Maize is a critically important source of food, feed, energy and forage in the USA

Field Crops Research 153 (2013) 5–11

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Maize is a critically important source of food, feed, energy and forage in the USA T.J. Klopfenstein a,∗ , G.E. Erickson a,1 , L.L. Berger b,2 a b

C220 Animal Science, University of Nebraska, Lincoln, NE 68583-0908, United States C203 Animal Science, University of Nebraska, Lincoln, NE 68583-0908, United States

a r t i c l e

i n f o

Article history: Received 20 December 2011 Received in revised form 21 June 2012 Accepted 7 November 2012 Keywords: Maize grain Maize silage Maize residue Ethanol byproducts

a b s t r a c t Maize production in the U.S. was about 316 million metric tons in 2010. That amount is expected to increase in the future due to greater yields/hectare and more hectares planted. From 1950 until 2006 the supply of maize grain was much greater than demand. Government programs supplemented farmers, enabling them to produce abundant amounts of maize grain at low prices. The low prices of maize grain encouraged feeding large amounts to livestock and poultry. As late as 2000, 60% of maize grain produced was fed to livestock and poultry. The development of the fuel ethanol industry has changed both the price of maize grain and the usage by livestock and poultry. In 2010 only 42.9% of U.S. maize grain was fed to livestock and poultry while 41.8% was used for fuel ethanol production, and 11.2% for food. There are two byproducts from fuel ethanol production that replace some of the maize grain, especially in cattle production—distillers grains and maize gluten feed. Both of these byproducts are very well utilized by cattle. Depending upon plant production logistics, distillers grains has 110–140% the feeding value of the maize grain replaced and maize gluten feed has 100–110% the feeding value of maize grain. Values are less for lactating dairy cows but both byproducts serve as excellent protein sources. Byproducts replace 35–45% of the maize grain used to produce fuel ethanol. Essentially all of the cattle in the U.S. are “finished” on diets containing 80–85% concentrates. In the past the concentrates were comprised primarily of maize grain but now are a mixture of maize and byproducts. In the US the forage part of the corn plant is utilized in three ways. Some is harvested as whole plant maize silage. The silage is used as both an energy source and a roughage source in feedlot diets. Maize silage is also used to “background” cattle. This term is used to describe a growing phase based on forages prior to cattle being placed on “finishing” diets. The second use of maize forage (referred to as residue) is residue harvest after grain harvest and fed as a roughage source in finishing diets or mixed with wet byproducts and fed as an energy source to “background” cattle or beef cows. The other use of the maize “residue” is through grazing after grain harvest. Beef cows or backgrounding calves are placed on the maize fields after grain harvest where they select the higher quality forage components and any residual grain left in the field after harvest. Residual grain in residue is of high quality and selected first by the cattle. The husk is palatable and highly digested while the leaf is palatable but not as digestible. Quality of the diet declines with time of grazing because the higher quality parts are selected first. Generally, about 15% of the residue is consumed leaving 85% for erosion control and soil organic matter. Under this system beef cows need little supplementation while growing calves need supplementation of both protein and energy to yield economical growth. © 2012 Elsevier B.V. All rights reserved.

1. Historical increase in corn production In 1935, 33.4 million ha of maize were harvested in the U.S., mostly by hand. The average yield was 1519 kg/ha for a total of 50.9 million metric tons production (NASS, 2010). Farms were small,

∗ Corresponding author. Tel.: +1 402 472 6443; fax: +1 402 472 6362. E-mail addresses: [email protected], [email protected] (T.J. Klopfenstein), [email protected] (G.E. Erickson), [email protected] (L.L. Berger). 1 Tel.: +1 402 472 6402; fax: +1 402 472 6362. 2 Tel.: +1 402 472 3571; fax: +1 402 472 6362. 0378-4290/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fcr.2012.11.006

labor requirements were high and most farms had several livestock species including some cattle. From 1935 to 1945 the U.S. became engaged in a World War which dramatically increased food demand. At the same time hybrid seed maize was being produced and sold commercially and the Haber–Bosch technology was being utilized to produce nitrogen fertilizer for maize. By 1950, maize acres had declined but yields had increased to 2400 kg/ha and total production had increased to 60 million metric tons. Because of the “war effort” to produce maize and because of technological developments, maize production exceeded demand. In 1956, the U.S. government addressed the “farm problem”, excessive maize grain, by encouraging farmers to “Soil Bank” cropland,

