 1.36 2 169 135 0.39% 0.20% —D 100% 9.1 1.69 1 212 169 0.48% 0.24% —E 100% 8.4 1.90 1 238 190 0.56% 0.28% 400—A 100% 9.8 0.32 1 53 43 0.19% 0.12% —B 100% 10.4 0.89 0 147 118 0.28% 0.16% —C 100% 10.2 1.36 2 223 178 0.37% 0.19% —D 100% 9.6 1.69 2 279 223 0.44% 0.23% —E 100% 8.8 1.90 1 314 251 0.52% 0.26% 425—A 100% 10.3 0.32 1 66 53 0.19% 0.12% —B 100% 10.9 0.89 0 182 146 0.27% 0.15% —C 100% 10.6 1.36 2 276 221 0.35% 0.19% —D 100% 10.0 1.69 2 346 277 0.42% 0.22% —E 100% 9.3 1.90 1 388 311 0.48% 0.25%

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 TABLE 9–3 Nutrient Requirements for Growing Bulls Wt @ Maturity 890 kg   Weight Range 300–800 kg ADG Range 0.50–2.50 kg Breed Code 1 Angus Body Weight, kg 300 400 500 600 700 800 Maintenance Requirements NEm Mcal/day 6.38 7.92 9.36 10.73 12.05 13.32 MP g/d 274 340 402 461 517 572 Ca g/d 9 12 15 19 22 25 P g/d 7 10 12 14 17 19 Growth Requirements ADG NEg Required for Gain, Mcal/d 0.5 kg/d 1.72 2.13 2.52 2.89 3.25 3.59 1.0 kg/d 3.68 4.56 5.39 6.18 6.94 7.67 1.5 kg/d 5.74 7.12 8.42 9.65 10.83 11.97 2.0 kg/d 7.87 9.76 11.54 13.23 14.85 16.41 2.5 kg/d 10.05 12.47 14.74 16.90 18.97 20.97   MP Required for Gain g/d 0.5 kg/d 158 145 122 100 78 58 1.0 kg/d 303 272 222 175 130 86 1.5 kg/d 442 392 314 241 170 102 2.0 kg/d 577 506 400 299 202 109 2.5 kg/d 710 617 481 352 228 109   Calcium Required for Gain, g/d 0.5 kg/d 12 10 9 7 6 4 1.0 kg/d 23 19 16 12 9 6 1.5 kg/d 33 27 22 17 12 7 2.0 kg/d 43 35 28 21 14 8 2.5 kg/d 53 43 34 25 16 8   Phosphorus Required for Gain, g/d 0.5 kg/d 5 4 3 3 2 2 1.0 kg/d 9 8 6 5 4 2 1.5 kg/d 13 11 9 7 5 3 2.0 kg/d 18 14 11 8 6 3 2.5 kg/d 22 17 14 10 6 3 EXAMPLE TABLES FOR BREEDING BULLS Tables 9–3 and 9–4 are example nutrient requirement (Table 9–3) and diet evaluation (Table 9–4) tables for growing bulls, using an 890-kg mature weight. Diet inputs for Table 9–4 were made as described for Table 9–2, with different diet TDN values. Weight ranges were set as 55 to 80 percent of the 28 percent fat weight of a steer of the same genotype (bull mature SBW * 0.6). (See Chapter 3 for the biological basis for computing bull requirements.) Diet CP, DIP, and UIP were balanced as described for Table 9–2 for 300 kg, except for diet A, for which upper bound of 80 percent DIP was used. The interpretations and applications are as described for Table 9–2.

