Proceedings, Western Section, American Society of Animal Science
Vol. 50, 1999
RUMINAL DIGESTION BY STEERS FED HIGH CONCENTRATE DIETS
CONTAINING CORN OR BARLEY[1]
T. J. Milner*, J.G.P. Bowman, and
L.M.M. Surber
Montana State University, Bozeman, MT 59717
ABSTRACT: Four ruminally and duodenally cannulated steers (Hereford/Angus avg wt 635 kg) were used in a 4 X 4 Latin square design to evaluate ruminal digestion characteristics of corn or barley high concentrate diets. Diets compared were: 1) corn; 2) Gunhilde, a six-row European feed barley (GUN); 3) Harrington, a two-row malting variety (HAR); and 4) 50% Gunhilde+50% Harrington (MIX). MIX diet was included to test for possible associative effects. Diets were balanced to be isonitrogenous (13.5% CP) and isocaloric (1.93 Mcal/kg NEm, and 1.28 Mcal/kg NEg). Diet adaptation was 14 d followed by a 7-d collection period. Duodenal samples were collected at 0, 3, 6, 9, 12, 15, 18, 21, 24, 30, 36, 42, 48, 54, 60, and 72 hr after feeding, and composited to determine ruminal digestion and flow to the duodenum of DM, OM, N and starch. Sustained release boluses containing Cr2O3 were used to estimate duodenal DM flow. Orthogonal comparisons were made: corn vs avg of barley treatments, GUN vs HAR, and avg GUN/HAR vs MIX. No differences were seen in duodenal DM flow (P > .10) when corn was compared to barley. Duodenal DM and N flow was greater (P < .05) for HAR (4.88 kg/d and 183 g/d, respectively) than for GUN (4.30 kg/d and 168 g/d, respectively). Ruminal DM digestion was 12% greater (P = .04) for GUN when compared to HAR (56.7 vs 50.6%). Ruminal starch digestibility was lower (P = .02) for steers fed corn than those fed barley (75.6 vs 86.1%), resulting in more (P = .004) starch flowing to the duodenum (1167 vs 549 g/d). No differences (P > .10) were seen for total N or microbial N flow to the duodenum. No associative effects (P > .01) were observed for nutrient flow to the duodenum or ruminal digestibility when MIX was fed. Differences in digestion characteristics of steers fed corn vs barley may result in different feeding values. There appear to be no associative effects when Gunhilde and Harrington barley varieties were fed in combination.
Key words: Barley, Ruminal digestibility, Starch.
Suited to the semi-arid growing conditions of the Pacific Northwest, barley is a major cash crop for the region. Wide availability of the grain has allowed area livestock producers to utilize barley in many aspects of their feeding programs. However, with a number of varieties on the market less is known about the feeding quality of the individual cultivars than about the malting quality. Classification of these cultivars, whether of a feeding or malting type, is typically based on malting characteristics rather than actual feeding value (Gibson et al., 1994).
Characterized by a fast rate of ruminal fermentation, barley varieties have demonstrated a wide range of performance differences in feeding as well as metabolism trials. Boss and Bowman (1996a) reported steer fed Harrington had higher ADG and DM intakes when compared to steers fed Gunhilde. Milner et al. (1996), in a similar trial, found no differences in ADG and DM intakes when comparing the same varieties. These differences may be attributed to rate and/or site of starch utilization by the ruminant animal. Surber and Bowman (1998) and Ørskov (1986) reported that more starch from corn escapes ruminal digestion than barley starch. Slow ruminal starch digestion has been reported to be desirable for animal performance (Tyrrell and Moe, 1974). Our objectives were to evaluate the ruminal digestion characteristics of corn or barley high concentrate diets, and to determine if associative effects resulted from feeding a malting barley variety in combination with a feed barley.
