Influence of Nonprotein Nitrogen and Protein of Low Rumen Degradability on Nitrogen Flow and Utilization in Lactating Dairy Cows1

Influence of Nonprotein Nitrogen and Protein of Low Rumen Degradability on Nitrogen Flow and Utilization in Lactating Dairy Cows 1 L. KUNG, J R ? and J. T. H U B E R Department of Animal Science Michigan State University East Lansing 48824 L. D. S A T T E R 2 Department of Dairy Science University of Wisconsin Madison 53706

ABSTRACT

availability of heated soybean meal in the intestine was not different, although ruminal degradability tended to be lower. Feeding diets containing nonprotein nitrogen did not decrease available nitrogen at the duodenum.

Four lactating cows, each fitted with a rumen cannula and duodenal and ileal t-cannulae, were used to measure flow and digestion of nitrogenous compounds in the digestive tract. Dietary dry matter contained 17% crude protein and 50:50 forage:concentrate. Treatments were: t) corn silage-soybean meal; 2) corn silageheated soybean meal; 3) ammonia-treated corn silage-soybean meal; and 4) ammonia-treated corn silage-heated soybean meal. Flow of organic matter to the duodenum was overestimated when lanthanum or chromium ethylenediaminetetraacetate was used as an indigestible marker. This resulted in low estimates of ruminal digestion of organic matter and high estimates of nitrogen flow to the duodenum. However, calculations using lanthanum or lignin as markers yielded similar organic matter flow to ileum and feces. With acid-detergent lignin as a marker, estimates of dietary nitrogen degraded in the rumen were: corn silage-heated soybean meal, 55.0%; ammonia-treated corn silage-heated soybean meal, 58.8%; ammonia-treated corn silage-soybean meal, 63.3%; and corn silage-soybean meal, 66.0%. Digestion in the small intestine of nonammonia nitrogen was equal for all treatments suggesting that

INTRODUCTION

Received December 9, 1982. 1Published with approval of the Director of the Agricultural Experiment Station as Journal Article No. 10684. 2United States Dairy Forage Research Center, 1925 Linden Dr. W., Madison, WI 53706. 1983 J Dairy Sci 66:1863--1872

Valid estimates of protein digestion and amino acid absorption in the ruminant are complicated by microbial fermentation in the rumen. Microbial, dietary, and endogenous protein are three sources of amino acids reaching the small intestine for digestion and absorption in ruminants. As yet, amino acid requirements for ruminants have not been determined because of extensive ruminal degradation of dietary protein and the contribution of microbial protein at the duodenum. Oldham and Tamminga (22) pointed out that increasing the supply of amino acids to the duodenum benefits the animal only if there is a concomitant increase of amino acids to the target tissue and a change of animal performance. Huber and Kung (20) suggested that quality as well as quantity o f amino acids reaching the tissues of high yielding cows must be improved. Peak lactation and persistency of lactation are influenced by nutrient intake and b o d y stores. Broster and Strickland (5) showed that every kilogram increase of peak milk production resulted in a 200 kg increase of total milk yield during the entire lactation. If cows are in good body condition at calving and are fed a balanced ration, protein may become a limiting nutrient in early lactation. Increasing protein in early lactation has not always increased milk production, suggesting that amount and types of protein, genetic

1863

1864

KUNG, JR., ET AL.

ability of cows, and management factors affect responsiveness (10). In a companion trial to this study, Kung and Huber (20) demonstrated that high producing cows early in lactation were most productive when fed rations containing nonprotein nitrogen (NPN) plus rumen undegradable protein at 17.5% crude protein. The results of this study describe digestion in the alimentary tract of cows fed diets containing NPN and protein of low ruminal degradability (20). MATERIALS AND METHODS Animals and Diets

