Chemical Composition and Ruminal Fermentability of Barley Grain, Hulls, and Straw as Affected by Planting Date, Irrigation Level, and Variety

The ProfessionalQuality Animal Scientist 19 (2003):273–280 Factors of Barley

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Composition and Ruminal Chemical Fermentability of Barley Grain, Hulls, and Straw as Affected by Planting Date, Irrigation Level, and Variety A. V. GROVE, J. HEPTON, PAS, and C.W. HUNT1, PAS Department of Animal and Veterinary Science, University of Idaho, Moscow, 83844

Abstract

respectively. Similar to the responses observed for grain and hulls, Steptoe Four spring barley cultivars (Steptoe, straw contained greater (P<0.05) NDF, Colter, Lud, and Gallatin) were grown ADF, and lignin, and was less ruminally under two planting dates and two postdegradable (P<0.05) than other varietflowering irrigation levels to determine ies. Lud had straw with lesser (P<0.05) the source of differences in fiber composi- fiber content than Gallatin straw and tion, starch, and ruminal in situ disapgreater (P<0.05) ruminal DM disappearpearance. Planting date and irrigation ance than Colter straw; however, these level generated few differences in the differences did not appear to be associchemical composition of barley grain, ated with hull characteristics. Hull hull, or straw. Steptoe grain contained percentage and chemical composition less (P<0.05) starch and greater (P<0.05) differed among barley sources which was acid detergent fiber (ADF) and neutral associated with differences in ruminal detergent fiber (NDF) than other varietdegradability. ies, which was associated with lesser (P<0.05) in situ disappearance. Hull (Key Words: Barley, Chemical Compercentage differed (P<0.05) between all position, Variety, Growing Condivarieties and ranged from 16.3 to 19.5% tions.) of kernel DM. Steptoe had a greater percentage of hulls, and Steptoe hulls contained more (P<0.05) ADF and NDF Barley is an important crop in the and were less (P<0.05) degradable than United States and throughout the hulls from other varieties. Colter, world. The grain is used primarily for Gallatin, and Lud grain did not differ malting and livestock feeding, and (P> 0.05) in grain starch content or in the straw is also an important situ disappearance; however, in situ feedstuff when more desirable forages disappearance of the hulls was different are not available. However, consider(P<0.05) with values of 35.2 > 33.2 > able variation exists in the fiber and 30.5% for Colter, Gallatin, and Lud, starch content of barley grain (Bowman et al., 2001; Reynolds et al, 1To whom correspondence should be ad- 1992) and the fiber content of barley dressed: [email protected] straw (Flachowsky et al.,

Introduction

1991;Mathison et al., 1999;Ørskov et al., 1990; Thomson et al., 1993), which results in a tremendous amount of variation in digestible energy content. Much research has been published on the variation in nutrient composition of barley grain and straw, but few research reports have been published evaluating the nutrient composition of the barley hull for ruminants. Barley differs from other feed grains in that it has an attached seed hull that must be penetrated before the starch can be digested. McAllister (1994) reported that initial attachment of microbes is critical to digestion and the barley hull prevents microbial decay of the starch. We hypothesize that hull percentage and fiber content are related to barley grain digestibility. The major factors contributing to variation in barley feeding value are variety and growing conditions. Growing conditions such as late planting and moisture stress usually result in lesser yields (Hohm, 1999); however, few researchers have conducted a full examination of their effects on the feeding value of grain and straw. The objective of this study was to compare varieties of barley grown under different environmental conditions to evaluate the hull

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percentage, fiber composition, and ruminal degradability of barley grain, hull, and straw.

Grove et al.