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T.J. Klopfenstein et al. / Field Crops Research 153 (2013) 5–11

paying them to not produce maize. The same farmers realized that it was profitable in most cases to feed the inexpensive maize grain to cattle—marketing the maize through the cattle. Feeding the maize grain to beef cattle led to the “high quality” beef that U.S. consumers have become accustomed to. Until 2006, the “farm problem” was too much maize grain. The inexpensive maize further encouraged cattle feeding with segmentation of the cattle feeding into feedlots, separating it from farming. For example, about 3.3 million cattle were fed for harvest (finished) in 1965 in Iowa. At the time, only 3.9% of the cattle were produced in feedlots of 1000 head capacity or larger. By 1980, about 2.7 million cattle were finished in Iowa of which 37.6% were finished in feedlots of 1000 head capacity. Over the same period, the number of cattle finished yearly in Texas increased from 1.1 million in 1965 to 4.2 million in 1980 with 98.7% in feedlots over 1000 head capacity. In 2007, 84.5% of the U.S. cattle were fed in feedlots over 1000 head capacity, 73.2% in feedlots over 5000 head capacity and 60% in feedlots over 16,000 head capacity (NASS, 2010). This growth in cattle feeding was supported primarily by inexpensive maize grain. Americans are currently consuming 29 kg/person of “high quality” beef each year. This “high quality” beef is somewhat unique to the U.S. and a very few developed countries such as Japan. This beef (maize-fed) contains more fat than forage fed beef. Bradford et al. (1999) report that only 11.5% of the beef produced in the world is produced in “industrial” systems such as the feedyards in the U.S. Maize production has continued to increase so that in 2006 the yield was 9103 kg/ha (149 bu/ac) and total production was 267 million tons (10.5 billion bushels). Because of technological advances, maize production has increased by nearly 125 kg/ha each year. With the growth of the ethanol industry and the anticipated expansion of that industry, the demand for maize has increased. During the last half of 2006, the price of maize grain increased from about $79/metric ton to above $157/metric ton. With more acres planted to maize and good yields, the price of maize grain in 2007 declined to $118–148/metric ton. In the past year the price has risen to $257/metric ton. Therefore, the cattle, swine and poultry industries are faced with the prospect of producing meat under the constraints of high priced maize after 60 years of “inexpensive maize”. The “farm problem” has changed from too much maize to a debate of food versus fuel. As late as 2000, 60% of maize grain produced was fed to livestock and poultry. The development of the ethanol industry has changed both the price of maize grain and the usage by livestock and poultry. In 2010, only 42.9% of U.S. maize grain was fed to livestock and poultry while 41.8% was used for fuel production and 11.2% for food (NASS, 2010). With 318 million tons of maize grain production and a U.S. population of 312 million, that is over one ton of maize grain produced per person or about 2.8 kg for each person daily. With wise allotment, this should be sufficient maize grain for food, feed and ethanol production.

2. Maize in livestock and poultry diets Swine and poultry diets are based primarily on maize grain and soybean meal. Some distillers grains (DDGs) are being used but the diets for these species have not changed markedly. Because ruminants can utilize a greater variety of feedstuffs, including forage and byproducts, our discussion will focus primarily on beef and dairy cattle as they are the primary users of maize forages in addition to grain. Most of the beef cattle in the U.S. are “finished” on a diet containing large quantities of maize grain. Further, essentially all feedlots employ nutritionists to assist them in making decisions on diet formulation and purchase of feedstuffs. These nutritionists may be independent and paid for consulting services or they may be employed by a feed company and paid indirectly through the

purchase of feed supplements. A few nutritionists are employed by the feedlot full-time. Most nutritionists have Ph.D. degrees and are critically important to the decision making process concerning maize purchase, usage and processing as well as substitution with byproducts. Vasconcelos and Galyean (2007) surveyed nutritionists in the U.S. and the results give a general description of cattle feeding in the U.S. They reported that maize grain content of the feedlot diets was 75–80% of the diet dry matter. In a similar survey done in 2001, the mean value was 80% (Galyean and Gleghorn, 2001). The amount of roughage (forage) ranged from 4.5 to 13.5% of diet dry matter. Most common roughages were alfalfa hay and maize silage. Roughage levels had not changed from those reported in 2001. Essentially all of the maize grain is processed (Vasconcelos and Galyean, 2007) with steam-flaking being the most common method of processing. Dry rolling and high-moisture maize grain harvest and storage are also common. The high-moisture maize grain is usually harvested at 26–30% moisture, rolled and placed in a bunker silo followed by covering with plastic. The majority of the U.S. feedlots are in the Plains States in the central part of the country. Steam flaking is used more commonly in the Southern Plains while highmoisture processing and storage and dry rolling is practiced more in the Northern Plains. Maize is produced in most states but the greatest amounts are produced in the northern states (Corn Belt). Many of the cattle feedlots are located in the Southern Plains so there is a surplus of maize grain in the Corn Belt and a deficit in the Southern Plains. Therefore, maize grain is shipped to the Southern Plains, usually in 100 car unit trains. Because of the surplus of maize grain in the Corn Belt, the fuel ethanol industry developed in the Corn Belt states of Iowa, Nebraska, Minnesota and Illinois.