Four lactating Holstein cows that averaged 55 days postpartum and 605 kg body weight were used in a 4 × 4 Latin square. Cows had been fitted with ruminal, duodenal, and ileal t-cannulae. The cannula in the duodenum was proximal to the pancreatic-bile duct, and the

ileal cannula was just proximal to the ileocecal junction. Diets consisted of 50% grain (soybean meal and ground shelled corn; Table 1), 40% corn silage, and 10% alfalfa hay dry matter (DM). Treatment combinations were: 1) corn silage-control soybean meal (CS-SBM); 2) corn silage-heated soybean meal (CS-HS); 3) ammonia-treated corn silage-control soybean m~al (AS-SMB); and 4) ammonia-treated corn silage and heated soybean meal (AS-HS). Heated soybean meal was prepared by placing commercially available soybean in a forced draft oven at 140°C for 2.5 h. Ammonia-treated corn silage was prepared by treatment with approximately 3.2 kg of anhydrous ammonia per ton of corn silage. These feeds were similar to those fed by Kung and Huber (20). Ammoniatreated silage was unloaded from a silo at the Michigan State University Dairy Cattle Research Center, packed in doubly-lined plastic bags, evacuated, and sealed. This material and normal and heated soybean meal were transported by

TABLE 1. Ingredient and chemical composition of feeds and rations. Rationa

Ingredients of grain mix, (%) Ground shelled corn Soybean meal Limestone Dicalcium phosphate Trace mineralized salt Calcium sulfate Vitamin premixb

AS-HS

AS-SBM

CS-HS

CS-SBM

63.3 32.7 1.0 1.5 1.0 .3 .2

63.3 32.7 1.0 1.5 1.0 .3 .2

55.9 40.1 1.0 1.5 1.0 .3 .2

55.9 40.1 1.0 1.5 1.0 .3 .2

Chemical composition of feeds and rations

Corn silage Ammonia silage Alfalfa hay Complete rations AS-HS AS-SBM CS-HS CS-SBM

Dry matter

Crude proteinc

Acid detergent c fiber

Ashc

35.1 34.2 85.0

8.1 12.5 17.1

29.3 26.7 36.5

5.5 4.2 8.6

55.0 54.4 54.6 55.0

17.7 17.8 17.0 17.2

18.1 18.1 18.0 17.7

aAS-ammonia-corn silage; HS-heated soybean meal; SBM-soybeanmeal; CS-corn silage. bcontains (IU/ton): A, 4 × 106 ; D, 4 X 10s ; E, 5 × 104 . Cpercentage of dry matter• Journal of Dairy Science Vol. 66, No. 9, 1983

NITROGEN FLOW AND USE truck from East Lansing, MI, to Madison, WI. Untreated corn silage, hay, and ground shelled corn were from local supplies at the University of Wisconsin. Corn silage, grain, and hay were fed in four equal portions at 0400, 1000, 1600, and 2200 h. Experimental periods were 14 days. Days 1 through 10 were for ration and marker equilibration, and days 11 through 14 were for collection of samples. Feeds and weighbacks were sampled daily and composited prior to dry matter determination in a forced draft oven at 65°C for 72 h. Total N was determined on ground wet samples by macro-Kjeldahl. Sample Collection and Analysis

Chromium (Cr)-ethylenediaminetetraacetic acid (EDTA) and lanthanum (La) were sprayed onto the entire grain mix and used as indigestible flow markers to determine digestibility (3, 12). Concentrations of markers fed were 191 mg Cr and 93 mg La/kg of grain mix. Duodenal, ileal, and fecal samples were collected at 8-h intervals on days 11 to 14 for a total of 12 samples representing the odd-numbered hours of the day. Approximately 400 ml of duodenal contents, 300 ml of ileal contents, and 500 g of feces were collected at each sampling. Visual observation of digesta samples from duodenal cannulae revealed marked sample variation in the ratio of liquid and solids. Sample collection was as follows: 1) all solid material from the cannula was removed; 2 ) t h e first 100 ml of digesta were discarded; 3) the next 400 ml of digesta were saved for cornpositing and analyses. All wet digesta and feces were homogenized prior to compositing on a

