Comparison of Cotton Gin Trash and Peanut Hulls as Low-Cost Roughage Sources for Growing Beef Cattle

The Professional Animal Scientist 24 (2008):40–46

Comparison of Cotton Gin Trash and Peanut Hulls as Low-Cost Roughage Sources for Growing Beef Cattle J. B. Kennedy1 and D. L. Rankins Jr.2 Department of Animal Science, Auburn University, AL 36849

ABSTRACT Two trials evaluated cotton gin trash and peanut hulls as roughage sources for beef cattle. In the production trial, 40 steers (initial BW = 233 ± 17.5 kg) were allotted randomly to 1 of 4 feed mixtures: 1) 45% peanut hulls + 55% cracked corn (PH+CC), 2) 45% peanut hulls + 47% cracked corn + 8% cottonseed meal (PH+CC+CSM), 3) 45% gin trash + 55% cracked corn (GT+CC), and 4) 45% gin trash + 47% cracked corn + 8% cottonseed meal (GT+CC+CSM). There were 2 pens/diet and 5 steers/pen. In addition, Bermudagrass hay was offered free choice via hay rings in each pen. In this trial, steers fed gin trash gained faster than those fed peanut hulls (1.19 vs. 0.94 kg/d; P < 0.01) and had greater DMI (10.3 vs. 7.6 kg/d; P < 0.05). Diets containing cottonseed meal produced faster ADG than those without cottonseed meal (1.14 vs. 0.99 kg/d; P < 0.02), and had greater DMI (9.7 vs. 8.3 kg/d; P < 0.05). In the second trial, 16 steers (initial BW = 301 ± 24.1 kg) were

1

Current address for J. B. Kennedy: University of Georgia Cooperative Extension, 555 Monroe St., Unit 50 Box 13, Clarksville, GA 30523. 2 Corresponding author: rankidl@auburn. edu

assigned randomly to 1 of the 4 diets used in trial 1 (4 steers/diet) and nutrient digestibilities were determined. Dry matter intake did not differ among diets and averaged 6.0 kg/d or 2.0% of BW. Dry matter and OM digestibilities tended to be greater (P < 0.07) for GT+CC compared with the other 3 diets. Crude protein digestibility was least (P < 0.05) for PH+CC (60%) and greatest for PH+CC+CSM (70%), with GT+CC and GT+CC+CSM being intermediate (66 and 63%). Key words: gin trash, peanut hulls, beef cattle

INTRODUCTION Peanut hulls have been used as a low-quality roughage source in beef cattle diets for many years (Utley and McCormick, 1972; Utley et al., 1973). When combined with a protein and energy source, peanut hulls can provide a low-cost feed for stocker cattle. Cotton gin trash, a by-product of the cotton ginning industry, is composed of stems, leaves, burrs, immature seeds, and sand from the cotton plant. Like peanut hulls, gin trash can be used as a low-quality roughage source (Lalor et al., 1975). An advantage to using gin trash over peanut hulls is that cotton is grown in a

larger region of the United States, making the gin trash available to more cattle producers. The nutritive quality of gin trash varies depending on the variety of cotton, the region grown, and the type of harvest method used (Bader et al., 1998). The ash content is the most variable component of gin trash and may be very high in areas with sandy soils or in stripper-harvested areas (Lalor et al., 1975; Baker et al., 1994). Protein concentration is also variable depending upon growing conditions of the cotton plant and the amount of immature seed remaining in the gin trash (Lalor et al., 1975). Several defoliants that are applied to cotton have not been approved for the food chain. Stewart et al. (1998) reported that residues in gin trash did not appear to be present at concentrations that pose a problem to the animal. Nevertheless, it may not be legal to feed gin trash in some instances. Gin trash is palatable to ruminants and can produce acceptable diets if supplemented with a protein or energy source (Erwin and Roubicek, 1958; Sagebiel and Cisse, 1984; Hill et al., 2000a). Some studies have been conducted on feeding gin trash to beef cows; however, minimal data is available with regard to the digestibil-

ity and the feeding value of gin trash when fed to stocker calves. Therefore, the objective of this research was to compare the performance of calves fed diets containing gin trash or peanut hulls and to determine the digestibility of the diets. In addition, the effects of added cottonseed meal were evaluated.