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 TABLE 9–4 Diet Evaluation for Growing Bulls Wt @ Maturity 890 kg   Breed Code 1 Angus Ration eNDF % DM TDN % DM NEm Mcal/kg NEg Mcal/kg CP % DM DIP % CP Weight Class NE Adjuster A 43 50 1.00 0.45 8.2 80 325 100% B 37 65 1.51 0.92 10.9 78 350 100% C 30 70 1.67 1.06 12.0 76 375 100% D 20 75 1.83 1.20 13.4 73 400 100% E 5 80 1.99 1.33 13.8 51 425 100% Body Weight, kg DMI Adjuster DMI kg/d ADG kg/d DIP UIP MP Ca P balances, g/d requirements, % of DM 300—A 100% 7.9 0.22 5 103 83 0.18% 0.12% —B 100% 8.3 1.02 4 8 6 0.39% 0.20% —C 100% 8.2 1.23 2 -3 -2 0.45% 0.23% —D 100% 8.0 1.41 3 10 8 0.51% 0.25% —E 100% 7.7 1.56 5 -2 -2 0.56% 0.27% 325—A 100% 8.4 0.22 5 119 95 0.18% 0.12% —B 100% 8.8 1.02 5 51 41 0.36% 0.19% —C 100% 8.7 1.23 2 49 39 0.42% 0.21% —D 100% 8.5 1.41 3 70 56 0.47% 0.24% —E 100% 8.2 1.56 6 63 51 0.52% 0.26% 350—A 100% 8.9 0.22 5 134 107 0.18% 0.12% —B 100% 9.4 1.02 5 94 75 0.34% 0.18% —C 100% 9.2 1.23 2 100 80 0.39% 0.20% —D 100% 9.0 1.41 3 129 103 0.44% 0.22% —E 100% 8.7 1.56 6 128 102 0.48% 0.24% 375—A 100% 9.4 0.22 6 149 119 0.18% 0.12% —B 100% 9.8 1.02 5 136 109 0.32% 0.17% —C 100% 9.7 1.23 2 150 125 0.37% 0.19% —D 100% 9.4 1.41 3 187 149 0.41% 0.21% —E 100% 9.1 1.56 6 191 153 0.45% 0.23% 400—A 100% 9.8 0.22 6 161 131 0.17% 0.12% —B 100% 10.3 1.02 5 177 142 0.31% 0.17% —C 100% 10.2 1.23 2 199 159 0.35% 0.19% —D 100% 9.9 1.41 3 244 195 0.39% 0.20% —E 100% 9.6 1.56 7 253 202 0.42% 0.22% 425—A 100% 10.3 0.22 6 169 143 0.17% 0.12% —B 100% 10.8 1.02 6 218 174 0.29% 0.16% —C 100% 10.6 1.23 2 247 198 0.33% 0.18% —D 100% 10.4 1.41 3 300 240 0.36% 0.19% —E 100% 10.0 1.56 7 314 251 0.40% 0.21%

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 TABLE 9–5 Nutrient Requirements of Pregnant Replacement Heifers Mature Weight 533 kg   Calf Birth Weight 40 kg Age @ Breeding 15 months Breed Code 1 Angus   Months since conception   1 2 3 4 5 6 7 8 9 NEm required, Mcal/d Maintenance 5.98 6.14 6.30 6.46 6.61 6.77 6.92 7.07 7.23 Growth 2.29 2.36 2.42 2.48 2.54 2.59 2.65 2.71 2.77 Pregnancy 0.03 0.07 0.16 0.32 0.64 1.18 2.08 3.44 5.37 Total 8.31 8.57 8.87 9.26 9.79 10.55 11.65 13.23 15.37 MP required, g/d Maintenance 295 303 311 319 326 334 342 349 357 Growth 118 119 119 119 119 117 115 113 110 Pregnancy 2 4 7 18 27 50 88 151 251 Total 415 425 437 457 472 501 545 613 718 Minerals Calcium required, g/d Maintenance 10 11 11 11 12 12 12 13 13 Growth 9 9 9 8 8 8 8 8 8 Pregnancy 0 0 0 0 0 0 12 12 12 Total 19 19 20 20 20 20 33 33 33 Phosphorus required, g/d Maintenance 8 8 8 9 9 9 10 10 10 Growth 4 4 3 3 3 3 3 3 3 Pregnancy 0 0 0 0 0 0 7 7 7 Total 12 12 12 12 12 13 20 20 20 ADG, kg/d Growth 0.39 0.39 0.39 0.39 0.39 0.39 0.39 0.39 0.39 Pregnancy 0.03 0.05 0.08 0.12 0.19 0.28 0.40 0.57 0.77 Total 0.42 0.44 0.47 0.51 0.58 0.67 0.79 0.96 1.16 Body weight, kg Shrunk body 332 343 355 367 379 391 403 415 426 Gravid uterus mass 1 3 4 7 12 19 29 44 64 Total 333 346 360 375 391 410 432 459 491 EXAMPLE TABLES FOR PREGNANT