1865

volume basis and subsequent analysis. Total N and ammonia-nitrogen (NHa-N) were analyzed on wet samples by macro-Kjeldahl (2) and ammonia ion specific electrode. Nonammonia nitrogen (NAN) flow to the duodenum was calculated by difference. Portions of composited feed, digesta and feces were lyophylized and ground through a 1-mm mesh screen. The following analyses were then performed: acid-detergent fiber and acid-detergent lignin (11), ash (2), and determination of marker concentration via neutron activation analysis (12). Rumen fluid was collected at 0, 2, 4, and 6 h after the 1000 h feeding on day 14, and pH was determined immediately. Fifty milliliters of fluid was acidified with 2 ml of 50% sulfuric acid (vol/vol), frozen, and stored at - 2 0 ° C until analyses for NHa-N by the method of Okuda et al. (21) directly adapted for ruminal contents. Volatile fatty acids were measured by gas chromatography in a column packed with 10% SP-1200/1% H3PO4 on 100/120 Chromosorb W-AW. Two hundred milliliters of rumen fluid was collected also at each sampling and combined with 60 ml .9% NaC1-37% formaldehyde solution. Composited fluid was centrifuged at 500 × g to remove protozoa and feed residues. Ruminal bacteria were isolated by centrifugation at 20,000 x g and were lyophilized and analysed for total N by Kjeldahl and for total nucleic acids by procedures of Zinn and Owens (30). Microbial protein was estimated from nucleic acid content of duodenal digesta. Organic matter was determined by subtraction of ash content in feed, digesta, and feces from total dry matter. Relative differences of ruminal protein

TABLE 2. Milk production and composition of cows fed different protein sources. Treatment a

Milk, kg/day Fat, % Protein, % Solids, %

AS-HS

AS-SBM

CS-HS

CS-SBM

SE

24.1 3.03

24.2 3.47 2.91 11.21

23.6 3.41 2.81 11.41

22.6 3.33 3.08 11.48

1.0 .24 .09 .28

2.69

11.00

aAs-ammonia-corn silage; HS-heated soybean meal; SBM-soybean meal; CS-corn silage. bMean of days 8 through 14 averaged for four periods. Journal of Dairy Science Vol. 66, No. 9, 1983

1866

KUNG, JR., ET AL.

degradability of soybean meals was measured by nylon bag technique as in (20). Milk production was recorded on days 8 to 14, and composite milk samples were collected on day 14. Milk fat and protein were determined by infrared analyses (2) and total solids by drying 2 ml of milk for 2 h at 100°C.

U z a_ o co c<

Statistical Analysis

z

Data were analyzed factorially to determine differences between silage type, protein type, and interaction of silage × protein by standard procedures of analysis of variance. Variation from animals and periods were removed from treatments by analysis of variance. One animal was off feed for treatment AS-SBM but was replaced subsequently for other treatments. Data for the missing block in a Latin square was estimated as described by Cochran and Cox (6). RESULTS A N D DISCUSSION

Composition of feeds is in Table 1. The ammonia-treated silage was free of spoilage despite being emptied from the silo, transported to Wisconsin, and stored for 30 to 45 days. No heating was detected, and only minimal mold at the tie of the bags was observed. These observations support those of Britt and Huber (4), who reported that ammonia treatment of corn silage retarded heating and spoilage. Ammoniatreated silage was slightly lower in ADF and ash content than control corn silage. Milk production and composition were not different among treatments (Table 2). Nitrogen disappearance of soybean meals

///

I

t8 I I 115 HOURS OF INCUBFIT[ON

---q 24

Figure 1. Nitrogen disappearance of normal soybean meal (SBM) and soybean meal heated for 2.5 h at 140°C from nylon bags suspended in the rumen.

from nylon bags suspended in the rumen is in Figure 1. Ruminal disappearance of N from nylon bags at 12 h of incubation was 75% for SBM and 40% for HS. Ammonia-N measured in rumen fluid at 0, 2, 4, and 6 h after feeding (Table 3) was greatest for cows fed AS-SBM, intermediate for AS-HS and CS-SBM, and lowest for CS-HS. Rumen fluid pH and volatile fatty acids were not different among treatments (Table 4). When La was an indigestible marker, estimated organic matter entering the duodenum was approximately 13.7 kg/day for all treatments (Table 5). This resulted in extremely low estimates of ruminal digestion of organic matter. Although not shown, use of Cr also led to low estimates of ruminal digestibility of

TABLE 3. Concentration of ammonia in rumen fluid of cows fed different protein sources.

