Effects of Rumen-Undegradable Protein on Dairy Cow Performance: A 12-Year Literature Review1

NUTRITION, FEEDING, AND CALVES Effects of Rumen-Undegradable Protein on Dairy Cow Performance: A 12-Year Literature Review1 F.A.P. SANTOS,2 J.E.P. SANTOS, C. B. THEURER,3 and J. T. HUBER4 Department of Animal Sciences, University of Arizona, Tucson 85721

ABSTRACT In order to integrate and analyze knowledge on the use of protein supplements and protein nutrition of lactating dairy cows, we compiled a review of 108 studies published throughout the world, but principally in the Journal of Dairy Science between 1985 and 1997. In 29 comparisons from 15 metabolism trials, soybean meal was replaced by high amounts of rumen undegradable protein (RUP) as a supplement; the benefits were not consistently observed for flow to the duodenum, essential amino acids, or lysine and methionine. High RUP diets resulted in decreased microbial protein synthesis in 76% of the comparisons. However, fish meal provided a good balance of lysine and methionine when calculated as a percentage of total essential amino acids. In 127 comparisons from 88 lactation trials that were published from 1985 to 1997, researchers studied the effects of replacing soybean meal with high RUP sources, such as heated and chemically treated soybean meal, corn gluten meal, distillers grains, brewers grains, blood meal, meat and bone meal, feather meal, or blends of these sources; milk yield was significantly higher in only 17% of the comparisons. Fish meal and treated soybean meal accounted for most of the positive effects on milk yield from RUP; corn gluten meal resulted in mostly negative results. The percentage of fat in milk was depressed more by fish meal than by other RUP sources. Protein percentage was decreased in 28 comparisons and increased in only 6 comparisons, probably reflecting the decrease in microbial protein synthesis, as was observed for diets high in RUP. The data strongly suggest that increased RUP per se in dairy cow diets, which often results in a

Received December 9, 1997. Accepted April 6, 1998. 1Invited paper. 2Present address: Departamento de Zootecnia de Ruminantes, Av. Padua Dias, Escola Superior Agricultura Luiz de Quiroz, Universidade da Sa˜o Paulo, Piracicaba, Sa˜o Paulo, Brazil 13418-900. 3Present address: Veterinarian Medical Teaching Center, University of California, 4032 W. Crowly Court, Visalia, CA 93291. 4Reprint requests. 1998 J Dairy Sci 81:3182–3213

decrease in RDP and a change in absorbed AA profiles, does not consistently improve lactational performance. ( Key words: rumen-undegradable protein, lactating cows, protein, review) Abbreviation key: ABP = animal by-products, AP = absorbed protein, BDG = brewers dried grains, BM = blood meal, BWG = brewers wet grains, CGM = corn gluten meal, DDG = distillers dried grains, DDGS = DDG with solubles, EAA = essential AA, ExpSBM = expeller soybean meal, FM = fish meal, FtM = feather meal, HSBM = heated soybean meal, LigSBM = lignosulfonate SBM, MBM = meat and bone meal, NANMN = nonammonia, nonmicrobial N; SBM = soybean meal, SI = small intestine. INTRODUCTION For many years, CP content was used in formulating diets for lactating dairy cows because little was known of the response to dietary protein of varying quality, and many researchers postulated that the high quality microbial protein synthesized in the rumen would complement deficiencies in the quality of dietary protein that escaped ruminal fermentation (98). Research conducted in the 1960s (114) showed that the rumen was capable of supplying all of the protein required by cows producing up to 4500 kg of milk per lactation. However, milk yield per cow in the US has more than doubled during the last 30 yr, and the general concern currently is for cows yielding from 9000 to 14,000 kg of milk yearly. For these high yielding cows, microbial protein synthesis supplies a decreasing proportion of the required protein, and significant amounts of dietary protein must escape ruminal degradation in order to meet protein needs (96). Because of the limitations of many of the older systems in predicting protein requirements of high producing dairy cows, new systems in North America (48, 77, 78, 106) and Europe ( 1 ) have been published during the past decade. The metabolizable protein system ( 1 ) of the United Kingdom estimates the

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degree to which dietary protein is degraded in the rumen to supply RDP, and the amount of RUP flowing to the small intestine ( SI) is calculated by difference (12). The Cornell Net Carbohydrate Protein System (48, 94, 106) is a model that has a fermentation submodel that compares rate of carbohydrate fermentation with rate of protein degradation and predicts ruminally digestible OM, microbial protein synthesis, ammonia production, and flow of undigested feed protein to the SI. The most widely used protein system in North America is the absorbed protein ( AP) model of NRC (77, 78), which employs a factorial method to derive requirements for AP for all classes of dairy cattle. The AP method recognizes differences in the proportion of dietary protein escaping rumen fermentation; older NRC systems considered only CP. The AP method introduced the concept of RUP and RDP, which are used as the dietary protein inputs needed to supply the required absorbed protein. Since publication of the AP method (77, 78), a great amount of research has been conducted to determine the ratios of RUP to RDP contained in protein supplements for dairy diets in order to optimize AA flow to the SI and consequent performance of dairy cows. Several research groups (29, 37, 55, 56, 84, 97) have pointed to the inadequacies of the RDP-RUP system to estimate protein needs for high producing cows compared with conventional supplements that are low in RUP, such as soybean meal ( SBM) . Based on the RDP-RUP model, increased milk yields are usually expected from substituting a high RDP with a high RUP source of supplemental protein. However, in this review, many studies are cited in which SBM (the most commonly used protein supplement in the US) replacement by a high RUP source resulted in a general lack of response in milk yield. Possible reasons for this lack of response to increased RUP are 1 ) microbial synthesis in the rumen decreased (36, 98, 100), 2 ) the RUP source had a poor essential AA ( EAA) profile (32, 98, 100), 3 ) RUP sources in the SI had low digestibility (98, 100), and 4 ) control diets already were sufficiently high in RUP (77, 78). Some studies (33, 36, 55, 84, 98, 100) have suggested that, for a RUP supplement to result in improved performance, the source of RUP should have an AA profile that would complement the profile of microbial protein. Infusion trials have indicated that Lys and Met are probably the first- and secondlimiting AA, respectively, for milk yield and milk protein synthesis (62, 101, 102) in diets of US dairy cattle. The amounts of Lys and Met as percentages of total EAA in duodenal digesta that were recom-

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mended for maximizing milk and milk protein yields were 15 and 5%, respectively (101, 102). Hence, RUP supplements that are low or unbalanced in Lys and Met might result in no increase or a decrease in yields of milk and milk protein (100). Published literature during the last 12 yr (from January 1985 to April 1997) is herein reviewed. These studies generally reveal inconsistent results when protein supplements that are high in RUP have partially or totally replaced conventional protein sources such as SBM. This review summarizes and evaluates the effects of the replacement of SBM with sources that are high in RUP on N fractions flowing to the duodenum, on DMI, and on milk yield and composition. CHARACTERIZATION OF PROTEIN SOURCES Common protein supplements that are high in RUP and are used in ruminant diets in the US are fish meal ( FM) , meat and bone meal ( MBM) , feather meal ( FtM) , blood meal ( BM) , corn gluten meal ( CGM) , distillers dried grains ( DDG) , DDG with solubles ( DDGS) , brewers dried grains ( BDG) , and brewers wet grains ( BWG) . These supplements have been discussed (31, 32, 37, 57, 71, 73) in terms of processing methods, AA profiles, and their potential to complement microbial protein in the intestine to simulate the AA profile of milk protein. Table 1 presents chemical scores of these protein sources in relation to milk protein. Table 2 calculates an EAA index, taking into account a utilization factor for each AA, and also lists the three most limiting EAA for each source from Table 1. These tables strongly suggest that microbial protein is the best available source of protein for milk synthesis. The second highest score was for SBM, which is considered to have a fairly good AA profile; FM was third highest and is an excellent source of Lys and Met. Schwab (100) pointed out the importance of both the amount and balance of EAA in duodenal digesta and proposed that protein sources should be compared for percentages of Lys and Met in relation to the amount of total EAA (Table 3). Assuming Lys and Met are the first two limiting AA for yields of milk and milk protein in most dairy diets (62, 101, 102) and that the ideal ratio of Lys to Met (as a percentage of total EAA) is 15:5 (100), then microbial protein has an excellent balance for these two EAA. Of the various protein supplements listed, only FM possesses a good balance of Lys and Met. Blood meal is high in Lys but low in Met. Such an imbalance might have a negative effect on the cow performance Journal of Dairy Science Vol. 81, No. 12, 1998

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SANTOS ET AL. TABLE 1. Extended chemical scores of protein sources in relationship to milk protein.1 Protein source

His

Phe

Leu

Thr

Met

Arg

Val

Ile

Trp

Lys

Blood meal Fish meal Feather meal Meat meal Meat and bone meal Corn gluten meal Alfalfa meal, dehydrated Brewers grain Distillers grains with solubles Soybean meal Microbes

100 77 11 67 64 67

100 69 59 65 64 100

93 58 66 46 46 100

86 68 59 59 59 60

45 100 23 49 49 100

33 59 32 76 76 36

70 59 38 51 48 48

10 47 32 36 36 40

76 71 29 39 32 30

91 80 13 58 55 18

69 56

100 100

55 83

80 65

60 78

50 53

66 65

51 74

100 87

46 34

74 89 90

84 100 97

72 56 54

63 74 100

81 56 97

42 89 79

53 60 66

38 55 61

45 75 99

24 70 100

1Adapted from Chandler ( 3 1 ) and calculated as follows: (percentage of AA in feed protein/ percentage of AA in milk protein) × 100. A score of 100 is the maximum allowed for each value.

in some situations. Corn gluten meal is an excellent source of Met but is low in Lys. Both DDG and BDG are low in Lys and average for Met; FtM is a poor source of both Lys and Met. The SBM and MBM are average in Lys and average to low in Met, but these sources do not present a serious imbalance in the ratio of Lys to Met, as occurs for BM and CGM. When SBM was replaced by high RUP supplements, microbial protein synthesis and flow to the duodenum decreased, and the flow of nonammonia nonmicrobial N ( NANMN) in the duodenum increased (36), but there was little change in the total protein flow to the duodenum. Because microbial protein is a better source of Lys and Met than are most high RUP supplements, one might not expect a benefit from the addition of such supplements, particularly if they lower microbial protein synthesis.

In summary, Schwab (100) suggested that an ideal ratio in duodenal digesta was 15:5 for Lys and Met, calculated as a percentage of the total EAA. Fish meal is the RUP source most likely to improve the balance of these two critical AA and to exert a positive effect on cow performance. EFFECTS OF PROTEIN SOURCES ON THE FLOW OF N FRACTIONS TO THE SI Soybean meal is the most common protein supplement in the US, and SBM has been used as the control supplement for most research trials; therefore, we summarized 15 metabolism trials (6, 24, 30, 34, 41, 63, 64, 67, 69, 74, 89, 110, 116, 121, 128) to evaluate the effects of replacing SBM with high RUP

TABLE 2. Essential AA (EAA) index and limiting AA as estimated by chemical score when compared with milk protein.1 Protein source

EAA Index

Blood meal Fish meal Feather meal Meat meal Meat and bone meal Corn gluten meal Alfalfa meal, dehydrated Brewers grain Distillers grains with solubles Soybean meal Microbes

60 68 34 53 51 52 65 67 54 71 82

Limiting amino acid2 Ile ( 1 0 ) Ile ( 4 7 ) His ( 1 1 ) Ile ( 3 6 ) Trp ( 3 2 ) Lys ( 1 8 ) Lys ( 4 6 ) Lys ( 3 4 ) Lys ( 2 4 ) Ile ( 5 5 ) Leu ( 8 4 )

Arg ( 3 3 ) Leu ( 5 8 ) Lys ( 1 3 ) Trp ( 3 9 ) Ile ( 3 6 ) Trp ( 3 0 ) Arg ( 5 0 ) Arg ( 5 3 ) Ile ( 3 8 ) Leu ( 5 6 ) Ile ( 6 1 )

Met ( 4 5 ) Val ( 5 9 ) Met ( 2 3 ) Leu ( 4 6 ) Leu ( 4 6 ) Arg ( 3 6 ) Ile ( 5 1 ) His ( 5 6 ) Arg ( 4 2 ) Met ( 5 6 ) Val ( 6 6 )

1Adapted from Chandler ( 3 1 ) and calculated as E = [(log of AA in feed protein)/(log of AA in milk protein)] × 100, where E = the 10 EAA. 2Listed in order of limitation. Number in parentheses is the chemical score for that AA from Table 1.