Materials and Methods
Four ruminally and duodenally cannulated steers (Hereford/Angus avg wt 635 kg) were used in a 4 X 4 Latin square design to evaluate site, rate, and extent of digestion of corn or barley high concentrate diets. Diets compared were: 1) corn; 2) Gunhilde, a six-row European feed grade barley (GUN); 3) Harrington, a two-row malting variety (HAR); or 4) 50% Gunhilde+50% Harrington (MIX). Steers were housed in individual concrete floored pens (15 m2). Diets were balanced to be isonitrogenous (13.5% CP) and isocaloric (1.93 Mcal/kg NEm, 1.28 Mcal/kg NEg). Diet compositions are presented in Table 1. Diets were hand mixed and limit fed at 12.0 kg/d, half at 0800 and the balance at 1800. Water and trace mineralized salt were available free choice.
Each period consisted of 21 d, consisting of 14 d for diet adaptation followed by a 7-d collection period. Diet changes between periods were done using a step-wise substitution of 25% of the new diet to the total as-fed diet per day over the first 4-d. Feed grab samples were taken at each feeding during the collection period, composited and ground through a 1-mm screen in a Wiley mill for analysis of DM, OM, N, starch (AOAC, 1997), and ADF (Van Soest et al., 1991).
On d 7 of the adaptation period, sustain release boluses (Captec Chrome, Nufarm, Aukland, New Zealand) were placed in the rumen of each steer. This administered Cr2O3 as an external marker to estimate DM flow to the duodenum and fecal output. Steers were pulse dosed 300 g of their respective grains which had been labeled with Yb (Poore et al., 1991) at first feeding of the collection period (time 0 h). Duodenal and fecal grab samples were taken at 0, 3, 6, 9, 12, 15, 18, 21, 24, 30, 36, 42, 48, 54, 60, and 72 h after dosing.
Fecal samples were dried at 60oC for 72 h in a forced-air oven then ground through a 1-mm screen in a Wiley mill. A portion of hourly fecal samples were composited on a DM basis within steer and period. Composited fecal samples were analyzed for DM, OM, N, ADF, starch and Cr (Hill and Anderson, 1958). A portion of each hourly duodenal samples, was dried at 60oC in a forced-air oven for 72 h, ground in a mortar and pestle, further ground in a Udy mill and composited within steer and period. These samples were analyzed for DM, OM, N, ADF, Cr, starch, and purine content (Zinn and Owens, 1986).
Half of the remaining portion of the hourly duodenal was used for VFA analysis, the other used for ammonia analysis (AOAC, 1997). Hourly dried duodenal, hourly dried fecal, and Yb-labeled grain samples were analyzed for Yb content (Poore et al., 1991) by a ICP-ES (Fison Instrument Accuris) with a wave length of 369.42 :m. Hourly duodenal Yb concentrations were fitted into a one-compartment model (Ellis et al., 1979) to estimate particulate flow rate, retention time, time delay (Tau) and DM output. On the final day of the collection period, 1.5 L/steer of rumen fluid was collected. Differential centrifugation (Smith and McAllen, 1974) was used to extract a microbial pellet which was then analyzed for DM, N and purine content.
Data were analyzed as a 4 X 4 Latin square design using the GLM procedure of SAS (1993). Orthognal comparisons were made for: corn vs barley, GUN vs HAR, and MIX vs GUN and HAR. Treatment least square means were separated by the LSD method of SAS (1993) if treatment F-test was significant (P < .10). Least square means and associated standard errors are reported.
Results and Discussion
No associative effect (P > .10) was seen in nutrient flow to the duodenum (Table 3). Corn fed steers had greater (P = .004) starch flow to the duodenum than steers fed barley (1167 vs. 549 g/d avg., respectively). This was due to lower (P = .02) ruminal starch digestion by steers fed corn than those fed barley (75.64 vs. 86.07% avg., respectively). This is in agreement with Ørskov (1986) and Feng et al. (1995) who reported corn had a slower rate of ruminal starch digestion than barley. However, these results differ from a previous study (Boss and Bowman, 1996b) where corn and barley had similar digestion rates. In their study GUN had lower (P = .04) ruminal DM digestion than HAR, resulting in more (P = .03) DM flowing to the duodenum (4895 vs 4882 g/d, respectively). In our study, daily starch flow, though not significant (P = .12), was over 300 g/d greater for steers fed HAR barley than for steers fed GUN barley (690 vs 389 g/d, respectively). Steers fed HAR had greater (P = .04) total N and non-ammonia N (P = .03) passage to the duodenum than GUN. Feng et al. (1995) found total N, microbial N, and non-ammonia N flow to the duodenum greater for barley than for corn, where as in our study there were no differences observed between corn or barley diets. Ruminal degradation of feed N was not different between treatments (P > .10).