Treatmenta

0

AS-HS AS-SBM CS-HS CS-SBM

10.8 14.9 9.4 19.7

Hours after feedingb 2 4

6

-X

SE

12.5 18.7 9.7 11.2

13.3 cd 17.9 c 9.9 d 15.8c

4.4 6.4 3.9 5.7

(mg/dl) 19.0 25.1 12.7 18.7

10.9 13.1 7.8 13.7

aAS-ammonia-corn silage; HS-heated soybean meal; SBM-soybeanmeal; CS-corn silage. bAverages from four animals. C'dMeanswith unlike superscripts differ (P<.05). Journal of Dairy Science Vol. 66, No. 9, 1983

NITROGEN FLOW AND USE organic matter. These findings are disturbing but similar to those of other experiments at the University of Wisconsin with ytterbium, lanthanum, samarium, CR-EDTA, and cobaltEDTA markers (D. K. Combs, personal communication). We believe our findings are attributable to a combination of factors. First, most studies utilizing rare earth elements as indigestible markers have measured digesta flow in animals consuming small amounts of dry matter relative to lactating dairy cows. Thus, attaining steady state flow of digesta may be more difficult when intakes are large. Digesta mixing and flow from the abomasum may present a second problem if disproportionate separation occurs between solids and liquids passing into the duodenum. Another potential problem has been identified by Wisconsin researchers who found a negative correlation between duodenal dry matter content and its rare earth concentration (7). This finding agrees with data from Allen and Van Soest (1), who reported migration of rare earth markers under acid conditions similar to those in the abomasum. Finally, sampling of liquids and solids from t-cannulae may not be representative of digesta flow. Preliminary results suggest that nonsteady state conditions and marker migration are primarily responsible for aberrant results (D. K. Combs, personal communication). Acid-detergent lignin was an internal marker for estimating digestibility because of the apparently erroneous ruminal digestion of organic matter with La and Cr. Apparent digestibility of organic matter in the rumen as a percent of total tract digestion averaged 63.3, 74.6, 73.3, and 67.6 for rations AS-HS, AS-

1867

SBM, CS-HS, and CS-SBM. Although some have cautioned against the use of lignin as a digestibility marker (9), lignin in our study resulted in a more reasonable estimate of apparent digestion in the rumen than La (Table 5). Heat was not used in preparation of feed duodenal or ileal samples for analysis, so there was no artifact lignin formation due to heat damage. Moderate heat (55°C for 48 h) was applied to feces. Estimates of organic matter flow to the ileum and feces by lignin averaged within 10% of flows calculated with La, suggesting that marker estimates were erratic only at the duodenum. Because lignin gave lower estimates than La of organic matter flow to the duodenum but similar ileal flows, apparent digestibility of organic matter in the small intestine was lower with lignin. Digestibilities of organic matter in the total tract were similar for all treatments regardless of marker. The finding that estimates of ruminal digestibility appeared to be more feasible with lignin has been observed in some experiments where rate earths or Ruthenium have given low estimates of rumen digestibility (D. K. Combs and R. C. Kellaway, personal communication). Nitrogen intake and comparisons of N flow and digestibility calculated with lignin and La are in Table 6. Total N intake was similar for all treatments. Because calculated N flow is influenced by estimated dry matter flow, N flow to the duodenum was less for lignin than for La. However, N flow to the ileum and feces was similar for the two markers, again suggesting that the discrepancy in marker flow occurred only at the duodenum. When based on La, apparent N digestion in

TABLE 4. Rumen pH and volatile fatty acids of cows fed different protein sources, ab Item

AS-HS

pH Acetate, molar % Propionate, molar % Butyrate, molar % Total, mmoles/dl

6.30 67.6 21.1 9.8 8.6

AS-SBM 6.42 66.3

20.1 9.9 8.7

CS-HS

CS-SBM

SE

6.41 67.8 17.4 11.3 9.1

6.3S 66.4 18.9 10.6 9.3

.21 1.7 1.2 .9 .7

aAs-ammonia corn silage; HS-heated soybean meal; SBM-soybean meal; CS-corn silage. bAverage of 0, 2, 4, and 6 h postfeeding. Journal of Dairy Science Vol. 66, No. 9, 1983

=. Ox 0o

o ¢z bq

TABLE 5. Flow and digestion of organic matter in the digestive tract of cows fed different protein sources,a < O

Item

AS-HS

AS-SBM

CS-HS

CS-SBM

Organic matter intake, kg/day Organic matter flow to: Duodenum (uncorrected),d kg/day Duodenum (corrected), e kg/day Ileum, kg/day Feces, kg/day Organic matter digestion in: Rumen/abomasum (uncorrected), d % of intake Rumen/abomasum (corrected), e % of intake Rumen/abomasum (corrected), e % of total tract digestion Small intestine, % entering Post ileum, % entering Total tract, % of intake