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supplements on the flow of N fractions to the SI (Table 4). There were 29 direct comparisons with SBM in these 15 trials, and the results of those comparisons follow. DMI and N Intake There were no statistically significant differences in DMI when SBM was replaced by the high RUP sources in any of the comparisons. Numerical values for DMI were consistently higher for cows fed SBM than for cows fed animal proteins (12 comparisons: 19.4 vs. 18.7 kg/d per cow); values also were higher for cows fed SBM than for those fed CGM or BDG (one comparison each; 17.9 vs. 16.9 kg/d per cow). Nitrogen intake was generally not affected by protein source. High RUP sources resulted in a numerical increase in N intake in 12 comparisons and a decrease in 13 comparisons. Flow to the SI Microbial N. Microbial N flow to the SI was significantly decreased by high RUP sources in 10 comparisons (Table 4 ) and was numerically higher for SBM in 25 of the 27 comparisons, suggesting that, when high RUP sources replaced SBM, a shortage of RDP might have limited microbial synthesis. Mean microbial N flow to the duodenum for the 27 comparisons was 275 g/d for SBM and 240 g/d for sources high in RUP.

TABLE 3. The Lys and Met contents of microbial protein and protein supplements compared with milk.1 Item Milk Bacteria Protein supplement Blood meal Brewers dried grains Corn gluten meal Corn DDG3 + solubles DDG + solubles Feather meal Fish meal (Menhaden) Meat and bone meal 45% CP 50% CP Soybean meal (solvent) Expeller soybean meal 1Adapted

Lys

EAA2

( % of total EAA) 16.4 5.1 15.9 5.2

( % of CP) 38.4 33.1

17.5 6.7 3.8 5.9 6.5 3.9 16.9

2.5 4.5 7.2 5.9 3.7 2.1 6.5

49.4 46.3 44.2 37.7 43.3 31.4 44.8

12.4 14.2 13.8 13.0

3.0 3.7 3.1 2.9

39.4 36.6 47.6 49.6

from Schwab (100). AA. 3Distillers dried grains. 2Essential

Met

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NANMN. The flow of NANMN to the SI was significantly increased by high RUP sources in 9 comparisons but was numerically higher for 24 comparisons, averaging 208 g/d for SBM versus 255 g/d for diets containing high RUP supplements. Hence, supplementation of high RUP sources effectively increased NANMN flow to the SI. NAN. The NAN flow, the sum of microbial N flow plus NANMN flow, should equal total N flow as protein to the duodenum. When high RUP sources are fed, an increase in protein flow to the SI of the dairy cow has been assumed; however, of the 24 comparisons that are summarized in Table 4, NAN (or total protein) flow was significantly increased in 5 and decreased in 1; no occurred change in 18. Mean NAN flow for the 20 comparisons was 480 g/d for SBM and 490 g/d for high RUP sources. The lack of an overall increase in NAN flow when high RUP sources replaced SBM was due to decreased microbial N flow that balanced the increase in NANMN flow. Microbial protein appears to have an AA profile that is favorable for milk protein synthesis (31, 73, 84, 100), but many high RUP sources, as mentioned previously, are inferior to microbial protein in terms of EAA index (31, 73, 84) or Lys and Met content (100). Hence, replacement of SBM with these high RUP sources would decrease microbial protein synthesis and the availability of Lys and Met. EAA Flow. The flow of EAA to the duodenum was generally not affected by replacement of high RUP sources for SBM; only 5 of 25 comparisons showed a significant increase (Table 4). Mean EAA flow was 1122 g/d for SBM and 1177 g/d for the high RUP sources. Two of the 5 comparisons that had increased EAA flow were with FtM, a poor source of EAA. Moreover, FtM, BM, and MBM are all lower in intestinal digestibility (<80%) than is SBM (>90%) (46, 100). Lys and Met. The flows of Lys and Met to the duodenum were not significantly increased by high RUP supplementation. Of 26 comparisons, Lys flow was increased significantly in 2 and decreased in 1 (Table 4). The two positive effects on Lys flow were observed for combinations of MBM, CGM, BM, FtM, and FM (34). The principal components of these supplements were BM and FM, which are high in Lys. A negative effect on Lys flow was observed for CGM, which is low in Lys (64). Mean Lys flow was 167 g/d for the high RUP comparisons and 157 g/d for SBM. For the 26 high RUP comparisons, Met flow was increased significantly in only 1 comparison [when FM was supplemented (128)]. In 2 comparisons, net Journal of Dairy Science Vol. 81, No. 12, 1998

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TABLE 4. Effect of protein source on N fractions flowing to the small intestine (SI). Intestinal absorption Diet

Protein source1

CP ( % of DM)

15.8 24.8 43.8 12.80 10.24 15.6 6.8 17.9 12.9 9.12 7.13 4.16 3.12 9.3 4.0 4.0 17 17 17 16 20

(%) 18.1 17.8 13.8 13.1 17.1 14.5 14.5 14.7 14.2 15.5 15.4 15 14.5 14.9 14.9 17.8 18.1

NI3

( % of CP) (g/d) 40 NS 40 NS 57 310 57 270 77 340 45 NS 45 NS 50 386 >50 382 56 432 56 408 30 544 30 567 14 483 14 504 33 725 33 686

Mic

N4

NANMN

NAN

219 214 120 120 100 361 316 273 256 216a 164b 294a 259b 310a 282b 340a 284b

351b 371a 140 190 180 148 183 103 170 149b 214a 372 373 289 307 335 343

570 585 260 310 280 510 505 376 426 365 378 666 632 599 589 675 627

EAA

Lys

Met

519 543 1726 1632 1478 1492 1560 1395

206 206 76 61 58 184a 155b 112.4 116.1 78 90 234 246 229 228 185 164

35 32 17.1 18.1 20.3 48 54 28.6 42.8 29b 35a 81 83 68 71 58 52

(g/d) 1346 1390 560 507 550 1217 1259

Duodenal Lys:Met

EAA

( % of EAA) 15.3:2.6 14.8:2.3 13.5:3.1 12.0:3.1 10.6:3.7 15.1:3.9 12.3:4.3

Lys

Met

Reference

(g/d) (69) (6)

(63) (89)

15.0:5.6 16.6:6.4 13.6:4.7 15.1:5.1 15.5:4.6 15.3:4.8 11.9:3.7 11.8:3.7

(128) (74)

(64)

16.5 17.2 16.3 15.5 15.0

52 50 52 50 50

443b 469a 445b 385 371

363a 273b 273b 364 333

130b 207a 207a 105ab 75b

493 480 480 469a 408b

1053 1115 1147 995ab 932b

145 229 201 152 139

31 34 34 38a 32b

13.8:2.9 20.5:3.0 17.5:3.0 15.3:3.8 14.9:3.4

847 864 888 714bc 665c

122 196 167 117ab 107b

24 25 23 33a 28b

19

15.2

50

373

332

127ab

459ab

1015a

148

39a

14.6:3.8

770ab

115ab

35a

19 17 9.60 9.80 4.85 4.85 5.99

15.3 16.2 15.8 16.3 16.0

50 50 50 50 50

383 419 364 412 389

326 192a 128b 152ab 126b

153a 196b 207ab 278a 246ab

479a 388ab 335b 430a 372ab

1030a 994b 1020b 1161a 1162a

154 149 159 138 144

32b 62 51 60 59

15.0:3.1 15.0:6.2 15.6:5.0 11.9:5.2 12.4:5.0

803a 753b 820ab 808ab 898a

122a 117ab 134a 97b 117ab

28b 44 36 36 39

16.6

21.3

576

238

374b

611b

1509c

200c

64

13.3:3.8

5.31 10.13

16.2 19.9

27.5 30.1

522 659

290 272

387ab 365b

677a 637b

1619b 1618b

217b 222b

61 65

13.4:3.8 13.7:4.0

9.06

19.2

39.2

611

182

576a

757a

1970a

264a

73

13.4:3.7

(121)

(110)

(116)

(34)

SANTOS ET AL.

SBM Lig SBM SBM BDG BDG SBM CGM SBM CGM SBM FM SBM + Corn FM + Corn SBM + Barley FM + Barley SBM SBM FM SBM XL-SBM Lig SBM SBM WSB Ext WSB, 132°C Ext WSB, 149°C SBM BM FtM BM FM SBM MM, CGM, BM, FtM, FM SBM MM, CGM, BM, FtM, FM

Flow to SI of SP2

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flow decreased (67, 110) and, in 23 comparisons, was not affected. The mean Met flow was 50 g/d for SBM and 48 g/d for high RUP diets. EAA Absorbed from the SI

jds 7458 Table 4

In 11 comparisons from 4 trials (Table 4), EAA absorption was significantly higher with supplemental high RUP sources than with SBM in 3 comparisons; however, EAA absorption was numerically higher in 8 comparisons. The mean values were 811 g/d for high RUP sources and 759 g/d for SBM. The higher EAA flow for diets supplemented with FtM was enough to counterbalance a lower EAA digestibility, resulting in greater EAA absorption by the SI for FtM than for SBM diets (116). The SI digestibility of EAA for BM diets tended to be higher than for SBM diets (116). The replacement of SBM with high RUP sources did not significantly increase the absorption of Lys in 9 of 11 comparisons. The numerical average for absorbed Lys was 115 g/d for SBM and 128 g/d for the high RUP diets. Most of this difference was due to large increases in 1 experiment (121) comparing normal SBM with SBM treated with xylose or lignosulfate. No increase in Met absorption was observed when high RUP sources replaced SBM in 7 of 11 comparisons, and there was a negative effect in 3 comparisons. The mean values for Met absorption were 37 g/d for SBM and 33 g/d for the high RUP sources. In summary, flow and absorption of the first two limiting AA (Lys and Met) for milk and milk protein synthesis (100) were not consistently increased by supplemental high RUP sources. Schwab (100) and Rulquin and Verite´ ( 9 3 ) suggested that the balance of Lys and Met in relation to EAA in duodenal digesta is a better predictor of AA adequacy than are absolute flows to the SI. A 15:5 ratio of Lys to Met (as percentage of the total EAA) in duodenal digesta was proposed by those researchers. Ratios of Lys to Met were calculated from values of duodenal flows for these AA and are in Table 4. The FtM diet, despite a positive effect on total EAA flow, had a poor balance of Lys to Met (116). Even when combined with BM, FtM negatively affected this balance. Imbalanced proteins such as CGM ( 6 4 ) and BDG ( 6 ) , which are low in Lys and high in Met, resulted in a poor Lys-Met balance because Lys flow was lower than in SBM diets. Despite an imbalance, BM promotes an adequate balance of these AA in duodenal digesta (46, 116). High RUP soy protein did not increase the proportions of either Lys or Met in the duodenum compared with those of SBM (41, 67). Journal of Dairy Science Vol. 81, No. 12, 1998

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TABLE 5. Summary of studies comparing soybean meal (SBM) with various protein sources high in RUP. Performance variable2 High RUP source1 SBM vs. Treated SBM HSBM or CTSBM

Exp SBM Exp SBM Subtotal SBM vs. FM or SFM FM

FM + SBM

SFM Subtotal SBM vs. ABP BM; BM + SBM BM + DDGS MBM; MBM + SBM Blend ABP; Blend of ABP + CGM Subtotal SBM vs. AVPB Subtotal SBM vs. BDG or BWG BDG BWG BWG + SBM BDG + SBM Subtotal

Milk

FCM

Fat percentage

–

0

+

–

0

+

0

16

4

0

14

1

0 0 0

4 3 23

0 2 6

0 0 0

4 5 23

0 0

3 3

3 0

0 0

0 0 0

1 7 1

1 0 0

0 0 0 0

4 2 3 24

CS; CS + AS; AS

1

CS + AS CS; AH; CS + AS CS; CS + AS; AS; CS + AH

CS + AS CS + AH WS or GS CS + HCS CS + AS AS > 50%

CS or GS >30 kg of milk/d <30 kg of milk/d CS; GH or GS >30 kg of milk/d <30 kg of milk/d AS (50% diet DM) >30 kg of milk/d AS or AH >30 kg of milk/d <30 kg of milk/d BrS (40–45%)

CS + AS CS + AH CS + AS CS CS

–

0

+

1

19

1

0 0 1

0 0 0

4 5 28

5 1

0 0

2 2

0 1 0

1 5 1

0 0 0

2 1 1 8

0 0 1 2

2 2 0 17

5

0

0

0

3

1

1 0

10 11

2

Protein percentage –

0

+

4

16

0

0 0 1

2 2 8

2 3 21

0 0 0

1 1

1 0

0 0

6 3

0 0

0 7 0

1 0 1

0 0 0

0 3 0

1 3 1

0 1 0

3 1 0 4

0 1 4 16

5 2 0 11

0 0 0 1

1 0 0 4

2 1 1 21

2 2 0 5

4

0

1

5

0

1

5

0

0

3

0

1

3

0

2

2

0

0 0

0 0

9 9

0 1

1 0

9 9

0 2

3 2

7 8

0 1

29

1

0

25

1

3

26

2

8

22

1

0

6

3

0

7

1

1

6

1

0

8

0

0 0

2 4

1 0

0 0

2 4

0 0

1 0

2 4

0 0

0 0

3 3

0 0

0 0 0

0 0 6

1 1 3

0 0 0

1 1 7

0 0 1

0 0 1

1 1 6

0 0 1

0 0 0

1 1 8

0 0 0

SANTOS ET AL.

