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Effects of wet corn gluten feed and yellow grease on digestive function of cattle fed steam-flaked corn-based finishing diets
Animal Feed Science and Technology 178 (2012) 20–26
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Effects of wet corn gluten feed and yellow grease on digestive function of cattle fed steam-flaked corn-based finishing diets夽 L.K. Conway, D.M. Hallford, S.A. Soto-Navarro ∗ Department of Animal and Range Sciences, New Mexico State University, Las Cruces, NM 88003, United States
a r t i c l e
i n f o
Article history: Received 24 February 2012 Received in revised form 28 August 2012 Accepted 3 September 2012
Keywords: Beef cattle Digestion Corn gluten feed Fat Feedlot
a b s t r a c t Twelve ruminally cannulated, English-crossbred steers (436 ± 16 kg) were used in a completely random experiment to evaluate the influence of dietary wet corn gluten feed (WCGF) and yellow grease (fat) in steam-flaked corn-based finishing diets on diet intake, digestibility, and rumen fermentation characteristics. Treatments consisted of steamflaked corn-based diets containing the following WCGF/fat combinations: (1) 0 g/kg WCGF/30 g/kg added fat (STD3), (2) 250 g/kg WCGF/0 g/kg added fat (WCGF0), and (3) 250 g/kg WCGF/30 g/kg added fat (WCGF3). Steers fed WCGF3 consumed more (P=0.01) dry matter (DM) than did those fed STD3 or WCGF0 (23.5 > 18.4 = 18.8 ± 0.9 g/kg of body weight (BW) daily, respectively). Organic matter intake was also greater (P≤0.02) for WCGF3-fed steers than steers fed STD3 and WCGF0 (22.1 > 17.7 = 17.8 ± 0.8 g/kg BW, respectively). Total tract digestibilities of DM, organic matter (OM), neutral detergent fiber (aNDF), acid detergent fiber (ADF), and crude protein (CP) were not different (P≥0.15) in the 3 groups. Digestion of aNDF was greater in cattle fed WCGF3 and WCGF0 than in those fed STD3 (1.6 = 1.3 > 0.8 ± 0.1 g/kg BW, respectively). Ruminal fluid dilution rate (0.075 > 0.057 = 0.052 ± 0.4/h for WCGF3, WCGF0, and STD3, respectively) and particulate passage rate (0.059 > 0.042 = 0.036 ± 0.4/h, for WCGF3, WCGF0, and STD3, respectively) increased (P<0.03) in steers fed WCGF3 compared with those fed WCGF0 and STD3. Ruminal pH was greater (P<0.05) in steers fed WCGF0 than in those fed WCGF3 and STD3 (5.9 > 5.4 = 5.3 ± 0.1, respectively). Total ruminal volatile fatty acids (VFA) in WCGF0-fed steers tended to be less (P<0.09) than in steers fed WCGF3 or STD3 (97.8 < 119.4 = 122.6 ± 6.8 mM, respectively). Ruminal propionate concentration (mol/100 mol) tended to be greater (P≤0.06) in steers fed WCGF3 (43.4 ± 2.1) than in those consuming WCGF0 (35.0 ± 2.1) or STD3 (34.0 ± 2.1). The acetate:propionate ration tended to be greater (P<0.09) in steers fed STD3 and WCGF0 than in those fed WCGF3 (1.3 = 1.3 > 0.9 ± 0.1, respectively). Supplementing 30 g/kg fat to a finishing diet containing 250 g/kg WCGF increased DM intake due to faster liquid and particle passage rates, and to increased total tract nutrient digested. © 2012 Elsevier B.V. All rights reserved.
Abbreviations: ADF, acid detergent acid; Co-EDTA, cobalt-ethylendiaminetetraacetic; CP, crude protein; DM, dry matter; EE, ether extract; fat, yellow grease; aNDF, neutral detergent fiber; OM, organic matter. 夽 This research was supported by the New Mexico Agricultural Experiment Station. Wet corn gluten feed and yellow grease. ∗ Corresponding author. Department of Animal and Range Sciences, MSC 3-I P.O. Box 30003, Las Cruces, NM 88003-8003, USA. Tel.: +1 575 646 2016; fax: +1 575 646 5441. E-mail address: [email protected] (S.A. Soto-Navarro). 0377-8401/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.anifeedsci.2012.09.003
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1. Introduction Corn wet milling has contributed a large supply of byproducts that are valuable animal feeds. One of the main products that has gained wide acceptance is wet corn gluten feed (WCGF). Over the last several years many feedyards in the Texas Panhandle, New Mexico, Oklahoma, and Kansas have been using WCGF as an energy and protein source, replacing a portion of the steam-flaked corn and supplemental protein in growing and finishing diets. Wet corn gluten feed is unique because it contains elevated levels of (CP) and rapidly fermentable neutral detergent fiber, and low levels of starch, yet has been found to have 0.9–1.0 times the net energy for gain value of steam-flaked corn (Ham et al., 1995). Energy in WCGF was estimated (Firkins et al., 1985) to be 0.9 times that in corn because of its greater content of aNDF (437 g/kg of dry matter; DM) that is digested in the rumen at a much lower rate than starch in corn. Because of the increased energy density of fats (Zinn, 1988), we hypothesized that supplementing fat may increase the feeding value of feedlot finishing diets based on steam-flaked corn and WCGF. However, it is unclear if high fat levels could negatively affect the value of these diets through adverse effects on fiber digestion. The objective of this study was to determine effects of fat supplementation on DMI, digestibility, and rumen fermentation characteristics of feedlot cattle consuming steam-flaked corn finishing diets containing 250 g/kg WCGF. 2. Materials and methods 2.1. Animals and experimental diets All surgical procedures, post surgical care, and experimental protocols were approved by the New Mexico State University Institutional Animal Care and Use Committee. Twelve ruminally cannulated English-crossbred steers (436 ± 16 kg) were used in a completely randomized experiment to evaluate effects of added dietary fat on ruminal nutrient disappearance and total tract digestibility by steers fed a finishing diet containing WCGF (Sweet Bran® , Cargill Inc., Blair NE, USA). The supplemental fat used was yellow grease (fat), a commercial feed fat composed of waste grease collected from bakeries, restaurants, school cafeterias, and the like. Yellow grease samples (Valley Rendering Co. Inc., Canutillo, TX, USA) were analyzed for moisture and volatiles, insoluble impurities, unsaponifiable matter, and free fatty acids (SDK Laboratories, Hutchinson, KS, USA). Yellow grease analyzed composition (as fed) was: moisture and volatiles, 3.2 g/kg; insoluble impurities, 8.8 g/kg; unsaponifiablematter, 4.3 g/kg; and free fatty acids, 279.0 g/kg. All WCGF used in the present experiment was from the same batch. Treatments consisted of steam-flaked based diets containing WCGF/yellow grease (fat) combinations: (1) no WCGF and 30 g/kg added fat (standard finishing diet; STD3); (2) 250 g/kg (DM basis) WCGF with no added fat (WCGF0); (3) 250 g/kg (DM basis) WCGF with 30 g/kg added fat (WCGF3). Diets contained (DM basis) 90 g/kg alfalfa hay, 25 g/kg supplement, 0 or 30 g/kg added fat (yellow grease), and 0 or 250 g/kg WCGF with the remainder consisting of steam-flaked corn (Table 1). Steers were individually penned (1.5 m × 4 m) in a barn and had free access to fresh water. The experiment consisted of an 18-d adaptation period and a 6-d collection period. Before the adaptation period, cattle were incrementally stepped-up from a 600 g/kg concentrate diet to the experimental
Table 1 Composition and analyzed nutrient content (g/kg, DM basis) of experimental diets. Item
Ingredient Steam-flaked corn WCGF Alfalfa hay Steep/molasses blendb Yellow grease Cottonseed meal Urea Supplementc Analyzed composition, g/kg DM basis DM CP ADF Ash Ca P
Treatmentsa STD3
WCGF0
WCGF3
778.0 – 90.0 40.0 30.0 28.0 9.0 25.0
633.0 250.0 90.0 – – – 2.0 25.0
595.5 250.0 90.0 – 30.0 7.5 2.0 25.0
782.0 145.3 59.9 53.8 8.9 3.4
731.2 139.9 76.0 54.0 7.7 4.8
735.2 140.4 81.7 57.3 8.3 4.4
a STD3 = standard finishing diet with 30 g/kg of added fat; WCGF0 = 250 g/kg (DM basis) of wet corn gluten feed (WCGF) with no added fat; WCGF3 = 250 g/kg (DM basis) of wet corn gluten feed with 30 g/kg added fat. b Steep/molasses blend = 700 g/kg corn steep and 300 g/kg molasses as-fed. c Supplement supplied the following per kg of the diet (DM basis): Ca = 6.0 g, K = 1.0 g, Mg = 0.8 g, NaCl = 3.0 g, (NH4 )2 SO4 = 1.0 g, Co = 0.20 mg, Fe = 66.47 mg, I = 0.50 mg, Mn = 40.09 mg, Se = 0.05 mg, Zn = 75 mg, Cu = 10.00 mg, Vitamin A = 2200 IU, Vitamin E = 17.5 IU, Monensin = 0.03 g, Tylosin = 0.01 g, and CP = 3.0 g.