16.5

16.5

17.2

16.0

SE

ox

.o

7~ 0~ uo

10.6 b (15.8) c 9.3 (13.8) 6.8 (6.6) 5.2 (5.1)

9.4 (13.9) 8.1 (12.0) 6.6 (6.9) 5.3 (5.6)

9.7 (12.5) 8.5 (10.5) 6.2 (5.9) 5.4(5.6)

4.4 (5.4)

35.5 (3.7)

42.7 (15.3)

42.1 (25.8)

41.6 (16.5)

3.70 (5.57)

43.5 (16.0)

50.6 (27.5)

49.8 (37.8)

49.3 (28.0)

3.65 (3.70)

63.3 34.2 24.7 68.7

74.6 (41.3) 30.4 (39.9) 19.8 (19.2) 67.8 (65.6)

73.3 34.8 13.3 67.9

67.6 (38.8) 41.2 (45.9) 20.4 (10.9) 72.9 (65.5)

2.81 (3.01) 3.27 (1.55) 3.89 (3.65) 2.53 (2.39)

CCalculated with lanthanum as a marker. dlncludes bacterial organic matter. eDoes not include bacterial organic matter.

9.6 (13.3) 8.4 (11.5)

5.7 (6.1)

.71 .69 .20 •44

(.81) (.51) (.41) (.35) Z

(23.3) (51.8) (23.2) (68.9)

aAs-ammonia-corn silage; HS-heated soybean meal; SBM-soybean meal; CS-corn silage. bcalculated with lignin as a marker.

.48

(57.8) (43.7) (4.8) (66.7)

P

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e~ o

o

o z ,6 <

m

N~2 ~

v

v

v

v

GG~K

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d ~ N d

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b

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NITROGEN FLOW AND USE

,-4

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1869

the rumen was positive for cows fed CS-SBM and slightly negative for other treatments. However, apparent N digestion in the rumen calculated with lignin averaged 27.3% for all treatments (Table 6). Cows fed unheated SBM (AS-SBM and CS-SBM) tended to have the greatest amount (P<.13) of N apparently digested anterior to the small intestine. Hume et al. (15) observed large net increases of N flow at the duodenum in sheep fed low N diets. Kaufman and Hagemeister (18) reviewed selected data and reported a net loss of N at the duodenum when dietary protein was 13% or greater, and rations containing less than 13% protein showed net gains. The net increase of N on low protein diets is probably due to microbial incorporation of endogenous N recycled back to the rumen. A net loss of N at the abomasum and duodenum suggests absorption of N as ammonia released from deamination of amino acids in the rumen. Crude protein in the present ration was greater than 17%, and rumen NH3-N was moderately high; thus, a net loss of N was expected. Theurer (28) observed a net loss of N from the rumen when lignin was the reference marker, but N flows at the abomasum and duodenum exceeded 100% of intake in studies where Cr was the marker. Apparent digestibilities of N in our study were similar to those of Crickenberger et al. (8) and Sachtleben (24). Both found lignin a more satisfactory marker than chromic oxide. Similar to rumen digestibilities of organic matter, lignin estimates were lower for apparent digestibility of N in the small intestine than La. However, post ileal N digestibility was greater with lignin. There were no differences between markers or treatments for total tract digestibilities. The following discussion and remaining data were based on lignin as a marker. Flow of NAN to the duodenum averaged 344 g/day for all treatments (Table 7) and was greater (P<.13) for cows fed CS-HS (391 g/day) and AS-HS (352 g/day) than CS-SBM (310 g/day) or AS-SBM (323 g/day), suggesting more degradation of dietary N with SBM than HS diets. Partial replacement of N in SBM with ammonia in silage did not decrease NAN flow to the duodenum. Rohr et al. (23) also reported that partial replacement of natural protein with NPN did not decrease NAN flow to the duodenum. In our study, the ammonia in corn Journal of Dairy Science Vol. 66, No. 9, 1983

1870

KUNG, JR., ET AL.

