Effect of Corn Harvest with a Chopping Head on Performance of Cattle Grazing Corn Residue

Authors: Connor Biehler, Associate Extension Educator and Graduate Student, Mary E. Drewnoski, Professor, Jim C. MacDonald, Professor, Animal Science, Lincoln.

Summary with Implications

The effects of harvesting corn using a chopping vs a standard, non-chopping combine head on steer performance when grazing corn residue were evaluated. Steers were supplemented with dry distillers grains at 0.6% of initial body weight. The amount of corn residue mass and the quality of the husk did not differ between harvest methods. Steer gains were over twice as high in year 2 (2.10 lb/d) than year 1 (0.76 lb/d), potentially due to greater husk digestibility and milder winter conditions. Corn residue harvested with a standard combine head resulted in a slightly higher average daily gain (1.48 vs. 1.36 lb/d) compared to residue harvested with a chopping corn head. This performance difference is likely due to reduced husk mass and finer leaf particle size in chopped residue, which may have limited intake. While differences were modest, the data suggest that chopped residue may decrease grazing value.

Introduction

Corn growers have increasingly adopted chopping combine heads to accelerate residue breakdown. These heads reduce the particle size of plant material, increasing surface area and promoting faster microbial decomposition. However, this practice alters the physical structure of the residue left behind. As more producers graze fields harvested with chopping heads, there are questions about how this harvest method affects residue quality, availability, and ultimately, cattle performance. To address these concerns, a study was conducted to compare corn residue harvested with a chopping head (CHP) versus a standard, non-chopping head (STD). The objective was to evaluate cattle selectivity and performance across harvest methods. Specifically, the study sought to determine whether reducing residue particle size limits the ability of cattle to select high-quality plant parts, such as husks and leaves.

Procedure

This study was conducted over two years (Year 1: 2023-2024, Year 2: 2024-2025) at the Eastern Nebraska Research Extension and Education Center, near Mead, NE. The study utilized a 26-acre irrigated field in a corn-bean rotation that was harvested on October 7, 2023, and October 15, 2024 using a John Deere S650 rotary combine, and yielded 220 bushels per acre in 2023 and 223 in 2024. A JD620F 20-foot flex header was used on the STD treatment, and a 2013 John Deere 608C Stalkmaster corn header was used on the CHP treatment. The varieties of corn that were planted were Pioneer P1366AM in year 1 and Pioneer P13050AM in year 2 and planted in 30-inch rows. 

Following corn harvest each year, the field was divided into 8, 2.6-acre paddocks for grazing. Within each half of the field, 4 grazed paddocks were assigned randomly to harvest methods STD or CHP. Spring-born steers (year 1: n = 40; year 2: n = 48) were limit fed at 2% (DM basis) of their body weight (BW) for five days, and the final 3 days of limited feeding were weighed and then stratified by BW and randomly assigned to a paddock. 

Cattle were turned out to corn residue on November 8, 2023 and November 20, 2024 and grazed for 63 and 53 days, respectively. All groups were supplemented with 18.3 lb/group daily (0.6% of initial body weight). The supplement contained dried distillers grains with solubles and mineral supplement. In year 1, all steers and diet samplers had to be removed from the study on January 10th due to inclement weather; the second-year cattle grazed until January 12th and were pulled off due to lack of residue availability. Following the trial, cattle were again limit fed for 5 days, and had weights recorded the final 3 days of limit feeding.  

During the first year, one half of the field, was stocked with 6 growing steers per paddock. On the other half, each paddock contained 4 growing steers and 1 ruminally cannulated steer. The cannulated steers (n = 4) averaged 1067 lb BW and were used in place of 2 stocker steers to ensure a consistent grazing pressure of 1.17 animal units per acre (AU/ac) and used to facilitate diet sample collections. Because cattle are selective grazers, relying solely on residue samples does not accurately reflect their actual diet consumed. Thus, to more accurately determine the nutrient content of the diet consumed, ruminally canulated steers were utilized. On the day of sample collection, rumen contents of steers were completely evacuated, then steers were allowed to graze for 2 hours. Subsequently, rumen contents from grazing were collected and used to assess the nutritive value of the diet. This sampling procedure was conducted on day 1 of the trial, day 37, and following grazing on February 7, 2024.  This last sampling was delayed for 28 days post-grazing, due to inclement weather and snow and ice covering the paddocks, making the residue inaccessible. Because the digestibility and CP data from year 1 showed no differences between treatments, diet samplers were not used again in year 2. Thus, in year 2, all grazed paddocks contained 6 growing steers.

