ABSTRACT: The objective of this study was to measure growth performance, carcass characteristics and diet digestibility by steers fed recombinant inbred lines developed by crossing Lewis and Baronesse barley. Eighty crossbred steers (avg initial wt 344 kg) were allotted to 16 pens in a randomized complete block design. During period 1 (70 d) steers consumed 83% barley diets based on Baronesse (BAR; a two-row feed variety) or Lewis (LEW; a two-row malt variety). During period 2 (77 d) steers were fed 83% barley diets based on BAR, LEW, and 6 experimental lines, LB2, LB5, LB6, LB32, LB48, and LB57. All diets were balanced to contain 13.5% CP. Steers were weighed and diet, ort, and fecal samples were collected every 28 d. Acid insoluble ash was used as an internal marker to calculate nutrient digestion. Steers were slaughtered when 70% were visually estimated to grade Choice. Data were analyzed by the GLM procedure of SAS. Hot carcass weight was used as a covariate for the analysis of carcass characteristics. At the end of period 1 steers fed BAR had greater (P = .09) ADG than steers fed LEW (1.7 vs 1.6 kg/d). After period 2, ADG was greater (P = .006) for steers fed LB2, LB32, and LB6 (avg 1.54 kg/d) compared with those fed LB5 (1.1 kg/d), or LB 48 (1.3 kg/d). Steers fed BAR, LEW, or LB57 were intermediate in ADG (avg 1.4 kg/d). Steers fed LB5 had higher (P = .03) quality grades (choice) than steers fed BAR, LEW, LB2, and LB32 (avg low choice), with steers fed LB48 having the lowest (select). No differences (P > .10) were found in backfat thickness (avg 1.02 cm), ribeye area (avg 80 cm²), % KPH (avg 2.4%), carcass weight (avg 329 kg), or yield grade (avg 2.7). Digestible starch intake was greatest (P = .06) by steers fed LB2 (4.31 kg/d), lowest by steers fed LB32 (3.51 kg/d), and intermediate for all other treatments (avg 4.0 kg/d). Results suggest that LB2, LB32 and LB6 have improved feeding performance over the parent varieties.

Key Words: Barley Genotype, Steers.

Introduction

Barley is widely used in feedlot diets and other livestock feeds throughout the Northwest. However, unlike malting barley there are no standard criteria for feed barley to determine feed value. Barley varieties used for animal feeding are rarely evaluated for feed quality until after they are introduced into agronomic production (Bowman and Blake, 1997). Evidence of this is apparent when performance by cattle fed different barley cultivars in feedlot studies is examined. Boss and Bowman (1996) and Surber et al. (1998) reported differences in ADG for steers fed different barley varieties. Carcass characteristics, diet digestibility and rate of digestion (Ovenell and Nelson, 1992; Surber and Bowman, 1998) were also affected by barley genotype.

Baronesse and Lewis were chosen as potential parent lines for a new barley variety because of their agronomic quality and their excellent feed values. Both varieties are grown in Montana and neighboring states. Sixty recombinant inbred lines (RIL’s) of a Baronesse x Lewis cross are being evaluated in the laboratory and in feedlot trials in hopes of developing a barley line with a high feed value and consistent performance in a feedlot setting.

The objective of this study was to evaluate the effects of six RIL’s of a Baronesse x Lewis cross on feedlot performance, nutrient digestion, and carcass characteristics of beef steers.

Materials and Methods

Eighty Angus x Hereford steers (344 kg) were assigned to 16 pens in a randomized complete block design for a 147-d feedlot trial. The trial was divided into two periods. During period 1 (70 d) steers received one of two diets based on either Baronesse (BAR) or Lewis (LEW) barley. During period 2 (77 d) steers were fed one of eight diets based on LEW, BAR or one of six RIL’s from a LEW x BAR cross. Diets were balanced to contain 13.5% CP (Table 2).

Steers were implanted with Ralgro on d 1 of the study and with Synovex on d 56. A 28-d adaptation period was used to adjust steers to their individual diets. Steers were allowed ad libitum access to water and were offered feed once daily at approximately 0900. Steers were weighed, and diet, ort and fecal samples were taken every 28 d. Initial and final weights were the average taken over two consecutive days. Diet and fecal samples were composited by pen and analyzed for dry matter (AOAC, 1997) acid insoluble ash (AIA; Van Keulen and Young 1977), and starch (AOAC, 1997). Acid insoluble ash was used as an internal marker to calculate apparent nutrient digestion.

Steers were slaughtered when 70% were visually estimated to grade choice. Hot carcass weights were obtained on the day of slaughter. All other carcass data were taken after a 24-h chill. A USDA grader assigned quality grade and marbling score.

