Balancing Rations on the Basis of Amino Acids: The CPM-Dairy Approach

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1 Balancing Rations on the Basis of Amino Acids: The CPM-Dairy Approach William Chalupa and Charles Sniffen Global Dairy Consultancy Co.; Ltd P.O. Box 153 Holderness NH Corresponding Author: Summary Amino acid supply to the mammary gland directly affects milk protein synthesis and milk volume and indirectly impacts productivity by affecting metabolism and immune function. The complexity of balancing rations on the basis of amino acids requires computer models. CPM-Dairy calculates amino acid requirements by a factorial method and by an ideal protein method. Balancing rations on the basis of amino begins with optimizing production of microbial protein in the rumen. Next, rumen outputs of amino acids are complemented with dietary sources that escape ruminal fermentation. Feeds with high concentrations of methionine and lysine in metabolizable protein are helpful but single sources of rumen-protected amino acids are usually needed. Introduction Like other mammalian species, the dairy cow's requirement for protein is a requirement for specific amounts and balances of amino acids. Amino acid supply to the mammary gland can affect milk protein content and milk volume (Chalupa and Sniffen, 1991; Rulquin and Verite, 1993; Rulquin et al. 1995, Socha et al. 2005; Xu et al. 1998). In addition, amino acids can impact productivity by affecting metabolism and immune function (Bauman et al. 1995; Okine et al. 1996). Amino Acid Requirements Requirements for absorbed essential amino acids can be defined using the classical factorial method (Chalupa and Sniffen, 1996; O'Connor et al. 1993) and by ideal protein methods (Chalupa and Sniffen, 1996; Rulquin and Verite, 1993; NRC, 2001). The factorial method requires knowledge of the amino acid content of products and the efficiency of amino acid use. Amino acid content of milk and tissues can be estimated reliably but an estimate of the efficiency of amino acid use is difficult and variable. The ideal protein method proposed Rulquin and Verite (1993) is based on responses of milk protein to methionine and lysine expressed as percentages of PDI (equivalent to metabolizable protein). Optimum milk protein was obtained with 2.5% methionine and 7.3% lysine Figures 1 and 2). However, it is hard to reach these concentrations without single sources of methionine and lysine. Because milk protein appears to be dramatically reduced when rations provide less than 2.10% methionine or 6.5% lysine, these levels are considered minimums. Inspection of graphs presented by Rulquin and Verite (1993) suggest that responses of milk protein to methionine may be negative if lysine is limiting (i.e. lysine in metabolizable protein<6.5). 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 96

2 Comparison of the factorial and ideal protein methods. Figure 3 shows potential responses of milk protein yield and milk yield to increased metabolizable lysine and methionine. Responses, based on the factorial and ideal protein methods, were estimated using CPM-Dairy (Boston et al. 2000). There are considerable differences in responses estimated by the two systems. The constant transfer coefficients for methionine and lysine dictate that production responses are linear regardless of amounts of metabolizable methionine and lysine. The factorial method may describe production responses correctly when nutrients are limiting but will over-estimate production responses when there are excesses of nutrients. The ideal protein method gives the curvilinear response to methionine and lysine that is expected in biology. However, the database used to calibrate the ideal protein method (Rulquin and Verite, 1993) was obtained with cows beyond peak production. Milk production was modest and many experiments were short-term switchback designs. Thus, responses to increasing proportions of lysine and methionine might be expected to be higher in early and peak lactation cows. Further Research on the Ideal Protein Method Since the report by Rulquin and Verite (1993), there has been verification of the methionine and lysine ratios (NRC, 2001; Sniffen et al. (2001) and expansion of the ideal protein concept to other amino acids (Sniffen et al. 2001, Rulquin et al.2001). NRC (2001) used an approach like Rulquin and Verite (1993) where responses of milk protein to abomasal or intestinal infusions of methionine and lysine or to feeding rumen-protected forms of methionine and lysine were recorded. Sniffen et al. (2001) applied multiple regression analyses using the JMP discovery software developed by the SAS Institute to transition cow experiments (three weeks before calving to 4-8 weeks postpartum) designed to study the efficacy of rumen-protected methionine and lysine products. Rulquin et al. (2001) used an amino acid profiling prediction system of intestinal contents to enable the inclusion of experiments where amino acids were not infused into the abomasum or small intestine or fed in protected form. Methionine and lysine. NRC (2001) reported that low concentrations of methionine in metabolizable protein limited responses of lysine in metabolizable protein and that low concentrations of lysine in metabolizable limited responses of methionine in metabolizable protein. When methionine was greater than 1.95% of metabolizable protein, the required concentration of lysine in metabolizable protein to maximize milk protein concentration was 7.24%. When lysine was 6.50% or more in metabolizable protein, the methionine requirement was 2.35%. Optimum ratios calculated by the Sniffen et al. (2001) multiple regression approach were 2.02% methionine in metabolizable protein and 7.04% lysine in metabolizable protein. Histidine. Increasing histidine in PDIE (metabolizable protein) increased total protein output. However, this was due mainly to an increased milk yield so that protein content in milk (g/kg) plateaued at 3.2% histidine in PDIE (Figure 4). The value suggested by Sniffen et al. (2001) was 2.7%. Histidine is more likely limiting with rations containing grass silage as a base (Rulquin et al. 2001). 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 97