Corn residue mass was sampled at the beginning (Year 1: November 7, 2023; Year 2: November, 15, 2024) and the end (Year 1: February 7, 2023; Year 2: January, 13, 2024) of the trial. To account for distribution behind the harvester, samples were collected between the corn rows. A sampling area of 6.25 ft2 (30 inch by 30 inch) was taken in the inter-row between rows 1-2, 4-5, and 7-8 rows of a single 8-row combine pass in each paddock. To estimate residue mass, samples were dried to a constant weight in a 140-degree Fahrenheit oven and dry weights were averaged across the three interrow spaces to get an estimate per paddock. 

Husk samples were collected in the same three inter-rows as the residue samples but separate from where the residue mass was sampled. All husks in the inter-row spaces (2.5 feet ft wide) along a 25 feet length were counted and collected resulting in the sampling of a 62.5 ft2 area per inter-row. Husk was specifically targeted because it is the most energy dense portion of the residue and is the first selected part by grazing cattle.

Following the collection, the husk and diet samples were tested for digestible organic matter (DOM), a proxy for total digestible nutrients (TDN), and crude protein (CP). 

Data were analyzed using the MIXED procedure in SAS. Fixed effects included harvest method, year, and their interaction. Block within year was included as a random effect. Treatment differences were considered significant when P ≤ 0.05 and considered a tendency between P > 0.05 and P ≤ 0.10.

Results

For both initial and end residue mass (Table 1), there was no (P ≥ 0.27) harvest method by year interaction. There was also no effect of harvest method (P ≥ 0.26) or year (P ≥ 0.14). Initial husk quantity and quality were examined in this study because it is the most nutrient dense portion of the residue, and cattle being selective grazers will choose this portion of the residue first. For number of husks (Table 2) in the interrow space there was no interaction (P = 0.26) between harvest method and year nor effects of harvest method (P = 0.45) or year (P = 0.27).  For the weight of individual husks there was no (P = 0.28) harvest method by year interaction. However, husk weight was greater (P = 0.04) for STD (0.20 oz) husk than CHP (0.16 oz). The CHP husks appeared to have the outer shucks removed during the harvest process. The husk weight was also greater (P = 0.04) in year 1 (0.23 oz) compared to year 2 (0.12 oz). For husk mass (lb DM/ac), there was a tendency (P = 0.06) for a treatment by year interaction. In year 1, husk mass of STD was greater (P < 0.01) than CHP. In year 2, husk mass of STD was not different (P = 0.59) from CHP.  For husk digestibility and protein content, there were no significant (P ≥ 0.21) harvest method by year interactions or harvest method (P ≥ 0.12) effects (Table 3). However, there were significant (P < 0.01) year effects. Both the digestibility and crude protein content was lesser in year 1 (56.0 % DOM and 3.3% CP) than in year 2 (69.5% DOM and 5.6% CP). 

Diet samples were taken over the course of the first year at 3 timepoints, prior to the start of grazing, half-way through grazing and after grazing was completed (Table 4). For both digestibility and protein content of the diet, there was no (P ≥ 0.54) harvest method by time interaction. There was also no effect of harvest method (P ≥ 0.20) or time (P ≥ 0.11).

For initial BW, end BW, and ADG there was no (P ≥ 0.43) harvest method by year interactions (Table 5). As designed, for initial BW there was no difference (P = 0.61) between harvest methods. However, there was a difference in ending BW with the STD weighing more (P = 0.05) than CHP at the end of the trial, resulting from a tendency for the ADG to be 0.12 lb/d higher (P = 0.06) in STD (1.48 lb/d) than CHP (1.36 lb/d). 

There was also a year effect for initial BW, ending BW, and ADG. The initial BW of the steers was slightly (8 lb) greater (P = 0.02) but the ending BW (64 lb) was lesser (P < 0.01) in year 1 than in year 2. This was because of lesser (P < 0.01) gains while grazing in year 1 (0.76 lb/d) than in year 2 (2.10 lb/d).  Given there were no differences in husk or diet quality, difference in ADG between harvest methods is likely a result of intake rather than quality of diet. The reduction in husk weight and the visually observed reduction in particle size of the leaf in the CHP may have resulted in less intake per bite and resulted in overall intake being lesser. 

The large difference in gains from year 1 to year 2 may be a reflection of the difference in husk quality, specifically the difference in digestibility and thus energy available from the husk. This difference may have been driven by differences in the corn variety used or growing conditions. Although weather may have also played a role as year 1 had more snow and extreme cold while year 2 was more mild. 

Conclusions

To conclude, steers grazing STD corn residue showed a tendency to have a greater ADG, gaining 0.12 lb/day more than their counterparts on the CHP residue. This suggests a potential performance disadvantage when chopping corn heads are used. The greater husk weight observed in the STD treatment likely played a role in the greater animal performance observed by allowing steers to consume more per bite. 

Acknowledgment

The authors would like to thank Iowa Beef Industry Council for providing partial support for this project. 

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