3. Maize use for ethanol There are two processes for producing fuel ethanol from maize grain (Stock et al., 2000). The wet milling process was developed primarily to produce starch and sweeteners (maize sugar) for human consumption. Sweetener production continues but essentially all wet milling plants also produce fuel ethanol. In this process, maize oil and maize gluten meal are also produced. The resulting byproduct is maize gluten feed which contains the fiber from the maize kernel plus the steep liquor, the fermented liquid used in the initial steeping and washing processes (i.e. wet milling). In the dry milling process, the maize grain is milled and the starch is hydrolyzed with enzymes and fermented with yeast to produce ethanol. The byproduct is distillers grains (DG) which can be marketed as a wet byproduct (30–35% dry matter; WDGs) or dried to produce dry distillers grains with solubles (88–92% DM; DDGs). In both wet and dry milling, the starch is converted to ethanol. The remaining byproducts are high in fiber, protein and, in the case of DDGs, lipid. Because it was perceived that the energy value of maize grain was due to the starch, it was assumed the byproducts would be lower in net energy than maize grain. Because of the higher protein contents of gluten feed and DG, they were used primarily as protein sources in ruminant diets. The maize byproducts are usually priced lower than maize grain and therefore could be economical sources of energy for cattle in addition to being good protein sources (Klopfenstein et al., 2008a). Cattle are accustomed to eating moist feeds such as grass, silage and high moisture maize grain. Therefore, it was logical to feed the DG to feedlot cattle in the wet form. Bremer et al. (2011) reported a meta-analysis showing the response by feedlot cattle to increasing amounts of WDGs in the diet (Table 1). Daily gains and feed efficiency increased as the amount of WDGs increased in the diet. Based on the feed efficiency values for the diets, the feeding value

T.J. Klopfenstein et al. / Field Crops Research 153 (2013) 5–11

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Table 1 Meta-analysis of finishing steer performance when fed different dietary inclusions of dried distillers grains plus solubles (DDGsa ) replacing dry-rolled and high-moisture corn. DGS inclusionb

P

0

10

20

30

40

Lc

Qc

d

WDGs DMI, kg/d ADG, kg G:F Feeding value, %d DDGsd DMI, kg/d ADG, kg G:F Feeding value, %d a b c d

10.4 1.60 0.155 –

10.6 1.71 0.162 150

10.6 1.77 0.168 143

10.4 1.78 0.171 136

10.2 1.75 0.173 130

0.01 <0.01 <0.01 –

<0.01 <0.01 <0.01 –

10.4 1.60 0.155

10.9 1.66 0.156 112

11.2 1.72 0.158 112

11.3 1.77 0.160 112

11.3 1.83 0.162 112

<0.01 <0.01 <0.01 –

0.03 0.50 0.45 –

Adapted from Bremer et al., 2011. WDGs, wet distillers grains with solubles; DDGs, dried distillers grains with solubles. Dietary treatment levels (DM basis) of distillers grains plus solubles (DGS), 0DGS, 0% DGS; 10DGS, 10% DGS; 20DGS, 20% DGS; 30DGS, 30% DGS; 40DGS, 40% DGS. Estimation equation linear and quadratic term t-statistic for variable of interest response to DGS level. Percentage of corn feeding value, calculated from DGS inclusion level feed efficiency relative to 0WDGs feed efficiency, divided by DGS inclusion.

of the WDGs was calculated relative to the maize grain replaced. The feeding value of the WDGs was 126–145% the value of maize grain, with higher values observed at lower inclusion levels. Feeding WDGs in the Northern Plains and Corn Belt is efficient and very economical (Klopfenstein et al., 2008a). However, many cattle are fed in feedlots in the Southern Plains which is maize grain deficient and, therefore, has few ethanol plants. This leads to the need to dry DG in order to transport it to the Southern Plains feedlots. There is a fossil fuel and economic cost to dry the DG. In addition, Bremer et al. (2011) have shown less feeding value of DDGs compared to WDGs. The feeding value of DDGs was 112% that of maize grain but less than the values for WDGs. The overall value of DG in the Southern Plains is further complicated by an interaction of level of DG in the diet and maize processing (Klopfenstein et al., 2008a). Steam flaking increases the value of the maize by 10–15%. Adding DG to steam flaked maize diets has little effect on feed efficiency indicating it has feeding value similar to steam flaked maize and 10–15% greater than dry rolled or high moisture maize (Fig. 1). Furthermore, optimal levels of DG in steam flaked maize diets is less than in dry rolled or high moisture maize diets. Dairy cow numbers have declined in the U.S. from 21.7 million in 1953 to 9.12 million in 2010. During that time milk output per cow has increased from 2519 kg/cow to 9613 kg/cow (NASS, 2010). This is a remarkable gain in productivity. Eastridge (2006) states it is common for herds to produce 12,500 kg milk/cow and for cows to consume 25–27 kg DM daily. Certainly, genetic

WDGS and Maize Processing 0.21 0.2

G:F

0.19

DRM

0.18

HMM SFM

0.17 0.16 0.15 0

10

20

30

40

Level of Diet DM (WDGS) Fig. 1. Feed efficiency of finishing steers fed differing levels of WDGs with dry rolled maize, high moisture maize, or steam flaked maize. Adapted from Corrigan et al. (2009).