3 Leucine. The curves for leucine in PDIE (metabolizable protein) versus total protein output and protein content in milk (g/kg) are similar (Figure 5). Thus, leucine does not appear to affect milk volume but has an impact on concentration of protein in milk. Leucine may limit milk protein concentration when less than 8.8% of PDIE. Sniffen et al. (2001) found that 8.4% leucine was needed. Leucine may be below suggested values with grass and barley based rations (Rulquin et al. 2001). Valine does not seem to be limiting so long as the concentration in PDIE (metabolizable protein) is greater than 5.3% (Rulquin et al. 2001). Sniffen et al. (2001) reported that concentration of protein in milk was optimized with 5.75% valine in metabolizable protein. Isoleucine does not seem to be limiting so long as the concentration in PDIE (metabolizable protein is greater than 5.0% (Rulquin et al. 2001). This is similar to the 4.7% suggested by Sniffen et al. (2001). Phenylalanine and tyrosine. The curves for in phenylalanine in PDIE (metabolizable protein) versus total protein output and protein content in milk (g/kg) are similar (Figure 6). Thus, phenylalanine does not have much of an affect on milk volume but has an impact on concentration of protein in milk. Phenylalanine in PDIE of about 5% seems to be sufficient, (Rulquin et al. 2001). The optimum phenylalanine reported by Sniffen et al (2001) was 5.1%. Rulquin et al. (2001) suggested that tyrosine might lower the requirement for phenylalanine. Because tyrosine is insoluble in water, it may not require protection to reach the small intestine. Threonine. As with histidine, increasing threonine in PDIE (metabolizable protein) increased total protein output. However, this was due mainly to an increased milk yield (Figure 7). Threonine in PDIE of about 4% seems to be sufficient, (Rulquin et al. 2001). This is similar to the 4.5% suggested by Sniffen et al. (2001). Arginine. Post ruminal administration of arginine has not increased milk protein yield or the concentration of protein in milk. Arginine in PDIE (metabolizable protein) of about 4.3% seems to be sufficient (Rulquin et al. (2001). However, Sniffen et al. (2001) reported that about 6% arginine was optimum. Tryptophane. According to Rulquin et al. (2001), tryptophane does not appear to be a limiting amino acid (Rulquin et al. 2001) with hay and corn-based rations. Sniffen et al. (2001) reported that 1.37% tryptophane in metabolizable protein was needed. Comparisons of amino acids in PDIE (metabolizable protein) to maximize the concentration of protein in milk are presented in Table 1. Methionine and lysine concentrations reported by Rulquin et al. (2001) and NRC (2001) are similar. Those reported by Sniffen et al. (2001) are a little lower. For the other amino acids, ideal values reported by Sniffen et al. (2001) and Rulquin et al. (2001) are similar. 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 98