mm screen and analyzed for ADF, NDF, lignin, ash (AOAC, 1990), and p-coumaric and ferulic acid phenolic monomers (Jung and Fahey, 1983), and in situ disappearance. In situ disappearance was determined as Two six-row (Steptoe and Colter) described earlier except 3 g were and two two-row (Gallatin and Lud) weighed into two bags and a bag spring barley cultivars were grown in from each sample was placed in one field plots at two planting dates and of two steers for 24 h. two levels of irrigation in a randomBarley straw samples were ground ized complete block design. Plots through a 1-mm screen and analyzed were in a subsubplot arrangement for NDF, ADF, CP, lignin, ash, pwith planting date being the whole coumaric acid, and ferulic acid. In plot, irrigation level the subplot, and situ disappearance was determined as barley variety the subsubplot. Whole previously described except 3 g of plots were replicated five times. Each each sample were weighed into three Eighteen grams of a second subplot was 0.5 m x 1.8 m with a 1.2- subsample of barley were ground bags and each bag was placed into m alley between ends of plots. one of three steers for 24 h. through a 3-mm screen in a Wiley Planting dates were May 11 and 25. Data were analyzed by ANOVA mill (Arthur H. Thomas, PhiladelIrrigation level was uniform until phia, PA) to determine ruminal in situ using the GLM procedure of SAS (33). head emergence, at which time levels disappearance. Triplicate samples of Planting date was the whole plot, of 50 and 100% of calculated daily irrigation level the subplot, and approximately 6 g of barley were evapo-transpiration were adminisvariety the subsubplot. The model weighed into 10-cm x 22-cm nylon tered at approximately 5-d intervals. included replication, planting date, bags (50 µm pore size). Three Barley grain and straw were harvested ruminally-fistulated steers were irrigation level, variety, and all from plots within a 2-d period, and combinations of interactions. Plantadapted to a barley-based diet (40% subsamples were collected for labora- of diet DM) for 7 d, and one bag ing date effects were tested by the tory analysis. from each triplicate set was placed in replication x planting date error A portion of the barley was term, irrigation level effects by the the rumen of each steer for 12 h. ground through a 1-mm screen and replication x irrigation level within After incubation, the bags were analyzed for NDF (Komarek, 1993a; planting date error term, and variety washed until the rinse water was Van Soest et al., 1991), ADF (AOAC, by the residual error term. Main clear, and then the samples were 1990; Komarek, 1993b), CP (AOAC, dried in a forced air oven at 55ºC for effect and variety means were sepa1990) and starch using a modificarated by LSD mean separation when 90 h. In situ disappearance of DM tion of the procedure by Aman and a significant (P<0.05) F-value was (ISDMD) during incubation was Hesselman (1984). Modifications of observed. Simple correlation coefficalculated as the weight loss of the the starch analysis included increascients for the grain, hulls, and straw substrate during incubation. ing the sample size to 0.4 g of ground criteria were also calculated (SAS, A third random sample of whole grain plus the following enzyme 1986). barley was pearled through a laborausage: 250 µL of amylase with 340 tory pearling machine (“Strong enzyme units/mL (Taka-Therm L-340; Scott” ® 17809 SS; Burrows Company, Chicago, IL) to separate hulls from Valley Research, Inc., South Bend, Grain. Planting date and irrigation IN), and 100 µL of amyloglucosidase grain. Duplicate subsamples of 50 g level generated few differences in the solution (58 units/mL) prepared with from each barley sample were added to the pearling machine for 15 s, and chemical composition of barley grain 5 g amyloglucosidaase (Sigma A(Table 1). Crude protein of grain from the pearled grain and hulls were 7255) in 100 mL pH 4.5 buffer, and the early planting was greater collected in separate compartments. filtered with Whatman No. 2 filter (P<0.05) than grain from the late paper. An enzyme unit was defined as Hulls were then sifted through a 2planting; however, bulk density, mm screen to separate any pearled the amount of enzyme necessary to neutral (NDF) and acid (ADF) detergrain that remained with the hulls. hydrolyze 1 g of starch in 30 min. Hulls were placed on a 300-µm screen gent fiber, starch, and ISDMD of After centrifuging, aliquots (0.4 mL) barley grain did not differ (P>0.05) to allow separation of hulls from of supernatant were diluted with distilled water to 100 mL in volumet- fines. Pearled grain was weighed, and between planting dates. This contrasts with Weston et al. (Weston et hull percentage of the original grain ric flasks. From this dilution, 1-mL al., 1993) who reported no differwas determined by difference. The aliquots were mixed with 2.0 mL of ences in protein content of grain hulls were then ground through a 1glucose color reagents (Sigma diag-

Materials and Methods

nostics, No. 510-A; Sigma Chemical Co., St. Louis, MO) and allowed to stand 30 min at 37ºC; absorbency was recorded at 450 nm using a spectrophotometer. Starch content of the samples was calculated using a regression equation from a calibration curve obtained from varying dilutions (0, 0.2, 0.4, 0.6, 1.2, 2.4, and 3.5 mg/dL) of a standard glucose solution and an enzyme blank incubated with glucose color reagents. A pure cornstarch sample was used as a reference standard to adjust starch recoveries for each sample.