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diet containing 900 g/kg concentrate. The adaptation period began (d 0) with feeding of the treatment diet and continued through d 17. Steers were adapted to the barn, stalls, and fecal bags during the final 3 d of the adaptation period (d 15–17). 2.1.1. Collections Steers were fed ad libitum once daily at 06:00. To prevent spoilage, diets were mixed for 2 d of feedings. Samples from each mixing were collected and composited. Total feces were collected (via fecal bags) once daily (07:00) on d 1 through 5 of the collection period. Daily feces and feed refusals (orts) were weighed and recorded and a 100 g/kg subsample was composited. Feed, fecal, and ort samples were stored (−20 ◦ C) until later analysis. Cobalt-ethylendiaminetetraacetic acid (Co-EDTA) and Yb-labeled steam-flaked corn were utilized as markers of fluid and particulate passage rates, respectively. Both mineral markers were prepared as described by Varga and Prigge (1982). Briefly, Yb labeling consisted of soaking 22 kg of steam-flaked corn in 1.2 kg YbCl3 (Alfa Aesar, Ward Hill, MA, USA) and 440 L distilled water for 24 h and stirring 4 times. This mixture was then filtered true 8 layers of cheesecloth and washed 6 times over a 6-h period and then dried at 60 ◦ C in a forced-air oven. Cobalt-EDTA was prepared by combining 75 g cobalt (II)·4 H2 O, 87.6 g disodium EDTA, and 12.9 g of lithium hydroxide with 600 mL distilled water, 60 mL of a 300 mL/L hydrogen peroxide solution, and 900 mL of a 950 mL/L ethanol solution. This mixture was allowed to stand at room temperature for 24 h and was then filtered through filter paper (Whatman number 1; GE Healthcare Life Science, Piscataway, NJ, USA) with 3 L of an 800 mL/L ethanol solution. The crystal that was filtered was subsequently dried (forced-air oven at 100 ◦ C), then resuspended in 3 L of distilled water. On d 3 of the collection period, steers were intraruminally dosed with 200 mL Co-EDTA and 1 kg Yb-labeled steam-flaked corn at 06:00, before feeding. Ruminal fluid and particulate samples were collected before dosing (h 0) and at 2, 4, 6, 8, 10, 12, 14, 18, 26, 34, and 50 h after dosing. Ruminal fluid was collected via the ruminal cannula using a suction strainer, which was rinsed with warm water between each sampling. At the time of sampling, pH of filtered ruminal fluid was measured, and a 200-mL sample was retained after adding 3 mL of concentrated sulfuric acid. Ruminal fluid was stored in whirl pack bags at −20 ◦ C for later analysis of Co and VFA. Ruminal particulate samples were sealed in individual plastic bags and frozen (−20 ◦ C) for subsequent analysis of Yb concentration. 2.1.2. Analyses Refrigerated feed, fecal, and ort samples were dried at 60 ◦ C in a forced-air oven for 48 h, then allowed to equilibrate at room temperature and ground in a Wiley mill (2-mm screen, Wiley mill model 4, Thomas Scientific, Swedesboro, NJ, USA). Feed, fecal, and orts samples were analyzed for DM, organic matter (OM), ether extract (EE), and CP (methods 930.15, 942.05, 945.16, and 990.02, respectively; AOAC, 1997). Neutral detergent fiber (aNDF) was determined (Van Soest et al., 1991) with ␣-amylase and sodium sulfite using an Ankom 200 fiber analyzer (Ankom Co., Fairport, NY, USA), and was expressed with ash included. Starch was analyzed according to Herrera-Saldana and Huber (1989). After thawing ruminal fluid samples were centrifuged at 4000 × g for 15 min and the supernatant was retained for subsequent analysis of VFA (Goetsch and Galyean, 1983) and Co. Cobalt was determined with an air-plus-acetylene flame using atomic absorption spectroscopy (model 3110, PerkinElmer, Waltham, MA, USA) as described by Uden et al. (1980). Ruminal particulate samples were dried in a forced-air oven at 60 ◦ C for 24 h, allowed to equilibrate at room temperature, then ground to pass a 2-mm screen in a Wiley mill. Ytterbium was extracted from these samples as outlined by Hart and Polan (1984) and marker concentration was determined by atomic absorption spectroscopy using a nitrous oxide-plus-acetylene flame. Briefly, Yb extraction was accomplished by combining 20 mL of a solution that was 0.05 M EDTA and 0.2 M KCl with 0.2 g ground ruminal particulate, shaking the solution for 30 min, and then filtering (#1 Whatman filter paper; Whatman Ltd., Maidstone, UK) twice. Ytterbium concentration was read at wavelength of 404.6 nm. 2.1.3. Calculations Fluid and particle passage rates were calculated as the absolute slope of the regression equation of time after dosing and the natural log of Co and Yb concentration, respectively. Rumen volume was calculated as mg of Co dosed divided by ruminal concentration extrapolated to 0 h. Outflow from the rumen or fluid flow rate (h) was calculated as rumen volume (L) multiplied by the dilution rate. Turnover time was calculated as 1 divided by the absolute value of the fractional dilution rate. Intake values (kg/d) were calculated as nutrient offered less the amount of nutrient in orts (DM basis). Intake values (g/kg BW) were calculated as nutrient intake (g) divided by BW. Fecal DM output values were calculated as the average fecal output multiplied by its DM concentration. Fecal nutrient output was calculated by multiplying DM fecal output by the nutrient concentration. Total tract digestibility values were calculated by dividing fecal nutrient output (g) by nutrient intake (kg). 2.1.4. Statistical analysis Feed intake, fecal output, digestibility, BW, and ruminal fluid and particulate characteristics data were subjected to ANOVA appropriate for a completely random design. Treatment was included in the model and steer was the experimental unit. Analyses were computed using the GLM procedure of SAS (SAS Inst. Inc., Cary, NC, USA). Ruminal pH and VFA were subjected to ANOVA for repeated measures using the mixed procedure of SAS. The model included treatment as a fixed effect, time as a repeated measure, and steer (treatment) as the error term. The covariance structure that most appropriately fit the data was compound symmetry. No treatment by sampling interactions were detected