MATERIALS AND METHODS A production trial was conducted at the Wiregrass Research and Extension Center in Headland, AL, and a digestibility study was conducted at the E. V. Smith Beef Research Unit in Tallassee, AL. All experimental procedures were reviewed and approved by the Auburn University Institutional Animal Care and Use Committee. The gin trash was obtained from the Henry County Gin in Headland, AL, that processes spindle-picked cotton. The gin trash was collected on the day that it was ginned and then was transported to the research center and stored in a shed. Peanut hulls were obtained from the State Peanut Laboratory in Headland, AL. Hulls were put into a wagon at shelling and then stored in a shed until they were fed. They were fed as an intact peanut hull with no further processing. The corn was grown in Henry County, AL. The same gin trash, peanut hulls, and corn were used for both trials. Bermudagrass hay was used in only the production trial, and it was grown at the Wiregrass Research and Extension Center.

Production Trial Forty Angus × Continental steers were allotted randomly to 1 of 4 diets for a 112-d study. Initial BW for the steers assigned to each treatment described below were 230, 233, 240, and 230 kg, respectively, for treatments 1 through 4. There were 2 pens/diet and 5 steers/pen. Pens were 0.2-ha dry-lots con-

Gin trash and peanut hulls for beef cattle

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taining a covered feed bunk 3.1 m in length. On a DM basis, the feed mixtures consisted of 1) 45% peanut hulls + 55% cracked corn, 2) 45% peanut hulls + 47% cracked corn + 8% cottonseed meal, 3) 45% gin trash + 55% cracked corn, and 4) 45% gin trash + 47% cracked corn + 8% cottonseed meal. Steers had ad libitum access to these feed mixtures and Bermudagrass hay. The hay was offered as round bales in hay rings. Feed mixtures were mixed using a power take off-driven Artsway feed mixer (Armstrong, IA). Feed bunks were always replenished in such a manner that bunks were never empty; feed was usually added 3 times/wk. All feed mixes contained lasalocid at a concentration of 18 to 20 mg/kg to provide 150 to 200 mg/d per animal. All feed mixes contained 0.5% dicalcium phosphate and 0.5% trace mineral salt to meet NRC (1996) requirements for Ca and P. Steers were weighed initially and every 28 d throughout the 112-d trial. Unshrunk BW were taken between 0700 and 0900 h. Feed and hay intakes were monitored by recording amount fed and then at completion of the trial, feed bunks were cleaned out and weight of orts was subtracted from the amount of feed offered to determine total feed intake over the 112-d trial.

cape through a slatted floor in the stall and was not collected. While in the metabolism stalls, each steer was initially offered 2% of BW as a daily allotment of feed. If the bunk was cleaned out, the steer was offered slightly more the next day, or if orts were present the steer was offered slightly less the next day. Each day, total fecal output, daily feed intake, and feed refusals were weighed and a 10% sample was taken. Each sample was dried at 55°C until dry and stored for further analysis. Apparent digestibilities were calculated as nutrient consumed minus nutrient excreted and then divided by nutrient consumed. Multiplication by 100 expressed it as a percent.

Digestibility Study Sixteen Angus × Charolais (BW = 301 ± 24.1 kg) steers were assigned randomly to 1 of the 4 previous feed mixtures, with 4 steers/group, and housed in metabolism stalls for an 8-d digestibility study. No hay was fed during the digestibility study. Steers were fed their respective diets for 14 d prior to entering the metabolism stalls. Steers were placed in the metabolism stalls for 10 d with a 2-d acclimation period prior to the start of collections. The stalls provided access to water and feed bunks and allowed for the total collection of feces on a collection mat. Urine was allowed to es-

Laboratory Analyses Table 1 shows the nutrient composition of the gin trash and peanut hulls used to formulate the experimental diets, as well as the Bermudagrass hay fed in the production trial. All samples from feeds, feed refusals, and fecal output were ground to pass a 1-mm screen using a Wiley mill. Dry matter and ash analyses were performed on each sample according to the AOAC (1995). The amount of CP in each sample was determined using the Kjeldahl method (AOAC, 1995). Concentrations of NDF and ADF for all samples were determined sequentially using the method outlined by Van Soest et al. (1991). This procedure was carried out using an ANKOM200/220 Fiber Analyzer and F57 Filter Bags (ANKOM Technology, Macedon, NY).