Results and Discussion

275

Quality Factors of Barley

TABLE 1. Effect of planting date (PD) and irrigation level (IL) on chemical composition and ruminal degradability of barley grain. ILb

PD Itema

11 May

25 May

SE

Low

High

SE

Bulk density, kg/hL CP, % NDF, % ADF, % Starch, % ISDMD, %

68.6 10.4d 20.0 5.4 56.0 81.9

68.2 9.9c 20.3 5.6 56.7 81.6

0.2 0.1 0.4 0.1 0.3 0.2

68.7d 10.6d 20.0 5.5 56.2 81.8

68.1c 9.8c 20.2 5.6 56.5 81.6

0.1 0.1 0.1 0.05 0.2 0.2

aValues

except bulk density are expressed on a DM basis. ISDMD = in situ DM disappearance after a 12-h ruminal incubation. NDF = neutral detergent fiber. ADF = acid detergent fiber. bLow and High = 50 and 100% of calculated evapo-transpiration following seed head emergence, respectively. c,dMeans within a row and main effect without a common superscript letter differ (P<0.05).

between two planting dates. Lauer and Partridge (1990) also reported that planting date did not influence grain protein content across 5 yr; however, in individual years late planting decreased protein 2 yr, increased protein 1 yr, and did not differ in the other 2 yr. While differences in CP between planting dates in our study were statistically significant, they only differed by 0.5 percentage units. Bulk density of barley grown under the low irrigation treatment was greater (P<0.01) than for barley grown under the high irrigation level. Moisture stress generally reduces grain yields (Hohm, 1999). Thomson et al. (1993) reported greater grain yields with increased water level, but Lauer and Partridge (1990) reported that a cutoff irrigation treatment did not affect barley kernel weight. The low irrigation level most likely did not stress the plant. The difference observed in bulk density was also quite small. Crude protein of barley receiving the low irrigation treatment was greater (P<0.05) compared with barley receiving the high irrigation

level; however, NDF, ADF, starch, and ISDMD of barley grain did not differ (P>0.05) between irrigation levels. This agrees with Bowman et al. (1996), who reported greater CP content for barley grain grown under dryland vs irrigated conditions; however, it differs from their conclusion that dryland-raised varieties had less starch and greater 6 h ISDMD

than irrigated varieties. Honeyfield et al. (1987) reported similar CP content and lesser DMD for barley grown under dryland vs irrigated conditions and also noted that the feeding values of Steptoe and Lud were not affected as much by growing conditions. There were no interactions (P>0.05) between variety, planting date, or irrigation level for any barley grain characteristics. Bulk density ranged from 65 to 71 kg/hL and differed (P<0.05) among all varieties being least for Steptoe and greatest for Gallatin (Table 2). Crude protein content of grain was lowest (P<0.05) for Colter, intermediate for Steptoe, and highest for Lud and Gallatin. Neutral and acid detergent fiber contents were least (P<0.05) for Gallatin, intermediate for Colter and Lud, and greatest (P<0.05) for Steptoe. Steptoe had lesser (P<0.05) grain starch content and 12-h ISDMD than all other varieties. There were no differences (P>0.05) in starch content or ISDMD between Colter, Lud, and Gallatin. Steptoe is considered to have poorer feeding value than other varieties (Ovenell and Nelson, 1992; Ovenell-Roy et al., 1998b), which is consistent with data from our study. Steptoe had more NDF and ADF, less starch and lower ISDMD than all

TABLE 2. Effect of variety on chemical composition and ruminal degradability of barley grain. Variety Itema

Steptoe

Colter

Lud

Gallatin

SE

Bulk density, kg/hl CP, % NDF, % ADF, % Starch, % ISDMD, %

65.4b 9.7c 22.6d 7.0d 54.3b 80.0b

67.0c 9.2b 19.7c 5.1bc 57.0c 82.5c

69.8d 10.9d 20.0c 5.4c 56.6c 82.4c

71.4e 10.9d 18.2b 4.7b 57.5c 82.1c

0.4 0.1 0.4 0.2 0.4 0.3

aValues

except bulk density are expressed on a DM basis. ISDMD = in situ DM disappearance after a 12-h incubation. NDF = neutral detergent fiber. ADF = acid detergent fiber. b,c,d,eMeans within a row without a common superscript letter differ (P<0.05).