FM

Forage in diet and milk yield

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Blends of meat meal, CGM, BM, FtM, and FM increased total flows of EAA and Lys to the SI but did not improve the balance of Lys to Met from that occurring with SBM (34). When supplied as >4% of diet DM, FM consistently increased the proportion of Lys in EAA flowing to the duodenum compared with SBM (67, 74, 128), but not when supplied at <4% of diet DM (63, 74). Also, FM had a positive effect on the proportion of Met in total EAA of duodenal digesta in 3 of 5 comparisons (63, 67, 74, 128). Thus, with the addition of FM, the ratio of Lys to Met at the duodenum, as a percentage of total EAA, was close to that recommended by Rulquin and Verite´ ( 9 3 ) and Schwab (100). Conclusion of Metabolism Trials

jds7458 Table 5

Most of the high RUP sources that are commercially available present an AA profile that is inferior to microbial protein. Hence, consistent benefits were not observed in the flow to the duodenum of EAA, Lys, or Met or in the ratio of Lys to Met when most high RUP sources replaced SBM. This lack of benefit was associated with greater flows of microbial protein for diets containing SBM than for those high in RUP. Supplementation of FM consistently provided a good balance of Lys and Met in duodenal digesta measured as a percentage of the total EAA. EFFECTS OF PROTEIN SOURCES ON MILK YIELD AND COMPOSITION There were 127 comparisons from 88 lactation trials published from 1985 to 1997, which were summarized to compare the effects on DMI, milk yield, and milk composition from total or partial replacement of SBM with high RUP supplements. Only comparisons with at least 3 cows per treatment were considered, and the 15 metabolism trials already discussed were not included in the lactation summaries. The high RUP sources that were compared with SBM were CGM, DDG, DDGS, BDG, BWG, heated SBM ( HSBM) , formaldehyde-treated SBM, specially processed SBM, lignosulfonate SBM (heated with sulfite liquor and xylose; LigSBM) , NaOH-treated SBM, expeller SBM ( ExpSBM) , FM, salmon FM, BM, FtM, MBM, and animal by-products ( ABP; includes combinations of BM, FtM, MBM, or FM). Treatments that included formaldehyde-treated SBM, specially processed SBM, LigSBM, and NaOH-treated SBM are combined into the category of chemically treated SBM. Table 5 summarizes the number of studies showing significantly negative, significantly positive, or no response in yields of milk and FCM and in percentages of fat and protein in milk. Journal of Dairy Science Vol. 81, No. 12, 1998

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SBM Versus Soy Protein Modified to Result in High RUP SBM versus HSBM or roasted soybeans. Seven comparisons from 5 trials (61, 83, 99, 115, 118) that are summarized in Table 5 show that DMI was not affected by these protein sources. Compared with SBM, HSBM significantly increased milk yield but decreased milk protein percentage in 2 of 5 comparisons. Mean values for milk yield were 34.7 kg/d for SBM and 35.9 kg/d for HSBM. When HSBM was blended with FM and CGM, the milk protein percentage increased (118). Roasted soybeans decreased DMI and milk protein percentage in 2 comparisons (83). Milk yield was not affected significantly by roasting of soybeans and averaged 39.6 kg for SBM versus 38.6 for roasted soybeans. SBM versus chemically treated SBM. Thirteen comparisons from 9 trials (8, 10, 17, 39, 41, 60, 66, 76, 105) were summarized comparing SBM with specially processed SBM, LigSBM, NaOH-treated SBM, or formaldehyde-treated SBM (Table 5). Increased RUP in the diet from these sources did not affect mean DMI, milk yield, or milk protein compared with those from SBM. These sources of treated SBM increased milk yields in 2 ( 8 ) of the 13 comparisons and increased DMI in 2 of the comparisons (10). Mean milk yield for 8 comparisons in which milk yield was >30 kg/d was 34.9 kg for SBM and 35.5 kg for the chemically treated SBM treatments. When LigSBM ( 7 6 ) was supplemented for half of the SBM, milk yield was not affected; however, the absence of a control SBM diet with 13% CP did not permit a valid comparison between SBM and LigSBM. SBM versus ExpSBM. Eight comparisons from 8 trials (18, 21, 50, 53, 112) compared SBM with ExpSBM for milk yield and composition. When corn silage was the major forage (18), there was no difference between SBM and ExpSBM for DMI and milk yield. The ExpSBM decreased the percentage of milk protein in 4 of the 8 comparisons. When alfalfa silage was fed at 30 to 58% of diet DM (21, 50, 53, 112), ExpSBM was significantly superior to SBM for milk yield in 2 of 5 comparisons. Mean milk yield was 33.0 for cows receiving diets that were supplemented with SBM and 33.3 kg/d for cows that were fed ExpSBM. In conclusion, comparison of SBM with high RUP supplements from soy protein showed that increasing RUP of SBM by heating or chemical treatment of SBM significantly increased milk yield in 6 of the 29 comparisons but decreased protein percentage in 8 of the 29 comparisons. Diets that were high in alfalfa silage (and also high in RDP) seemed to respond more favorably to RUP than to energy supplementaJournal of Dairy Science Vol. 81, No. 12, 1998

tion (23, 43, 44). Mean milk yield was 35.2 for all cows fed SBM, and 36.0 kg/d for cows fed soy protein treated for a high RUP. SBM Versus FM Thirty-two comparisons of SBM and FM from 21 lactation trials were summarized (2, 7, 15, 19, 22, 25, 38, 45, 49, 59, 72, 82, 85, 96, 104, 105, 108, 119, 120, 123, 124). Menhaden FM was used in 28 comparisons, and salmon FM was used in 4. Data were categorized according to milk yield ( > or < 30 kg/d) and forage source (Table 5). Intake of DM was not significantly different between cows fed SBM and Menhaden FM. However, in several comparisons, DMI of FM diets was numerically lower than that of SBM diets. Salmon FM decreased the DMI when fed at >5% of the diet DM. This negative effect of salmon FM is probably because of its high content of unsaturated fat. Milk yield was significantly increased by FM in 8 of the 32 comparisons. Cows yielding >30 kg/d milk benefitted more from FM supplementation. Milk fat percentage was significantly decreased by FM in 16 of 28 comparisons. Most of the negative effects of FM on fat percentage were observed in cows yielding <30 kg/d or those receiving salmon FM. Milk protein percentages were not consistently affected by FM supplementation, but cows yielding <30 kg/d of milk tended to decrease milk protein percentages on FM. Cows fed diets of alfalfa silage showed greater increases in milk protein percentage when fed FM than did cows fed other forages, perhaps because such diets are generally lower in EAA flow to the duodenum. In conclusion, replacement of SBM with Menhaden FM beneficially affected cows yielding >30 kg/d of milk in 6 of 14 comparisons. Mean milk yield was 36.3 kg/d for cows yielding >30 kg/d supplemented with Menhaden FM and 35.1 kg/d for cows fed diets supplemented with SBM. SBM Versus ABP Eight comparisons from 5 trials (5, 83, 92, 95, 113) in which BM or BM and DDGS replaced part of the SBM in corn silage or alfalfa silage diets showed essentially no change in DMI, milk yield, or milk protein content (Table 5). Mean values for milk yield were 35.1 kg/d for cows fed SBM diets and 34.5 kg/d for the cows fed BM or BM and DDGS diets. Three comparisons from 3 trials (2, 14, 20) using diets based on corn silage plus alfalfa tested MBM as a partial or complete replacement for SBM and showed no differences in DMI or milk yield; MBM

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

significantly increased DMI and milk yield in 1 comparison. Milk protein percentage decreased significantly in 2 of the 4 comparisons. Decreased percentage of milk protein might be the result of an inferior AA profile in duodenal digesta because MBM is lower in EAA than is SBM. The MBM diets also would tend to support less microbial protein synthesis in the rumen because of their higher RUP content. Milk yield tended to be numerically higher for MBM (33.0 k/d) than for SBM (32.0 kg/d). Some studies compared blends of ABP (MBM, BM, and FtM). At times, meat meal and FM were also included. No difference in DMI was observed in 8 of 11 comparisons from 8 trials (11, 45, 65, 70, 72, 81, 107, 117), and DMI decreased in 3 comparisons when a blend of ABP replaced SBM. Milk yield was not affected in 10 comparisons and tended to decrease in 1, but milk protein percentage was decreased in 3 comparisons and not affected in 7. Mean values for milk yield for trials with cows averaging >30 kg/d were 36.3 kg for SBM and 35.3 kg/d for blends of ABP. Eleven comparisons from 8 trials (35, 42, 50, 68, 85, 90, 122) in which a combination of single sources or blends of ABP plus CGM replaced SBM showed no difference in DMI and milk yield, nor was milk protein percentage affected in 8 comparisons, although it increased in 1 and decreased in 2 comparisons. Mean milk yield for cows that yielded >30 kg/d was 35.2 kg/ d for cows fed diets supplemented with SBM and 35.0 for cows fed diets supplemented with ABP plus CGM. In summary, these 32 comparisons showed no net benefit in milk yield (35.6 vs. 35.1) or milk protein percentage by replacement of part or all of the SBM with only 1 type of ABP, blends of ABP, or combinations of ABP plus CGM. Negative effects on milk yield and protein percentages were more frequent than were positive effects. SBM Versus Brewers Grains or Distillers Grains In 7 comparisons in which brewers grains (BDG or BWG) were substituted for SBM (13, 52, 58, 103), with similar ratios of forage to concentrate, milk yield increased in only 1 (Table 5). Milk protein percentage was not affected by brewers grains; however, DMI was lower for diets containing brewers grains in 2 comparisons (58), resulting in higher feed efficiencies. The mean milk yield of cows was 31.0 kg/d for SBM and 31.7 kg/d for brewers grains when ratios of forage to concentrate were similar (13); however, in 2 comparisons (40, 87) in which BDG significantly increased DMI and milk yield, the forage:concentrate

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ratio was lower for the diets containing brewers grains than for SBM diets [36:64 vs. 63:37 (87); and 42:58 vs. 50:50 (40)], making data difficult to interpret for effects of RUP. Eight comparisons of SBM, DDG, DDGS, or a combination of DDGS and CGM from 6 trials (5, 21, 75, 80, 115) were summarized (Table 5). When DDG or DDGS partially or totally replaced SBM and consisted of 13.5 to 19.2% of diet DM (5, 75, 80), DMI was significantly increased by DDG or DDGS in 2 of 4 comparisons and was numerically higher in all 4. Milk yield also was significantly increased by distillers grains in 2 of the 4 comparisons, but milk protein percentage was significantly decreased in 2 and numerically lower in all 4. When DDGS was supplemented at about 36% of diet DM (80), DMI, milk yield, and milk protein percentage were all significantly lower than for diets with 21% SBM. In 3 comparisons (21, 115), DDG or DDGS were combined with CGM as a replacement for SBM; DMI, milk yield, and milk protein percentage were significantly decreased in 1 comparison and not affected in 2. The negative effect was noted on a high corn silage diet (56% of diet DM), which might be attributable to the low Lys content of the basal diet and of the DDGS and CGM. When alfalfa silage partially (115) or totally replaced corn silage (21), the negative effect of distillers grain plus CGM was attenuated. Even though data from a Florida study ( 8 8 ) are presented in Appendix Table A5, those data were not used in summaries on distillers grain because of the different types of DDGS that were compared and because of other variables in the experiment that made interpretation difficult. The mean milk yields for 10 comparisons of DDGS with SBM controls were 27.0 kg/d for SBM and 27.6 kg/d for DDGS; none was significantly different. In conclusion, high amounts of distillers grain (36% of diet DM) or combinations of distillers grain with CGM generally decreased milk yields. Milk protein percentages were significantly decreased by distillers grain or distillers grain plus CGM compared with SBM in half the comparisons and numerically lower in 7 of 8 comparisons. Milk protein synthesis is sensitive to the EAA profile of duodenal digesta (100, 101, 102). The poor EAA profile of distillers grain and CGM, especially for Lys, and a shortage of RDP to support microbial protein synthesis might explain their negative effects on milk protein percentages. SBM Versus CGM Seventeen comparisons of SBM with CGM from 12 studies (3, 4, 15, 40, 51, 54, 61, 79, 86, 91, 111, 123) Journal of Dairy Science Vol. 81, No. 12, 1998

