Effects of Replacing Dry Rolled Corn with Dry Rolled Wheat on Feedlot Performance and Carcass Merit

R.A. Ross, L.J. McBeth, C.R. Krehbiel, D.L. Step, J.P. Banta, D.L. Lalman, and R.A. Ball

Story in Brief

The objective of these experiments was to determine the effects of replacing a portion of dry-rolled corn with dry-rolled wheat on feedlot performance and carcass merit.  Two trials were conducted where 25% (DM basis) of the dry-rolled corn was replaced with dry-rolled wheat and fed throughout the finishing phase.  Performance and carcass data showed no significant differences between those cattle fed corn only vs. those fed corn and wheat.  The only numerical difference was in the marbling and quality grades of the two treatment groups.  Steers fed the corn finishing diet had slightly more marbling and higher quality grades than cattle finished on corn and wheat.  These results showed that wheat had no significant impact on feedlot performance or carcass merit when replacing 25% of dry-rolled corn.

Key Words: Carcass Merit, Feedlot Cattle, Grain Source, Performance 

Introduction

The selection of a grain source to be used in feedlot finishing diets is influenced by many factors such as availability, cost, and effects on performance and carcass merit.  Site and extent of starch digestion are influenced by grain source and grain processing, with the primary goal of grain processing being to increase starch (energy) availability.  In addition, grain sources can be characterized by their rate of ruminal starch fermentation. The greatest rate of ruminal starch fermentation occurs with wheat.  Combinations of grains can be used to spread starch digestion throughout the digestive tract, and also to decrease the incidence of ruminal acidosis (Bock et al., 1991).

Zinn et al. (2002) reported that steam flaking increased the NEm of corn by 14% and NEg by 19% compared with dry-rolled or whole corn.  In part, this is a result of greater ruminal and total tract starch digestibility of steam-flaked compared with dry-rolled corn, resulting in a positive effect on ADG, feed efficiency, and final live weight (Huck et al., 1998).  Due to the greater ruminal starch digestibility of wheat grain, we hypothesized that replacing dry-rolled corn with dry-rolled wheat would improve performance of finishing cattle.  The objective of this study was to determine the effect of replacing 25% of corn grain (DM basis) with wheat on performance and carcass merit of yearlings and calves.

Materials and Methods

Two experiments were conducted at the Willard Sparks Beef Research Center.  Experiment 1 utilized 71 crossbred yearling steers (avg initial BW = 822 ± 66 lbs). On arrival (July 17, 2003), steers were individually weighed and ear tagged.  On July 22, 2003, steers were weighed, horn tipped as needed, vaccinated subcutaneously with 2 mL of Titanium 5 (Intervet Inc., Millsboro, DE), dewormed with 7 mL Ivomec-Plus injectable (Merial, Duluth, GA), and implanted with Revalor-S (Hoechst Roussel Vet, Clinton, NJ).  Steers were sorted by initial body weight and randomly allocated to one of 12 pens (6 pens/treatment, 6 steers/pen).  Steers were fed for 140 d (July 30, 2003 – December 16, 2003).

Treatment diets are shown in Table 1.  Diets were formulated to meet or exceed NRC (1996) nutrient requirements, and contained monensin (30 g/ton of DM) and tylosin (10 g/ton of DM).  Steers were gradually adapted to their final treatment diet by offering 55, 65, 75, and 85% concentrate diets for seven d each.  Feed refused was weighed every 28 d.  In addition, diet samples were collected, and DM content of the diets and dietary ingredients was determined.  Diet and ingredient samples were composited by 28-d periods, dried in a forced-air oven, and ground in a Wiley mill to pass a 1-mm screen.  Interim unshrunk BW was determined at 28-d intervals.  Steers were harvested at a commercial facility.  Hot carcass weight, external fat, internal fat, longissimus muscle area, marbling score, yield grade, and quality grade were determined.

Data for BW, dry matter intake, average daily gain, feed efficiency, hot carcass weight (HCW), carcass-adjusted variables (calculated using carcass-adjusted final weight, which was calculated as HCW/average dressing percent), and normally distributed carcass characteristics were analyzed as a complete randomized design using the Proc Mixed procedure of SAS Release 8.02 (SAS Institute Inc., Cary, NC).  Non-parametric USDA quality grade data were analyzed and transformed using Friedman’s test by listing the percentage of Choice and Select for each pen within a block and then analyzed as normally distributed data as above (Elam et al., 2003).  Pen was the experimental unit.

Experiment 2 utilized 87 steer calves (avg initial BW = 498 ± 72 lbs). On arrival (October 2, 2003), calves were individually weighed and ear tagged, vaccinated for Bovine Rhinotracheitis and Bovine Viral Syncytial Virus with 2 mL of Bovishield FP4+Lepto (Pfizer, New York, NY), dewormed with 4.5 mL Ivomec Plus, and implanted with Component E-S (Intervet Inc., Millsboro, DE). On December 18, 2003, steers were re-implanted with Revalor-S (Hoechst Roussel Vet, Clinton, NJ). Steers were blocked by previous cow supplementation treatment (Banta et al., 2004) and randomly allocated within block to one of the nine pens (9 pens/treatment, 4 or 5 steers/pen).  Pens were randomly allotted to treatments (Table 1).  Steers were fed for 189 days (October 24, 2003 – April 20, 2004).