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other varieties. Similar to our results, Ovenell-Roy et al. (1998b) reported that Steptoe had more NDF and less starch than other varieties, and Ovenell-Roy et al. (1998a) also reported that Steptoe had a lesser rate of in situ DM disappearance than other varieties. Bowman et al. (2001) evaluated variation in spring barley varieties and reported that six-row types (i.e., Colter and Steptoe) had greater ADF, lesser starch content, and less DMD than two-row types (i.e., Gallatin and Lud). Hulls. Irrigation level did not (P>0.05) contribute to differences in barley hull quality; however, some hull characteristics were affected by planting date (Table 3). Barley hull percentage for early-planted barley was greater (P<0.05) than for lateplanted barley (17.9 and 17.3%, respectively). There was no difference (P>0.05) in NDF or ADF content of barley hulls between planting dates;

however, lignin content, as well as pcoumaric acid content, was lesser (P<0.05) for hulls from the early- vs late-planted barley. Ferulic acid content did not differ (P>0.05) between planting dates. In situ DM and NDF disappearance of barley hulls did not differ (P>0.05) between planting dates averaging 32 and 13.8%, respectively. Lignin and pcoumaric acid content of forages generally increase as the plant matures while ferulic acid levels remain constant (Moore and Hatfield, 1994). Our ferulic acid data are in agreement with this while our lignin and p-coumaric acid results differ. The conclusions of Moore and Hatfield (1994) are based on data from forages rather than from grain hulls. The percentage of hull in the four barley varieties ranged from 16.3 to 19.5% and differed (P<0.05) for all varieties, being least for Colter,

TABLE 3. Effect of planting date (PD) and irrigation level (IL) on chemical composition and ruminal degradability of barley hulls. ILb

PD Itema

11 May

25 May

SE

Low

High

SE

Hull, % of kernel NDF, % ADF, % Lignin, % Coumaric acid mg/g DM mg/g NDF mg/g lignin Ferulic acid mg/g DM mg/g NDF mg/g lignin ISDMD, % ISNDFD, %

17.9d 74.3 37.1 7.4c

17.3c 75.4 37.9 7.9d

0.1 0.6 0.5 0.1

17.5 75.2 37.6 7.6

17.7 74.5 37.3 7.8

0.1 0.3 0.2 0.1

2.33c 3.15c 31.20

2.65d 3.53d 33.67

0.06 0.05 0.87

2.45 3.28 32.38

2.53 3.41 32.48

0.05 0.07 0.66

2.73 3.67 36.76 32.3 13.6

2.82 3.74 36.18 31.6 14.0

0.04 0.02 0.40 0.8 0.4

2.76 3.76 36.45 31.9 14.1

2.79 3.75 36.49 32.0 13.5

0.04 0.05 0.77 0.3 0.3

aValues expressed on a DM basis. ISDMD = in situ DM disappearance after a 24-h ruminal incubation. ISNDFD = in situ NDF disappearance after a 24-h incubation. NDF = neutral detergent fiber. ADF = acid detergent fiber. bLow and High = 50 and 100% of calculated evapo-transpiration following seedhead emergence, respectively. c,dMeans within a row and main effect without a common superscript letter differ (P<0.05).