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were summarized (Table 5). Data were compared on the basis of the type of forage and other protein sources in diets. In 5 comparisons (54, 86, 123) in which CGM totally replaced SBM in diets based on corn silage, DMI significantly decreased for cows fed CGM in 2 comparisons and was numerically lower in the other 3 comparisons. Milk yield was significantly decreased for cows that were fed CGM in 3 comparisons and averaged 34.1 kg/d for SBM versus 31.0 kg/d for CGM diets. Milk protein percentages significantly decreased on CGM in 2 comparisons, and milk fat percentage was increased on CGM in 2 comparisons. In 6 comparisons in which SBM was replaced by a mixture of CGM and soy protein (3, 4, 40, 61, 79, 91), there were no significant differences in DMI and milk yield, regardless of forage source. The mean milk yield was 35.0 for SBM diets and 34.8 for those diets with CGM plus soy protein. When CGM replaced SBM in alfalfa-based diets in the 6 comparisons (15, 51, 91, 111), there were no differences in DMI or milk protein percentage; milk yield was not changed in 4 comparisons, decreased in 1, and increased in 1. Mean milk yields were 30.3 kg/ d for SBM and 30.3 kg/d for cows fed CGM with alfalfa silage or hay. In conclusion, increasing RUP in the diet by totally replacing SBM with CGM had a negative effect on the performance of cows that were fed diets based on corn silage, probably because of low Lys in CGM and corn silage. Although only 4 experiments support the decrease, 1 ( 8 6 ) was a large, six-university study involving about 300 cows. Supplementation of CGM in diets containing alfalfa silage or alfalfa hay did not alter cow performance compared with supplemental SBM. Effect of SBM Versus Blends of Several Protein Sources on AA Flow to the Duodenum and Cow Performance It has been suggested that combining protein sources with different AA profiles to obtain a com-

plementary effect on the dietary EAA profile might improve performance of cows. Already summarized in this report are many comparisons in which SBM alone was compared with blends of at least 2 protein sources. A blend of FM plus SBM ( 6 3 ) did not increase the duodenal flow of NAN, EAA, Lys, and Met compared with SBM alone. When BM plus FtM replaced SBM, the duodenal flow of EAA was increased, but the flow of Lys and Met did not change, resulting in a negative effect on the ratio of Lys to Met as percentage of total EAA in the duodenal digesta (116). In 2 comparisons ( 3 4 ) in which a blend of BM, FM, FtM, meat meal, plus CGM replaced SBM, duodenal flow of NAN, EAA, and Lys were increased, but the balance of Lys and Met did not improve. Also summarized were 39 comparisons (Table 5 ) of SBM with a blend of at least 2 protein sources for milk yield and composition. Milk yield was not affected in 32 comparisons, but decreased in 3 and increased in 4. Milk protein percentage did not change in 30 comparisons, increased in 1, and decreased in 7. Thus, no consistent benefits in milk yield or milk protein percentages were obtained by replacing SBM with a blend of protein sources higher in RUP. High Quality (FM) Versus Low Quality (CGM) Protein Assuming Lys and Met are the first- and secondlimiting AA for diets in high producing cows, as has been proposed by Schwab (100) Schwab et al. (101, 102), and King et al. (62), FM might be classified as a high quality protein source and CGM as a low quality source. In 9 comparisons (15, 16, 33, 109, 123, 126) in which FM or a combination of FM and other sources were compared directly with CGM (Appendix Table A7), DMI was lower on FM in 1 comparison and was not significantly affected in 8, but milk yields on FM

TABLE 6. Summary of studies comparing fish meal ( F M ) and corn gluten meal (CGM) or urea and various protein supplements. Performance variable1 Milk Protein source FM vs. CGM Urea vs. protein 1Effect

– 0 3

Fat percentage

FCM 0 4 20

+ 5 0

– 1 7

0 2 14

+ 2 0

– 6 1

0 3 22

Protein percentage + 0 0

was significantly negative ( – ) , not different ( 0 ) , or positive (+).

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– 1 1

0 8 17

+ 0 5

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increased in 5 (Table 6). Greater milk increases occurred in trials with higher yield averages. When cows yielded >30 kg/d of milk (16, 33, 123, 126), the mean milk yields were 33.7 kg/d for cows fed FM and 30.5 kg/d for cows fed CGM. Milk fat percentages were lower for most FM comparisons, and milk protein percentages were not different. These data clearly show that diets of similar RUP can affect cow performance differently. The differences are probably related to the EAA profile of the RUP sources. A commercial blend of protein supplements composed of BM, FM, MBM, FtM, plus ruminally protected Met (Pro-Lak, animal-marine protein blend; H. J. Baker & Bros., Inc., New York, NY) was developed by Mantysaari et al. ( 7 3 ) and Chandler (31, 32) with the objective of obtaining a protein mixture that was high in RUP with an AA profile balanced to complement rumen microbial protein. A large field study ( 4 7 ) involving 35 dairies and over 5500 dairy cows was coordinated by 5 university investigators in the US. Inclusion of this blend of RUP sources to replace the normal dietary supplement on an isonitrogenous basis increased milk yield in 19 herds, had no effect in 11, and showed decreases in 5. The mean increase in milk yield was 1.2 kg/d higher for cows that received the high RUP blend than for cows that received the normal protein supplements in the various herds.

Increased RDP in the Diet from Urea Supplementation Based on the proposed hypotheses of NRC (77, 78) regarding benefits of increasing RUP in the diet, the partial replacement of protein with urea for high yielding dairy cows would often have a negative impact on the performance of cows because of a lower than recommended (77, 78) RUP content of the diets. Twenty-three comparisons (Table 6 ) were summarized from 12 reports (10, 11, 18, 20, 26, 27, 28, 58, 65, 117, 119, 127) in which urea was added at 0.4 to 1.8% of diet DM. The urea partially or totally replaced SBM, BWG, ExpSBM, SBM plus FM, or ABP in diets (Table 6). The data show that DMI did not change with urea supplementation in 17 comparisons, increased in 2, and decreased in 5 (Appendix Table A8). Milk yield was not affected by urea supplementation in 20 comparisons and decreased in 3. In 1 of the comparisons ( 2 0 ) in which milk yield decreased, the diet contained 27% of the DM as high moisture alfalfa silage, and urea was supplemented at 1.8% of diet DM. The high RDP content of the silage probably made it unsuitable for such a large addition of urea. Production of FCM was not changed by urea supplementation in 14 comparisons but decreased in 6. Milk protein percentage was not affected by urea

TABLE 7. Comparison of milk yields of cows fed soybean meal (SBM), a high RUP supplement, or RUP of differing protein quality. RUP Source1

Cows

SBM3

(no.) 641

FM

662

ABP

725

BG and DG

334

CGM

297

FM vs. CGM

156

With or without blocks2

Treatment milk SBM

+ – + – + – + – + – + –

34.23 34.23 31.27 31.27 34.07 34.04 31.45 31.45 33.15 33.15 29.094 29.094

High RUP

P <

34.91 35.27 32.09 31.96 33.76 33.94 31.76 30.78 32.41 32.32 28.015 28.015

0.032 0.259 0.010 0.648 0.343 0.661 0.341 0.644 0.124 0.550 0.016 0.661

(kg/d)

1ABP = Animal by-product protein, BG = brewers grains, CGM = corn gluten meal, DG = distillers grains, and FM = fish meal. 2Each block was a single comparison within each RUP source; hence, variance between each block was removed from the error term in statistical analyses of data. The number of comparisons for each RUP source was SBM (chemical and heat treated), 27; FM, 26; ABP, 26; BG and DG, 18; CGM, 15; and FM vs. CGM, 7. 3Chemically treated or heat treated. 4FM. 5CGM.

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supplementation in 17 comparisons, increased in 5, and decreased in 1. Mean milk yield for cows that were fed a diet supplemented with urea was 32.7 kg/d versus 33.3 kg/d for cows that were fed control diets. In conclusion, decreasing RUP in diets in which SBM, ExpSBM, BWG, or ABP were the protein supplements, by replacing part or all of these supplements with urea, did not decrease milk yield in 20 of 23 comparisons and increased milk protein percentage in 5 of 23 comparisons. As mentioned, FCM decreased in 6 of 20 comparisons when supplemental urea was fed. In 2 of these comparisons, barley was the grain source (27, 28); in 3 comparisons, alfalfa silage was fed at about 28% of diet DM (18, 20) and was incorporated at up to 1.8% of diet DM (18, 20). These negative effects of urea on FCM might be explained by excessive RDP coming from the barley and alfalfa silage in addition to incorporation of excessive urea. Summary of Lactation Studies In 127 comparisons from 88 lactation trials published from 1985 to 1997, an increase in RUP by FM or treated SBM had a slightly beneficial effect on milk yield ( ∼0.7 kg/d), which was significant ( P < 0.05) when variations because of comparisons within a single RUP source were removed (Table 7). Menhaden FM was the high RUP source that most frequently increased milk yield over that of SBM controls; treated SBM was next highest. Cows yielding >30 kg/ d of milk responded more favorably to FM than did cows with lower yields. More negative than positive effects on milk yield were observed when CGM replaced SBM in substantial amounts, particularly in corn silage diets. Other high RUP supplements did not consistently affect cow performance. Milk fat percentages were more frequently depressed by FM than by other supplements high in RUP, and protein percentages seemed to be affected equally by animal and vegetable protein supplements. When a high quality RUP source, such as FM, replaced a low quality source, there was often an increase in milk yield, confirming that dietary protein quality is the major factor in determining whether RUP improves lactational performance. Dietary RUP decreases with urea did not negatively affect milk yield in most comparisons, but positively affected milk protein percentages in some trials. EVALUATION OF THE RDP-RUP SYSTEM FOR PREDICTING PROTEIN NEEDS OF LACTATING DAIRY COWS From the data presented in this paper, several inherent weaknesses have been demonstrated for the Journal of Dairy Science Vol. 81, No. 12, 1998

RDP-RUP system as described in the current Nutrient Requirements for Dairy Cattle (77, 78); these weaknesses have contributed to the failure of the system to predict lactational performance accurately and include the following: 1. Decreased microbial protein production when diets rich in RUP are fed. Current recommendations for furnishing the needs of the rumen microbial population (36, 94) should preclude such an effect and should necessarily be incorporated into any future recommendations. 2. A lack of consideration of requirements for limiting AA for synthesis of milk protein, tissue protein, and other protein needs of the animal. Within this review, a number of articles (31, 32, 36, 55, 84, 98, 100, 101, 102) dealing with AA requirements for milk yield have been mentioned. Even though considerably more research is needed to delineate clearly the AA needs during lactation, many established findings were not available when the currently used NRC (77, 78) was prepared, but might be used to refine future recommendations. 3. No consideration is given to the changes in the AA composition of the protein exiting the rumen for absorption in the SI when the various RUP sources are fed. The assumption that the AA profile of the original RUP supplement is the same as that escaping rumen degradation might not always be true ( 6 2 ) and needs further investigation. However, in the review of Clark et al. (36), it was concluded that AA profiles in duodenal digesta generally reflected that of the RUP supplement when 35% or more of the total dietary CP came from that source. 4. Other important factors affecting the protein requirements for lactation, but not considered in the current NRC (77, 78), were the differential efficiency of absorption of essential AA in the SI, the use of essential AA by gut and liver tissues prior to being released for mammary uptake, and the efficiency of mammary use of essential AA for milk protein synthesis. Few data are presently available with respect to these latter factors, but useful estimates can be made by modeling from data in the literature and by use of the postabsorptive data currently being generated. Pertaining to the usefulness and accuracy of the Cornell system (48, 94, 106) for predicting lactation

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

requirements, Wu et al. (125) employed that system to evaluate absorbable AA for milk and milk protein yield in 5 previous experiments with cows that were fed diets based on corn. The database came from 29 treatment means for milk yields using 367 cows. Overall conclusions were that the Cornell system was moderately predictive for milk yields from absorbed AA and explained differences in some, but not all, experiments. Generally, milk yields were overpredicted by the Cornell system. A computer evaluation of the Cornell system (48, 94, 106) by us revealed a lack of agreement with known experimental results in predicting lactational performance when various RUP sources were added in dairy diets. Diets were formulated for cows that were 90 DIM and 650 kg of BW. Cows were consuming 23.7 kg of DM/d and yielding 45 kg of milk/d. Diets contained alfalfa hay, alfalfa silage plus corn silage, or only corn silage as the only forage sources; ground corn, whole cottonseed, and tallow were major ingredients. Supplemental protein was derived from SBM, BM plus SBM, FM, or CGM, and each source furnished isonitrogenous amounts within all forage sources. The metabolizable energy that was available for milk was essentially equal for all diets containing the different protein supplements, but the high RUP supplements all predicted higher metabolizable protein available for milk, regardless of forage source. Using metabolizable protein available for milk as the predictor, the mean advantage in predicted milk yield between SBM and the high RUP supplements (BM plus SBM, FM, and CGM) was 4.8 kg/d; little difference was found between the high RUP sources. As mentioned in this review, there was little benefit from increasing the RUP in lactation diets, so we conclude that the Cornell Net Carbohydrate and Protein System grossly overestimates the value of protein supplements high in RUP compared with SBM controls. Moreover, the Cornell system (48, 94, 106) predicted a significantly higher metabolizable protein flow to the duodenum for diets high in RUP and did not account for a decrease in microbial protein flow from the rumen to the duodenum when RUP replaced RDP in diets, as was demonstrated in this review. Even though we regard the Cornell Net Carbohydrate and Protein System as a first step in the development of a dynamic model for prediction of the protein needs of lactating cows, its precision is severely lacking, perhaps because of a shortage of verified experimental data to test the many assumptions contained in the model.