selection has enhanced productivity but nutritional changes have also enhanced production efficiency. Dairy diets were based primarily on forages in 1953. Grain feeding has steadily increased (primarily maize) until current diets contain 40–60% concentrate (grain and protein source; Eastridge, 2006). Because of the availability of DG in the past few years, much research has been conducted on the use of DG as a replacement for both the protein source and the maize grain in lactation diets (Schingoethe, 2008). The dairy cow efficiently uses the protein, fat and fiber in the DG. A meta-analysis (Schingoethe, 2008) shows similar milk production when DG replaced up to 30% of diet dry matter replacing protein (primarily soybean meal) and maize. This suggests the DG has equivalent energy to maize grain in lactation diets. There is not an apparent difference between WDGs and DDGs in dairy diets, contrary to beef finishing diets. Certainly, feeding DG reduces diet costs, especially when fed at 30% of diet dry matter (Janicek et al., 2008). The byproduct produced by the wet milling industry is maize gluten feed which contains various proportions of maize bran, maize steep liquor and maize germ meal. About 70% of the maize used by the milling industries is used by the dry milling industry and because of lower amounts of byproduct produced in wet milling, about 75% of the byproduct is DG and 25% maize gluten feed. Before 1990 much of the maize gluten feed was dried and exported. Currently much of the maize gluten feed is marketed wet to feedlots and dairies. Cargill ships 100 car unit trains of wet maize gluten feed from a plant in Eddyville, IA, to Dalhart, TX, where it is distributed by truck to feedlots and dairies in the Southern Plains. Stock et al. (2000) reported that wet maize gluten feed has 100–112% the feeding value of maize grain in feedlot diets. The dry gluten feed has much lower feeding value (Stock et al., 2000). Unlike DG, the wet maize gluten feed has value at least as high in diets containing steam flaked maize as in diets containing dry rolled or high moisture maize (Block et al., 2005). Because of the fiber content, wet maize gluten feed minimizes acidosis in high maize finishing diets (Krehbiel et al., 1995), especially those containing steam flaked and high moisture maize. Boddugari et al. (2001) determined the maximum levels of maize gluten feed that could be fed in dairy lactation diets. They concluded that a diet containing 40% wet maize gluten feed, replacing both concentrate and forage, gave 21% greater efficiency of milk production compared to a control diet without byproducts. Kononoff et al. (2006) obtained excellent milk production feeding maize gluten during the dry period and during the full lactation.

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Table 2 Finishing performance of cattle fed diets containing wet distillers grains plus solubles with three types of roughage at low or normal NDF levels. Item

CON

LALF

LCSIL

LCSTK

NALF

NCSIL

NCSTK

SE

DMI, kg/d ADG, kg G:F

10.1a 1.96a 0.195

11.1b 2.06ab 0.186

11.0b 2.05a 0.186

11.3bc 2.17c 0.192

11.7c 2.16bc 0.185

11.5c 2.15bc 0.188

11.6c 2.18c 0.188

0.2 0.05 0.003

Adapted from Klopfenstein et al. (2008a). a,b,c Means within a row with unlike superscripts differ (P < 0.05). CON, control; LALF, low alfalfa hay (4%); LCSIL, low maize silage (6%); LCSTK, low maize stalks (3%); NALF, normal alfalfa hay (8%); NCSIL, normal maize silage (12%); NCSTK, normal maize stalks (6%).

65

4.1. Whole plant maize silage

60

Maize hybrids produced in the U.S. typically have 50% grain and 50% forage at physiological maturity of the plant. This maturity would be at the time when 100% of the starch has been deposited in the maize kernel (referred to as black layer formation). At that stage of maturity, the whole plant is usually 70–75% moisture and, at that moisture, can be readily harvested and stored (ensiled) as whole plant maize silage. In 2010, 6.4% of the maize crop was harvested as whole plant silage (NASS, 2010). Forages typically represent 40–60% of lactating dairy cow diets. Most of the forage fed is maize silage or good quality alfalfa. Even though the maize silage is about 50% grain, the whole plant silage is considered forage by dairy nutritionists (Johnson et al., 1999). The proportion of maize silage varies from zero to 100% of the forage in lactation diets. Quality of silage is influenced by plant maturity and hybrid (Johnson et al., 1999). In addition to chopping at harvest, further mechanical processing is often used to further process the maize kernels. This further processing has increased starch digestibility and, in some cases, increased milk production (Johnson et al., 1999; Eastridge, 2006). Because only 6.4% of maize is harvested as silage, much less research effort has been directed toward selection for silage quality or yield. In many situations, the decision to harvest as grain or silage is made after hybrid selection and planting so emphasis is on high grain yielding hybrids. Many times maize is harvested as silage if lack of moisture has limited grain production. If the maize is intended for silage at planting time, longer season hybrids may be planted because they yield more grain and forage than shorter season hybrids and grain drying in the field is not needed if silage harvest is the objective. The primary advancement in selection for increased digestibility is through the use of the brown midrib mutant (Oba and Allen, 2000). Compared to the control silage, feeding brown midrib mutant silage increased milk yields. We are not aware of research on use of the brown midrib mutant in maize if the residue is designated for grazing. This has been researched with grain sorghum where weanling calf gains increased from 0.34 to 0.56 kg/d when they grazed brown midrib mutant sorghum residue compared to a control (Schwarz et al., 2008). Whole plant maize silage is often used as a roughage (forage source) in feedlot finishing diets for beef cattle (Vasconcelos and Galyean, 2007). The roughage is used at about 7% of the diet dry matter in the finishing diets. At that level most nutritionists would consider the whole plant maize silage to be 50% grain so in order to supply 7% roughage, 14% maize silage would be fed. The silage is also used to acclimate the cattle to the finishing diet by feeding high levels of roughage initially and then decreasing the roughage and increasing the maize grain; 35–50% of the roughage is used during this adaptation phase. Seventy to 80% of the beef calves in the U.S. are backgrounded (i.e. grown) on forage based diets before being fed high concentrate finishing diets in feedlots. In the past (Vance et al., 1972), maize silage was a primary forage used in these backgrounding programs.