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Table 2 Characteristics of digestion in steers fed wet corn gluten feed and (or) supplemental fat. Itemi
Animals, no. BW (kg) Intake DM (kg) DM (g/kg BW) OM (kg/d) OM (g/kg BW) aNDF(kg/d) CP (kg/d) Starch (kg/d) EE (kg/d) Fecal output OM (kg/d) aNDF(kg/d) ADF (kg/d) CP (kg/d) Starch (kg/d) EE (kg/d) Total tract nutrient digestibility DM OM aNDF CP Starch EE Total tract nutrient digestion (g/kg BW) DM OM aNDF CP Starch EE
Treatmenta,b
SE
STD3
WCGF0
WCGF3
4 473.6
4 435.8
4 403.9
8.7 18.4g 8.4 17.7g 0.98g 1.2 4.7 0.4g
7.3 18.8h 7.8 17.8g 1.2a,b 1.1 3.7 0.3h
1.2 0.6 0.3 0.3 0.03 0.04 0.819 0.854 0.398 0.779 0.994 0.904g 15.1g 15.1g 0.8g 1.9g 9.8d 0.8g
16.52
9.5 23.5i 8.9 22.1h 1.5h 1.4 4.1 0.7i
0.56 0.90 0.53 0.84 0.088 0.083 0.25 0.03
1.1 0.7 0.3 0.2 0.03 0.03
1.4 0.8 0.4 0.3 0.03 0.04
0.09 0.07 0.04 0.02 0.005 0.003
0.816 0.854 0.458 0.806 0.990 0.886h
0.811 0.844 0.433 0.804 0.992 0.935i
0.008 0.006 0.039 0.009 0.001 0.003
15.4g 15.2g 1.3h 2.1g 8.4h 0.6h
19.1h 18.7h 1.6h 2.7h 10.0f 1.5i
0.75 0.71 0.12 0.11 0.40 0.05
a,b,c
Row values with different superscripts differ (P≤0.02). d,e,f Row values with different superscripts differ (P=0.06). STD3 = standard finishing diet with 30 g/kg of added fat; WCGF0 = 250 g/kg (DM basis) of wet corn gluten feed (WCGF) with no added fat; WCGF3 = 250 g/kg (DM basis) of wet corn gluten feed with 30 g/kg added fat. h Row values without superscripts do not differ (P>0.73). i EE = ether extract (fat). g
(P>0.20); therefore, effects of treatment on pH and VFA were examined across time. For all variables, when significant treatment effects were detected, treatment means were separated using the predicted difference test of SAS. 3. Results 3.1. Intake and digestibility Nutrient intake, fecal content, and digestibilities are shown in Table 2. Steers fed WCGF3 consumed more (P=0.01) DM (g/kg BW) than did those fed STD3 or WCGF0. Organic matter intake (g/kg BW basis) was also greater (P≤0.02) for WCGF3-fed steers than steers fed STD3 and WCGF0. Intake of ether extractable nutrients (kg/d) also differed (P<0.001) among the 3 diets (WCGF3 > STD3 > WDGF0). Likewise, EE digestibility differed (P=0.002) among diets (WCGF3 > STD3 > WCGF0). Fecal output of OM, aNDF, CP, starch, and EE were similar (P>0.11) among treatments. Also, total tract digestibilities of DM, OM, aNDF, ADF, and CP were not different (P>0.15) in the 3 groups. Total tract digestibility (g/kg BW) of DM, OM, and CP digested were greater in steers fed WCGF3 (P≤0.02) compared to steers fed STD3 and WCGF0. Digestion of ether extractable nutrients (g/kg BW) differed (P≤0.02) as expected with inclusion of dietary fat (WCGF3 > STD3 > WCGF0, respectively). Neutral detergent fiber digestion was greater (P≤0.02) in cattle fed WCGF3 and WCGF0 than in those fed STD3. Starch digestion (g/kg BW) was greater (P=0.06) in steers fed STD3 and WCGF3 than in those fed WCGF0. 3.2. Ruminal kinetics Ruminal particulate and fluid kinetic characteristics are shown in Table 3. Ruminal volume and fluid flow rate were similar (P≥0.12) in steers fed STD3, WCGF0, and WCGF3. Ruminal fluid dilution rate and particulate passage rate were increased (P<0.03) in steers fed WCGF3 compared with those fed WCGF0 and STD3. As would be expected from the increase in passage rates, turnover time in the WCGF3-fed steers was decreased (P=0.03) compared with those of WCGF0 and STD3.
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Table 3 Ruminal particulate and fluid kinetic characteristics of beef steers fed diets containing wet corn gluten feed and (or) supplemental fat. Item
Ruminal volume (L) Fluid dilution rate (/h) Fluid flow rate (L/h) Particulate flow rate (/h) Turnover time (h)
Treatmenta,b
SE
STD3
WCGF0
WCGF3
43.4 0.052c 2.2 0.036c 19.5c
38.8 0.057c 2.3 0.042c 17.6c
32.0 0.075d 2.4 0.059d 13.3d
3.32 0.0038 0.23 0.0042 1.16
a,b
Row values with different superscripts differ (P<0.03). STD3 = standard finishing diet with 30 g/kg of added fat; WCGF0 = 250 g/kg (DM basis) of wet corn gluten feed (WCGF) with no added fat; WCGF3 = 250 g/kg (DM basis) of wet corn gluten feed with 30 g/kg added fat. d Row values without superscript do not differ (P>0.12). c
Table 4 Ruminal particulate and fluid kinetic characteristics of beef steers fed diets containing wet corn gluten feed and (or) supplemental fatRuminal pH and volatile fatty acids in beef steers fed diets containing wet corn gluten feed and (or) supplemental fat. Itemg
Animals, no. pH Total volatile fatty acids (mM) Volatile fatty acids Acetate Propionate Butyrate Valerate Isovalerate Isobutyrate Caproate Isocaproate Heptanoate Acetate:propionate ratio
Treatmenta,b
SE
STD3
WCGF0
WCGF3
4 5.3e 122.6f mol/100 mol 43.0 34.0e 15.7 5.4 0.8 0.4e 0.7 0.004 0.9 1.3f
4 5.9f 97.8d
4 5.4e 119.4f
43.5 35.0e 14.1 5.0 1.1 0.6f 0.6 0.004 0.1 1.3f
39.1 43.4f 13.4 2.2 0.7 0.4e 0.6 0.006 0.1 0.9d
0.16 6.81 2.39 2.07 1.92 1.04 0.23 0.04 0.23 0.0032 0.03 0.06
a,b
Row values with different superscripts differ (P≤0.06). c,d Row values with different superscripts differ (P<0.09). STD3 = standard finishing diet with 30 g/kg of added fat; WCGF0 = 250 g/kg (DM basis) of wet corn gluten feed (WCGF) with no added fat; WCGF3 = 250 g/kg (DM basis) of wet corn gluten feed with 30 g/kg added fat. f Row values without superscripts do not differ (P>0.40). g Ruminal pH and volatile fatty acids were determined before and at 2, 4, 6, 8, 10, 12, 14, and 18 h after feeding on d 3 of the 6-d collection period. Because a diet × sampling time interaction was not detected (P>0.20), overall means are presented. e