silage c o n t r i b u t e d 2.2% crude protein or a b o u t 13% of the total dietary N. Use of a m m o n i a treated corn silage m a y be m o r e advantageous than o t h e r NPN supplements. In addition to reducing partially the need for p r e f o r m e d protein supplements, a m m o n i a t r e a t m e n t inhibits proteolysis during silage f e r m e n t a t i o n (16). J o h n s o n et al. (16) r e p o r t e d less free amino acids in a m m o n i a - t r e a t e d corn silage as c o m p a r e d to u n t r e a t e d corn silage. Huber et al. (13) showed an increase of insoluble N in a m m o n i a - t r e a t e d corn silage, which was utilized m o r e efficiently for milk p r o d u c t i o n than soluble N (25). Cows consuming treated corn silage fed in a c o m p l e t e m i x e d ration also w o u l d tend to reduce excessive c o n s u m p t i o n of readily degradable protein during specific eating periods. Microbial N flow to the d u o d e n u m was similar for all t r e a t m e n t s (Table 7). Theurer (29) summarized data f r o m 12 e x p e r i m e n t s where ribonucleic acid ( R N A ) was a microbial marker and r e p o r t e d a m e a n of 24 g microbial N/kg organic m a t t e r apparently f e r m e n t e d in the r u m e n (OMFR), but w h e n lignin was used as a flow marker and R N A the microbial marker, microbial efficiencies averaged 19 g/kg

O M F R . In our study, efficiency of microbial protein synthesis averaged 20 g/kg O M F R corrected for microbial organic matter. A p p a r e n t degradation of dietary N in the tureen averaged 58.8, 63.3, 55.0, and 67.4% for the four diets. Digestion of N A N in the small intestine tended to be greater for HS diets (P<. 15). However, N A N digested as a percentage of flow was similar for all treatments. These findings suggest that although protein f r o m heated soybean meal was less degradable in the rumen, its availability in the small intestine did n o t decrease c o m p a r e d to u n h e a t e d soybean meal. Digestion of N A N was lower than for the literature average of 68 -+ 3% as summarized by Zinn and Owens (31). With cows, V a n ' t Klooster and Rogers (19) reported N A N digestion ranging f r o m 61 to 72%. A l t h o u g h our percents appear low, total N intake was also considerably higher than before. Digestibility of A D F was lowest (P<.11) for cows fed ammonia-treated silages (Table 8). On the average, 90% of total A D F digestion occurred in the rumen. Summary and Conclusions

When C R - E D T A or La was used as a di-

TABLE 7. Flow and digestion of nonammonia nitrogen and efficiency of rumen microbial protein synthesis of cows fed different protein sources, ab Item Nonammonia nitrogen flow t o : Duodenum (total), g/day c Duodenum (bacterial), g/day Duodenum (dietary, endogenous) protozoa), g/day Ileum (total), g/day Microbial N, g/kg OM truly digested Dietary N apparently degraded in rumen/abomasum, % of intake d N A N apparent digestion in small intestine, g/day e NAN apparent digestion in small intestine, % entering a

.

AS-HS

AS-SBM

CS-HS

CS-SBM

SE

352 148

323 141

391 170

310 150

33.0 14.4

204 161

183 142

222 166

161 146

28.0 11.5

22

17

20

20

2.5

58.8

63.3

55.0

66.0

5.08

192 54.1

182 56.0

.

226 57.0

AS-ammoma-corn silage; HS-heated soybean meal, SBM-soybean meal; CS-corn silage.

bCalculated using lignin. cAS-HS and CS-HS are different from AS-SBM and CS-SBM (P<.I 3). dAS-HS and CS-HS are different from AS-SBM and CS-SBM (P<.15). eAS-HS and CS-HS are different from AS-SBM and CS-SBM (P<.15). Journal of Dairy Science Vol. 66, No. 9, 1983

165 54.8

23.2 1.49

NITROGEN FLOW AND USE

1871

TABLE 8. Acid detergent fiber (ADF) intake and digestion in cows fed different protein sources. Item

AS-HS

ADF intake, kg/day Apparent ADF digestion: Rumen/abomasum, % intake c Rumen/abomasum, % of total tract Small intestine, % entering Post ileum, % entering Total tract, % intake a

AS-SBM

CS-HS

3.2

3.2

3.3

42.1 87.7 4.2 6.1 48.0

46.6 96.1 --8.1 1.5 48.5

51.1 101.4 -- 15.2 5.7 50.4

CS-SBM

SE

3.0

.09

50.2

3.33 5.10 6.74 6.18 4.10

92.1

--7.1 13.3 54.4

.