% IVDMD

4. Maize forage use in U.S.

55 50 45 40

0

1

2

3

4

5

6

7

8

9

10

Weekly Maize Stalklage Sampling, 1976 Fig. 2. Effect of maize plant maturity on in vitro dry matter digestibility (IVDMD). Represents plants minus ears starting at maturity (black layer formation in kernel; Berger et al., 1979).

The use of maize silage has declined but is still widely used and produces excellent gains on growing calves (Folmer et al., 2002; Weber et al., 2011a). 4.2. Maize residues At current levels of maize grain production and assuming residue (forage) is 50% of the whole plant, then about 250 million tons of maize residue is produced annually in the U.S. The vast majority of that residue is allowed to remain in the field and not utilized for livestock feed. This residue represents an excellent forage resource for beef production. Because of maize use for ethanol production, some forage producing hectares have been converted to maize production reducing the supply of “conventional” forage for beef and dairy production. Therefore, there is great interest in the use of maize residues to replace conventional forages such as alfalfa, grass pasture, grass hay and maize silage. In the future, cellulosic ethanol may compete for the maize residue (U.S. Department of Energy, 2011). At physiological maturity of the maize plant, about 50% of the dry matter is forage. However, about 20% of that forage is soluble carbohydrates (Berger et al., 1979) and these carbohydrates decline with time due to plant metabolism and microbial usage (Fig. 2). Therefore, the amount of dry residues remaining in the field after dry grain harvest is about 40% the amount of grain dry matter. When maize is harvested as high moisture grain (26–32% moisture) the residue is of reasonably high quality because of the content of soluble carbohydrates and can be harvested as silage and utilized as a good quality forage (Berger et al., 1979). There is little harvest of this material currently, likely because it would just be harvested as a part of maize silage. Most maize grain is harvested when the grain is 15–20% moisture so that it can be placed in storage with minimal drying expense. The relatively dry residue may be grazed or harvested as dry forage. As the prices of conventional forage have increased, more maize residue is being harvested and used as forage replacement (Table 2). Byproducts from the ethanol industry, especially in the wet form, have enhanced the utilization of maize residue in feedlot (Klopfenstein et al., 2008a) and backgrounding (Klopfenstein

T.J. Klopfenstein et al. / Field Crops Research 153 (2013) 5–11 Table 3 Growing calf performance over 84 days when fed native grass hay (CP = 8.7%) supplemented with either maize or DDGs for two levels of gain. Net energy was 27% greater for DDGs compared to maize. Low

Table 5 Performance of cattle fed GMO maize, maize silage or maize residue. Grain/silage

High

ADG, kg

Maize DDGs

0.37 0.45

0.71 0.86

G:F

Maize DDGs

0.139 0.172

0.222 0.278

Adapted from Loy et al. (2008). Low, supplement fed at 0.21% BW; high, supplement fed at 0.81% BW.