followed by Gallatin, Lud, and Steptoe (Table 4). Crude protein content of hulls was least (P<0.05) for Colter, intermediate for Steptoe, and greatest for Lud and Gallatin. Hull NDF and ADF contents were least (P<0.05) for Gallatin and Colter, intermediate for Lud, and highest for Steptoe. The varieties we examined had numerically greater hull percentages than reported by Bhatty et al. (1975), and our hulls had numerically lesser NDF and ADF than reported by Lockart et al. (1980) and Bell and Keith (1988); however, these researchers evaluated different varieties of barley. Bhatty et al. (1975) reported barley hull percentages of 10 to 13% and concluded that the hull was a major factor influencing barley DE content. Removing the hull increased in situ DM disappearance of barley grain (Pauly et al., 1992). In our study, barley percentage and chemical composition varied between varieties, and the hull percentage was positively correlated with barley grain ADF (r = 0.77) and NDF (r = 0.63) contents, and was negatively correlated with bulk density (r = –0.51), starch content (r = –0.53), and in situ disappearance (r = –0.47). Hull percentage differed between all varieties, but ISDMD of grain was only different for Steptoe compared with the other three varieties. Grinding the grain for in situ incubations disrupts the grain and hull and likely diminishes the effects the hull has on DM and starch degradabilities. Additional research is certainly warranted examining factors associated with ruminal degradability of barley grain. There was an interaction (P<0.05) between planting date and variety for lignin content of hulls. Lignin content of barley hulls did not differ (P>0.05) between varieties from the early planting date; however, from late-planted barley, lignin content was lesser (P<0.05) for Lud than Steptoe and Colter, and intermediate for Gallatin. This interaction could reflect differences in growth development between varieties that equal-

Quality Factors of Barley

277

planted barley. This is different than the report of Capper et al. (1992), TABLE 4. Effect of variety on chemical composition and ruminal a who observed that late-planted degradability of barley hulls . barley straw had greater ADF content, Variety but a similar in vitro degradability, than early-planted barley; however, Itemb PD Steptoe Colter Lud Gallatin SE this study was conducted with fallplanted winter barley. They also e b d c observed that the leaf fraction had Hull, % of kernel 19.5 16.3 17.8 16.9 0.2 e c d c less ADF and lignin concentrations NDF, % 78.7 72.0 76.2 72.3 0.7 ADF, % 41.3e 34.6c 38.5d 35.5c 0.6 and was more digestible than the Lignin, % 11 May 7.8c 7.7c 7.2c 7.6c 0.3 stem (Capper et al., 1992). Taller 25 May 8.4d 8.2d 7.2c 7.8cd 0.3 straws have less leaf proportion Coumaric acid (Ørskov et al., 1990; Thomson et al., mg/g DM 2.71d 2.79d 1.88c 2.59d 0.08 1993), and the leaf is more digestible mg/g NDF 3.44d 3.87e 2.47c 3.59d 0.10 than the stem (Capper et al., 1992). mg/g lignin 33.63d 35.39d 26.47c 34.23d 1.19 Flachowsky et al. (1991) reported Ferulic acid c c d c that ISDMD of cereal straws was 2.68 2.97 2.73 0.04 mg/g DM 2.72 c d e de negatively correlated with stem 3.72 3.90 3.77 0.06 mg/g NDF 3.45 mg/g lignin 33.91c 34.05c 42.02d 35.89c 1.22 proportion and positively correlated ISDMD, % 28.8c 35.2f 30.5d 33.2e 0.6 with the proportion of leaf. ISNDFD, % 13.7d 15.7e 13.4cd 12.4c 0.4 Crude protein content was greater (P<0.05) from barley at the low aVarieties were cultivated at two planting dates (PD). Values for varieties at each PD compared with the high irrigation are provided when an interaction (P<0.05) was observed. level; however, there were no differbValues expressed on a DM basis. ISDMD = in situ DM disappearance after a 24-h ences between irrigation levels for incubation. ISNDFD = in situ NDF disappearance after a 24-h incubation. NDF = NDF, ADF, lignin, or ISDMD. neutral detergent fiber. ADF = acid detergent fiber. Thomson et al. (1993) reported that c,d,e,fMeans within a row without a common superscript letter differ (P<0.05). increasing water level decreased CP of barley straw; tended to increase ADF, lignin and ash; and decreased ized as the plants matured. Pattributed variation in nutritional 48-h in situ DM loss. Similarly, the coumaric acid as a proportion of DM quality among barley varieties to least potential degradability of barley and lignin was less (P<0.05) for Lud digestibility of NDF or NDF polystraw occurred in the year with the than all other varieties. P-coumaric meric monosaccharides (Erickson et greatest rainfall (Ørskov et al., 1990). acid as a proportion of NDF was least al., 1982; Ovenell-Roy et al., There were no interactions (P<0.05) for Lud, intermediate for 1998b,c). (P>0.05) between variety, irrigation Steptoe and Gallatin, and greatest for In situ DM disappearance of hulls level, or planting date for chemical Colter. In contrast, ferulic acid was different (P<0.05) among all composition of barley straw. Crude content as a proportion of DM and varieties (28.8, 30.5, 33.2, and 35.2% protein content was low and similar lignin was greater (P<0.05) for Lud for Steptoe, Lud, Gallatin, and Colter, (P>0.05) between barley varieties than all other varieties. Ferulic acid respectively) while in situ NDF averaging 3.4% (Table 6). Neutral as a proportion of NDF was least disappearance was least (P<0.05) for detergent fiber content of barley (P<0.05) for Steptoe, intermediate for Gallatin, intermediate for Lud and straw was least (P<0.05) for Colter Colter, and greatest for Lud with Steptoe, and greatest for Colter. Hull and Lud, intermediate for Gallatin, Gallatin being similar to Colter and ISDMD was negatively correlated and greatest for Steptoe. Acid deterLud. with hull ADF (r = –0.90) and NDF (r gent fiber content was least (P<0.05) Ferulic and p-coumaric acids are = –0.91) contents. for Lud, intermediate for Colter and the primary phenolics of noncore Straw. Similar to barley grain and Gallatin, and greatest for Steptoe. lignin (Moore and Hatfield, 1994) hulls, planting date and irrigation Lignin was least (P<0.05) for Lud, and may limit digestibility of cell level generated few differences in the intermediate for Colter and Gallatin, walls (Hartley and Ford, 1989). chemical composition of barley straw and greatest for Steptoe. Barley straw Garleb et al. (1991) found this to be (Table 5). Neutral and acid detergent in our study had similar nutritional true for cereal hulls, but in our study fiber values were greater (P<0.05) value to that reported by Erickson et there was no clear relationship from the early vs late-planting date, al. (1982). Other researchers have between p-coumaric and ferulic acids and consequently straw ISDMD was reported that six-row varieties had and digestibility. Other researchers lesser (P<0.05) for early- than lateless nutritive quality than two-row