In a study comparing six barley varieties, Ovenell and Nelson (1992) found no differences between varieties in total tract starch digestion. In our study, GUN had greater (P = .04) total tract starch digestion than HAR. Corn fed steers had greater (P < .05) DM, starch, and N post-ruminal and total tract digestion than did steers fed barley. No associative effects were observed in post-ruminal and total tract DM and N digestion. Nutrient flow to the duodenum and ruminal digestion were not different (P > .10) for MIX when compared to GUN and HAR. Post-ruminal and total tract digestion of DM and N were less (P < .05) for MIX than for GUN and HAR.
No associative effects (P > .10) were seen in flow rates of digesta to the duodenum when a feed barley and malting barley were fed together. No differences (P > .10) were detected in particulate flow rate or retention rate between corn or barley diets. However, HAR had a lower (P = .003) retention time (27.26 vs 43.18 h, respectively) resulting in a greater (P = .007) flow rate (.06 vs .03 h-1, respectively) to the duodenum than GUN. No differences (P > .10) were seen between the four diets in fill (avg. 38.92 kg).
Implications
This
study agrees with previous findings that differences in digestion
characteristics exist between and within barley cultivars from year to
year. Feeding a combination of a
malting variety and a feeding variety barley, demonstrated no associative
benefits.
Literature Cited
AOAC. 1997. Official Methods of Analysis of AOAC International (16th. Ed.) AOAC International, Gaitherburg, MD.
Boss, D. L., and J.G.P. Bowman. 1996a. Barley varieties for finishing steers: I. Feedlot performance, in vivo diet digestion, and carcass characteristics. J. Anim. Sci. 74:1967-1972.
Boss, D. L., and J.G.P. Bowman. 1996b. Barley varieties for finishing steers: II. Ruminal characteristics, and rate, site and extent of digestion. J. Anim. Sci. 74:1973-1981.
Ellis, W. C., J. H. Matis, and C. Lascano. 1979. Quantitating ruminal turnover. Ped. Proc. 38:2702-2706.
Feng, P., C. W. Hunt, G. T. Pritchard, and S. M. Parish. 1995. Effect of barley variety and dietary Barley content on digestive function in beef steers fed grass hay-based diets. J. Anim. Sci. 73:3476-3484.
Gibson, L. A., J.G.P. Bowman, L. E. Oberthur, and T. K. Blake. 1994. Determination of genetic markers associated with ruminant digestion of barley. Proc. West. Sect. Am. Soc. Anim. Sci. 45:317-320.
Hill, F. W., and D. L. Anderson. 1958. Comparison of metabolizable energy and productive energy determinations with growing chicks. J. Nutr. 64:587.
Milner, T. J., J.G.P. Bowman, L.M.M. Surber, S. D. McGinley, T. K. Daniels, and J. T. Daniels. 1996. Feedlot performance and carcass characteristics of beef steers fed corn or barley. Proc. West. Sect Am. Soc. Anim. Sci. 47:32-35.
Poore, M. H., J. A. Moore, T. P. Eck, and R. S. Swingle. 1991. Influence of passage model, sampling site, and marker dosing time on passage of rare earth-labeled grain through Holstein cows. J. Anim. Sci. 69:2646-2654.
Ovenell, K. H., and M. L. Nelson. 1992. Feedlot performance, carcass characteristics of steers, and digestibility of diets containing different barley cultivars. Proc. West. Sect. Am. Soc. Anim. Sci. 39:406.
Ørskov, E. R. 1986. Starch digestion and utilization in ruminants. J. Anim. Sci. 63:1624-1633.