et al., 2008b) diets. The wet byproducts add palatability, protein and energy to the diets containing maize residue (Table 3). 4.3. Residue grazing Dry maize residue is an excellent resource for grazing by beef cattle (Klopfenstein et al., 1987). When the residue is harvested, most of the plant parts are collected, processed and fed. The quality of this mixture is low (<50% TDN). However, when cattle graze they are allowed to select the more palatable and digestible parts providing a diet of higher quality than that supplied by the harvested residue. Typically 30% of the residue is harvested by the cattle leaving 70% for soil tilth, erosion control and enhancement of water usage by subsequent crops (van Donk et al., 2012). In measurements made in the 1980s, 3–4% of the maize ears remained in the field after harvest (Fernandez-Rivera and Klopfenstein, 1989a; Gutierrez-Ornelas and Klopfenstein, 1991a). However, with improved hybrids and improved combine harvest efficiency, only 1–2% of the maize ears remain in the field (Warner et al., 2012). Because grain yields have increased, 1–2% of the yield is still a significant amount of grain per hectare. Of course forage production per hectare has increased as well but the amount of grain as a proportion of total residue is only 35–50% of that 25 years ago. Cattle grazing residues select remaining grain (ears) and the husks and leaves. These three plant parts are the most palatable. Of course the grain is highly palatable and digestible. Not as obvious is the digestibility of the husk that can range from 60 to 75% (Fernandez-Rivera and Klopfenstein, 1989a; Gutierrez-Ornelas and Klopfenstein, 1991a). Leaves are less digestible and certainly have less digestible energy than the husks or grain. Only a small amount of stalk or cob are consumed. Ten hybrids were harvested in 2009 and amounts of leaf, husk, stem and cob determined as well as in vitro digestibility, showing some variation among hybrids (Musgrave et al., 2011; Table 4). About 7.3 kg of husk and leaf dry matter are produced for each 25.5 kg (as is) maize yield. Grain yields of 12,000 kg/ha are common and this would produce 3500 kg husk and leaf. It is assumed grazing cattle harvest the leaf and husk with 50% efficiency (Gutierrez-Ornelas and Klopfenstein, 1991b). Therefore, 1750 kg/haplus 180 kg grain would be consumed. This amount of residue and grain will maintain two 600 kg cows for 70 days.

9

DMI, kg/d ADG, kg G:F

Silage

Residue

PAR

MON

PAR

MON

PAR

MON

10.3 1.68 0.164

10.1 1.70 0.168

9.44 1.64 0.174

9.26 1.65 0.178

– 0.18 –

– 0.24 –

Adapted from Weber et al. (2011a) and Weber et al. (2011b). PAR, non-transgenic parental hybrid; MON, maize rootworm resistant hybrid MON89034.

Because of the digestibility of the husk and the grain, the quality of the diet is sufficient to at least maintain body weight of gestating beef cows without any supplementation (Warner et al., 2012). There is very little expense to the cattle producer/farmer because the cost of production is charged to the harvested grain production. Less than 15–20% of the residue is removed and very few soil nutrients are removed because most are excreted back onto the field by the cattle. Because the cattle are selective, diet quality is highest at initiation of grazing and declines daily (Fernandez-Rivera and Klopfenstein, 1989b; Gutierrez-Ornelas and Klopfenstein, 1991b; Fig. 3). In order to maintain diet quality, it is necessary to rotate cattle through maize residue fields. Producers more commonly use gestating beef cows for grazing maize residues because the production objective is live weight maintenance. However, maize residue is an excellent resource for growing calves. In the primary maize producing states of the U.S., most calves are weaned in October and are available for maize residue grazing by November when most of the maize grain has been harvested. Weanling calves can gain 0.3–0.5 kg/d with appropriate protein supplementation while grazing maize residue (Gutierrez-Ornelas and Klopfenstein, 1991b; FernandezRivera et al., 1989). Ethanol byproducts are excellent supplements for calves grazing maize residues. They supply protein, phosphorus and high levels of digestible energy (Jordon et al., 2001; Gustad et al., 2006; Oliveros et al., 1989). Daily gains up to 1 kg/d can be achieved with byproducts and maize residue at a very economical cost of production (Fig. 4). Stocking rate influences the amount of grain, husk and leaf available per animal. The amount of grain and husk available affect diet quality because both are highly digested . . . much higher than leaf. Therefore, with reduced stocking rate, diet quality is higher and daily gain of calves is enhanced (Fernandez-Rivera and Klopfenstein, 1989b; Gutierrez-Ornelas and Klopfenstein, 1991a). The extra diet quality resulting from lower stocking rates may not be needed for the gestating cows.

Table 4 Effect of maize hybrida on amounts and digestibility of plant parts. Grain Yieldb SDc IVOMDd SDc a b c d

13.17 0.78 – –

Leaf

Husk

Stem

Cob

3.33 0.29 51.4 0.75

0.96 0.13 56.9 1.71

4.76 0.65 47.6 1.41

1.58 0.18 48.1 2.25

Ten hybrids grown under irrigation, Musgrave et al. (2011). ×1000 kg/ha (dry matter). Standard deviation across hybrids. In vitro organic matter digestibility.

Fig. 3. Digestibility of diets selected by cows when grazing maize residue (digestibility = in vitro dry matter digestibility; Fernandez-Rivera et al., 1989). Stocking rate was 2.47, 257 kg steers/ha. Grain yield was 5024 kg/ha and leaf plus husk was 1674 kg/ha.

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Table 6 Soybean and maize yieldsa following maize residue grazing. Soybean yieldsb

Year

Maize yieldsc

d

2004 2005 2006 2007 2008 2009 2010 a b c d e

e

Fall grazed

Spring grazed

Ungrazed

Fall grazedd

Spring grazede

Ungrazed

3.81 4.59 4.62 4.36 4.61 4.97 3.68

3.94 4.52 4.55 4.34 4.41 4.81 3.57

3.82 4.41 4.53 4.28 4.25 4.77 3.57

11.22 11.55 12.46 12.70 11.87 16.34 14.84

11.34 11.66 12.45 12.18 11.87 16.00 14.95

11.55 11.63 12.20 12.32 11.71 15.99 14.54

×1000 kg/ha, adapted from McGee et al. (2012). Soybean yields crop year following grazing (SEM = 0.291; P = 0.35). Maize yields year following soybean production (second year after grazing; SEM = 0.685; P = 0.30). Grazed, November to February. Grazed, February to April.