AS-arnmoma-corn silage; HS-heated soybean meal; SBM-soybean meal; CS-corn silage. bCalculated with lignin. cAS-HS and AS-SBM are different from CS-HS and CS-SBM (P<.ll).

gestibility marker, organic m a t t e r digestion in the r u m e n was underestimated. However, ruminal pH, volatile fatty acids, ruminal ammonia, and milk p r o d u c t i o n were within normal ranges, Mean m a r k e r c o n c e n t r a t i o n s o f Cr:La in duodenal, ileal, and fecal c o n t e n t s as a percent of their ratios in feed were 87, 93, and 93%, suggesting that the d u o d e n a l samples had a proper p r o p o r t i o n o f liquid and solids. However, failure of rare earth markers to remain b o u n d on their original feed particle w o u l d invalidate this logic. Based on findings in this e x p e r i m e n t , use of rare earth markers for estimating digestibility warrants further investigation. Research is currently u n d e r w a y to investigate behavior of rare earth markers in the digestive tract of ruminants. Lignin as a digestibility marker showed that dietary N was degraded less in the r u m e n with diets containing HS than SBM. There were no t r e a t m e n t differences in N A N digestion in the intestine expressed as a p e r c e n t of N A N flow, suggesting t h a t in all diets N A N was digested and absorbed equally in the small intestine. Increased N A N flow to the d u o d e n u m for diets AS-HS and CS-HS support findings of Kung and H u b e r (20), who r e p o r t e d that cows fed rations containing HS gave m o r e milk than SBM controls. F u r t h e r m o r e , partial substitution of N f r o m SBM with N f r o m a m m o n i a added to corn silage did n o t decrease N A N flow to the small intestine. ACKNOWLEDGMENTS

The authors w o u l d like to thank D. Sue

Brecht, D. Snyder, and D. Davis for assistance in sample processing. The senior a u t h o r gratefully acknowledges the D e p a r t m e n t of Dairy Science, University of Wisconsin, for allowing this w o r k to be accomplished.

REFERENCES

1 Allen, M. S., and P. J. Van Soest. 1982. Comparative affinities of rare earth elements for plant cell walls. J. Anita. Sci. 55(Suppl. 1):403. (Abstr.) 2 Association of Official Analytical Chemists. 1975. Official methods of analysis. 12th ed. Assoc. Offic. Anal. Chem., Washington, DC. 3 Binnerts, W. T., A. Th. Van't Klooster, and A. M. Frens. 1968. Soluble chromium indicator measured by atomic absorption in digestion experiments. Vet. Rec. 82:470. 4 Britt, D. G., and J. T. Huber. 1975. Fungal growth during fermentation and refermentation of nonprotein nitrogen treated corn silage. J. Dairy Sci. 58:1666. 5 Broster, W. H., and M. F. Strickland. 1977. Feeding the dairy cow in early lactation. ADAS Q. Rev. 26:87. 6 Cochran, W. G., and G. M. Cox. 1957. Experimental designs. John Wiley and Sons, New York, NY. 7 Combs, D. K., H. Tagari, S. Reddy, T. Klusmeyer, and L. D. Satter. 1982. Sample frequency required for estimation of digestibility by the rare earth marker technique. J. Anita. Sci. 55(SuppI. 1):414. (Abstr.) 8 Crickenberger, R. G., W. G. Bergen, D. G. Fox, and L. A. Gideon. 1979. Effect of protein level in corn-corn silage diets on abomasal nitrogen passage and utilization by steers. J. Anita. Sci. 49:177. 9 Fahey, G. C., G. A. McLaren, and J. E. Williams. 1979. Lignin digestibility by lambs fed both low quality and high quality roughages. J. Anita. Sci. 48:941. Journal of Dairy Science Vol. 66, No. 9, 1983