4 Production Responses to Methionine and Lysine Production responses to supplemental methionine and/or lysine have been variable. We selected four reports where diets were evaluated with a nutrition model (CPM-Dairy, 1998; NRC, 2001) to illustrate that balancing for methionine and lysine in metabolizable protein can be beneficial. Sloan et al. (1999) used CPM-Dairy (1998) to examine responses to methionine and lysine in the data set compiled by Garthwaite et al. (1998). Increases in yield of milk (1.7 kg/d), yield of milk protein (90 g/d) and concentration of protein in milk (0.10%) only occurred when methionine in metabolizable protein was greater than 2.2%, lysine in metabolizable protein was greater than 6.8% and lysine:methionine ratio exceeded 3 (Table 2). Chalupa et al. (1999) used CPM-Dairy (1998) to formulate amino acid (Ajinomoto Corp. Inc., Tokyo) enriched fresh-cow rations. Methionine in metabolizable protein was increased from 1.89 to 2.35%. Lysine in metabolizable protein was increased from 6.38 to 7.45%. The lysine:methionine ratio in the amino acid enriched ration was 3.2 (Table 3). Feeding the amino acid enriched ration increased mammary synthesis of protein in both multiparous and primiparous cows. Because milk yield increased in multiparous cows, the increased mammary synthesis of protein was diluted and concentration of protein in milk was not changed. In primiparous cows, milk yield was only marginally increased so the increased mammary synthesis of protein was seen as an increase in the concentration of protein in milk. Feeding the amino acid enriched ration did not affect mammary synthesis of fat in either multiparous or primiparous cows. Both Garthwaite et al. (1998) and Chalupa et al. (1999) reported that production responses were greater when RPAA were provided both prior to and after calving. Noftsger and St-Pierre (2003) showed that cows fed rations that contained RUP sources with high (>89%) intestinal digestibility produced more milk, more dietary nitrogen was captured in milk (gross nitrogen efficiency) and less nitrogen was excreted per kg of nitrogen in milk (environmental efficiency) than cows fed rations that contained RUP sources with low (55%) intestinal digestibility (Table 4). Supplementing a ration that contained RUP sources with high (>89%) intestinal digestibility with methionine (Rhodimet AT-88 and Smartamine) allowed crude protein to be decreased from 18 to 17% with no drop in milk yield, an increase in the concentration of protein in milk and improvements in gross nitrogen efficiency and environmental efficiency (Table 4). Schwab et al. (2003) examined the impact of increasing concentrations of methionine and lysine in metabolizable protein in six commercial dairies (Table 5). Lysine was increased by adding blood meal and reducing or eliminating distillers grains or a protected soy product. Methionine concentrations in metabolizable protein were increased with Smartamine. These ration changes resulted in a lysine-methionine of 3:1. Methionine in metabolizable protein ranged from 2.01 to 2.35%. Lysine in metabolizable protein ranged from 6.18 to There was no attempt to measure changes in milk yield but in most cases, producers thought they observed higher milk yields. All herds responded with increases in concentrations of protein and fat in milk. Based upon evaluation of published research, we propose that balancing rations on the basis of amino acids will increase mammary synthesis of protein but the type of production response will vary depending upon parity and stage of lactation. Because growth 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 99

5 is a higher metabolic priority than milk secretion, response in primiparous animals may depend upon body size at calving. Amino acids seem to increase milk volume if started at or prior to calving. If delayed until after peak production, milk volume increases are small so the main response to amino acids is increased concentration of protein in milk. Efficiency of Utilizing Metabolizable Protein for Milk Protein Synthesis. Rats and chickens grow more efficiently when fed diets that contain high quality proteins like casein or egg protein versus diets with poor quality protein like zein. Dairy cattle should respond in a similar manner to metabolizable protein that has good balances of amino acids. Efficiencies of milk protein synthesis from metabolizable protein are in Table 6. The CPM-Dairy efficiency is.65 (Boston et al. 2000). The NRC (2001) efficiency is.67. Calculations by Piepenbrink et al. (1999) and Sloan et al. (2002) showed that increasing the concentrations of methionine and lysine in metabolizable protein increases the efficiency of milk protein synthesis. When formulating rations with CPM-Dairy, one might increase the metabolizable protein efficiency in the constants screen to.69 or formulate for a metabolizable deficiency of about 100 g. Some caution to the above may be prudent for transition cows. In early lactation, amino acids have an important role apart from their use in protein synthesis. The increased whole body demand for glucose after calving requires metabolic adaptations that may be enhanced by protein nutrition (Overton, 1998). Propionate is the main substrate for gluconeogenesis but after calving conversion of alanine (used as an indicator of gluconeogenesis from amino acids) to glucose increases more than the conversion of propionate to glucose (Overton et al. 1998). Since glucose uptake by the mammary gland is a major determinant of milk volume, limiting the supply of nonessential amino acids by reducing metabolizable protein may compromise rapid acceleration of milk yield. Reducing Nitrogen Excretion. Increasing pressure to reduce nitrogen excretion of dairy herds requires feeding rations that maximize conversion of feed nitrogen to milk nitrogen. There are several routes that can be followed. Matching dietary protein to animal requirements is obvious but this means feeding different rations to groups of cattle at different levels of production. Mainly, because of simplicity, many dairymen are not willing to follow this strategy and choose to feed one ration to all production groups. Another alternative is to maximize the ruminal production of microbial protein. Finally, the experiment by Noftsger and St. Pierre (2003), which was discussed previously, showed a 35% improvement in nitrogen efficiency when a ration was balanced for methionine and lysine in metabolizable protein. Application of CPM-Dairy Diets for ruminant animals should first formulated to optimize the supply of nutrients provided by ruminal microbes. The rumen system, however, cannot provide sufficient nutrients for high levels of growth or milk production. Thus, rumen inert (bypass) nutrients (fat, protein, amino acids and perhaps some vitamins) are needed to supplement nutrients from the rumen so that productivity of growing and lactating cattle can be optimized. 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 100