REPLACEMENT HEIFERS Tables 9–5 and 9–6 contain requirements (Table 9–5) and diet evaluations (Table 9–6) for pregnant heifers. As with the preceding table sets, these two tables are related in that the animal described in the requirements table is then used in the diet evaluator. The program computes energy and protein balances expected for each of the three diets (rations A through C) entered as well as percent Ca and P needed in the diet DM to meet requirements. Animal descriptions entered were 533 kg mature weight, 40 kg expected birth weight, 15 month age at breeding, and breed code 1. Table 9–5 shows predicted NEm, MP, Ca, and P required daily for maintenance, growth, and pregnancy and target ADG, SBW, and expected gravid uterus weight used to compute requirements for each of 9 months of gestation, using the equations presented in Chapter 10. As described previously, all can be used directly to formulate dietary requirements for the specified level of performance, except diet CP intake to meet the MP requirement, which can be computed as described for Table 9–2. Table 9–6 shows diet evaluations for this same heifer. The diet concentration of TDN and CP and DIP as a percentage of CP were entered for each of the three diets and the intake multiplier was set at 100 percent. All DIP values were then set at 80 percent, and diet CP was adjusted until DIP requirement was approximately met. Predicted DMI increased as pregnancy progressed because of increasing predicted SBW (shown in Table 9–5). As with the growing and finishing cattle, the DIP balance was constant over gestation for a given diet because microbial requirement is a constant proportion of TDN. However, the UIP balance changes with composition of the ADG (reduced protein content of ADG with increasing weight) and conceptus requirements. The CP, DIP, and UIP requirements are determined as described for growing and finishing cattle. Diet A (50 percent TDN) does not supply enough energy to support target heifer growth during any month. Diet B (60 percent TDN) exceeds target energy allowable ADG in all but the last month of pregnancy and exceeded UIP requirements for the energy allowable ADG in all but the first month. Diet C (70 percent TDN) exceeded target ADG in all months, but UIP was deficient for the energy allowable ADG in all but months 7 and 8.

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 TABLE 9–6 Diet Evaluation for Pregnant Replacement Heifers Mature Weight 533 kg   Calf Birth Weight 40 kg Age @ Breeding 15 months Breed Code 1 Angus Ration TDN % DM NEm Mcal/kg NEg Mcal/kg CP % DM DIP % DM DMI Factor   A 50 1.00 0.45 8.2 80 100% B 60 1.35 0.77 9.8 80 100% C 70 1.67 1.06 11.4 80 100% Months Since Conception   1 2 3 4 5 6 7 8 9   NEm Req. Factor 100% 100% 100% 100% 100% 100% 100% 100% 100% A DM, kg 8.5 8.8 9.0 9.2 9.4 9.7 9.9 10.1 10.3   NE allowed ADG 0.35 0.34 0.33 0.31 0.28 0.22 0.12 0.00 0.00 DIP Balance, g/d 5 5 5 6 6 6 6 6 6 UIP Balance, g/d 75 79 83 87 90 92 90 66 -53 MP Balance, g/d 