278

Grove et al.

tions of p-coumaric and ferulic acids in barley straw and their values were similar to our observed values. In situ DM disappearance was least (P<0.05) for Steptoe, intermediate for Colter and Gallatin, and greatest for Lud. As observed with the barley grain and hulls, straw in situ DM disappearance was negatively correlated with NDF (r = –0.83), ADF (r = – 0.89), and lignin (r = –0.76) contents. We observed that Steptoe is an example of a barley variety that is inferior in grain, hull, and straw nutritive qualities that would logically have a negative impact on animal performance. On the other land, Lud had lesser quality grain and hull, but straw with less fiber content and greater ruminal degradability. Clearly, barley grain and straw quality can be improved by selecting genotypes with enhanced nutritional qualities. Heritability estimates and molecular markers associated with nutritive quality of barley grain and forage have been identified (Bowman et al., 1996; Surber et al., 2001a; Surber et al, 2001b), and new barley

TABLE 5. Effect of planting date (PD) and irrigation level (IL) on chemical composition and ruminal degradability of barley straw. ILb

PD Itema

11 May

25 May

SE

Low

High

SE

Protein, % NDF, % ADF, % Lignin, % Ash, % Coumaric acid Mg/g DM Mg/g NDF Mg/g lignin Ferulic acid Mg/g DM Mg/g NDF Mg/g lignin ISDMD, %

3.45 74.78d 50.84d 8.54 9.81

3.30 73.65c 50.16c 8.39 9.94

0.06 0.29 0.12 0.07 0.09

3.58d 74.12 50.39 8.37 9.83

3.17c 74.31 50.61 8.56 9.92

0.11 0.53 0.44 0.15 0.06

3.87 5.16 45.27

4.04 5.48 48.01

0.06 0.10 1.01

3.94 5.31 47.13

3.96 5.33 46.15

0.10 0.10 0.90

2.31 3.10 27.39 34.0c

2.35 3.20 28.19 35.7d

0.01 0.03 0.37 0.17

2.35 3.19 28.46 35.4

2.30 3.11 27.11 34.2

0.04 0.05 0.57 0.65

aISDMD

= in situ DM disappearance after a 24-h ruminal incubation. NDF = neutral detergent fiber. ADF = acid detergent fiber. bLow and High = 50 and 100% of calculated evapo-transpiration following seedhead emergence, respectively. c,dMeans within a row and main effect without a common superscript letter differ (P<0.05).