Data were analyzed by the GLM procedure of SAS (1993) with pen as the experimental unit. Period 1 and period 2 data were analyzed separately. Hot carcass weight was used as a covariate for the analysis of carcass characteristics. Data was analyzed for effects of treatment. Treatment least square means were separated by the LSD procedure if a significant F value was detected (P < .10).

Results and Discussion

After period 1 (70 d) steers fed BAR had higher (P = .09) ADG than steers fed LEW (1.71 vs 1.61 kg/d; data not shown). During period 2 (77 d) steers fed LB2, LB32, and LB6 had higher (P = .006) ADG (avg 1.53 kg/d) than steers fed LB5 (1.1 kg/d; Table 3). Steers fed BAR, LEW, LB48 and LB57 were intermediate in ADG (avg 1.37 kg/d). Steers fed LB2 and LB48 consumed more DM (P = .0001) than steers fed BAR, LEW, LB32, LB5 and LB57 (Table 3). Steers fed LB6 being intermediate in DMI. No differences (P > .10) were found in feed efficiency.

Steers fed LB5 had higher (P < .10) marbling scores than steers fed other diets (5.5 vs 4.45 avg; Table 3). Steers fed LB5 had higher quality grades (P = .03) than steers fed LB48, with steers on all other diets being intermediate. Boss and Bowman (1996) also found differences in marbling score and quality grade for steers fed different barley varieties. However Surber et al. (1998) and Ovenell et al. (1993) found no differences in carcass measurements from steers fed different barley cultivars.

Steers fed LB2 consumed more (P = .05) starch than those fed LB32 with all other treatments intermediate in starch intake (Table 4). No differences (P > .10) were found in starch digestibility. No diet effects were found (P > .10) for DMD. However, steers fed LB2 and LB6 consumed more digestible DM than steers fed LB32, LB48, and LB57, with other treatments being intermediate. Steers fed LB2 consumed more digestible starch than steers fed LB32 with all other treatments being intermediate.

Implications

Results from this trial support previous conclusions that barley genotype influences feedlot performance, nutrient digestion, and carcass characteristics. Steers fed several recombinant inbred lines from a Lewis x Baronesse cross showed improvement in ADG, quality grade, and marbling score over steers fed either parent lines. In this study LB5 had poorer feeding value than did the parent lines while LB2, LB6, and LB32 had improved feeding value over the parent lines.

Literature Cited

AOAC. 1997. Official Methods of Analysis of AOAC International (16^th. Ed.) AOAC International, Gaithersburg, MD

Boss, D. L., and J.G.P. Bowman. 1996. Barley varieties for finishing steers: I. Feedlot performance, in vivo diet digestion, and carcass characteristics. J. Anim. Sci. 74:1967-1972.

Bowman, J.G.P. and T. K. Blake. 1997. Building a better feed barley for beef cattle. Proc. 8^th Austr. Barley Tech. Symp., 1997, Queensland, Australia. pp. 2:6.1-2:6.4.

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. 43: 35-38.

Ovenell, K.H., M. L. Nelson, J. A. Froseth, S. M. Parish, and E. L. Martin. 1993. Feedlot performance, carcass characteristics of steers, and digestibility of diets containing different barley cultivars. Proc. West. Sect. Am. Soc. Anim. Sci. 44:416-419.

SAS. 1993. SAS/STAT User Guide. SAS Inst. Inc., Cary, NC.

Surber, L.M.M., J.G.P. Bowman, T. K. Daniels, T. J. Milner, A. L. Lewis, D. M. Coulson, and T. K. Blake. 1998. Feeding value of barley varieties for finishing cattle. Proc. West. Sect. Am. Soc. Anim. Sci. 49:268-271.

Surber L.M.M., and J.G.P. Bowman. 1998. J. Anim. Sci. 76:1945-1954.

Van Keulen, J. and B. A. Young. 1977. Evaluation of acid-insoluble ash as a natural marker in ruminant digestibility studies. J. Anim. Sci. 44:282.

Table 1. Chemical composition of Baronesse, Lewis, and six recombinant inbred barley lines from a Lewis x Baronesse cross.

Item

BAR

LEW

LB 2

LB 5

LB 6

LB 32

LB 48

LB 57

DM, %

91.7

89.7

89.0

92.3

90.3

91.3

90.6

89.2

CP, % of DM

12.5

13.5

15.7

12.6

13.3

16.4

14.8

14.4

ADF, %of DM

5.75

4.76

5.01

5.52

4.19

6.33

6.26

5.22

Starch, % of DM

59.75

62.44

56.90

58.81

59.82

57.03

54.48

59.36

Table 2. Diet composition and chemical composition of barley diets based on Lewis, Baronesse and six Lewis x Baronesse recombinant inbred lines.