1.4

spring over 13 years. The yield of soybeans in the subsequent crop years was not decreased and maize yield the following year was not influenced by grazing (McGee et al., 2012; Table 6). At least on the soil types in the experiments reported, grazing of residues in the winter had no effect on subsequent crops and even grazing in the spring had no effect.

y = -0.02x2 + 0.26x + 0.24

ADG kg/d

1.2 1 0.8 0.6 0.4

4.6. Chemical treatment

0.2 0 0

0.5

1

1.5

2

2.5

3

3.5

DDGS intake kg/d Fig. 4. Gain response of weanling calves grazing maize residue to incremental amounts of distillers dried grains with solubles (DDGs; Gustad et al., 2006).

4.4. Genetically modified corn Weed pressure and insect damage might affect maize residue and GMO have been developed and widely used in the U.S. Maize residue grazing studies have been conducted with weanling calves (Folmer et al., 2002). No differences in calf gains have been observed when GMO were compared to near iso-genetic controls. Further, when offered a choice, calves grazed equal time in the fields containing GMO residues. Any preferences observed by producers likely relate to amount of residual grain in the field, not differences in forage quality. Because of less insect damage, GMO hybrids have fewer ears left in the field (Folmer et al., 2002). Recent research was conducted with a root worm resistant GMO (Weber et al., 2011a, 2011b) using grain and silage for feeding and residue for grazing. There were no differences in cattle performance between the GMO and the near isogenic parental hybrid (Table 5). 4.5. Crop yields Of major concern with cattle grazing maize residues is the impact of grazing on subsequent crop yields. Most producers put cows or calves on maize fields soon after grain harvest in November and allow them to graze until mid to late February. Removal before late February usually ensures some frost in the ground that will help prevent soil compaction. Subsequent maize yield was not affected by grazing over a 3-year period (Jordon et al., 1997). Most producers have adopted a maize–soybean rotation. A summary of 13 years data show grazing of maize residue actually slightly increased (P = 0.35) subsequent soybean yields (McGee et al., 2012; Table 6). Because maize residue is an economical feed source for cows and calves, it would be advantageous to graze maize residue during March and April, until time to plant soybeans and until green grass is available for the cattle. Calves grazed maize residue in the

Mature, dry maize residue is highly lignified and therefore fiber digestibility is both slow and low. Chemicals can markedly increase both extent and rate of fiber digestion. Ammonia was used some for practical treatment of maize residue in the past (Klopfenstein et al., 1987) but that use has declined. Because the supply of conventional forages is decreasing and because of increased feeding of wet byproducts, there is renewed interest in chemical treatment of maize residue (Shreck et al., 2012). In this situation calcium oxide was used as the chemical. While calcium oxide is a weak base, it is much safer to use than sodium hydroxide or ammonia. The resulting alkaline mixture compliments ethanol byproducts that are acidic, high in phosphorus and high in protein. References Berger, L.L., Paterson, J.A., Klopfenstein, T.J., Britton, R.A., 1979. Effect of harvest data and chemical treatment on the feeding value of corn stalklage. J. Anim. Sci. 49, 1312–1316. Block, H.C., Macken, C.N., Klopfenstein, T.J., Erickson, G.E., Stock, R.A., 2005. Optimal wet corn gluten and protein levels in steam-flaked corn-based finishing diets for steer calves. J. Anim. Sci. 83, 2798–2805. Boddugari, K., Grant, R.J., Stock, R., Lewis, M., 2001. Maximal replacement of forage and concentrate with a new wet milling product for lactating dairy cows. J. Dairy Sci. 84, 873–884. Bradford, E., Baldwin, R.L., Blackburn, H., Cassman, K.G., Crosson, P.R., Delgado, C.L., Fadel, J.G., Fitzhugh, H.A., Gill, M., Ottjen, J.W., Rosegrant, M.W., Vavra, M., Wilson, R.O., 1999. Animal agriculture and global food supply. Council for Agricultural Science and Technology, Task Force No. 135. Bremer, V.R., Watson, A.K., Liska, A.J., Erickson, G.E., Cassman, K.G., Hanford, K.J., Klopfenstein, T.J., 2011. Effect of distillers grains moisture and inclusion level in livestock diets on greenhouse gas emissions in the corn ethanol livestock life cycle. Prof. Anim. Sci. 27, 449–455. Corrigan, M.E., Erickson, G.E., Klopfenstein, T.J., Luebbe, M.K., Vander Pol, K.J., Meyer, N.F., Buckner, C.D., Vanness, S.J., Hanford, K.J., 2009. Effect of corn processing method and corn wet distillers grains plus solubles inclusion level in finishing steers. J. Anim. Sci. 87, 3351–3362. Eastridge, M.L., 2006. Major advances in applied dairy cattle nutrition. J. Dairy Sci. 89, 1311–1323. Fernandez-Rivera, S., Klopfenstein, T.J., 1989b. Diet composition and daily gain of growing cattle grazing dryland and irrigated cornstalks at several stocking rates. J. Anim. Sci. 67, 590–596. Fernandez-Rivera, S., Klopfenstein, T.J., 1989a. Yield and quality components of corn crop residues and utilization of these residues by grazing cattle. J. Anim. Sci. 67, 597–605. Fernandez-Rivera, S., Klopfenstein, T.J., Britton, R.A., 1989. Growth response to escape protein and forage intake by growing cattle grazing cornstalks. J. Anim. Sci. 67, 574–580.