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CONCLUSIONS The data that were reviewed suggest that replacement of SBM with protein supplements high in RUP results in decreased microbial protein flow to the duodenum if RDP is insufficient to meet microbial needs. Moreover, there will not be a substantial increase in total protein, EAA, or Lys and Met flows to the duodenum if microbial synthesis is limited by high RUP and low RDP. The adequacy of RUP and RDP in diets for lactating cows should be considered independently, and it is illogical to increase RUP at the expense of RDP unless RDP is excessive. The sources high in RUP that most consistently benefitted the lactational performance were FM and treated SBM. These protein supplements also ranked highest in this EAA index when compared with milk protein, as listed in Table 2. Any revision by NRC in recommendations for feeding protein to high yielding dairy cows should necessarily consider EAA needs, specifically those of Lys and Met, which currently appear the most limiting, in relationship to milk yields. REFERENCES 1 Agricultural and Food Research Council, 1992. Technical Committee on Responses to Nutrients. Rep. No. 9. Nutritive Requirements of Ruminant Animals: Protein. Nutr. Abstr. Rev. Ser. B., Livest. Feeds Feeding 62:787–835. 2 Akayezu, J. M., W. P. Hansen, D. E. Otterby, G. D. Marx, and B. A. Crooker. 1994. Response of Holstein dairy cows to dietary fish meal or meat and bone meal during early lactation. J. Dairy Sci. 77(Suppl. 1):237.(Abstr.) 3 Annexstad, R. J., M. D. Stern, D. E. Otterby, J. G. Linn, and W. P. Hansen. 1987. Extruded soybeans and corn gluten meal as supplemental protein sources for lactating dairy cattle. J. Dairy Sci. 70:814–822. 4 Arieli, A., Z. Shabi, I. Bruckental, H. Tagari, Y. Aharoni, S. Zamwell, and H. Voet. 1996. Effect of degradation of organic matter and crude protein on ruminal fermentation of dairy cows. J. Dairy Sci. 79:1774–1780. 5 Armentano, L. E. 1994. Altered milk production due to changes in protein quality for diets based on distillers dried grains with solubles. J. Dairy Sci. 77(Suppl. 1):244.(Abstr.) 6 Armentano, L. E., T. A. Herrington, C. E. Polan, A. J. Moe, J. H. Herbein, and P. Umstadt. 1986. Ruminal degradation of dried brewers grains, wet brewers grains, and soybean meal. J. Dairy Sci. 69:2124–2133. 7 Atwal, A. S., and J. D. Erfle. 1992. Effects of feeding fish meal to cows on digestibility, milk production, and milk composition. J. Dairy Sci. 75:502–507. 8 Atwal, A. S., S. Mahadevan, M. S. Wolynetz, and Y. Yu. 1995. Increased milk production of cows in early lactation fed chemically treated soybean meal. J. Dairy Sci. 78:595–603. 9 Baker, M. J., H. E. Amos, A. Nelson, C. C. Williams, and M. A. Froetschel. 1996. Undegradable intake protein: effect on milk production and amino acid utilization by cows fed wheat silage. Can. J. Anim. Sci. 76:367–376. 10 Baker, L. D., J. D. Ferguson, and W. Chalupa. 1995. Response in urea and true protein of milk to different protein feeding schemes for dairy cows. J. Dairy Sci. 78:2424–2434. Journal of Dairy Science Vol. 81, No. 12, 1998

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APPENDIX TABLE A1. Effect of soybean meal (SBM), heat-treated SBM (HSBM), or chemically treated SBM (CTSBM) on cow performance. Diet1

CP (%)

CS-35 AH-10 AS-10 B-11.7 or 13.8 WS-46 GSC:8 or 10.5 GW:9.6

CS-35 AS-20 C-31 CS-29 AS-28 C-36, 37, 32 or 36 AS-54 C45, 41, 41 or 38 AS-57

CS-62 B-2

CS-4 AH-10 HMC-22.6 27.3 CS-17 AHL-33 C-29.6

DIM

DMI

Milk

49–112 49–112 49–112 49–112 54 54 54

20.8 21.0 21.3 20.9 25.0b 26.9a 27.4a

(kg/d) 34.2b 36.5a 34.8b 36.7a 34.9 36.1 37.5

FCM

32.1 32.5 32.6

(%) 3.70 3.74 3.61 3.60 3.4 3.4 3.1

Fat

Protein (kg/d) 1.217 1.360 1.278 1.294 1.2 1.2 1.2

(%) 2.83 2.80 2.85 2.77 2.9 2.9 2.8

1.07

3.16b 3.08b 3.30a 3.17a 2.98a

SBM-7.8 CTSBM-7.8 SBM-12.1 CTSBM-12.1 SBM-15 CTSBM-15 CTSBM-5 CGM-4.18 FM-4.26 SBM-11 NaSBM-11 SBM-19 NaSBM-11 + U-0.7 SBM-12.2

15 15 17 17 17.6 18.1 17.6

15 15 17 17 16.4

9 9 9 9 6

22–92 22–92 22–92 22–92 31

22.4 21.8 20.7e 23.0f 20.4

32.9 31.1 32.2 32.6 35.1

31.3 29.6 31.2 30.8 30.2

3.54 3.59 3.70 3.58 3.04

ExpSBM-12.4 SBM-6.3 ExpSBM-4.0 + U SBM-10.0 ExpSBM-6.6 . . . 0 SBM-4 ExpSBM-4.3

16.4 15.5 15.5 16.5 15.5 18 19.1 19.1

6 5 5 5 5 5 5 5

31 47 47 47 47

19.8 22.8a 22.4a 21.2b 22.4a 24 24.2 24.4

35.4 34.4ab 32.6c 33.3bc 35.2a 36.7a 36.5a 37.5b

30.4 31.7ab 30.6b 31.3ab 32.5a 35.5 35.6 36.3

3.02 3.50 3.61 3.52 3.52 3.32 3.37 3.33

1.08

SBM-6.8 . . . 0 SBM-3.85

19.5 16.7 17.9

5 5 5

24.9 19.5 20.3

36.5a 29.0c 30.2b

35.5 31.0a 32.1a

EXPSBM-4.05 SBM-6.4 . . . 0 SBM-7.2 ExpSBM-4.6 SBM-11 SBM+Met+Lys-10.9 FTSBM-10.9 FTSBM+Met+Lys11.0 SBM-11 SPSBM-11 SBM-14.5 SPSBM-14.6 SBM-12.3

17.5 18.8 17 18.9 18.1 15 15 14.9

5 5 6 6 6 16 16 16

40–96 40–96 40–96

20.3 19.9 22.4 22.9 22.7 19.6 19.1 18.8

31.1a 30.7ab 30.1b 31.1a 31.0a 35.3 34.8 35.3

15 16.4 16.4 18.4 18.4 17.4

16 9 9 9 9 12

40–96 38–122 38–122 38–122 38–122 57

18.9 20.6 21.0 20.5 20.6 22.9

35.3 35.8 38.3 36.5 38.9 33.4

ExpSBM-9.8

17.8

12

57

21.7

33.3

(kg/d) 0.982 1.021 0.992 1.009 1.0 1.0 1.1

Reference (8)

(9)

(17)

1.47 1.04

1.21 1.22 1.24

2.84b 3.09 3.04 3.06 3.04 3.13 3.18 3.15

3.35 3.97a 3.92b

1.25 1.14b 1.17a

3.20 2.95b 3.04a

1.16 0.85b 0.91a

32.7a 32.4a 30.2b 31.5a 31.4a 33.2 34.0 34.5

3.85b 3.88b 3.55 3.58 3.59 3.65 3.89 3.83

1.19a 1.18a 1.06b 1.11a 1.11a 1.273 1.335 1.356

3.04a 3.02a 3.11 3.12 3.10 2.85b 2.96a 2.87b

0.94a 0.92a 0.93b 0.97a 0.96ab 0.996 1.020 1.003

34.4

34.3

3.89 2.51 2.38 2.50 2.68 3.74

1.356 0.899 0.908 0.893 1.027 1.25

2.97a 2.90 2.90 2.88 2.85 2.99

1.035 TP2 1.0334 1.100 1.033 1.100 1.00

34.4

3.77

1.25

2.94

0.98

(18)

(18)

1.15 1.15 1.18

(21)

(39)

(41)

(50) (continued)

3199

Journal of Dairy Science Vol. 81, No. 12, 1998

HMC-41 38, 38 or 36 AS-58 HMC-34

(no.) 12 12 12 12 12 12 12

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

CS-26 HCS-18 HMEC-42

Cows per treatment

3200

Journal of Dairy Science Vol. 81, No. 12, 1998

TABLE A1. (Continued) Effect of soybean meal (SBM), heat-treated SBM (HSBM), or chemically treated SBM on cow performance.

a,b,c,d,e,fValues

SBM-9.6

18

12

21–150

22.7

33.1

30.9

3.60

1.18

3.04a

1.00

(53)

ExpSBM-9.8 SBM-7.4

18 15

12 31

21–150 0–105

22.7 17.7

32.7 37.5

31.2 . . .

3.82 2.81

1.21 . . .

3.00b 3.17

0.96 . . .

(60)

SBM-17.4

19

31

0–105

17.0

39.2

. . .

2.96

. . .

3.25

. . .

FTSBM-16.8 SBM-22 HSBM-15.1 SBM-6.3 FTSBM-6.3

19 20 18 15.5 15.5

31 6 6 12 12

0–105 0–56 0–56 4–112 4–112

18.2 17.6 16.6 17.3 17.5

39.3 34.6 34.6 28.7 29.5

. . . 26.8 27.6 25.9 25.9

2.87 2.5 2.7 3.38 3.18

. . . .90 .90 .96 .94

3.12 3.0 3.0 3.15 3.03

. . . 1.0 1.0 .90 .89

SBM-18 SBM-13.6

18 16

12 18

4–112 21–105

17.2 23.9

28.3 37.5

25 38.3

3.21 3.71

.94 . . .

3.14 2.88

.89 . . .

LigSBM-6.8 LigSBM-6.8 + U SBM-16 GRSB-18 WRSB-18 SBM-14

13 16 17.0 16.8 16.8 15.6

18 18 9 9 9 25

21–105 21–105 21–126 21–126 21–126 28–112

23.6 23.2 23.6a 22.7ab 21.3b 19.3

36.6 36.5 39.6 40.7 36.4 32.2b

38.3 37.6 35.4 35.0 33.3 27.2b

3.78 3.84 3.33 3.09 3.50 2.98

. . . . . . 1.307 1.248 1.255

2.89 2.88 3.03a 2.83b 2.88b 2.99a

. . . . . . 1.179 1.158 1.048

15 . . . . . . 18.5

25 6 6 22

28–112 11–98 11–98 95

20.1 16.2 16.5 25.6

34.5a 26.2 26.7 31.1

29a 26.2 25.7 31.7

2.89 4.0 3.76 3.62

18.5 16

22 15

95 13–73

25.3 20.3

32.0 37.2

32.9

16 18.5 18.7

15 8 8

13–73 0–84 0–84

20.7 22.8ab 21.9b

38.5 38.8b 41.6ab

19.1

8

0–84

23.2a

43.05a

HSBM-14 SBM FtSBM SBM-11.4 ExpSBM-12.1 SBM-11.5 HSBM-11 SBM-16.45 HSBM-5.83 FM-3.62 CGM-4.73 HSBM-4.82 SBM-5.32 FM-3.04 CGM-3.84

(61) (66)

(76)

(83)

(99)

. . . . . . 1.12

2.90b 3.02 3.00 3.14a

. . . . . . 0.98

(112)

3.69 3.52

1.18 1.31

3.08b 2.89

0.98 1.07

(115)

36.1 38.9 39.1

3.58 3.50a 3.20b

1.38 1.35 1.30

2.77 3.05 3.00

1.07 1.20b 1.30a

41.9

3.35ab

1.45

3.05

1.35a

(105)

(118)

within a group followed by a different superscript letter differ ( P < 0.05). = Alfalfa hay, AHL = alfalfa haylage, AS = alfalfa silage, BH = bermudagrass hay, B = barley, C = corn, CM = corn meal, CS = corn silage, GC = ground corn, ExpSBM = expeller SBM, FM = fish meal, FTSBM = formaldehyde-treated SBM, GRSB = ground roasted soybean, GS = grass silage, GSC = ground shelled corn, GW = ground wheat, HCS = haycrop silage, HMC = high moisture corn, HMEC = high moisture ear corn, NaSBM = NaOH-treated SBM, O = oats, SPSBM = specially processed SBM, SS = sorghum silage, U = urea, VH = vetch hay, WRSB = whole roasted soybean, and WS = wheat silage. 2TP = true protein. 1AH

SANTOS ET AL.