3.3. Ruminal pH and VFA concentration Ruminal pH and VFA profiles are shown in Table 4. Ruminal pH was greater (P<0.05) in steers fed WCGF0 than in those fed WCGF3 and STD3. Total ruminal VFA in WCGF0-fed steers tended to be less (P<0.09) than in steers fed WCGF3 or STD3. Ruminal propionate concentration (mol/100 mol) tended to be greater (P≤0.06) in steers fed WCGF3 than in those consuming WCGF0 or STD3. Isobutyrate concentration was 0.4, 0.6, and 0.4 ± 0.04 mol/100 mol in steers receiving STD3, WCGF0, and WCGF3, respectively (P<0.06). The acetate:propionate ration tended to be greater (P<0.09) in steers fed STD3 and WCGF0 than in those fed WCGF3. 4. Discussion 4.1. Intake and digestibility Intake has been reported to increase with inclusion of WCGF in a growth experiment (Ham et al., 1995) as well as in finishing studies (Defoor et al., 2003; Sindt et al., 2003; Macken et al., 2004; Parsons et al., 2007). However, in our experiment, inclusion of WCGF did not alter intake, but inclusion of WCGF and fat increased intake of the diet compared with STD3. The increased intake of EE, and the subsequent increase in EE digestibility, occurred when supplemental fat was added to the diet, as would be expected. Because total tract digestibilities (g/kg of intake) of DM, OM, aNDF, and CP were not different in the 3 groups, one can speculate that addition of WCGF and (or) addition of fat does not affect digestibility. This finding contradicts results of Montgomery et al. (2004) who reported that addition of WCGF increased total tract digestion (g/kg of intake) of OM, aNDF, and starch. In contrast, Sindt et al. (2003) reported that inclusion of WCGF decreased total tract OM digestibility. Even though digestibility of DM, OM, and CP were not affected by treatment, total tract nutrients digested (g/kg
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of BW; DM, OM, and CP) were greater in WCGF3-fed steers than in WCGF0- and STD3-fed steers. Also, with inclusion of WCGF, regardless of the presence of supplemental fat, digestion of aNDF (g/kg BW) increased. 4.2. Ruminal kinetics Increased ruminal fluid dilution and ruminal particulate passage rates in cattle fed WCGF were reported by Sindt et al. (2003) and Montgomery et al. (2004), respectively. The current study did not produce similar findings when only WCGF was fed, but similar results were observed when supplemental fat was added to the WCGF-containing diet. As would be expected from the increase in passage rates, turnover time in the WCGF3-fed steers was decreased compared with those of WCGF0 and STD3. The increase in passage rate and turnover time and of total tract nutrient digested in the WCGF3-fed steers allowed the steers to increase feed consumption. Defoor et al. (2003) reported that supplementing fat to steam-flaked corn-based finishing diets that contained WCGF increased DMI and ADG, but no effects were observed on G:F. The greater ADG was probably caused by the greater DMI; however, because no effects on G:F were reported (Defoor et al., 2003), no effect were expected on total tract nutrient digested in the present study. 4.3. Ruminal pH and VFA concentration The inclusion of WCGF in feedlot diets increased pH (Sindt et al., 2002; Montgomery et al., 2004). This greater pH was expected because steam-flaked corn decreased in the diet with the inclusion of WCGF, and therefore starch in the diet decreased. Ruminal pH decreased with increasing starch concentration in the diet (Calderon-Cortes and Zinn, 1996). In the present experiment, a greater pH was expected for both diets containing WCGF than SDT3, but WCGF3 was lower than WCGF0 probably due to the greater DMI. Total ruminal VFA decreased with the inclusion of WCGF (Krehbiel et al., 1995; Sindt et al., 2002) which resulted from the lower starch concentration in the diet. However, the reason for the greater total VFA concentration is not clear. It might be due to the greater intake observed for such diets. Supplemental fat sinks H ion in the rumen, reducing the need for methane production to sink H ions which results in increased propionate and decreased acetate methane production (Zinn and Plascencia, 1996). Fat supplementation consistently increased molar concentration of propionate and decreased the acetate:propionate molar ratio in several studies involving high-concentrate finishing diets (Zinn, 1988, 1989; Zinn and Plascencia, 1996; Ramirez and Zinn, 2000). Reduced methane energy loss with fat supplementation is a consistently positive associative effect observed with fat supplementation (Davison and Woods, 1960; Zinn and Plascencia, 1993, 1996; Ramirez and Zinn, 2000). Diets with greater fiber proportion produce more methane and supplemental fat reduces methane production to a greater degree as compare with diets with lower fiber content (Zinn and Plascencia, 1996). Therefore, supplemental fat has the potential to increase propionate to a greater degree with increased fiber content in the diet. In the present study the inclusion of WCGF increased fiber content (Table 1). 5. Summary and conclusions In conclusion, adding fat to steam-flaked corn diets containing WCGF increases DMI as a result of increasing fluid and particle passage, and total tract nutrient digested. Also, a greater ruminal propionate molar concentration was observed for diets containing WCGF and supplemental fat. Therefore, improvements or no negative effects in performance should be expected in steam-flaked finishing diets supplemented with fat. References AOAC, 1997. Official Methods of Analysis, 16th ed. Assoc. Office, Anal. Chem., Arlington, VA. 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Sci. 63, 727–730. Ham, G.A., Stock, R.A., Klopfenstein, T.J., Huffman, R.P., 1995. Determining the net energy value of wet and dry corn gluten feed in beef growing and finishing diets. J. Anim. Sci. 73, 353–359. Hart, S.P., Polan, C.E., 1984. Simultaneous extraction and determination of ytterbium and cobalt ethylenediaminetetra–acetate complex in feces. J. Dairy Sci. 67, 888–892. Herrera-Saldana, R., Huber, J.T., 1989. Influence of varying protein and starch degradability on performance of lactating cows. J. Dairy Sci. 72, 1477–1483. Krehbiel, C.R., Stock, R.A., Herold, D.W., Shain, D.H., Ham, G.A., Carulla, J.E., 1995. Feeding wet corn gluten feed to reduce subacute acidosis in cattle. J. Anim. Sci. 73, 2931–2939. Macken, C.N., Erickson, G.E., Klopfenstein, T.J., Stock, R.A., 2004. Effects of concentration and composition of wet corn gluten feed in steam-flaked corn-based finishing diets. J. Anim. Sci. 82, 2718–2723. Montgomery, S.P., Drouillard, J.S., Titgemeyer, E.C., Sindt, J.J., Farran, T.B., Pike, J.N., Coetzer, C.M., Trater, A.M., Higgins, J.J., 2004. Effects of wet corn gluten feed and intake level on diet digestibility and ruminal passage rate in steers. J. Anim. Sci. 82, 3526–3536.