60 63 67 69 72 74 72 52 -42 Ca % DM 0.22% 0.21% 0.21% 0.20% 0.19% 0.18% 0.28% 0.25% 0.25% P % DM 0.17% 0.17% 0.16% 0.16% 0.15% 0.14% 0.19% 0.16% 0.16% B DM, kg 9.0 9.3 9.5 9.7 10.0 10.2 10.4 10.7 10.9   NE allowed ADG 0.96 0.96 0.95 0.92 0.88 0.82 0.71 0.54 0.30 DIP Balance, g/d 4 4 4 4 4 4 4 4 4 UIP Balance, g/d 5 14 22 30 38 49 54 46 18 MP Balance, g/d 4 11 18 24 31 40 43 37 14 Ca % DM 0.36% 0.35% 0.33% 0.32% 0.31% 0.29% 0.38% 0.34% 0.29% P % DM 0.27% 0.27% 0.26% 0.26% 0.25% 0.23% 0.27% 0.24% 0.20% C DM, kg 8.8 9.1 9.3 9.5 9.8 10.0 10.2 10.4 10.7   NE allowed ADG 1.47 1.46 1.45 1.42 1.38 1.31 1.19 1.02 0.77 DIP Balance, g/d 2 2 2 2 2 2 2 2 2 UIP Balance, g/d -66 -54 -43 -32 -19 -1 10 8 -18 MP Balance, g/d -53 -43 -34 -26 -15 -1 8 6 -14 Ca % DM 0.48% 0.47% 0.45% 0.43% 0.41% 0.39% 0.48% 0.43% 0.38% P % DM 0.37% 0.36% 0.35% 0.35% 0.33% 0.31% 0.35% 0.32% 0.28% NOTE: Requirements are for NE allowed ADG and target weight. NE allowed ADG is ADG independent of conceptus gain.

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 Table 9–7 Nutrient Requirements of Beef Cows Mature Weight 533 kg Milk Fat 4.0 %   Calf Birth Weight 40 kg Milk Protein 3.4 % Age @ Calving 60 months Calving Interval 12 months Age @ Weaning 30 weeks Time Peak 8.5 weeks Peak Milk 8 kg Milk SNF 8.3 % Breed Code 1 Angus   Month since Calving   1 2 3 4 5 6 7 8 9 10 11 12 NEm Req. Factor 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% NEm required, Mcal/d Maintenance 10.25 10.25 10.25 10.25 10.25 10.25 8.54 8.54 8.54 8.54 8.54 8.54 Growth 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Lactation 4.78 5.74 5.17 4.13 3.10 2.23 0.00 0.00 0.00 0.00 0.00 0.00 Pregnancy 0.00 0.00 0.01 0.03 0.07 0.16 0.32 0.64 1.18 2.08 3.44 5.37 Total 15.03 15.99 15.43 14.41 13.42 12.64 8.87 9.18 9.72 10.62 11.98 13.91 MP required, g/d Maintenance 422 422 422 422 422 422 422 422 422 422 422 422 Growth 0 0 0 0 0 0 0 0 0 0 0 0 Lactation 349 418 376 301 226 163 0 0 0 0 0 0 Pregnancy 0 0 1 2 4 7 14 27 50 88 151 251 Total 770 840 799 724 651 591 436 449 471 510 573 672 Calcium required, g/d Maintenance 16 16 16 16 16 16 16 16 16 16 16 16 Growth 0 0 0 0 0 0 0 0 0 0 0 0 Lactation 16 20 18 14 11 8 0 0 0 0 0 0 Pregnancy 0 0 0 0 0 0 0 0 0 12 12 12 Total 33 36 34 31 27 24 16 16 16 29 29 29 Phosphorus required, g/d Maintenance 13 13 13 13 13 13 13 13 13 13 13 13 Growth 0 0 0 0 0 0 0 0 0 0 0 0 Lactation 9 11 10 8 6 4 0 0 0 0 0 0 Pregnancy 0 0 0 0 0 0 0 0 0 5 5 5 Total 22 24 23 21 19 17 13 13 13 18 18 18 ADG, kg/d Growth 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Pregnancy 0.00 0.00 0.02 0.03 0.05 0.08 0.12 0.19 0.28 0.40 0.57 0.77 Total 0.00 0.00 0.02 0.03 0.05 0.08 0.12 0.19 0.28 0.40 0.57 0.77 Milk kg/d 6.7 8.0 7.2 5.8 4.3 3.1 0.0 0.0 0.0 0.0 0.0 0.0 Body weight, kg Shrunk Body 533 533 533 533 533 533 533 533 533 533 533 533 Conceptus 0 0 1 1 3 4 7 12 19 29 44 64 Total 533 533 534 534 536 537 540 545 552 562 577 597 EXAMPLE TABLES FOR BEEF COWS Tables 9–7 and 9–8 contain requirements (Table 9–7) and