Barley Variety

Item

BAR

LEW

LB2

LB5

LB6

LB32

LB48

LB57

Ingredient , % of DM

Cracked Barley

83.00

Grass Hay

6.00

Oil

3.00

Supplement^abc

8.00

Chemical Composition

OM, %

91.6

93.2

91.9

93.0

92.4

90.3

90.9

91.8

N, % of DM

2.31

2.23

2.12

2.73

2.27

1.95

1.79

2.00

ADF, %of DM

10.80

10.12

10.38

9.85

10.31

11.43

11.18

12.62

Starch, % of DM

45.44

43.50

42.73

41.92

43.20

38.69

40.53

44.26

^aTM premix contained 20.0% Mg, 6.0% Mn, 5.0% Fe, 2.7% S, 1.5% Cu, .11% I, .01% Se, and .01% Co.

^b Vitamin A, D, E premix contained 30,000 IU/g vitamin A, 6,000 IU/g vitamin D, and 7.5 IU/g vitamin E.

^c Rumensin premix contained 132 g/kg of monensin, Tylan premix contained 88 g/kg of tylosin.

Table 3. Performance and carcass characteristics of steers fed barley diets based on Lewis, Baronesse and six Lewis x Baronesse recombinant inbred lines.

Barley Variety

Item

BAR

LEW

LB2

LB5

LB6

LB32

LB48

LB57

No. of pens

Initial wt, kg

464.5

443.3

469.7

474.3

471.7

454.6

464.0

455.9

19.2

.24

77-d wt, kg

541.6

542.2

549.7

530.0

551.8

541.6

536.8

540.5

9.25

.04

ADG, kg/d

1.41^bc

1.40^bc

1.54^c

1.10^a

1.52^c

1.54^c

1.31^b

1.38^bc

.08

..006

DMI, kg/d

9.03^ab

8.94^a

10.11^d

8.67^a

9.52^cb

9.17^ab

9.76^cd

9.13^ab

.242

.0001

FE, feed/gain

6.4

6.5

7.2

6.3

5.9

7.5

6.6

.50

.47

Carcass wt, kg

334.2

327.9

326.5

327.8

334.3

321.0

320.9

338.0

8.04

.69

KPH fat, %

2.4

2.3

2.5

2.3

2.5

2.3

2.4

.09

.58

Fat thickness, cm

1.02

.76

1.27

1.02

.127

.50

REA, cm²

81.2

80.0

81.9

74.2

79.3

80.6

81.9

80.6

2.58

.55

Marbling score^y

4.5^a

4.7^a

5.5^b

4.3^a

4.6^a

4.0^a

4.4^a

.29

.05

Quality grade

12.2^b

12.3^b

12.2^b

13.3^c

12.0^ab

12.3^b

11.5^a

12.1^ab

.32

.03

Yield grade^z

2.7

2.8

2.4

3.3

2.6

2.8

2.6

2.7

.22

.39

^{a,
b, c} Within a row, means lacking a common superscript letter differ (P<.10).

^y Marbling score: slight = 3, small = 4, modest = 5.

^z Quality grades are: select = 11, low choice = 12, choice = 13, high choice = 14.

Table 4. In vivo digestibility of barley diets Lewis, Baronesse and six Lewis x Baronesse recombinant inbred lines.

	Barley Variety
Item	BAR	LEW	LB2	LB5	LB6	LB32	LB48	LB57	SE	P
No. of pens	2	2	2	2	2	2	2	2	-	-
Intake, kg/d
DM	9.03^ab	8.94^a	10.11^d	8.67^a	9.52^cb	9.17^ab	9.76^cd	9.13^ab	.242	.0001
Starch	4.05^ab	3.92^ab	4.33^b	3.66^ab	4.13^ab	3.56^a	3.94^ab	4.11^ab	.310	.05
In vivo digestibility, %
DM	74.9	76.1	73.7	76.9	75.9	68.5	68.0	71.1	2.66	.54
Starch	99.9	99.5	99.5	99.9	99.9	99.5	99.9	98.9	.20	.40
Digestible intake, kg/d
DM	6.76^ab	6.79^ab	7.43^b	6.71^ab	7.23^b	6.29^a	6.59^a	6.48^a	.324	.08
Starch	4.04^ab	3.90^ab	4.31^b	3.66^ab	4.12^ab	3.54^a	3.94^ab	4.07^ab	.311	.06

^{a,
b, c}Within a row, means lacking a common superscript letter differ (P < .10).

T. C. Blackhurst*, J.G.P. Bowman, L.M.M. Surber, T. J. Milner, T. K. Daniels and T. K. Blake

Introduction

Materials and Methods

Results and Discussion