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Parsons, C.H., Vasconcelos, J.T., Swingle, R.S., Defoor, P.J., Nunnery, G.A., Galyean, M.L., 2007. Effects of wet corn gluten feed and roughage level on performance, carcass characteristics and feeding behavior of feedlot cattle. J. Anim. Sci. 85, 3079–3089. Ramirez, J.E., Zinn, R.A., 2000. Interaction of dietary magnesium level on the feeding value of supplemental fat in finishing diets for feedlot steers. J. Anim. Sci. 78, 2072–2080. Sindt, J.J., Drouillard, J.S., Thippareddi, H., Phebus, R.K., Lambert, D.L., Montgomery, S.P., Farran, T.B., LaBrune, H.J., Higgins, J.J., Ethington, R.T., 2002. Evaluation of finishing performance, carcass characteristics, acid-resistant E. coli and total coliforms from steers fed combinations of wet corn gluten feed and steam-flaked corn. J. Anim. Sci. 80, 3328–3335. Sindt, J.J., Drouillard, J.S., Titgemeyer, E.C., Montgomery, S.P., Coetzer, C.M., Farran, T.B., Pike, J.N., Higgins, J.J., Ethington, R.T., 2003. Wet corn gluten feed and alfalfa hay combinations in steam-flaked corn finishing diets. J. Anim. Sci. 81, 3121–3129. Uden, P., Colucci, P.E., Van Soest, P.J., 1980. Investigation of chromium, cerium, and cobalt as markers in digesta. Rate of passage studies. J. Sci. Food Agric. 32, 625–632. Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods of dietary fiber, neutral detergent fiber and non-polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583–3597. Varga, G.A., Prigge, E.C., 1982. Influence of forage species and level of intake on ruminal turnover rates. J. Anim. Sci. 55, 1498–1504. Zinn, R.A., 1988. Comparative feeding value of supplemental fat in finishing diets for feedlot steers supplemented with and without monensin. J. Anim. Sci. 68, 767–775. Zinn, R.A., 1989. Influence of level and source of dietary fat on its comparative fedding value in finishing diets for feedlot steers: metabolism. J. Anim. Sci. 67, 1038–1049. Zinn, R.A., Plascencia, A., 1993. Interaction of whole cottonseed and supplemental fat on digestive function in cattle. J. Anim. Sci. 71, 11–17. Zinn, R.A., Plascencia, A., 1996. Effects of forage levels on the comparative feeding value of supplemental fat in growing-finishing diets for feedlot cattle. J. Anim. Sci. 74, 1194–1201.
Contents lists available at SciVerse ScienceDirect
Animal Feed Science and Technology journal homepage: www.elsevier.com/locate/anifeedsci
Effects of wet corn gluten feed and yellow grease on digestive function of cattle fed steam-flaked corn-based finishing diets夽 L.K. Conway, D.M. Hallford, S.A. Soto-Navarro ∗ Department of Animal and Range Sciences, New Mexico State University, Las Cruces, NM 88003, United States
a r t i c l e
i n f o
Article history: Received 24 February 2012 Received in revised form 28 August 2012 Accepted 3 September 2012
Keywords: Beef cattle Digestion Corn gluten feed Fat Feedlot
a b s t r a c t Twelve ruminally cannulated, English-crossbred steers (436 ± 16 kg) were used in a completely random experiment to evaluate the influence of dietary wet corn gluten feed (WCGF) and yellow grease (fat) in steam-flaked corn-based finishing diets on diet intake, digestibility, and rumen fermentation characteristics. Treatments consisted of steamflaked corn-based diets containing the following WCGF/fat combinations: (1) 0 g/kg WCGF/30 g/kg added fat (STD3), (2) 250 g/kg WCGF/0 g/kg added fat (WCGF0), and (3) 250 g/kg WCGF/30 g/kg added fat (WCGF3). Steers fed WCGF3 consumed more (P=0.01) dry matter (DM) than did those fed STD3 or WCGF0 (23.5 > 18.4 = 18.8 ± 0.9 g/kg of body weight (BW) daily, respectively). Organic matter intake was also greater (P≤0.02) for WCGF3-fed steers than steers fed STD3 and WCGF0 (22.1 > 17.7 = 17.8 ± 0.8 g/kg BW, respectively). Total tract digestibilities of DM, organic matter (OM), neutral detergent fiber (aNDF), acid detergent fiber (ADF), and crude protein (CP) were not different (P≥0.15) in the 3 groups. Digestion of aNDF was greater in cattle fed WCGF3 and WCGF0 than in those fed STD3 (1.6 = 1.3 > 0.8 ± 0.1 g/kg BW, respectively). Ruminal fluid dilution rate (0.075 > 0.057 = 0.052 ± 0.4/h for WCGF3, WCGF0, and STD3, respectively) and particulate passage rate (0.059 > 0.042 = 0.036 ± 0.4/h, for WCGF3, WCGF0, and STD3, respectively) increased (P<0.03) in steers fed WCGF3 compared with those fed WCGF0 and STD3. Ruminal pH was greater (P<0.05) in steers fed WCGF0 than in those fed WCGF3 and STD3 (5.9 > 5.4 = 5.3 ± 0.1, respectively). Total ruminal volatile fatty acids (VFA) in WCGF0-fed steers tended to be less (P<0.09) than in steers fed WCGF3 or STD3 (97.8 < 119.4 = 122.6 ± 6.8 mM, respectively). Ruminal propionate concentration (mol/100 mol) tended to be greater (P≤0.06) in steers fed WCGF3 (43.4 ± 2.1) than in those consuming WCGF0 (35.0 ± 2.1) or STD3 (34.0 ± 2.1). The acetate:propionate ration tended to be greater (P<0.09) in steers fed STD3 and WCGF0 than in those fed WCGF3 (1.3 = 1.3 > 0.9 ± 0.1, respectively). Supplementing 30 g/kg fat to a finishing diet containing 250 g/kg WCGF increased DM intake due to faster liquid and particle passage rates, and to increased total tract nutrient digested. © 2012 Elsevier B.V. All rights reserved.
Abbreviations: ADF, acid detergent acid; Co-EDTA, cobalt-ethylendiaminetetraacetic; CP, crude protein; DM, dry matter; EE, ether extract; fat, yellow grease; aNDF, neutral detergent fiber; OM, organic matter. 夽 This research was supported by the New Mexico Agricultural Experiment Station. Wet corn gluten feed and yellow grease. ∗ Corresponding author. Department of Animal and Range Sciences, MSC 3-I P.O. Box 30003, Las Cruces, NM 88003-8003, USA. Tel.: +1 575 646 2016; fax: +1 575 646 5441. E-mail address: [email protected] (S.A. Soto-Navarro). 0377-8401/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.anifeedsci.2012.09.003