6 Amino acids are the only nitrogenous nutrients that are used for synthesis of tissue proteins and milk protein. Amino acids are provided by ruminal microbes and by dietary protein that escapes fermentative digestion in the rumen and, depending upon protein nutrition during the dry period, by body reserves of labile proteins. Commercial sources of rumen protected methionine include Megalac Plus (Church and Dwight Co., Inc.), Mepron (Degussa Corp.), Smartamine (Adisseo), MetaSmart (Adisseo) and Met Plus (Nisso America). HMB, (2-Hydroxy-4-(Methylthio) Butanoic Acid), is available as Alimet (Novus International) and as Rhodimet AT-88 (Adisseo). Koenig et al. (2002) reported that the ruminal escape of Alimet was 40%. Noftsger and St. Pierre (2003) cited a personal communication from Schwab (University of New Hampshire) that the ruminal escape of Rhodimet AT-88 was only 5%. In a subsequent study, Noftsger et al. (2005) concluded that HMB is primarily a rumen degradable source of methionine, and its positive effects are mainly due to stimulation of microbial growth, predominantly protozoa in the rumen. There are no commercial sources of rumen-protected lysine. As shown in Table 7, blood meal, rumen bacteria and fish meal have the highest concentration of lysine. It is easier to achieve high lysine in metabolizable protein with rations that provide at least 50% of the metabolizable protein from bacteria. Fermentability of carbohydrates in the rumen is the main determinant of bacterial growth. While fermentability of total ration carbohydrates can be increased by providing more non-fiber carbohydrate, this can lead to low ruminal ph so that the efficiency of bacterial growth is reduced. High digestibility of forage NDF is a key to obtaining good growth of bacteria in the rumen. Optimum milk protein is obtained with 2.5% methionine and 7.3% lysine (Rulquin and Verite, 1993). It is hard to reach these concentrations without single sources of methionine and lysine. Because milk protein appears to be dramatically reduced when rations provide less than 2.10% methionine or 6.5% lysine, these levels are considered minimums. To see larger increases in milk protein, 2.20% methionine and 6.9% lysine may be needed. Both Rulquin and Verite (1993) and NRC (2001) indicated that it is important to have methionine and lysine balanced with respect to each other. In CPM- Dairy, keep lysine:mehionine at 3.10:1. Even when 6.5% lysine cannot be achieved, supplemental methionine should be provided to obtain lysine:methionine of 3.10:1 References Bauman, D.L., R.J. Harrell and M.A. McQuire Proc. Cornell Nutr. Conf. 57:198. Cornell Univ., Ithaca. Boston R., D Fox, C Sniffen, E Janczewski, R Munson and W. Chalupa In: McNamara JP, J France and DE Beever (eds.) Modeling Nutrition of Farm Animals, p 361, CAB International, U.K. Chalupa, William and Charles J. Sniffen The Veterinary Clinics of North America-Food Animal Practice: Dairy Nutrition Management. Page 353. W.B. Saunders CO., Philadelphia. Chalupa, W. and C.J. Sniffen Adv. Dairy Technol. 8:69. Univ. Alberta, Canada. Chalupa, W, C.J. Sniffen, W.E. Julien, H. Sato, T. Fujieda, T. Ueda and H. Suzuki J. Dairy Sci. 82(Suppl.1):121. CPM-Dairy Cornell Univ., Ithaca NY; Univ. Pennsylvania, Kennett Square PA; W.H. Miner Agricultural Research Institute, Garthwaite, B.D, C.G. Schwab and B.K. Sloan Proc. Cornell Nutr. Conf, p st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 101