SAS. 1993. SAS/STAT User Guide. SAS Inst. Inc., Cary NC.
Smith, R. H., and A. B. McAllen. 1974. Some factors influencing the chemical composition of mixed rumen bacteria. Br. J. Nutr. 31:27.
Surber, L.M.M., and J.G.P. Bowman. 1998. Monensin effects on digestion of corn or barley high-concentrate diets. J. Anim. Sci. 76:1945-1954.
Tyrrell, H. F. and P. W. Moe. 1974. Net energy value of a corn and barley ration for lactation. J. Dairy Sci. 57:451.
Van Soest, P. J., J. B. Robertson, and B. A. Lewis. 1991. Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccarides in relation to animal nutrition. J. Dairy Sci. 74:3583.
Zinn, R. A. and F. N. Owens. 1986. A rapid procedure for purine measurement and its use for estimating net ruminal protein synthesis. Can. J. Anim. Sci. 66:157.
Table 1. Composition of finishing diets containing corn, Gunhilde barley (GUN), Harrington barley (HAR), or 50% Gunhilde+50% Harrington (MIX) as basal grains.
|
Item |
Corn |
GUN |
HAR |
MIX |
|
Ingredients, % of DM |
|
|
|
|
|
Corn |
82.00 |
------ |
------ |
------ |
|
Gunhilde barley |
------ |
83.00 |
------ |
41.50 |
|
Harrington barley |
------ |
------ |
83.00 |
41.50 |
|
Oatlage |
6.00 |
6.00 |
6.00 |
6.00 |
|
Molasses |
4.00 |
5.00 |
5.00 |
5.00 |
|
Soybean meal |
3.54 |
1.69 |
1.31 |
2.24 |
|
Urea |
1.25 |
.30 |
.80 |
.42 |
|
Sodium bicarbonate |
1.30 |
1.30 |
1.30 |
1.30 |
|
Calcium carbonate |
.57 |
1.38 |
1.25 |
.72 |
|
Sodium chloride |
.50 |
.50 |
.50 |
.50 |
|
Potassium chloride |
.50 |
.50 |
.50 |
.50 |
|
TM premixa |
.25 |
.25 |
.25 |
.25 |
|
Vit. A, D, E premixb |
.05 |
.05 |
.05 |
.05 |
|
Rumensin 80c |
.024 |
.024 |
.024 |
.024 |
|
Tylan 40c |
.013 |
.013 |
.013 |
.013 |
aContains 20.0% Mg, 6.0% Zn, 4.0% Mn, 5.0% Fe, 2.7% S, 1.5% Cu, .11% I, .01% Se, and .01% Co.
bContains 30,000 IU/g vitamin A, 6,000 IU/g vitamin D, and 7.5 IU/g vitamin E.
cRumensin 80 contains 132 g/kg of monensin. Tylan 40 contains 88 g/kg tylosin.
Table 2. Nutrient composition of finishing diets containing corn, Gunhilde barley (GUN), Harrington barley (HAR), and 50% Gunhilde+50% Harrington (MIX) as basal grains.
|
Item |
Corn |
GUN |
HAR |
MIX |
|
Nutrient content |
|
|
|
|
|
OM, % of DM |
94.17 |
92.53 |
93.99 |
92.83 |
|
CP, % of DM |
13.46 |
14.36 |
15.07 |
14.36 |
|
Starch, % of DM |
48.47 |
37.00 |
41.85 |
40.43 |
|
NEm, Mcal/kga |
1.93 |
1.93 |
1.93 |
1.93 |
|
NEg, Mcal/kga |
1.28 |
1.28 |
1.28 |
1.28 |
aCalculated values.