Statistical Analysis Data were analyzed as a completely randomized design with a 2 × 2 factorial arrangement of treatments using GLM procedures of SAS (SAS Institute Inc., Cary, NC). Pen was the experimental unit in the production trial, and animal was the experimental unit for the digestibility study. When a significant in-

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Table 1. Chemical composition (DM basis) of gin trash, peanut hulls, and Bermudagrass hay used to formulate experimental diets Item DM, % OM, % NDF, % ADF, % CP, %

Gin trash

Peanut hulls

Bermudagrass hay

93.1 73.4 69.2 60.8 12.4

92.0 96.5 88.7 79.1 5.4

91.7 94.4 72.2 36.0 12.1

teraction dictated that interactive means be presented, mean separation was accomplished by protected least significant difference.

RESULTS AND DISCUSSION Nutrient Composition The nutrient composition of the gin trash used to formulate the feed mixtures for this study (Table 1) was similar to published tabular values (Preston, 2006). The largest discrepancy was that the gin trash used in these experiments contained greater concentrations of ash (26.6 vs. 14%). According to Lalor et al. (1975), the ash concentration is the most variable component of gin trash and can range from 8 to 28%. Ash concentration is influenced by the amount of sand in the gin trash; therefore, cotton grown in sandy areas or that has been stripper-harvested will produce gin trash that has a higher ash concentration (Lalor et al., 1975; Baker et al., 1994). The gin trash used in these studies was produced from spindlepicked cotton raised in the Wiregrass region of south Alabama, which has sandy soils. The high ash concentration (i.e., 26.6%) of the gin trash used in these experiments may be attributed to the sandy soils in the region. Crude protein is the second most variable component of gin trash (Lalor et al., 1975). The CP concentration of the gin trash used in these trials was 12.4%. This value is greater than the 5.6% CP reported

by Brown et al. (1979) and the 8.7% CP reported by Whiting and Schuh (1988). Similar values (13.6 and 15.1%) were reported by Hill et al. (2000a,b). Variations in CP concentrations are attributed to the amount of immature seed remaining in the gin trash and the weather conditions that existed during growth and harvest of the cotton plant (Lalor et al., 1975). The moderately high CP content of the gin trash used in this study was probably reflective of the amount of immature seed present in the gin trash. The gin trash used in the current study had an ADF content of 60.8%, which is greater than the 46% reported by Waller (2006). However, ADF in our study was similar to values reported by Brown et al. (1979) and Hill et al. (2000b) of 55.1 and 63.5%, respectively. It should also be noted that the gin trash used for these trials was collected as it was ginned and then was stored in a shed until it was used for the feeding studies. Much gin trash is left outside at the gin until it is fed to cattle, which will likely decrease the nutritive value of the material if this time period is lengthy. Also, some gins will add water to the gin trash while it is being removed from the gin to cut down on dust problems. Obviously, there will be much variation with regard to the nutritive quality of gin trash across the cotton ginning region of the United States. The nutrient composition of the peanut hulls (Table 1) was similar

to published tabular values (Preston, 2006) and values published by Utley and McCormick (1972). Peanut hulls used in the current study were analyzed to contain a CP concentration of only 5.4%. However, the CP concentration of the diets formulated with the peanut hulls suggests that the peanut hull CP should be approximately 8%. Random samples of the peanut hulls were taken from the lot used to formulate the diets. These random samples then were pooled to form a composite sample that was analyzed for CP concentration. Values of 5 to 5.5% were obtained with each analysis. Thus, the discrepancy is attributed to an unrepresentative sample as opposed to an error with analysis.