7 Koenig, K.M., L. M. Rode, C. D. Knight, and M. Vázquez-Añón J. Dairy Sci. 85: 930. National Research Council, Nutrient Requirements of Dairy Cattle (7 th Rev. Ed.) Washington D.C.: National Academy Press. Noftsger, S and N. R. St-Pierre J. Dairy Sci. 86:958. Noftsger, S N. R. St-Pierre and J. T. Sylvester J. Dairy Sci. 88:223. Okine, E.K., F. Zhao and J.J. Kennelly Adv. Dairy Technol. 8:277. Univ. Alberta, Canada. O'Connor, J.D., C.J. Sniffen, D.G. Fox and W. Chalupa J. Anim. Sci.71:1298. Overton, T.R., J.K. Drackley, G.N. Douglas, L.S. Emmert and J.H. Clark J. Dairy Sci. 81(Suppl. 1):295. Piepenbrink, M.E., C.G. Schwab, B.K. Sloan and N.L. Whitehouse Abstract P236. ADSA. Memphis. Rulquin, H. and R. Verite Recent Advances in Animal Nutrition. Univ Nottingham Press. Rulquin, H., R. Verite, J. Guinard and P.M. Pisulewski Page 143 in Animal Science Research and Development: Moving Toward a New Century. M. Ivan, Ed. Centre for Food Animal Research Contribution Ottawa, Ontario. Rulquin, H., R. Verite, J. Guinard-Flament and P.M. Pisulewski INRA Prod. Anim. 14:201. Schwab, C.G., R.S. Ordway and N.L. Whitehouse Four States Nutrition Conference. Sloan, B.K Sloan, B.K., B.D. Garthwaite and C.G. Schwab Feedstuffs 71(33): 11. Socha, M.T., D. E. Putnam, B. D. Garthwaite, N. L. Whitehouse, N. A. Kierstead, C. G. Schwab, G. A. Ducharme, and J. C. Robert J. Dairy Sci : Sniffen, C.J, W. Chalupa, T. Ueda, H. Suzuki, I. Shinzato, T. Fujieda, W. Julien, L. Rode, P. Robinson, J. Harrison, A. Freeden and J. Nocek Proc. Cornell Nutr. Conf.. Xu, S., J.H. Harrison, W. Chalupa, C. Sniffen, W. Julien, H. Sato, T. Fujieda, K. Watanabe, T. Ueda and H. Suzuki J. Dairy Sci. 781: st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 102

8 Figure 1. Responses of milk protein to lysine in protein digested in the small intestine (Rulquin et al. 1993). Figure 2. Responses of milk protein to methionine in protein digested in the small intestine (Rulquin et al. 1993) 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 103

9 Milk Protein Response (g/d) M ilk P rotein R esp onse (g /d) Milk Protein Responses to Lysine Ideal Protein vs Factorial Method Ideal Protein Factorial Lysine/Metabolizable Protein Lysine (g/d) Milk Protein Responses to Methionine Ideal Protein vs Factorial Method 600 Ideal Protein Factorial Methionine/Metabolizable Protein Methionine (g/d) Milk Yield Response (kg/d) Milk Yield Response (Kg/d) Milk Yield Responses to Lysine Ideal Protein vs Factorial Method Ideal Protein Factorial Lysine/Metabolizable Protein Lysine (g/d) Milk Yield Responses to Methionine Ideal Protein vs Factorial Method Ideal Protein Factorial Methionine/Metabolizable Protein Methionine (g/d) Figure 3. Responses of protein and milk yields to lysine and methionine: comparison of ideal protein and factorial methods. Figure 4. The change in production (a: g/day) and ratio (b: total protein (g.kg) of milk proteins as a content of histidine in protein digestible in the intestines (metabolizable protein) in early lactation (de but de lactation) and mid lactation (milieu de lactation) cows (Rulquin et al. 2001). 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 104

10 Figure 5. The change of the production (a: g/d) and the ratios (b: g/kg) of milk proteins as a function of leucine in protein digestible in the intestines (metabolizable protein). (Rulquin et al. 2001). Figure 6. The change of the production (a) and the ratio (b) of milk proteins as a function of the content of phenylalanine in PDIE (Metabolizable protein). (Rulquin et al. 2001). 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 105