AS-49 HMC-37 Fat-2.8 CS-13 VH-10 WCS-5 B-23 GC-30 WS-28 or 25 C-29 or 31 CS-22 AH-14 GC-32 O-16 CS-33 AH-15 BH-15 C-20 or 27 CS-30 AS-20 DSC-26.8 CS-30 AH-15 GC-40 GS-58 B AH-29.6 CS-10.3 SG:27.2 CS-27.5 AS-27.5 HMEC-32 WS+SS-37 C-25.5, 26.1 or 25.3

TABLE A2. Effect of soybean meal (SBM) or fish meal ( F M ) compared with solvent-extracted SBM on cow performance. Diet1

CP

Cows per treatment

(%)

DIM

DMI

Milk

FCM

Fat

Protein

AS CS HMC

SBM

16

(No.) 20

30–150

21.1

(kg/d) 35

33.5

(%) NS

FM

16

20

30–150

21.3

37.1

35.6

NS

3.02b

CS-25 AS-25 GC-30 or 32 Fat-5 AS-52

SBM-8.5

15.8

6

33

21.1a

31.4b

3.33b

2.91

FM-6.5

15.5

6

33

19.4b

32.1a

3.21a

2.88

SBM FM SBM-6.1 FM-4.2 SBM-9.2 FM-6.4 SBM-4.3 FM-2.9 SBM-5.4 FM-3.7 SBM-13.2

18.5 18.5 21 22 22 22.6 19.2 19.2 18.2 18.2 22

8 8 4 4 4 4 10 10 8 8 50(M)

138 138 154 154 154 154 52 52 33 33 0–168

22.6 22.6 20.8 18.8 20.3 19.5 22.9 23.2 21.5 21.7 22.2

26.5b 28.7a 24.3b 25.0b 25.7a 25.7a 36b 37.1a 35.7b 36.9a 40.0

24.4b 26.8a 23.4 24.3 24.8 24.9 34.6b 35.9a 34.5b 35.6a 33.0

3.53 3.43 3.31 3.31 3.32 3.30 3.29 3.33 3.32 3.31 2.96a

NS NS 3.0 3.05 3.02 3.06 2.83b 2.92a 2.84b 2.93a 3.08

(22)

FM-7.3 SBM-13.2 FM-7.3 SBM

22 22 22 21

50 30(P) 30 31

0–168 0–112 0–112 12–125

20.5 22.2 20.5 . . .

40.8 31.2 33.4 34.3b

32.3 28.3 27.6 . . .

2.60b 3.43a 2.77b 1.26b

3.11 3.13 3.15 1.12b

(25)

SBM FM-3.5 SMB-10 SBM-5.4 FM-3.6 SMB-6.3

21

31

12–125

. . .

35.8a

. . .

1.29a

1.19a

57 57

15.35 15.70

23.0 23.6

. . . . . .

3.60a 3.45b

17

13

0–100

23.1

36.8

. . .

. . .

. . .

FM-4.3

17

13

0–100

21.6

36.5

. . .

. . .

. . .

SBM-4.49 U-0.85 SBM-5.85 FM-3.60 SBM-6 U-0.5 FM-7 SBM-15.4

. . .

6

28–91

14.0

22.5

22.7

4.04a

2.87

. . .

6

28–91

14.0

23.8

21.5

3.24b

2.81

. . .

6

0–140

18.2

27.7

. . .

4.99

. . .

2.75

(59)

. . . 17

6 20

0–140 0–100

17.5 15.9

27.3 26.2

. . . 25

4.89 3.74a

. . .

2.75 3.19

(72)

SBM-6.7 FM-7.4 SBM-5.8

17 20

20 9

0–100 21–77

14.7 20.8

26.8 32.2

24 31.2

3.39b 3.86

3.13 2.84

(82)

FM-4.5

20

9

21–77

21.3

32.9

33.3

4.04

2.97

HMC-10 AS-70 HMC-25 AS-56 HMEC-37 or 39 CS-13 GH-8 WCS-13

CS AH B GS-54

GH B BP CS-55 WM-11 C-17 or 19 AS-ad lib HMEC-32 35

6 6

. . . . . .

3.00b 3.13a

(kg/d) (2)

(7)

(15) (19)

. . . . . .

(38)

(45)

(49)

(continued)

3201

Journal of Dairy Science Vol. 81, No. 12, 1998

AS-43 CS-13 C-31 or 35 U-0.4 GH-35 B

18 18.6

(%) 3.12a

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

AS-80 to 85

(kg/d)

Reference

CS-40 AHL-10 C-18 B-9 CS-35 AHL-3.1 C-6 B-11 AH-37 CSH-3 SFS-40 WCS-10 GS-43 B-55 51 or 48 GS-58 BCS-83 U-1

BrS-40 B-10 C-26 or 31 BrS-45

CS-50 CM-12 O-6 U-0.8 CS-50

a,b,cValues

17.1

6

96

24.5

36.6

36.6

3.52

1.28

2.07

1.12

SBM-8.4 FM-2.7 SBM-12.5

17.2

6

96

24.4

37.3

36.9

3.45

1.28

3.07

1.14

16.2

4

96

22.6a

32.6

32.6

3.63

1.15

2.79

0.88

31.8

31.8

3.53

1.12

2.80

0.89

(85)

SBM-8.4 FM-2.7 SBM-6

16.1

4

96

20.9b

18.4

8

90–150

26.3

38.5

34.6

2.82

3.25

FM-5

18.4

8

90–150

25.6

40.1

35.5

2.74

3.23

FM-2

13

10

28–91

17.6

26.6

3.86a

3.52

(104)

SBM-8.5 FM-5.7 SBM

15 15

10 10 6

28–91 28–91 11–98

17.9 17.9 16.2

26.1 26.3 26.2

26.2

3.97b 3.64c 4.00

3.45 3.47 3.02

(105)

6 7

11–98 90

16.4 17.0

26.3 24.6

26.6 24.7

4.06 3.83a

3.10 3.30a

(108)

3.25a

FM SBM-13 SBM-10 FM-2 SBM-9 FM-4 SBM-11.5 SBM-8.7 FM-2.0 SBM-5.7 FM-4.0 SBM-13.7 SBM-5.5 SFM-5.6 SBM SBM SFM-1.4 SBM SFM-2.8 SBM SFM-4.2 SBM-9.7

15.8 15.7

7

90

17.3

25.6

25.6

3.60b

16.5

7

90

16.4

26.5

25.1

3.58b

3.17b

15.5

7

90

18.5

27.3

27.4

3.83a

3.6a

15.5

7

90

17.3

27.6

26.0

3.38b

3.3b

15.5

7

90

17.5

28.1

25.6

3.18c

3.11c

17.2

10

22–106

22.2a

42.1

35.9a

3.03a

3.04

17.2

10

22–106

20.2b

40.2

31.5b

2.56b

3.06

17

9

19.7a

34.3b

3.79a

NS

17

9

19.0a

35.4ab

3.75b

NS

17

9

19.7a

36.4a

3.57c

NS

17 16

9 10

28–126

17.6b 21.4

34.9b 36.3a

32.2

3.09d 3.34

NS 3.15

FM-7.0

16

10

28–126

20.8

38.9b

31.6

2.81

2.98

SBM FM bST+SBM bST+SBM

15.5 15.5 15.5 15.5

6 6 6 6

35–126 35–126 35–126 35–126

24.1 22.3 21.8 23.1

33.5 33.0 36.6 39.2

2.97 2.94 3.02 2.93

(96)

SANTOS ET AL.

CS-60 HMC-24, 25, or 26 U-1.0

SBM-12.5

(119)

(120)

(123)

(124)

within a group followed by different superscript letters differ ( P < 0.05). = Alfalfa hay, AHL = alfalfa haylage, AS = alfalfa silage, B = barley, BP = beet pulp, BrS = bromegrass silage, C = corn, CM = corn meal, CS = corn silage, CSH = cottonseed hulls, GC = ground corn, GH = grass hay, GS = grass silage, HMC = high moisture corn, HMEC = high moisture ear corn, ( M ) = multiparous cows, O = oats, ( P ) = primiparous cows, SFM = salmon fish meal, SFS = steam-flaked sorghum, U = urea, WCS = whole cottonseed, and WM = wheat middlings. 1AH

3202

Journal of Dairy Science Vol. 81, No. 12, 1998

TABLE A2. (Continued) Effect of soybean meal (SBM) or fish meal ( F M ) compared with solvent-extracted SBM on cow performance.

TABLE A3. Effect of animal by-products (ABP) compared with solvent-extracted soybean meal (SBM) on cow performance. Cows per treatment

DIM

DMI

Milk

16

(no.) 20

30–150

21.1

(kg/d) 35.0 33.5

(%)

SBM MBM SBM BM+DDGS SBM BM FM SBM MBM SBM-9.3

16

30–150

20.6 25.9 26.7 23.7

36.6 44.1 44.4 32.9

NS

31.5 27.8b 29.0a 32.6

(%) AS CS HMSC AS-44

CS-30.1 AS-25.5 GC-32, 36 or 34 CS-25 AS-25 GC-33, 41, 32 or 37 CS-60 C+O-22, 27 or 29

AS-43 CS-13 ShC-31 or 35 U-0.4

55

33.8

Fat (kg)

Protein (%) 3.12a

Reference

(kg) (2)

3.05b NS NS

NS NS

3.44

3.06 3.07

32.1

3.62 3.57a 3.35b 3.44

3.27a

(5) (11)

55

15.7

8 6 6 3

6

22.6 22.9b 24.6a 25.3

15.7

3

6

24.7

33.4

33.0

3.44

3.14b

15.6 16.4 16.4

3 11 11

6 15–154 15–154

24.9 17.5 17.9

32.9 37.1 37.2

33.3 30.6 32.7

3.57 2.87b 3.22a

3.25a 2.83 2.89

19.0 19.0 16.4

11 11 3

15–154 15–154 84

18.1 16.9 21.0

39.8 36.6 24.8

33.2 31.6 25.5

2.92b 3.12a 3.67

2.92 2.84 3.40

16.8

3

84

20.2

25.7

25.9

3.58

3.40

14.3 17.0

3 13

84 0–100

19.9 23.1a

24.5 36.8

25.4

3.74

3.39

17.0

13

0–100

21.8b

35.8

17.4

12

57

22.9

33.4

34.3

3.74

1.25

2.99

1.00

AVPB2-6.4 SBM-2.9

17.8

12

57

21.2

32.7

33.7

3.73

1.23

2.94

0.97

SBM-6.8 AVPB-4.2

15.3 14.9

4 4

82 82

17.1 18.5

31.7 28.5

24.5 22.2

2.50 2.50

0.78 0.72

3.0 3.1

0.99 0.88

(65)

SBM-16.3

18.9

10

28–112

22.0

33.3ab

32.4b

3.42

1.13

3.09a

1.02

(68)

AVPB-5.8 SBM-7.8

19

10

28–112

21.3

32.8b

32.6b

3.55

1.16

2.98b

0.97

AVPB-5.9 SBM-8.0 Molasses

19

10

28–112

22.1

35.9a

35.2a

3.46

1.23

2.97b

1.06

MBM-8.2 SBM-4.7 MBM-4.7 SBM-6 CGM-ABP-5.3 SBM-10 CGM-ABP-9 SBM-11 CGM-3.6 BM-2.6 CGM-2.0 BM-1.5 SBM-6.3 MBM FtM-3.9 BM SBM-12.3

(14) (20)

(35)

(42)

(45)

(50)

(continued)

3203

Journal of Dairy Science Vol. 81, No. 12, 1998

CS-17 AHL-33 GSC:29 or 33 AVPB = BM, 25%; MBM, 42%; CGM, 33% AH-44.7 CS-46 C-40 CS-25 AH-25 C:31, 34 or 25

20 6 6 8

FCM

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

CP

Diet1

3204

Journal of Dairy Science Vol. 81, No. 12, 1998

TABLE A3. (Continued) Effect of animal by-products (ABP) compared with solvent-extracted soybean meal (SBM) on cow performance. AVPB = BM, 26%; MBM, 41%; CGM, 33% AH-36 CS-17 C-28 or 32 U-.53 CS-55 WM-11 ShC-17, 19 or 20

CS-25 AH-25 GC

CS-30 AS-20 C-27

18.0

23

28–120

21.1

31.9

33.3

3.78

3.0a

MBM-2.4 FtM-2.4 BM-1.2 SBM-15.4

18.0

23

28–120

20.7

32.1

33.2

3.68

2.91b

17.4

20(P)

0–100

15.9

26.2

25.0

3.74

3.19a

SBM-6.7 ABP1-7.6 SBM-6.7 ABP2-6.3 SBM

17.7

20(P)

0–100

16.4

27.2

25.4

3.59

3.03b

17.1 18.0

20(P) 13

0–100 0–60

16.1 19.45

27.1 43.75

25.9 36.15

3.68 2.46

3.09ab 3.00

19.0

13

0–60

17.41

41.07

35.88

2.81

2.89

20.7 17

13 9

0–60 21–126

19.60 23.6a

43.72 39.6

39.15 35.4

2.86 3.33

1.307

2.94 3.03

1.179

17

9

21–126

21.3b

36.1

33.9

3.63

1.297

3.08

1.104

17.1

6

96

24.5

36.6

36.6

3.52

1.28

3.07

1.12

AVPB-3.8 SBM-12.2 SBM-12.5

17.2

6

96

24.2

36.9

36.6

3.48

1.28

3.05

1.12

16.2

4

96

22.6

32.0

32.6

3.63

1.15

2.79

0.88

AVPB-2.8 SBM-7.8

16.2

4

96

21.8

32.5

32.4

3.61

1.19

2.75

0.90

SBM

16

12

26.1

35.9

. . .