Production Trial The feed mixtures fed to steers in the production trial are shown in Table 2. One steer was removed from the group consuming peanut hulls, corn, and cottonseed meal due to failure to respond to treatment for pneumonia. Data for this group was adjusted accordingly. A roughage source × protein supplement interaction was detected for feed intake (P < 0.05; Table 3). Neither total DMI nor daily hay intake was different; however, daily intake of the individual mixtures was greater (P < 0.05) for those containing gin trash than for mixtures comprised of peanut hulls (Table 3). Intake of the mixture containing peanut hulls may have been less because the peanut hulls are bulky and have a low digestibility; therefore, they take up more space in the rumen and have a slower rate of passage. This is supported by Blaxter et al. (1961) and Conrad et al. (1964) who found that DMI increases as digestibility and, therefore, rate of passage, increases. Also, Campling and Balch (1961) reported that the amount of DM in the rumen affects voluntary intake. This fill effect causes the animal to consume less DM, leading to a de-

Gin trash and peanut hulls for beef cattle

Table 2. Chemical composition (DM basis) of feed mixtures used in the production trial Feed mixtures1 Item DM, % OM, % NDF, % ADF, % CP, %

PH+CC

PH+CC+CSM

GT+CC

GT+CC+CSM

91.4 93.2 42.9 33.3 9.6

91.3 95.3 44.4 34.8 12.3

90.9 89.6 42.1 31.7 11.5

91.1 89.7 49.0 38.4 13.6

1

PH+CC = 45% peanut hulls + 55% cracked corn; PH+CC+CSM = 45% peanut hulls + 47% cracked corn + 8% cottonseed meal; GT+CC = 45% gin trash + 55% cracked corn; GT+CC+CSM = 45% gin trash + 47% cracked corn + 8% cottonseed meal.

creased feed intake. Therefore, the more digestible a feedstuff, the faster it disappears from the rumen, and the more feed can be consumed. Feed intake of mixtures containing gin trash was not improved by the addition of cottonseed meal (P > 0.05; Table 3), whereas cottonseed meal significantly improved intake (P < 0.05; Table 3) of the mixture containing peanut hulls. Based on nutrient composition data (Table 2) and intake data (Table 3) from the production trial, calculated CP intake was 1.43 kg/d for steers consuming the gin trash mixture and 0.97 kg/d for steers consuming the peanut hull mixture.

Based on NRC (2000) requirements, additional CP to steers already receiving 1.43 kg/d would not be expected to elicit a response. Previous studies have shown an increase in digestibility of low-quality forages when a protein supplement is provided (Kartchner, 1980; Guthrie and Wagner, 1988; DelCurto et al., 1990b). This increased digestibility led to a faster rate of passage, which led to an increase in DMI (Blaxter et al., 1961; Campling and Balch, 1961; Kartchner, 1980; Guthrie and Wagner, 1988). Daily hay intake and total DMI were not different among diets (P > 0.05; Table 3). All steers in this trial consumed in excess of 3%/d of their BW. Typi-

Table 3. Effects of roughage source and protein supplementation on DMI of steers in the production trial1 Gin trash Item Feed mix, kg/d Hay, kg/d Total, kg/d

3

Peanut hulls

No CSM

CSM

No CSM

CSM

SE2

10.0a 2.3 12.3

10.7a 1.8 12.5

6.6c 2.8 9.4

8.7b 2.0 10.7

0.26 0.65 0.67

Means within a row with different superscripts differ (P < 0.05). ANOVA showed a roughage source × protein supplement interaction (P < 0.05) for feed intake. 2 SEM (n = 2). 3 CSM = cottonseed meal. a–c 1