diet evaluations (Table 9–8) for beef cows. As with the bred heifers, these two tables are related; the animal described in the requirements table is used in the diet evaluator. It computes energy and protein balances expected for each of the three diets (rations A through C) entered and percent Ca and P needed in the diet DM to meet requirements. Animal descriptions entered were 533 kg mature weight, breed code 1, 40 kg expected birth weight, 60 months age, the breed default peak milk (8 kg), the default values for milk composition (4 percent fat, 3.4 percent protein, 8.3 percent solids not fat), 8.5 weeks at peak milk, and 30 months duration of lactation. Table 9–7 shows predicted NEm, NEg, MP, Ca, and P required daily for maintenance, growth, lactation, and pregnancy as well as predicted target ADG, SBW, daily milk production, and expected gravid uterus weight used to compute the requirements for each of the 12 months of the reproductive cycle using the equations presented in Chapter 10. As described previously, all can be used directly to formulate dietary requirements for the specified level of performance, except diet CP intake to meet DIP and UIP requirements, which can be computed as described for Table 9–2. Table 9–8 shows diet evaluations for this same cow. The diet concentration of TDN and CP and DIP as a percentage of CP were entered for each of the three diets and the

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 TABLE 9–8 Diet Evaluation for Beef Cows Mature Weight 533 kg Milk Fat 4.0 %   Calf Birth Weight 40 kg Milk Protein 3.4 % Age @ Calving 60 months Calving Interval 12 months Age @ Weaning 30 weeks Time Peak 8.5 weeks Peak Milk 8 kg Milk SNF 8.3 % Breed Code 1 Angus   Ration TDN % DM ME Mcal/kg NEm Mcal/kg CP % DM DIP % CP DMI Factor   A 50 1.84 1.00 7.9 82.5 100% B 60 2.21 1.35 7.8 100.0 100% C 70 2.58 1.67 9.1 100.0 100% Months since Calving   1 2 3 4 5 6 7 8 9 10 11 12   NEm Req. Factor 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100%   Milk kg/d 6.7 8.0 7.2 5.8 4.3 3.1 0.0 0.0 0.0 0.0 0.0 0.0 A DM, kg 11.14 11.40 12.12 11.83 11.54 11.30 10.68 10.68 10.68 10.68 10.68 10.68   Energy Balance, Mcal/d -3.90 -4.59 -3.31 -2.58 -1.88 -1.34 1.81 1.50 0.95 0.06 -1.30 -3.24 DIP Balance, g/d 7 7 7 7 7 7 6 6 6 6 6 6 UIP Balance, g/d -201 -270 -169 -96 -24 34 175 170 142 93 14 -110 MP Balance, g/d -161 -216 -136 -77 -19 27 149 136 113 75 11 -88 Ca % DM 0.65% 0.70% 0.62% 0.57% 0.52% 0.47% 0.34% 0.34% 0.34% 0.59% 0.59% 0.59% P % DM 0.20% 0.21% 0.19% 0.18% 0.16% 0.15% 0.12% 0.12% 0.12% 0.17% 0.17% 0.17% Reserves Flux/mo, Mcal -148 -174 -126 -98 -71 -51 55 46 29 2 -50 -123 B DM, kg 11.96 12.23 12.72 12.43 12.14 11.90 11.28 11.28 11.28 11.28 11.28 11.28   Energy Balance, Mcal 1.07 0.47 1.69 2.32 2.92 3.38 6.32 6.00 5.46 4.56 3.20 1.27 DIP Balance, g/d 5 5 5 5 5 5 5 5 5 5 5 5 UIP Balance, g/d 18 -47 44 114 182 233 221 221 221 221 209 85 MP Balance, g/d 14 -38 35 91 146 189 304 291 269 230 167 68 Ca % DM 0.27% 0.30% 0.27% 0.25% 0.22% 