varieties (Herbert and Thomson, 1992; Erickson et al., 1982), which is largely consistent with our observations. Lud had a lesser (P<0.05) pcoumaric acid content on a DM and NDF basis than all other varieties. Pcoumaric acid as a proportion of lignin was least (P<0.05) for Lud, intermediate for Steptoe and Colter, and greatest for Gallatin. Ferulic acid content on a DM basis was less (P<0.05) for Colter than all other varieties while Lud had a greater (P<0.05) ferulic acid content as a proportion of NDF and lignin than all other varieties. Ferulic acid on a lignin basis was least (P<0.05) for Steptoe and Colter, intermediate for Gallatin, and greatest for Lud. Similar to our data, Ford and Elliott (1987) did not observe a relationship between concentration of phenolic acids and straw degradability. Ford and Elliot (1987) and Hartley and Ford (1989) reported low concentra-

TABLE 6. Effect of variety on chemical composition and ruminal degradability of barley straw. Variety Itema

Steptoe

Colter

Lud

Gallatin

SE

CP, % NDF, % ADF, % Lignin, % Ash, % Coumaric acid mg/g DM mg/g NDF mg/g lignin Ferulic acid mg/g DM mg/g NDF mg/g lignin ISDMD, %

3.4 77.9d 53.8d 9.4d 10.0c

3.4 72.7b 49.6bc 8.5c 10.5d

3.5 71.8b 48.5b 7.7b 9.6b

3.3 74.5c 50.0c 8.3c 9.4b

0.2 0.6 0.5 0.2 0.1

4.35c 5.58c 46.50c

4.12c 5.68c 48.46cd

3.07b 4.28b 39.79b

4.27c 5.73c 51.83d

0.11 0.13 0.13

2.41c 3.11b 26.02b 29.4b

2.17b 2.99b 25.56b 34.9c

2.40c 3.35c 31.21d 38.4d

2.34c 3.14b 28.36c 36.6cd

0.06 0.08 0.80 0.7

aValues expressed on a DM basis. ISDMD = in situ DM disappearance after a 24-h incubation. NDF = neutral detergent fiber. ADF = acid detergent fiber. b,c,dMeans within a row without a common superscript letter differ (P<0.05).

Quality Factors of Barley

279

varieties with improved feed quality have been developed (Boss et al., 1999; Endecott et al., 2001).

inbred barley lines, LB13 and LB30, for finishing steers. Proc. West. Sec. Am. Soc. Anim. Sci. 50:293.

Komarek, A.R. 1993b. Improved efficiency of ADF analysis using a filter bag procedure. J. Anim. Sci. 71(Suppl. 1):284. (Abs.).

Implications

Bowman, J. G. P., T. K. Blake, L. M. M. Surber, D. K. Habernicht, and H. Bockelman. 2001. Feed-quality variation in the barley core collection of the USDA national small grains collection. Crop Sci. 41:863.

Lauer, J. G., and J. R. Partridge. 1990. Planting date and nitrogen rate effects on spring malting barley. Agron. J. 82:1083.

Planting date and irrigation level generated few differences in the chemical composition and ruminal degradability of barley grain, hull, and straw. Results of this study confirm that the nutritive value of barley grain, hulls, and straw differs among barley varieties. The percentage of grain hulls for the barley varieties evaluated ranged from 16.3 to 19.5%, and the hull varied in ruminal degradability (24 h) from 28.8 to 35.2%. Varieties having the greater proportion of hull also had hulls lesser in in situ disappearance. Our observations indicate that hull fraction can account for a large portion of the variability in barley quality. Consequently, barley of improved nutritive value can be identified by routine fiber analysis. Additional research is warranted examining factors associated with ruminal degradability of barley grain as ruminal degradability is highly variable and has a large impact on animal performance.

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