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Oba, M., Allen, M.S., 2000. Effects of brown midrib 3 mutation in corn silage on productivity of dairy cows fed two concentrations of dietary neutral detergent fiber: 1. Feeding behavior and nutrient utilization. J. Dairy Sci. 83, 1333–1341. Oliveros, B.A., Klopfenstein, T.J., Goedeken, F.K., Nelson, M.L., Hawkins, E.E., 1989. Corn fiber as an energy supplement in high-roughage diets fed to steers and lambs. J. Anim. Sci. 67, 1784–1792. Schingoethe, D., 2008. Use of distillers co-products in diets fed to dairy cattle. In: Bruce, A., Babcock, Dermot, J., Hayes, John, D., Lawrence (Eds.), Using Distillers Grains in the U.S. and International Livestock and Poultry Industries. , pp. 57–78. Schwarz, A.K., Godsey, C.M., Luebbe, M.K., Erickson, G.E., Klopfenstein, T.J., Mitchell, R.B., Pederson, J.F., 2008. Forage quality and grazing performance of beef cattle grazing brown mid-rib grain sorghum residue. Nebraska Beef Cattle Report MP91, pp. 31–33. Shreck, A.L., Nuttelman, B.L., Griffin, W.A., Erickson, G.E., Klopfenstein T.J., Cecava, M.J., 2012. Chemical treatment of low quality forages to replace corn in finishing diets. Nebraska Beef Cattle Report MP95, pp. 106–107, available at: http://beef.unl.edu Stock, R.A., Lewis, J.M., Klopfenstein, T.J., Milton, C.T., 2000. Review of new information on the use of wet and dry milling byproducts in feedlot diets. In: Proceedings of American Society of Animal Science, 1999, p. E20 (online serial). Klopfenstein, T.J., Erickson, G.E., Bremer, V.R., 2008b. Use of distillers co-products in diets fed to beef cattle. In: Bruce, A., Babcock, Dermot, J., Hayes, John, D., Lawrence (Eds.), Using Distillers Grains in the U.S. and International Livestock and Poultry Industries. , pp. 5–49. U.S. Department of Energy, 2011. U.S. Billion-Ton Update: Biomass Supply for a Bioenergy and Bioproducts Industry. R.D. Perlack and B.J. Stokes (Leads), ORNL/TM-2011/224. Oak Ridge National Laboratory, Oak Ridge, TN, 227pp. van Donk, S., McGee, A.L., Klopfenstein, T.J., Stalker, L.A., 2012. Effect of corn stalk grazing and baling on cattle performance and grazing needs. Nebraska Beef Cattle Report MP95, pp. 8–10, available at: http://beef.unl.edu Vance, R.D., Preston, R.L., Cahill, V.R., Klosterman, E.W., 1972. Net energy evaluation of cattle finishing rations containing varying proportions of corn grain and corn silage. J. Anim. Sci. 34, 851–856. Vasconcelos, J.T., Galyean, M.L., 2007. Nutritional recommendations of feedlot consulting nutritionists: The 2007 Texas Tech University survey. J. Anim. Sci. 85, 2772–2781. Warner, J.M., Martin, J.L., Hall, Z.C., Kovarik, L.M., Hanford, K.J., Rasby, R.J., Dragastin, M., 2012. Supplementing gestating beef cows grazing cornstalk residue. Nebraska Beef Cattle Report MP95, pp. 5–7, available at: http://beef.unl.edu Weber, B.M., Nuttelman, B.L., Griffin, W.A., Benton, J.R., Erickson, G.E., Klopfenstein, T.J., 2011a. Performance of growing cattle fed corn silage or grazing corn residue from second generation insect-protected (MON 89034), parental, or reference corn hybrids. Nebraska Beef Cattle Report MP94, pp. 16–17. Weber, B.M., Nuttelman, B.L., Griffin, W.A., Benton, J.R., Erickson, G.E., Klopfenstein, T.J., 2011b. Feedlot cattle performance when fed silage and grain from secondgeneration insect protected corn, parental line or reference hybrids. Nebraska Beef Cattle Report MP94, pp. 76–77.