11 Figure 7. The change of the production (a) and the ratio (b) of milk protein as a function of the content threonine PDIE (metabolizable protein). (Rulquin et al. 2001). Table 1. Comparisons of percentages of amino acids in PDIE (metabolizable protein) to maximize the concentration of protein in milk. Amino Acid Sniffen et al. (2001) Rulquin et al NRC (2001) Met Lys Thr 4.54 >4.3 Val 5.75 >5.3 Leu 8.37 <8.8 Ile 4.73 >5.0 Phe Trp 1.37 Not limiting His Arg 6.22 >4.3 Table 2. Responses of milk and components to rumen protected amino acids 1 Measurement Control Treatment Range DMI (kg/d) to 0.9 Milk (kg/d) to 3.9 Protein (%) to 0.29 Protein (g/d) to 161 Fat (%) to 0.24 Fat (g/d) to Sloan et al. (1999). Seven experiments 2. According to CPM-Dairy (1998), Met/MP of amino acid supplemented diets was 2.13 to 2.30, Lys/MP was 6.83 to 7.09 and Lys/Met was 2.97 to st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 106

12 Table 3. Responses of lactating cows to rumen protected methionine and lysine 1 Rulquin Ratio 2 (% AA in MP) Met Lys Met Lys Measurement 3 Parity Response P Milk (kg/d) M <.05 P >.10 C Protein (%) M >.10 P <.01 C Protein (g/d) M <.01 P <.01 Fat (%) M >.10 P >.10 Fat (g/d) M >.10 P > Chalupa et al. (1999); 2. Rulquin and Verite. (1993) 3. For the first 4 weeks of lactation when the amino acid enriched ration was fed 4. M = multiparous; P = primiparous Table 4. Impact of dietary crude protein, intestinal digestibility of RUP and methionine supplementation on production and nitrogen utilization 1 Measurement High CP Low CP Intestinal digestibility of RUP Low 2 High 3 High 3 High 3 + Met 4 CP, % of DM RUP, % of DM MP balance, g Met, % of MP Lys, % of MP Lys:Met in the MP Fat, % of DM DMI (kg/d) 21.7 a 23.3 b 23.2 b 23.6 b Milk yield (kg/d) 40.8 a 46.2 b 42.9 a 46.6 b Protein production (kg/d) Protein (%) 2.95 a 2.98 a 2.99 a 3.09 b Gross N efficiency a 31.1 b 31.7 b 35.0 c Environmental efficiency a 2.25 b 2.19 b 1.89 c 1. Noftsger and St-Pierre (2003) 2. Porcine meat meal as the source of RUP. 55% digestible. 3. Blood, poultry and feather meals as the source of RUP. Digestibility > 89% 4. Rhodimet AT-88 and Smartamine 5. Calculated using CPM-Dairy version 1 (Boston et al.2000) 6. Milk N/N intake * Kg N excreted/kg N in milk 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 107

13 Table 5. Responses in commercial dairies of milk protein and fat in to increased concentrations of methionine and lysine in metabolizable 1 1. Schwab et al. (2003) Table 6. Impact of concentration of methionine and lysine in metabolizable protein on the utilization of metabolizable protein for synthesis of milk protein. Reference Met/MP Lys/MP MP Efficiency CPM-Dairy (Boston et al. 2000).65 NRC (2001).67 Piepenbrink et al. (1999) Piepenbrink et al. (1999) Sloan et al (2002) Sloan et al (2002) Sloan (2002) Sloan (2002) st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 108

14 Table 7. Crude protein, bypass protein and methionine and lysine in bypass protein. Crude Protein Bypass Protein Methionine Lysine Ingredient (%DM) (%CP) (%BP) (%BP) Blood Meal Rumen Bacteria Fish Meal Canola Meal Soybean Meal Soy Best Soy Plus Prolak Soy Pass Meat Meal Cottonseed Meal Feather Meal Brewers Grains Distillers Grains Corn Gluten Meal Urea Ration Minimum (% Metab. Protein) Bacterial true protein. Corrected for nucleic acid nitrogen and indigestible cell wall protein. 2. Methionine and lysine are expressed as a percentage of bacterial true protein 21 st Annual Southwest Nutrition & Management Conference February 23-24, 2006 Tempe, AZ - 109