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1. Introduction Corn wet milling has contributed a large supply of byproducts that are valuable animal feeds. One of the main products that has gained wide acceptance is wet corn gluten feed (WCGF). Over the last several years many feedyards in the Texas Panhandle, New Mexico, Oklahoma, and Kansas have been using WCGF as an energy and protein source, replacing a portion of the steam-flaked corn and supplemental protein in growing and finishing diets. Wet corn gluten feed is unique because it contains elevated levels of (CP) and rapidly fermentable neutral detergent fiber, and low levels of starch, yet has been found to have 0.9–1.0 times the net energy for gain value of steam-flaked corn (Ham et al., 1995). Energy in WCGF was estimated (Firkins et al., 1985) to be 0.9 times that in corn because of its greater content of aNDF (437 g/kg of dry matter; DM) that is digested in the rumen at a much lower rate than starch in corn. Because of the increased energy density of fats (Zinn, 1988), we hypothesized that supplementing fat may increase the feeding value of feedlot finishing diets based on steam-flaked corn and WCGF. However, it is unclear if high fat levels could negatively affect the value of these diets through adverse effects on fiber digestion. The objective of this study was to determine effects of fat supplementation on DMI, digestibility, and rumen fermentation characteristics of feedlot cattle consuming steam-flaked corn finishing diets containing 250 g/kg WCGF. 2. Materials and methods 2.1. Animals and experimental diets All surgical procedures, post surgical care, and experimental protocols were approved by the New Mexico State University Institutional Animal Care and Use Committee. Twelve ruminally cannulated English-crossbred steers (436 ± 16 kg) were used in a completely randomized experiment to evaluate effects of added dietary fat on ruminal nutrient disappearance and total tract digestibility by steers fed a finishing diet containing WCGF (Sweet Bran® , Cargill Inc., Blair NE, USA). The supplemental fat used was yellow grease (fat), a commercial feed fat composed of waste grease collected from bakeries, restaurants, school cafeterias, and the like. Yellow grease samples (Valley Rendering Co. Inc., Canutillo, TX, USA) were analyzed for moisture and volatiles, insoluble impurities, unsaponifiable matter, and free fatty acids (SDK Laboratories, Hutchinson, KS, USA). Yellow grease analyzed composition (as fed) was: moisture and volatiles, 3.2 g/kg; insoluble impurities, 8.8 g/kg; unsaponifiablematter, 4.3 g/kg; and free fatty acids, 279.0 g/kg. All WCGF used in the present experiment was from the same batch. Treatments consisted of steam-flaked based diets containing WCGF/yellow grease (fat) combinations: (1) no WCGF and 30 g/kg added fat (standard finishing diet; STD3); (2) 250 g/kg (DM basis) WCGF with no added fat (WCGF0); (3) 250 g/kg (DM basis) WCGF with 30 g/kg added fat (WCGF3). Diets contained (DM basis) 90 g/kg alfalfa hay, 25 g/kg supplement, 0 or 30 g/kg added fat (yellow grease), and 0 or 250 g/kg WCGF with the remainder consisting of steam-flaked corn (Table 1). Steers were individually penned (1.5 m × 4 m) in a barn and had free access to fresh water. The experiment consisted of an 18-d adaptation period and a 6-d collection period. Before the adaptation period, cattle were incrementally stepped-up from a 600 g/kg concentrate diet to the experimental
Table 1 Composition and analyzed nutrient content (g/kg, DM basis) of experimental diets. Item
Ingredient Steam-flaked corn WCGF Alfalfa hay Steep/molasses blendb Yellow grease Cottonseed meal Urea Supplementc Analyzed composition, g/kg DM basis DM CP ADF Ash Ca P
Treatmentsa STD3
WCGF0
WCGF3
778.0 – 90.0 40.0 30.0 28.0 9.0 25.0
633.0 250.0 90.0 – – – 2.0 25.0
595.5 250.0 90.0 – 30.0 7.5 2.0 25.0
782.0 145.3 59.9 53.8 8.9 3.4
731.2 139.9 76.0 54.0 7.7 4.8
735.2 140.4 81.7 57.3 8.3 4.4
a STD3 = standard finishing diet with 30 g/kg of added fat; WCGF0 = 250 g/kg (DM basis) of wet corn gluten feed (WCGF) with no added fat; WCGF3 = 250 g/kg (DM basis) of wet corn gluten feed with 30 g/kg added fat. b Steep/molasses blend = 700 g/kg corn steep and 300 g/kg molasses as-fed. c Supplement supplied the following per kg of the diet (DM basis): Ca = 6.0 g, K = 1.0 g, Mg = 0.8 g, NaCl = 3.0 g, (NH4 )2 SO4 = 1.0 g, Co = 0.20 mg, Fe = 66.47 mg, I = 0.50 mg, Mn = 40.09 mg, Se = 0.05 mg, Zn = 75 mg, Cu = 10.00 mg, Vitamin A = 2200 IU, Vitamin E = 17.5 IU, Monensin = 0.03 g, Tylosin = 0.01 g, and CP = 3.0 g.
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diet containing 900 g/kg concentrate. The adaptation period began (d 0) with feeding of the treatment diet and continued through d 17. Steers were adapted to the barn, stalls, and fecal bags during the final 3 d of the adaptation period (d 15–17). 2.1.1. Collections Steers were fed ad libitum once daily at 06:00. To prevent spoilage, diets were mixed for 2 d of feedings. Samples from each mixing were collected and composited. Total feces were collected (via fecal bags) once daily (07:00) on d 1 through 5 of the collection period. Daily feces and feed refusals (orts) were weighed and recorded and a 100 g/kg subsample was composited. Feed, fecal, and ort samples were stored (−20 ◦ C) until later analysis. Cobalt-ethylendiaminetetraacetic acid (Co-EDTA) and Yb-labeled steam-flaked corn were utilized as markers of fluid and particulate passage rates, respectively. Both mineral markers were prepared as described by Varga and Prigge (1982). Briefly, Yb labeling consisted of soaking 22 kg of steam-flaked corn in 1.2 kg YbCl3 (Alfa Aesar, Ward Hill, MA, USA) and 440 L distilled water for 24 h and stirring 4 times. This mixture was then filtered true 8 layers of cheesecloth and washed 6 times over a 6-h period and then dried at 60 ◦ C in a forced-air oven. Cobalt-EDTA was prepared by combining 75 g cobalt (II)·4 H2 O, 87.6 g disodium EDTA, and 12.9 g of lithium hydroxide with 600 mL distilled water, 60 mL of a 300 mL/L hydrogen peroxide solution, and 900 mL of a 950 mL/L ethanol solution. This mixture was allowed to stand at room temperature for 24 h and was then filtered through filter paper (Whatman number 1; GE Healthcare Life Science, Piscataway, NJ, USA) with 3 L of an 800 mL/L ethanol solution. The crystal that was filtered was subsequently dried (forced-air oven at 100 ◦ C), then resuspended in 3 L of distilled water. On d 3 of the collection period, steers were intraruminally dosed with 200 mL Co-EDTA and 1 kg Yb-labeled steam-flaked corn at 06:00, before feeding. Ruminal fluid and particulate samples were collected before dosing (h 0) and at 2, 4, 6, 8, 10, 12, 14, 18, 26, 34, and 50 h after dosing. Ruminal fluid was collected via the ruminal cannula using a suction strainer, which was rinsed with warm water between each sampling. At the time of sampling, pH of filtered ruminal fluid was measured, and a 200-mL sample was retained after adding 3 mL of concentrated sulfuric acid. Ruminal fluid was stored in whirl pack bags at −20 ◦ C for later analysis of Co and VFA. Ruminal particulate samples were sealed in individual plastic bags and frozen (−20 ◦ C) for subsequent analysis of Yb concentration. 