3.60

3.12

(90)

BM CGM SBM-13.1

16 15.9

12 24

Early

26.1 36.9 . . . 23.2(H) 32.3(H) 31.2(H) 18.0(J) 22.5(J) 26.3(J)

3.60 3.72a( H ) 1.22(H) 5.19a( J ) 1.15(J)

3.12 3.27a( H ) 1.06a( H ) 3.95a( J ) 0.87(J)

(92)

BM-3.4 SBM-5.5

16

24

Early

23.1(H) 33.2(H) 32.4(H) 17.9(J) 22.7(J) 25.8(J)

3.55b( H ) 1.28(H) 4.98b( J ) 1.11(J)

3.06b( H ) 1.01b( H ) 3.80b( J ) 0.85(J)

SBM-13.1 Fat

15.9

24

Early

22.0(H) 34.8(H) 32.6(H) 17.1(J) 24.0(J) 27.6(J)

3.87(H) 1.24(H) 5.00(J) 1.20(J)

3.00(H) 1.05a( H ) 3.64(J) 0.88(J)

16

24

Early 3.60(H) 1.26(H) 5.19(J) 1.26(J) 3.95a

2.94(H) 1.01b( H ) 3.51(J) 0.84(J) 3.02

3.79b

3.01

SBM ABP SBM ABP SBM-15.9 BM-2.69 SBM-10.7 SBM-6.8

BM-3.4 SBM-5.5 Fat SBM SBM BM-2.5

17.6

30

78–141

21.6(H) 35.2(H) 32.9(H) 16.6(J) 24.5(J) 28.8(J) 23.4 31.4

17.9

30

78–141

23.2

31.3

(70)

(72)

(81)

(83)

(85)

(92)

(95)

SANTOS ET AL.

CS-40 AHL-10 C-18 B-9 CS-35 AHL.-30 C-6 B-11 AVPB = BM + FtM + CGM AS 47 TS C B CS-30 AS-29 C:25.7, 29.9, 21.7 or 25.9

SBM-9.2

CS-24.5 AHL-40.8 C-23.9 or 17.9 Tallow-3 CS-16.7 AHL-32.7 C-41 or 35 CS-50 CM-21 or 26

a,b,cValues

18.3

17

14–84

22.8b

33.1

31.66

3.71

2.75

SBM-12.4

18.3

17

14–84

24.1a

33.0

31.06

3.61

2.87

FtM+BM-5

18.0

17

14–84

24.2a

33.0

30.03

3.41b

2.80b

SBM-13.9 SBM-18

18.4 18

17 6

14–84 28

25.1a NS

32.5 NS

31.4 NS

3.78a NS

2.97a NS

SBM-4.6 BM-8.2 SBM

18 19.5

6 30

28 28–126

NS 26.2a

NS 40.4

NS

NS

NS

NS

NS

NS

(107)

(113)

(117)

AVPB SBM-7.8

19.5 14.5

30 10

28–126 60

24.7b 22.37

39.1 35.72

35.15

3.42

2.86b

CGM-2.5 MBM-3.13

14.5

10

60

22.12

34.08

35.19

3.71

3.14a

(122)

within a group followed by different superscript letters differ ( P < 0.05). = Alfalfa hay, AHL = alfalfa haylage, AS = alfalfa silage, AVPB = animal-vegetable protein blend, B = barley, BM = blood meal, BP = beet pulp, C = corn, CGM = corn gluten meal, CM = corn meal, CS = corn silage, DDGS = distillers dried grains plus solubles, FtM = feather meal, GC = ground corn, GSC = ground shelled corn, ( H ) = Holstein, HMSC = high moisture shelled corn, ( J ) = Jersey, MBM = meat and bone meal, O = oats, ( P ) = primarous, ShC = shelled corn, TS = timothy silage, U = urea, and WM = wheat middlings. 1AH

3205

Journal of Dairy Science Vol. 81, No. 12, 1998

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

AS-60 ShC-25 or 29 CS-50 AH-10 BP-6 B+C-27

FtM+BM-5

3206

Journal of Dairy Science Vol. 81, No. 12, 1998

TABLE A4. Effect of brewers grains ( B G ) compared with solvent-extracted soybean meal (SBM) on cow performance. CP

Cows per treatment

SBM-18

16.5

(no.) 10

BWG-16 SBM-12 SBM-18.3 SBM-11 BDG-16 SBM-12.6

16.5

Diet1

DMI

Milk

FCM

60–20

18.0

(kg/d) 21.7b

21.1b

(%) 3.82b

(kg) 0.83b

(%) 3.10

(kg) 0.67

10

60–20

17.8

24.8a

25.1a

4.08a

1.01a

3.23

0.80

15.8

8

22–92

17.4b

30.8b

31.4

3.7

3.0

(40)

15.8 18

8 5

22–92 7

18.8a 22.0

35.0a 35.7

33.6 36.2

3.4 3.6

2.9 2.9

(52)

BWG-23.1 BDG-21.5 SBM-14.3 BWG-26 EBWG-26

18 18 15 15 15

5 5 9 9 9

7 7 130–200 130–200 130–200

22.4 21.7 25.2a 21.9b 20.8b

36.6 38.1 29.28 29.37 27.72

36.7 37.8 26.16 25.57 25.56

3.5 3.6 3.33 3.17 3.39

2.8 2.8 3.27 3.20 3.23

BWG-15 U-0.72 SBM-14.6

15 18.3

9 4

130–200 114–177

22.8b 20.1

29.0 26.2b

25.95

3.33 3.45a

3.16 3.44

BDG-24

17.4

4

114–177

22.3

29.4a

3.09b

3.28

SBM-10

14.7

21

0–105

23.9

31.4

32.0

3.7

3.2

BDG-19

14.7

21

0–105

23.7

32.3

33.1

3.7

3.2

(%) CS-45 39 C-20 CS-50 or 42 HMC-28

a,b,cValues

Fat

Protein

Reference (13)

(58)

(87)

(103)

within a group followed by different superscript letters differ ( P < 0.05). = Alfalfa hay, AS = alfalfa silage, BDG = brewers dried grains, BG = brewers grains, BWG = brewers wet grains, C = corn, CS = corn silage, EBWG = ensiled BWG, GC = ground corn, HMC = high moisture corn, HMEC = high moisture ear corn, HMGC = high moisture ground corn, and U = urea. 1AH

SANTOS ET AL.

CSAS-27 AH-8 GC CS-25 AH-25 HMEC-35, 23, 22 or 34 CS-49 or 22 AS-14 HMGC-17 or 35 CS-35 AS-20 HMC-29 or 20

DIM

TABLE A5. Effect of distillers grains compared with solvent-extracted soybean meal (SBM) on cow performance. Diet1 AS-44

DIM

DMI

Milk

18.9

(no.) 6 6 6

Early Early 64

25.9b 27.0a 22.9

(kg/d) 44.1 43.6 31.1

31.5

3.58

3.12

FCM

Fat (%)

Protein (%)

18.9

6

64

22.7

31.0

31.6

3.64

3.12

17.6

8

Early

20.7

33.0b

31.3b

3.15

3.19

17.8

8

Early

21.9

35.2a

34.0a

3.29

3.12

14.0

8

Early

21.6

32.4

30.3b

3.11

3.17

SBM-3.0 DDG-13.5 SBM-10.6 DDGS-18.8

13.8 14.6 14.6

8

Early

21.8 23.7b 25.1a

33.5 33.8a 34.3a

31.8a 34.5a 35.1a

3.22 3.65 3.62

3.12 2.99a 2.76b

SBM-21

18.7

24.0

34.1a

35.1a

3.68

3.03a

DDGS-36 SBM-8.8 DDGS1-13.0 DDGS2-13.0 DDGS3-13.0

17.7 13.7 13.7 14.2 13.8

23.0b 24.2 24.1 23.6 23.6

28.5b 26.5 27.4 27.5 26.4

29.4b

3.76 3.25 3.61 3.60 3.39

2.77b 3.13 3.05 3.12 2.95

SBM-7.3 DDG-19.2 SBM-8.4

12 11 11 8

133 133 133 133

Reference (kg) 1.39a 1.26b

(5) (21)

(75)

(80)

(88)

(continued)

3207

Journal of Dairy Science Vol. 81, No. 12, 1998

CS-30 AS-10 HMC-30 23 CC-8 0 CS-30 AS-10 HMC-30 23 CC-15.6 4.65 CS-50 RO-16 RC-18, 10, 9 or 0 CS-50 CM-30, 23, 23 or 23

DDG-4.2 CGM-1.5 SBM-16.2

Cows per treatment

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

AS-58 HMC-34 36

(%) SBM DDGS-18.5 SBM-7.2

CP

3208

Journal of Dairy Science Vol. 81, No. 12, 1998

TABLE A5. (Continued) Effect of distillers grains compared with solvent-extracted soybean meal (SBM) on cow performance.

CS-27.5 AS-27.5 HMEC-31

a,b,cValues

SBM-17.6 DDGS1-26.0 DDGS2-26.0 DDGS3-26.0

17.5 17.6 18.7 17.8

12 11 10 8

133 133 133 133

23.5 24.3 23.8 24.4

27.0 28.0 28.0 27.0

3.47 3.68 3.32 3.59

3.25 3.25 3.07 3.08

SBM-7.1 DDGS1-13.0 DDGS2-13.0

13.8 13.9 14.4

10 9 10

133 133 133

24.0 23.9 23.9

26.7 26.0 27.8

3.51 3.45 3.30

3.15 3.21 3.18

SBM-14.2 DDGS1-26.0 DDGS2-26.0

17.7 17.9 19.0

10 9 10

133 133 133

23.5 24.9 24.5

27.7 29.2 28.4

3.51 3.51 3.51

3.10 3.28 3.18

SBM-15.5

14.8

13–73

22.5a

37.5a

32.7

3.14

3.14a

DDGS-11 CGM-5.5 SBM-11.5

14.5 16

13–73 13–73

19.9b 20.3

31.8b 37.2

29.1 34.5

3.45 3.52

2.72b 2.89

DDGS-7.1 CGM-4.9

16

13–73

20.3

35.2

34.2

3.84

2.85

(115)

within groups within column followed by different superscript letters differ ( P < 0.05). = Alfalfa silage, BM = blood meal, CC = cracked corn, CGM = corn gluten meal, CM = corn meal, CS = corn silage, DDG = distillers dried grains, DDGS = DDG with solubles, GC = ground corn, HMC = high moisture corn, HMEC = high moisture ear corn, RC = rolled corn, and RO = rolled oats. 1AS

SANTOS ET AL.