Steers were gradually adapted to their final treatment diet by offering 55, 65, 75 and 85% concentrate diets for seven d each.  All data collections were the same as for Exp. 1.  Data were analyzed as a randomized complete block design using the Proc Mixed procedure of SAS.  Pen was the experimental unit.  The model statement included treatment, and the random statement included block.

Table 1: Feedstuff composition of diets (%DM)

 

Wheat Finisher

Corn  Finisher

Rolled corn

58.5

77.5

Rolled wheat

19.5

-

Alfalfa hay

10.0

10.0

Cane molasses

4.0

4.0

Yellow grease

2.0

2.0

Wheat midds

1.48

.56

Soymeal 47.7

1.56

3.0

Cottonseed meal

.52

1.0

Vitamin A-30,000

.011

.011

Limestone 38%

.85

.85

Salt

.20

.20

Urea

.80

.80

Dical

.50

.50

Manganous oxide

.003

.004

Zinc sulfate

.009

.0114

Availa Zinc 100

.029

.029

Rumensin 80

.019

.019

Tylan 40

.013

.013

Availa Copper 100

.0011

.0015

Selenium 600

-

.0040

 

Table 2: Calculated nutrient composition of experimental diets

 

Wheat Finisher

Corn Finisher

NEm Mcal/CWT

95.82

96.58

NEg Mcal/CWT

62.10

62.71

Fat

5.08

5.47

ADF

6.4

6.2

NDF

12.9

12.0

Crude Protein %

13.6

13.6

Potassium %

.74

.76

Calcium %

.66

.66

Phosphorus %

.40

.39

 

Results and Discussion

Feedlot performance for Exp. 1 is presented in Table 3. Body weight was not affected (P=.39 to .82) by treatment.  Similarly, there was no difference in dry matter intake from d 1-27 (P=.93) or d 1-139 (P=.45).  From day 1-27, steers fed wheat had numerically (P=.14) greater average daily gain; however, treatment groups were similar (P=.50) from d 1-139.  Feed to gain ratio was numerically improved (P=.12) for steers fed wheat during the first 27 d.  However, across the finishing phase, feed:gain did not differ (P=.98) among treatments.  Carcass adjusted performance did not differ among treatments (Table 3).

Table 3. Performance data, Exp. 1

 

Wheat

Corn

SEM

P-Value

Body Weight

 

 

 

 

Day 1

809

835

28

.53

Day 28

926

936

32

.82

Finish, d 140

1321

1358

34

.45

Adj. final BWa

1319

1358

31

.39

DMI

 

 

 

 

Day 1-27

22.9

22.8

.31

.93

Day 1-139

24.3

24.9

.54

.45

ADG

 

 

 

 

Day 1-27

4.3

3.8

.34

.14

Day 1-139

3.7

3.8

.09

.50

Adj. ADGa

3.7

3.8

.09

.46

Feed:Gain

 

 

 

 

Day 1-27

5.4

6.2

.36

.12

Day 1-139

6.6

6.6

.14

.98

Adj. F:Ga

6.6

6.6

.17

.94

aAdjusted final BW was calculated as hot carcass weight/average dress of 0.6335. Adjusted daily gain was calculated as (adjusted final BW − initial BW)/days on feed. Adjusted feed:gain was the ratio of adjusted daily gain and daily DMI

Performance data for Exp. 2 is presented in Table 4.  Initial weights for calves fed corn were greater (P<.03) compared with calves fed wheat; therefore initial BW was used as a covariate for all subsequent statistical analyses.  Final weights were not different (P=.22) among treatments.  Across the finishing phase, average daily gain did not differ (P=.23) among treatment groups.  Overall dry matter intake tended (P<.10) to be lower for cattle fed wheat; however, overall feed:gain was very similar (P=.48) among treatment groups.  Feed:gain was improved (P=.03) for calves fed wheat from d 1-83.  Similar to Exp. 1, carcass adjusted performance did not differ among treatments (Table 4).

Table 4. Performance data, Exp. 2

 

Wheat

Corn

SEM

P-Value

Body Weight

 

 

 

 

Day 1

509

524

11

.03

Day 28

664

663

5

.88

Day 83

874

874

9

.97

Day 149

1065

1079

8

.13

Final, d 169

1160

1173

9

.22

Adj. final BWa

1165

1174

8

.30

ADG

 

 

 

 

Day 1-28

5.3

5.3

.18

.88

Day 1-83

4.3

4.3

.11

.97

Day 1-finish

3.8

3.9

.05

.23

Adj. ADGa

4.4

4.5

.05

.30

DMI

 

 

 

 

Day 1-28

14.7

15.3

.43

.24

Day 1-83

16.3

18.3

1.7

.36

Day 1- finish

19.2

19.6

.22

.10

Feed:Gain

 

 

 

 

Day 1-28

2.8

2.9

.09

.32

Day 1-83

4.2

4.4

.05

.03

Day 1-finish

5.1

5.2

.07

.48

Adjusted F:Ga

4.2

4.3

.08

.15

aAdjusted final BW was calculated as hot carcass weight/average dress of 0.63. Adjusted daily gain was calculated as (adjusted final BW − initial BW)/days on feed. Adjusted gain:feed was the ratio of adjusted daily gain and daily DMI