2.1.2. Analyses Refrigerated feed, fecal, and ort samples were dried at 60 ◦ C in a forced-air oven for 48 h, then allowed to equilibrate at room temperature and ground in a Wiley mill (2-mm screen, Wiley mill model 4, Thomas Scientific, Swedesboro, NJ, USA). Feed, fecal, and orts samples were analyzed for DM, organic matter (OM), ether extract (EE), and CP (methods 930.15, 942.05, 945.16, and 990.02, respectively; AOAC, 1997). Neutral detergent fiber (aNDF) was determined (Van Soest et al., 1991) with ␣-amylase and sodium sulfite using an Ankom 200 fiber analyzer (Ankom Co., Fairport, NY, USA), and was expressed with ash included. Starch was analyzed according to Herrera-Saldana and Huber (1989). After thawing ruminal fluid samples were centrifuged at 4000 × g for 15 min and the supernatant was retained for subsequent analysis of VFA (Goetsch and Galyean, 1983) and Co. Cobalt was determined with an air-plus-acetylene flame using atomic absorption spectroscopy (model 3110, PerkinElmer, Waltham, MA, USA) as described by Uden et al. (1980). Ruminal particulate samples were dried in a forced-air oven at 60 ◦ C for 24 h, allowed to equilibrate at room temperature, then ground to pass a 2-mm screen in a Wiley mill. Ytterbium was extracted from these samples as outlined by Hart and Polan (1984) and marker concentration was determined by atomic absorption spectroscopy using a nitrous oxide-plus-acetylene flame. Briefly, Yb extraction was accomplished by combining 20 mL of a solution that was 0.05 M EDTA and 0.2 M KCl with 0.2 g ground ruminal particulate, shaking the solution for 30 min, and then filtering (#1 Whatman filter paper; Whatman Ltd., Maidstone, UK) twice. Ytterbium concentration was read at wavelength of 404.6 nm. 2.1.3. Calculations Fluid and particle passage rates were calculated as the absolute slope of the regression equation of time after dosing and the natural log of Co and Yb concentration, respectively. Rumen volume was calculated as mg of Co dosed divided by ruminal concentration extrapolated to 0 h. Outflow from the rumen or fluid flow rate (h) was calculated as rumen volume (L) multiplied by the dilution rate. Turnover time was calculated as 1 divided by the absolute value of the fractional dilution rate. Intake values (kg/d) were calculated as nutrient offered less the amount of nutrient in orts (DM basis). Intake values (g/kg BW) were calculated as nutrient intake (g) divided by BW. Fecal DM output values were calculated as the average fecal output multiplied by its DM concentration. Fecal nutrient output was calculated by multiplying DM fecal output by the nutrient concentration. Total tract digestibility values were calculated by dividing fecal nutrient output (g) by nutrient intake (kg). 2.1.4. Statistical analysis Feed intake, fecal output, digestibility, BW, and ruminal fluid and particulate characteristics data were subjected to ANOVA appropriate for a completely random design. Treatment was included in the model and steer was the experimental unit. Analyses were computed using the GLM procedure of SAS (SAS Inst. Inc., Cary, NC, USA). Ruminal pH and VFA were subjected to ANOVA for repeated measures using the mixed procedure of SAS. The model included treatment as a fixed effect, time as a repeated measure, and steer (treatment) as the error term. The covariance structure that most appropriately fit the data was compound symmetry. No treatment by sampling interactions were detected
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Table 2 Characteristics of digestion in steers fed wet corn gluten feed and (or) supplemental fat. Itemi
Animals, no. BW (kg) Intake DM (kg) DM (g/kg BW) OM (kg/d) OM (g/kg BW) aNDF(kg/d) CP (kg/d) Starch (kg/d) EE (kg/d) Fecal output OM (kg/d) aNDF(kg/d) ADF (kg/d) CP (kg/d) Starch (kg/d) EE (kg/d) Total tract nutrient digestibility DM OM aNDF CP Starch EE Total tract nutrient digestion (g/kg BW) DM OM aNDF CP Starch EE
Treatmenta,b
SE
STD3
WCGF0
WCGF3
4 473.6
4 435.8
4 403.9
8.7 18.4g 8.4 17.7g 0.98g 1.2 4.7 0.4g
7.3 18.8h 7.8 17.8g 1.2a,b 1.1 3.7 0.3h
1.2 0.6 0.3 0.3 0.03 0.04 0.819 0.854 0.398 0.779 0.994 0.904g 15.1g 15.1g 0.8g 1.9g 9.8d 0.8g
16.52
9.5 23.5i 8.9 22.1h 1.5h 1.4 4.1 0.7i
0.56 0.90 0.53 0.84 0.088 0.083 0.25 0.03
1.1 0.7 0.3 0.2 0.03 0.03
1.4 0.8 0.4 0.3 0.03 0.04
0.09 0.07 0.04 0.02 0.005 0.003
0.816 0.854 0.458 0.806 0.990 0.886h
0.811 0.844 0.433 0.804 0.992 0.935i
0.008 0.006 0.039 0.009 0.001 0.003
15.4g 15.2g 1.3h 2.1g 8.4h 0.6h
19.1h 18.7h 1.6h 2.7h 10.0f 1.5i
0.75 0.71 0.12 0.11 0.40 0.05
a,b,c
Row values with different superscripts differ (P≤0.02). d,e,f Row values with different superscripts differ (P=0.06). STD3 = standard finishing diet with 30 g/kg of added fat; WCGF0 = 250 g/kg (DM basis) of wet corn gluten feed (WCGF) with no added fat; WCGF3 = 250 g/kg (DM basis) of wet corn gluten feed with 30 g/kg added fat. h Row values without superscripts do not differ (P>0.73). i EE = ether extract (fat). g
(P>0.20); therefore, effects of treatment on pH and VFA were examined across time. For all variables, when significant treatment effects were detected, treatment means were separated using the predicted difference test of SAS. 3. Results 3.1. Intake and digestibility Nutrient intake, fecal content, and digestibilities are shown in Table 2. Steers fed WCGF3 consumed more (P=0.01) DM (g/kg BW) than did those fed STD3 or WCGF0. Organic matter intake (g/kg BW basis) was also greater (P≤0.02) for WCGF3-fed steers than steers fed STD3 and WCGF0. Intake of ether extractable nutrients (kg/d) also differed (P<0.001) among the 3 diets (WCGF3 > STD3 > WDGF0). Likewise, EE digestibility differed (P=0.002) among diets (WCGF3 > STD3 > WCGF0). Fecal output of OM, aNDF, CP, starch, and EE were similar (P>0.11) among treatments. Also, total tract digestibilities of DM, OM, aNDF, ADF, and CP were not different (P>0.15) in the 3 groups. Total tract digestibility (g/kg BW) of DM, OM, and CP digested were greater in steers fed WCGF3 (P≤0.02) compared to steers fed STD3 and WCGF0. Digestion of ether extractable nutrients (g/kg BW) differed (P≤0.02) as expected with inclusion of dietary fat (WCGF3 > STD3 > WCGF0, respectively). Neutral detergent fiber digestion was greater (P≤0.02) in cattle fed WCGF3 and WCGF0 than in those fed STD3. Starch digestion (g/kg BW) was greater (P=0.06) in steers fed STD3 and WCGF3 than in those fed WCGF0. 3.2. Ruminal kinetics Ruminal particulate and fluid kinetic characteristics are shown in Table 3. Ruminal volume and fluid flow rate were similar (P≥0.12) in steers fed STD3, WCGF0, and WCGF3. Ruminal fluid dilution rate and particulate passage rate were increased (P<0.03) in steers fed WCGF3 compared with those fed WCGF0 and STD3. As would be expected from the increase in passage rates, turnover time in the WCGF3-fed steers was decreased (P=0.03) compared with those of WCGF0 and STD3.