CS-50 CM-21, 6, 6 or 6 CS-50 BM-1 CM-31, 24 or 24 CS-50 BM-2 CM-23, 9 or 9 CS-56 GC-26

TABLE A6. Effect of corn gluten meal (CGM) compared with solvent-extracted soybean meal (SBM) on cow performance. Cows per treatment

SBM-8

15.7

(no.) 12

ExtSB-1.5 CGM-4.5 SBM-8.4

15.7

12

16.4

10

CGM-3.6 CSM-3.3

16.4

CGM-3.0 SBM-9.4 CSM-1.4 SBM CGM SBM-18.3

DMI

Milk

FCM

4–116

19.7

(kg/d) 34.3

33.3

(%) 3.74

4–116

19.6

32.8

32.0

3.81

69

24.1

38.2

33.3

2.80

1.05

2.97b

10

69

24.5

38.2

33.2

2.71

1.03

2.97b

16.4

10

69

22.8

37.7

33.0

2.73

1.02

3.01ab

16.4

10

69

24.5

37.1

33.4

2.93

1.09

3.05a

18.4 18.6 16

8 8 8

138 138 22–92

22.6 22.6 17.4

26.5b 27.4a 30.8

24.4 25.2 31.4

3.53 3.59 3.70

NS NS 3.00

16

8

22–92

19.2

31.7

31.4

3.50

3.00

22 22 15 15

5 5 5 5 15

100–160 100–160 100–160 100–160 0–305

22.4b 23.3b 26.3a 25.6a

28.3c 30.0bc 31.5a 31.1a

25.5b 29.0a 29.9a 29.5a

2.90 3.30 3.20 3.20

3.0 3.1 3.2 3.1

NS

NS

NS

NS

(%) CS-38 AH-12 O-10 GC-32 or 34 CS-29 VH-9 C:0, 11, 0 or 9 B:12.9, 4.4, 17.3 or 44 AS-52 CS-50 HMC-2.5 or 30.0

SS S CGF C

CGM SBM-22

Fat

Protein (kg)

(%) 3.02

Reference (3)

3.00 (4)

(15) (40)

(51)

(54) NS

NS

20

15 6

0–305 0–56

17.6

34.6

26.8

2.50b

3.00

HSBM-8.8 CGM-9.4 SBM

20

6

0–56

16.0

32.3

27.6

3.00a

3.20

17.3

3

Early Lactation

19.6

38.6

29.2

2.40

3.30

60 HSB 40 CGM

17.8

3

Early Lactation

19.6

40.1

30.6

2.50

3.30

(61)

(79)

(continued)

3209

Journal of Dairy Science Vol. 81, No. 12, 1998

AH-39 CSH-12 WCS-10 GC-22 CS HCS CM WS-28 25 SH-7 CGF-7 C-30

SBM-9.4 CGM-7.0 SBM-9.7 CGM-9.7 SBM-3.0 CGM-3.5 SBM

DIM

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

CP

Diet1

3210

Journal of Dairy Science Vol. 81, No. 12, 1998

TABLE A6. (Continued) Effect of corn gluten meal (CGM) compared with solvent-extracted soybean meal (SBM) on cow performance. CS-50 GC-28 or 32 CS GC AS-Ad lib GB

a,b,cValues

16 16 14.5

24 24 24

22–112 22–112 112–230

22.6a 20.7b 21.2a

37.4a 32.9b 28.5a

33.5a 31.4b 26.0a

3.30b 3.71a 3.40b

3.05a 2.91b 3.26a

CGM SBM CGM + SBM CGM SBM

14.5 . . . . . . . . . 16.8

24 5 5 5 4

112–230 Midlactation

19.5b 24.0 24.5 24.5 21.1

25.2b 31.5 30.8 31.3 32.7

24.0b . . . . . . . . .

3.70a 3.83 3.97 3.99 3.44

CGM SBM-15.5

16.8 18.8

4 12

Midlactation 150–209

21.2 21.6

32.3 31.0a

25.0

3.23 2.37

2.93 3.085

CGM-10.2

18.4

12

150–209

21.9

29.6b

24.5

2.42

3.10

SBM-9.7

16

10

28–128

21.4

36.3a

32.2

3.34

1.19

3.15

CGM-7.3

16

10

28–128

19.8

33.7b

31.0

3.39

1.15

2.98

. . . . . . . . .

3.11b 2.97 3.07 3.08 2.85

(86 2) (86 2)

(91)

(111)

(123)

within a group within a column followed by different superscript letters differ ( P < 0.05). = Alfalfa hay, AS = alfalfa silage, B = barley, BM = blood meal, C = corn, CGM = corn gluten meal, CM = corn meal, CS = corn silage, CGF = corn gluten feed, CSH = cottonseed hulls, CSM = cottonseed meal, ExtSB = extended soybeans, GB = ground barley, GC = ground corn, HCS = haycrop silage, HMC = high moisture corn, HSB = heat-treated soybeans, O = oats, SS = sorghum silage, SH = soyhulls, VH = vetch hay, W = wheat, wheat silage, and WCS = whole cottonseed. 2This was a six-university study involving about 800 cows. 1AH

SANTOS ET AL.

AS-56 GCGBAH-43 W-9 GC-30 or 35 BM-1.2 CS-50 CM-12 O-5 U-0.8

SBM-18.4 CGM-14.7 SBM

TABLE A7. Effects of fish meal ( F M ) or combinations with FM compared with corn gluten meal (CGM) on cow performance. Cows per treatment

DIM

DMI

Milk

FCM

FM CGM FM-5.1

18.6 18.6 16.6

(no.) 8 8 10

138 138 0–60

22.6 22.6 17.1

(kg/d) 28.7a 27.4b 32.43

26.8a 25.2b 28.5b

(%) 3.43 3.59 3.21b

CGM-5.1

16.6

10

0–60

16.2

29.1

29.5a

4.19a

2.88

SBM-5.1 BM-2.0 FM-2.6

18.6

12

110–170

24.7

30.3a

28.7a

3.20

3.11

CGM-8.5 CGM-7.3 FM-2.6 FM-5.2 FM-7.8 CGM-3.7 FM-3.8 FM-7

19.2 17.2 17.5 17.3 17.2 15.7 16.3 16

12 8 8 8 8 12 12 10

110–170 131 131 131 131

27.2b 25.3 26.2 25.5 25.6 30.1 30.3 38.9a

25.5b

28–126

23.5 20.6ab 21.2a 20.1b 19.5b 21.6 21.2 20.8

31.6

3.23 3.5a 3.2ab 3.1b 3.0b 3.8 3.7 2.81b

3.14 3.4 3.4 3.4 3.3 3.1 3.1 2.98

CGM-7.3

16

10

28–126

19.8

33.7b

31.0

3.39a

2.98

(%) AS-52 CS-37 HCS-25 GC-27 SBM-2 DDG-2 4 AH-28 CSH-9 WCS-10 B-8 C-33 CS:62 HMC:20

Protein (kg)

(%) NS

(kg) (15)

3.04

1.1 1.1

FM

10

0

16.1b

33.0a

34.9

3.91b

3.04

CGM DDG

10

0

19.1a

31.8b

35.4

4.24a

3.11a

Reference

(16)

(33)

(109)

0.9 0.9 (123)

(126)

a,b,cValues

within a group within a column followed by different superscript letters differ ( P < 0.05). = Alfalfa hay, AS = alfalfa silage; B = barley, BP = beet pulp, BS = barley silage, C = corn, CM = corn meal, CS = corn silage, CSH = cottonseed hulls, GC = ground corn, GH = grass hay, HCS = haycrop silage, HMC = high moisture corn, O = oats, SBM = soybean meal, V = vetch, W = wheat, WCS = whole cottonseed, and U = urea. 2Reference ( 8 7 ) is the summary of six universities studies. 3Tendency. 1AH

3211

Journal of Dairy Science Vol. 81, No. 12, 1998

AS-36 BS-38 CS-50 CM+O-18 W-6 BP-2 V-0.8 GH-42 WCS-8 C B

Fat

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

CP

Diet1

3212

Journal of Dairy Science Vol. 81, No. 12, 1998

TABLE A8. Effect of urea ( U ) supplementation compared with various protein sources [mostly soybean meal (SBM)] on cow performance. CP

Cows per treatment

SBM-6.0 U-1.0

15.1

(no.) 4

SBM-3.9 CGM-6.3 SBM-7.3 BM-1.4 FM-1.5 SBM SBM+AA SBM+U SBM+U+AA BM+FM ExpSBM-6.6

14.3

Diet1 AHL-17 CS-34 C-36

CS-29 AS-28 C-36 or 37 CS-30.1 AS-25.5 GC-39.8, 32.2, 35.6 or 34.1 CS-27 AS-27 GC-42.8 or 35.5 CS-27 AS-27 GC-42.8 or 35.5 CS-40 AH-10 GC-34, 37 or 24 DW-0, 0 or 15 CS-40 AH-10 GC-30 or 33 CS-40 AH-10 RB-33 or 37

DIM

Milk

86–136

27.0

(kg/d) 29.0

FCM (%) 3.80

Fat

Protein

4

86–136

21.9

31.1

3.75

3.10b

15.1

4

86–136

21.1

29.6

3.78

3.20a

15.5

8 8 8 8 8 5

55 55 55 55 55 47

23.7 23.9 23.3 24.7 22.6 22.4

32.9 30.1 31.6 33.8 31.5 35.2a

32.5a

3.44 3.89 3.43 3.56 3.62 3.52

3.06 3.17 3.04 3.07 3.11 3.04

ExpSBM-4.0 U U-1.5 SBM-9.3

15.5 15.4 15.4

5 3 3

47 6 6

22.4 25.4 25.3

32.6b 32.9 32.6

30.6b 33.1 32.1

3.61 3.59 3.44

3.04 3.23a 3.27a

MBM-8.2

15.7

3

6

24.7

33.4

33.0

3.44

3.14b

SBM-4.7 MBM-4.7 U-1.8

15.6 16.3

3 4

6 41

24.9 26.0

32.9 35.9

33.3 35.7b

3.57 3.47

3.25a 3.04

SBM-5.5 MBM-5.5 U-1.8

16.3 16.4

4 4

41 41

26.1 24.2b

36.9 35.4b

37.1a 36.0b

3.54 3.70

3.02 3.09

41

26.2a

38.5a

38.2a

3.48

3.01

(kg)

(%) 3.11b

SBM-5.5 MBM-5.5 SBM-14.3

16.2

4

16.3

11

21–112

22.0b

33.8

29.9a

3.23a

3.10

SBM-10.8 U-0.5

16.3

11

21–112

20.2c

33.4

28.0b

2.94b

3.04

SBM-9.0 U-0.5

16.3

11

21–112

23.0a

33.2

29.2a

3.23a

3.04

SBM-16

16

10

28–98

20.0

32.7

29.6

3.36

2.99b

SBM-12.8 U-0.5 SBM-12.6

16 16

10 10

28–98 28–98

20.9 19.1

32.9 31.9

30.4 28.6b

3.38 3.31

3.11a 2.95b

SBM-8.6 U-0.5

16

10

28–98

18.5

31.3

27.1c

3.41

3.05a

Reference

(kg) (10)

(11)

(18)

(20) SANTOS ET AL.

DMI

(%)

(26)

(27)

CS-40 AH-10 GC DW CS-40 AH-10 GC-30 or 33 CS-40 AH-10 RB-33 or 37

BS-40 B-9.4 C-26

10

28–98

20.7

32.1

30.0

3.50

2.90b

SBM-10.7 U-0.05 SBM-16

16

10

28–98

20.3

30.4

29.1

3.51

3.06a

16

19

28–98

20.4b

32.1

28.9

3.39

3.05b

16 16

19 19

28–98 28–98

21.0a 19.8c

32.2 31.7

29.2 28.1b

3.38 3.25

3.14a 3.08

16

19

28–98

18.7d

31.9

26.7c

3.20

3.07 3.20

SBM-12.3 U-0.5 SBM-12.6

(28)

SBM-8.7 U-0.5 WBG-25.6

15.4

9

170–200

21.91

29.4

25.57

3.17

WBG-14.7 U-0.72 SBM-6.8

15.2 15.3

9 4

170–200 82

22.75 18.3

29.0 31.7

25.95 24.5

3.33 2.50

0.78

3.16 3.08

0.99

U-1.2

15.7

4

82

19.7

31.9

26.4

2.82

0.90

3.00

0.96

SBM-9.4

19.5

10

28

26.1a

40.7

39.6

3.45

2.87

19.5 19.5

10 10

28 28

26.3a 24.6b

40.2 39.7

39.6 39.6

3.39 3.61

2.81 2.76

19.5 17.2

10 10

28 22

24.0b 20.2

38.7 40.2

39.7 31.5

3.56 2.56

2.80 3.06

17.4

10

22

21.2

40.8

31.4

2.50

3.08

16.2

18

22–41

18.1b

20.5b

4.88

1.01b

3.43

0.71b

16.2

18

22–41

18.9a

23.0a

4.88

1.12a

3.44

0.79a

SBM-4.91 U-0.70 ABP-7.03 ABP-4.87 U-0.40 SBM-5.6 SFM-5.6 SBM-3.3 SFM-5.2 U-0.7 SBM-2.3 U-1.2 SBM-18.9

(58)

(65)

(117)

(119)

(127)

a,b,cValues

within a group within a column followed by different superscript letters differ ( P < 0.05). = Animal by-product protein, AH = alfalfa hay, AHL = alfalfa haylage, AS = alfalfa silage, B = barley, BM = blood meal, BS = bromegrass silage, C = corn, CGM = corn gluten meal, CS = corn silage, DW = dried whey, FM = fish meal, GEC = ground ear corn, GC = ground corn, GSC = ground shelled corn, HMEC = high moisture ear corn, MBM = meat and bone meal, RB = rolled barley, SFM = salmon fish meal, ShC = shelled corn, and WBG = wet brewers grain. 1ABP

3213

Journal of Dairy Science Vol. 81, No. 12, 1998

GS-46 Molasses-25 B:18.0 or 2.6

16

REVIEW: EFFECTS OF RUMEN-UNDEGRADABLE PROTEIN

CS-25 AH-25 HMEC-23 or 34 AH-45 CS-5 GEC-20 or 35 GSC-19.5 or 9.5 AS-60 ShC-25 or 29

SBM-14.2