0.20% 0.15% 0.15% 0.15% 0.25% 0.25% 0.25% P % DM 0.19% 0.20% 0.18% 0.17% 0.16% 0.14% 0.11% 0.11% 0.11% 0.16% 0.16% 0.16% Reserves Flux/mo, Mcal 32 14 51 71 89 103 192 183 166 139 97 39 C DM, kg 13.16 13.42 13.79 13.50 13.21 12.97 12.35 12.35 12.35 12.35 12.35 12.35   Energy Balance, Mcal/d 6.99 6.48 7.65 8.18 8.69 9.07 11.80 11.49 10.95 10.05 8.69 6.76 DIP Balance, g/d 3 3 3 3 3 3 2 2 2 2 2 2 UIP Balance, g/d 295 233 314 308 301 296 282 282 282 282 282 282 MP Balance, g/d 236 187 256 308 360 401 509 496 473 435 371 272 Ca % DM 0.25% 0.27% 0.25% 0.23% 0.20% 0.19% 0.13% 0.13% 0.13% 0.23% 0.23% 0.23% P % DM 0.17% 0.18% 0.17% 0.15% 0.14% 0.13% 0.10% 0.10% 0.10% 0.14% 0.14% 0.14% Reserves Flux/mo, Mcal 212 197 233 249 264 276 359 349 333 306 264 205 intake multiplier was set at 100 percent. All DIP values were then set at 80 percent, and diet CP was adjusted until DIP requirements were close to being balanced. Predicted DMI varies with daily milk production and forage quality. The CP required to meet diet DIP required for microbial growth is constant for a given diet but increased as diet TDN increased because microbial growth is a constant proportion of TDN. However, the UIP balance changes with milk and pregnancy requirements. Diet A (50 percent TDN) met energy and UIP requirements in months 7 to 10 (cows just dry), became deficient in energy in month 11, and deficient in both energy and UIP in month 12. Diet B (60 percent TDN) is adequate in energy in all months and UIP in all but month 2 of lactation. Diet C (70 percent TDN) exceeded energy and UIP requirements in all months. The energy reserves flux (Mcal/mo) is given for each month of the reproductive cycle for each diet evaluated. Appendix Table 13 can be used to estimate days for a CS change by dividing the Appendix Table 13 value by the predicted daily energy balance. To reduce a negative energy balance, 1 Mcal diet NEm will substitute for 1 Mcal negative energy balance. To utilize energy reserves, 1 Mcal diet NEm can be replaced by 0.8 Mcal tissue energy. TABLE OF ENERGY RESERVES FOR BEEF COWS Appendix Table 13 gives Mcal mobilized in moving to the next lower CS, or required to move from the next lower CS to the one being considered, for cows with different mature weights. For example, a 500-kg cow at CS 5 will mobilize 207 Mcal in declining to a CS 4. If NEm intake is deficient 3 Mcal/day, this cow will lose 1 CS in (207 * 0.8)/3=55 days. If consuming 3 Mcal NEm above

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 daily requirements, this cow will move from a CS 4 to a CS 5 in 207/3=69 days. The equations developed for computation of energy reserves are discussed in Chapter 3. TABLE OF MAINTENANCE REQUIREMENT MULTIPLIERS FOR ENVIRONMENTAL CONDITIONS The program used to develop the tables of requirements does not adjust for environmental conditions. Appendix Table 14 gives multipliers developed from the computer model level 1 that can be used to adjust NEm requirements for environmental stress.