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cally, growing steers are not predicted to consume more than 3% of their BW each day (NRC, 2000). The high DMI observed in this trial is consistent with previous studies conducted using by-product feeds in growing steers in which DMI exceeded 3% of BW (Rankins and Gamble, 2000). Also, some of the DMI may be attributed to feed that was not consumed, but was lost on the ground (i.e., rooted out of the bunk by the cattle). It is the authors’ estimate that the amount of wasted feed is approximately 6 to 8% of the total feed allotted based on several years of doing research with these facilities. For ADG, there was no roughage source × protein supplementation interaction (P > 0.25; Table 4). Steers fed gin trash gained 21% faster (P < 0.01; Table 4) than those fed peanut hulls. Also, mixtures containing cottonseed meal produced greater ADG (P < 0.02; Table 4) than those without cottonseed meal. This increase in gain may be attributed to the greater DMI of the mixtures containing gin trash than those containing peanut hulls (Table 3). The ADG of calves consuming gin trash mixtures was 1.19 kg/ d (Table 4). There is no data available with regard to calf gains for gin trash-based diets. With regard to cow data, Rogers et al. (2002) reported that cows fed gin trash and cottonseed gained 1.1 kg/d. Similarly, Erwin and Roubicek (1958) reported cow ADG of 0.9 to 1.05 kg/d for diets composed of milo and gin trash and diets containing silage added to the milo and gin trash, respectively. However, Sagebiel and Cisse (1984) reported that diets containing sorghum silage and gin trash or molasses and gin trash resulted in weight loss. Hill et al. (2000a) also reported weight loss on diets consisting of gin trash alone and gains of only 0.018 kg/d for diets containing gin trash and corn. Steers consuming mixtures containing peanut hulls had an ADG of 0.94 kg/d (Table 4). This is less than

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Kennedy and Rankins

Table 4. Effects of roughage source and protein supplementation on ADG of steers in the production trial1 Roughage source Variable

Protein supplement

Gin trash

Peanut hulls

No CSM3

CSM

1.19a

0.94b

0.99c

1.14d

ADG, kg/d

SE2 0.043

Main effect means with different superscripts differ (P < 0.01). Main effect means with different superscripts differ (P < 0.02). 1 ANOVA showed no roughage source × protein supplement interaction (P > 0.25); therefore, main effect means are shown. 2 SEM (n = 4). 3 CSM = cottonseed meal. a,b c,d

Table 5. Chemical composition (DM basis) of diets used in the digestibility study

Digestibility Study

Diet1 Item

PH+CC

PH+CC+CSM

GT+CC

GT+CC+CSM

96.2 96.9 45.2 34.9 8.1

96.3 96.5 51.6 40.9 10.1

95.9 82.8 42.5 34.7 11.9

96.4 83.1 48.2 39.1 14.7

DM, % OM, % NDF, % ADF, % CP, % 1

PH+CC = 45% peanut hulls + 55% cracked corn, PH+CC+CSM = 45% peanut hulls + 47% cracked corn + 8% cottonseed meal; GT+CC = 45% gin trash + 55% cracked corn; GT+CC+CSM = 45% gin trash + 47% cracked corn + 8% cottonseed meal.

Table 6. Effects of roughage source and protein supplementation on DMI of steers in the digestibility study1 Roughage source Item BW, kg Daily DMI, kg/d DMI, % BW

Protein supplement

Gin trash

Peanut hulls

No CSM3

CSM

SE2

299 5.89 1.97

303 6.17 2.03

301 5.54 1.83

301 6.51 2.17

8.53 0.404 0.116

ANOVA showed no roughage source × protein supplement interaction (P > 0.15); therefore, main effect means are shown. 2 SEM (n = 4). 3 CSM = cottonseed meal. 1

gains of 1.13 kg/d reported by Rankins and Gamble (2000) with a similar diet consisting of 55% corn and

10% CP supplement, and 20% peanut hulls. Utley and McCormick (1972) reported ADG of 1.44, 1.49, and 1.48 kg/d, respectively, for diets containing 10, 20, and 30% peanut hulls in addition to corn and hay. Mixtures containing cottonseed meal produced ADG that were 13% faster (P < 0.02; Table 4) than ADG from mixtures without cottonseed meal. This is supported by previous research that reported improved gains when a protein supplement was included in diets deficient in protein (Foster et al., 1945; Speth et al., 1962; Clanton and Zimmerman, 1970; DelCurto et al., 1990a). In this trial, the cottonseed meal increased rate of gain by stimulating DMI for peanut hull-based diets.