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KUNG, JR., ET AL,

10 Foldager, J., and J. T. Huber. 1979. Influence of protein percent and source on cows in early lactation. J. Dairy Sci. 52:954. 11 Goering, H. K., and P. J. Van Soest. 1970. Forage fiber analyses. Agric. Handbook 379. Agric. Res. Serv., US Dep. Agric., Washington, DC. 12 Harmell, G. F., and L. D. Satter. 1979. Extent of particulate marker (samarium, lanthanum and cerium) movement from one digesta particle to another. J. Anita. Sci. 48:375. 13 Huber, J. T., N. E. Smith, and J. Stiles. 1980. Influences of time after ensiling on distribution of nitrogen in corn silage treated with ammonia. J. Anim. Sci. 51:1387. 14 Huber, J. T., and L. Kung, Jr. 1981. Protein and nonprotein nitrogen utilization in dairy cattle. J. Dairy Sci. 64:1170. 15 Hume, I. D., R. J. Moir, and M. Somers. 1970. Synthesis of microbial protein in the rumen. I. Influence of level of nitrogen intake. Australian J. Agric. Res. 21:283. 16 Johnson, C.O.L.E., J. T. Huber, and W. G. Bergen. 1982. Influence of ammonia treatment and time of ensiling on proteolysis in corn silage. J. Dairy Sci. 65:1740. 17 Johnson, D. E., and W. G. Bergen. 1982. Fraction of organic matter digestion occurring in the rumen: a partial literature summary. Page 113 in Protein requirements for cattle. F. N. Owens, ed. Oklahoma State Univ., Stillwater. 18 Kaufmann, W., and H. Hagemeister. 1976. Zum einflub der Behandlung yon protein mit formaldehyd auf die bakterielle protein synthese und die abbaurate yon protein in den Vormagen yon Milchkuhen sowie auf die Verdauliehkeit des proteins in darm. Kieter Milchw. Forsch. Ber. 28:355. 19 Klooster, A. Th. Van't, and P.A.M. Rogers. 1969. Observation on the digestion of food along the gastro-intestinal tract of fistulated cows. I. The rate of flow of digesta and the net absorption of dry matter, organic matter, ash, nitrogen and water. Meded. Landbounhogesch., Wageningen 69:3. 20 Kung, L., Jr., and J. T. Huber. 1983. Performance of high producing cows in early lactation fed protein of varying amounts, sources, and de-

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gradability. J. Dairy Sci. 66:227. 21 Okuda, H., S. Fuji, and Y. Kawashima. 1965. A direct colormetric method for blood ammonia. Tokushima J. Exp. Med. 12:11. 22 Oldham, J. D., and S. Tamminga. 1980. Amino acid utilization by dairy cows. I. Methods of varying amino acid supply. Livest. Prod. Sci. 7:437. 23 Rohr, K., M. Brondt, O. Castrillo, P. Lebzein, and G. Assmus. 1979. Der Einflub eines teilweisen Ersatzes von Futterprotein dutch Harnstoff auf den stickstoff-und aminosaurenflub am duodenum. Landbauforsh. Volkenrode 29:32. 24 Sachteleben, S. S. 1980. Studies on the effect of diet on nitrogen passage to the lower gastrointestinal tract in steers. Ph.D. thesis, Michigan State Univ., East Lansing. 25 Smith, N. E., J. T. Huber, J. Stiles, and J. Taylor. 1982. Utilization of nitrogen in [lSNitrogen] ammonia treated corn silage fed to lactating cows. J. Dairy Sci. 65:1734. 26 Tamminga, S. 1973. The influence of the protein source on the protein digestion in the ruminant. Z. Tierphysiol. Tiererhahr. Futtermittelkd. 32:185. 27 Tamminga, S. 1975. The influence of method of preservation of forages on the digestion in dairy cows. 2. Digestion of organic matter, energy, and amino acids in the forestomachs and intestines. Netherlands J. Agric. Sci. 28:89. 28 Theurer, C. B. 1979. Microbial protein synthesis as influenced by diet. Page 157 in Regulation of acid-base balance. W. H. Hale, and P. Meinhardt, ed. Church and Dwight Co., Inc., Piscataway, NJ. 29 Theurer, C. B. 1982. Microbial protein estimates using DAP, AEP and other amino acids as markers. Page 10 in Protein requirements for cattle. F. N. Owens, ed. Oklahoma State University, Stillwater. 30 Zinn, R. A., and F. N. Owens. 1982. Rapid procedure for quantifying nucleic acid content of digesta. Page 26 in Protein requirements for cattle. F. N. Owens, ed. Oklahoma State University, Stillwater. 31 Zinn, R. A., and F. N. Owens. 1982. Predicting net uptake of nonammonia N from the small intestine. Page 133 in Protein requirements for cattle. F. N. Owens, ed. Oklahoma State University, Stillwater.