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Table 3 Ruminal particulate and fluid kinetic characteristics of beef steers fed diets containing wet corn gluten feed and (or) supplemental fat. Item
Ruminal volume (L) Fluid dilution rate (/h) Fluid flow rate (L/h) Particulate flow rate (/h) Turnover time (h)
Treatmenta,b
SE
STD3
WCGF0
WCGF3
43.4 0.052c 2.2 0.036c 19.5c
38.8 0.057c 2.3 0.042c 17.6c
32.0 0.075d 2.4 0.059d 13.3d
3.32 0.0038 0.23 0.0042 1.16
a,b
Row values with different superscripts differ (P<0.03). STD3 = standard finishing diet with 30 g/kg of added fat; WCGF0 = 250 g/kg (DM basis) of wet corn gluten feed (WCGF) with no added fat; WCGF3 = 250 g/kg (DM basis) of wet corn gluten feed with 30 g/kg added fat. d Row values without superscript do not differ (P>0.12). c
Table 4 Ruminal particulate and fluid kinetic characteristics of beef steers fed diets containing wet corn gluten feed and (or) supplemental fatRuminal pH and volatile fatty acids in beef steers fed diets containing wet corn gluten feed and (or) supplemental fat. Itemg
Animals, no. pH Total volatile fatty acids (mM) Volatile fatty acids Acetate Propionate Butyrate Valerate Isovalerate Isobutyrate Caproate Isocaproate Heptanoate Acetate:propionate ratio
Treatmenta,b
SE
STD3
WCGF0
WCGF3
4 5.3e 122.6f mol/100 mol 43.0 34.0e 15.7 5.4 0.8 0.4e 0.7 0.004 0.9 1.3f
4 5.9f 97.8d
4 5.4e 119.4f
43.5 35.0e 14.1 5.0 1.1 0.6f 0.6 0.004 0.1 1.3f
39.1 43.4f 13.4 2.2 0.7 0.4e 0.6 0.006 0.1 0.9d
0.16 6.81 2.39 2.07 1.92 1.04 0.23 0.04 0.23 0.0032 0.03 0.06
a,b
Row values with different superscripts differ (P≤0.06). c,d Row values with different superscripts differ (P<0.09). STD3 = standard finishing diet with 30 g/kg of added fat; WCGF0 = 250 g/kg (DM basis) of wet corn gluten feed (WCGF) with no added fat; WCGF3 = 250 g/kg (DM basis) of wet corn gluten feed with 30 g/kg added fat. f Row values without superscripts do not differ (P>0.40). g Ruminal pH and volatile fatty acids were determined before and at 2, 4, 6, 8, 10, 12, 14, and 18 h after feeding on d 3 of the 6-d collection period. Because a diet × sampling time interaction was not detected (P>0.20), overall means are presented. e
3.3. Ruminal pH and VFA concentration Ruminal pH and VFA profiles are shown in Table 4. Ruminal pH was greater (P<0.05) in steers fed WCGF0 than in those fed WCGF3 and STD3. Total ruminal VFA in WCGF0-fed steers tended to be less (P<0.09) than in steers fed WCGF3 or STD3. Ruminal propionate concentration (mol/100 mol) tended to be greater (P≤0.06) in steers fed WCGF3 than in those consuming WCGF0 or STD3. Isobutyrate concentration was 0.4, 0.6, and 0.4 ± 0.04 mol/100 mol in steers receiving STD3, WCGF0, and WCGF3, respectively (P<0.06). The acetate:propionate ration tended to be greater (P<0.09) in steers fed STD3 and WCGF0 than in those fed WCGF3. 4. Discussion 4.1. Intake and digestibility Intake has been reported to increase with inclusion of WCGF in a growth experiment (Ham et al., 1995) as well as in finishing studies (Defoor et al., 2003; Sindt et al., 2003; Macken et al., 2004; Parsons et al., 2007). However, in our experiment, inclusion of WCGF did not alter intake, but inclusion of WCGF and fat increased intake of the diet compared with STD3. The increased intake of EE, and the subsequent increase in EE digestibility, occurred when supplemental fat was added to the diet, as would be expected. Because total tract digestibilities (g/kg of intake) of DM, OM, aNDF, and CP were not different in the 3 groups, one can speculate that addition of WCGF and (or) addition of fat does not affect digestibility. This finding contradicts results of Montgomery et al. (2004) who reported that addition of WCGF increased total tract digestion (g/kg of intake) of OM, aNDF, and starch. In contrast, Sindt et al. (2003) reported that inclusion of WCGF decreased total tract OM digestibility. Even though digestibility of DM, OM, and CP were not affected by treatment, total tract nutrients digested (g/kg
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of BW; DM, OM, and CP) were greater in WCGF3-fed steers than in WCGF0- and STD3-fed steers. Also, with inclusion of WCGF, regardless of the presence of supplemental fat, digestion of aNDF (g/kg BW) increased. 4.2. Ruminal kinetics Increased ruminal fluid dilution and ruminal particulate passage rates in cattle fed WCGF were reported by Sindt et al. (2003) and Montgomery et al. (2004), respectively. The current study did not produce similar findings when only WCGF was fed, but similar results were observed when supplemental fat was added to the WCGF-containing diet. As would be expected from the increase in passage rates, turnover time in the WCGF3-fed steers was decreased compared with those of WCGF0 and STD3. The increase in passage rate and turnover time and of total tract nutrient digested in the WCGF3-fed steers allowed the steers to increase feed consumption. Defoor et al. (2003) reported that supplementing fat to steam-flaked corn-based finishing diets that contained WCGF increased DMI and ADG, but no effects were observed on G:F. The greater ADG was probably caused by the greater DMI; however, because no effects on G:F were reported (Defoor et al., 2003), no effect were expected on total tract nutrient digested in the present study. 4.3. Ruminal pH and VFA concentration The inclusion of WCGF in feedlot diets increased pH (Sindt et al., 2002; Montgomery et al., 2004). This greater pH was expected because steam-flaked corn decreased in the diet with the inclusion of WCGF, and therefore starch in the diet decreased. Ruminal pH decreased with increasing starch concentration in the diet (Calderon-Cortes and Zinn, 1996). In the present experiment, a greater pH was expected for both diets containing WCGF than SDT3, but WCGF3 was lower than WCGF0 probably due to the greater DMI. Total ruminal VFA decreased with the inclusion of WCGF (Krehbiel et al., 1995; Sindt et al., 2002) which resulted from the lower starch concentration in the diet. However, the reason for the greater total VFA concentration is not clear. It might be due to the greater intake observed for such diets. Supplemental fat sinks H ion in the rumen, reducing the need for methane production to sink H ions which results in increased propionate and decreased acetate methane production (Zinn and Plascencia, 1996). Fat supplementation consistently increased molar concentration of propionate and decreased the acetate:propionate molar ratio in several studies involving high-concentrate finishing diets (Zinn, 1988, 1989; Zinn and Plascencia, 1996; Ramirez and Zinn, 2000). Reduced methane energy loss with fat supplementation is a consistently positive associative effect observed with fat supplementation (Davison and Woods, 1960; Zinn and Plascencia, 1993, 1996; Ramirez and Zinn, 2000). Diets with greater fiber proportion produce more methane and supplemental fat reduces methane production to a greater degree as compare with diets with lower fiber content (Zinn and Plascencia, 1996). Therefore, supplemental fat has the potential to increase propionate to a greater degree with increased fiber content in the diet. In the present study the inclusion of WCGF increased fiber content (Table 1). 5. Summary and conclusions In conclusion, adding fat to steam-flaked corn diets containing WCGF increases DMI as a result of increasing fluid and particle passage, and total tract nutrient digested. Also, a greater ruminal propionate molar concentration was observed for diets containing WCGF and supplemental fat. Therefore, improvements or no negative effects in performance should be expected in steam-flaked finishing diets supplemented with fat. References AOAC, 1997. Official Methods of Analysis, 16th ed. Assoc. Office, Anal. Chem., Arlington, VA. Calderon-Cortes, J.F., Zinn, R.A., 1996. Influence of dietary forage level and forage coarseness of grind on growth performance and digestive function in feedlot steers. J. Anim. Sci. 74, 2310–2316. Davison, K.L., Woods, W., 1960. Influence of fatty acids upon digestibility of ration components by lambs and upon cellulose digestion in vitro. J. Anim. Sci. 19, 54–59. Defoor, P.J., Walker, D.A., Malcolm-Callis, K.J., Gleghorn, J.F., 2003. Effects of Sweet Bran® and added fat level on performance and carcass quality responses by finishing beef steers. Clayton Livestock Research Center Progress Rep. No. 108. New Mexico State University, Las Cruces, NM. Firkins, J.L., Berger, L.L., Fahey Jr., G.C., 1985. Evaluation of wet and dry distillers grains and wet and dry corn gluten feeds for ruminants. J. Anim. Sci. 60, 847–860. Goetsch, A.L., Galyean, M.L., 1983. Influence of feeding frequency on passage of fluid and particle markers in steers fed a concentrate diet. Can. J. Anim. 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Montgomery, S.P., Drouillard, J.S., Titgemeyer, E.C., Sindt, J.J., Farran, T.B., Pike, J.N., Coetzer, C.M., Trater, A.M., Higgins, J.J., 2004. Effects of wet corn gluten feed and intake level on diet digestibility and ruminal passage rate in steers. J. Anim. Sci. 82, 3526–3536.
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