45% peanut hulls. Utley et al. (1973) reported gains of 1.17 kg/d on a diet consisting of 70% corn,

Table 5 shows the composition of diets fed to steers in the digestibility study. No hay was fed during this study. There was no roughage source × protein supplement interaction for daily DMI or DMI as a percent of BW (P > 0.15; Table 6). There were no significant differences among the diets for these variables. Steers in the digestibility study consumed less DM per day than steers in the production trial (Table 3 and Table 6). These differences may be attributed to the different feeding methods used in the 2 trials. In the production trial the diets were offered with ad libitum access, whereas in the digestibility study diets were limited to the approximate amount each individual animal would consume to reduce the amount of orts produced. Analysis of fiber (NDF and ADF) digestibility data showed no roughage source × protein supplement interaction (P > 0.65; Table 7). The NDF and ADF digestibility of diets containing gin trash were 55.7 and 52%, respectively. These numbers are greater than those reported by Hill et al. (2000b) of 13.7 and 11.8%, respectively, when a similar diet of 43% gin trash and 57% corn was used. Hill et al. (2000b) attrib-

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Gin trash and peanut hulls for beef cattle

Table 7. Effects of roughage source and protein supplementation on apparent digestibility of fiber components1 Roughage source Item NDF, % ADF, %

Protein supplement

Gin trash

Peanut hulls

No CSM3

CSM

SE2

55.7 52.0

50.0 46.0

49.9 44.5

55.9 53.5

4.58 5.73

ANOVA showed no roughage source × protein supplement interaction (P > 0.65); therefore, main effect means are shown. 2 SEM (n = 4). 3 CSM = cottonseed meal. 1

previous research (Rankins and Gamble, 2000) indicates that protein supplementation was beneficial for stocker calves consuming peanut hull-based feeds, especially when corn is the energy source. Gin trash provides a low-cost roughage source to a large segment of the beef cattle industry that is located in the Cotton Belt of the United States.

LITERATURE CITED AOAC. 1995. Official Methods of Analysis. Association of Official Analytical Chemists, Washington, DC.

Table 8. Effects of roughage source and protein supplementation on apparent digestibility of nutritive components1 Gin trash Item DM, % OM, % CP, %

Peanut hulls

No CSM

CSM

No CSM

CSM

80.0a 80.3c 65.7cd

69.2b 71.5d 62.9cd

72.8b 72.3d 60.3c

72.6b 72.7d 70.2d

SE2 1.82 1.61 2.16

Means within a row with different superscripts differ (P < 0.07). Means within a row with different superscripts differ (P < 0.05). 1 ANOVA showed a roughage source × protein supplement interaction (P < 0.07). 2 SEM (n = 2). a,b c,d

uted their low fiber digestibilities to a reduction in fiber digestibility caused by the large amount of corn in the diet. This is supported by Chase and Hibberd (1987) who stated that fiber digestibility decreases when corn is fed at more than 1 kg/d. Dry matter digestibility tended to be greater (P < 0.07) and OM digestibility was greater (P < 0.05) in diets of gin trash without cottonseed meal than in the other 3 diets (Table 8). The CP digestibility of peanut hulls with cottonseed meal was greater (P < 0.05; Table 8) than the CP digestibility of peanut hulls without cottonseed meal, but neither was significantly different from the CP digestibility of diets containing gin trash (P > 0.05; Table 8).

IMPLICATIONS In summary, the production trial showed that stocker calves were capable of gaining approximately 1 kg/d on both by-product based feeds — cotton gin trash or peanut hulls. Gin trash produced significantly faster gains, and based on intakes and the digestibility data it would appear that the greater BW gain was reflective of greater intake of the gin trash-based feed vs. the peanut hull-based feed. In addition, based on this research and numerous producer interactions, most of the gin trash in this area will contain in excess of 11% CP, resulting in no benefit from protein supplementation with gin trash-based feeds. Conversely, this research and

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Utley, P. R., R. S. Lowrey, and W. C. McCormick. 1973. Types of roughage and intermittent changes of roughage types in beef cattle finishing diets. J. Anim. Sci. 37:395. Utley, P. R., and W. C. McCormick. 1972. Level of peanut hulls as a roughage source in beef cattle finishing diets. J. Anim. Sci. 34:146. Van Soest, P. J., J. B. Robertson, and B. A. Lewis. 1991. Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74:3583. Waller, J. C. 2006. By-products and unusual feedstuffs. Feedstuffs Reference Issue and Buyer’s Guide 77:18. Whiting, F. M., and J. D. Schuh. 1988. Use of cotton gin trash in the diets of growing dairy heifers. p 399 in Proc. West. Sec. Am. Soc. Anim. Sci.