Table 3. Characteristics of digestion in steers fed high concentration diets of corn, Gunhilde barley (GUN), Harrington barley (HAR), and 50% Gunhilde+50% Harrington (MIX) as basal grains.
|
|
|
|
|
|
|
P |
|||
|
Item |
Corn |
GUN |
HAR |
MIX |
SE |
corn vs barleya |
GUN vs HARb |
GUN/HAR vs MIXc |
|
|
Intake, g/d |
|
|
|
|
|
|
|
|
|
|
DM |
9886 |
9912 |
9887 |
9846 |
.018 |
.84 |
.36 |
.05 |
|
|
Starch |
4792 |
3793 |
4016 |
3983 |
.177 |
.006 |
.41 |
.73 |
|
|
N |
213 |
228 |
238 |
226 |
.002 |
.0003 |
.01 |
.04 |
|
|
Flow to duodenum, g/d |
|
|
|
|
|
|
|
||
|
DM |
4830 |
4295 |
4882 |
4665 |
.152 |
.26 |
.03 |
.70 |
|
|
Starch |
1167 |
389 |
690 |
567 |
.119 |
.004 |
.12 |
.86 |
|
|
Total N |
169 |
168 |
183 |
175 |
.004 |
.24 |
.04 |
1.0 |
|
|
NH3N |
9.93 |
11.50 |
12.06 |
11.15 |
.615 |
.06 |
.54 |
.43 |
|
|
Nonammonia N |
159.20 |
156.12 |
171.19 |
164.29 |
3.77 |
.33 |
.03 |
.90 |
|
|
Microbial N |
51.50 |
61.31 |
61.40 |
53.71 |
4.73 |
.23 |
.99 |
.23 |
|
|
Feed N |
107.70 |
94.81 |
109.80 |
110.58 |
6.12 |
.72 |
.13 |
.31 |
|
|
Ruminal digestion, % |
|
|
|
|
|
|
|
||
|
DM |
51.16 |
56.66 |
50.62 |
52.62 |
1.59 |
.29 |
.04 |
.62 |
|
|
Starch |
75.64 |
89.79 |
82.79 |
85.63 |
2.92 |
.02 |
.14 |
.86 |
|
|
Feed N |
49.61 |
58.34 |
53.93 |
51.09 |
2.58 |
.16 |
.27 |
.16 |
|
|
Total N |
20.67 |
26.34 |
23.10 |
22.43 |
1.71 |
.15 |
.23 |
.32 |
|
|
Microbial efficiency, g of N/kg |
|
|
|
|
|||||
|
|
10.61 |
10.90 |
12.33 |
10.19 |
.81 |
.59 |
.26 |
.19 |
|
|
Postruminal digestion, % |
|
|
|
|
|
|
|
||
|
DM |
32.63 |
39.56 |
41.56 |
34.93 |
2.04 |
.04 |
.51 |
.07 |
|
|
Starch |
45.17 |
77.64 |
63.56 |
70.31 |
5.63 |
.008 |
.13 |
.97 |
|
|
N |
57.06 |
65.81 |
65.17 |
59.97 |
1.46 |
.008 |
.77 |
.02 |
|
|
Total tract digestion, % |
|
|
|
|
|
|
|
||
|
DM |
67.68 |
73.80 |
71.10 |
69.19 |
1.08 |
.03 |
.13 |
.05 |
|
|
Starch |
88.10 |
97.73 |
93.53 |
95.92 |
1.13 |
.001 |
.04 |
.84 |
|
|
N |
66.09 |
74.87 |
73.31 |
69.00 |
.97 |
.001 |
.30 |
.005 |
|
|
Duodenal, one-compartment model |
|
|
|
|
|
|
|||
|
Tau, h |
8.04 |
3.01 |
5.41 |
2.86 |
.83 |
.004 |
.09 |
.23 |
|
|
Flow rate, h-1 |
.04 |
.03 |
.06 |
.04 |
.005 |
.48 |
.007 |
.32 |
|
|
Retention time, h |
39.70 |
43.18 |
27.26 |
36.62 |
2.40 |
.20 |
.003 |
.65 |
|
|
Fill, kg |
33.71 |
32.68 |
43.18 |
46.11 |
6.43 |
.39 |
.29 |
.34 |
|
aComparison of corn vs barley.
bComparison of Gunhilde and Harrington barley.
cComparison of Gunhilde and Harrington barley vs MIX.
[1] This work was supported in part by the Montana Beef Council and the Montana Wheat and Barley Committee