JOURNAL TRANSCRIPT
University of Nebraska - Lincoln
DigitalCommons@University of Nebraska - Lincoln Faculty Papers and Publications in Animal Science
Animal Science Department
1-1-2000
Interactions Between Forage and Wet Corn Gluten Feed as Sources of Fiber in Diets for Lactating Dairy Cows D. M. Allen University of Minnesota
R. J. Grant University of Nebraska-Lincoln
Follow this and additional works at: http://digitalcommons.unl.edu/animalscifacpub Part of the Animal Sciences Commons Allen, D. M. and Grant, R. J., "Interactions Between Forage and Wet Corn Gluten Feed as Sources of Fiber in Diets for Lactating Dairy Cows" (2000). Faculty Papers and Publications in Animal Science. Paper 709. http://digitalcommons.unl.edu/animalscifacpub/709
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Interactions Between Forage and Wet Corn Gluten Feed as Sources of Fiber in Diets for Lactating Dairy Cows1 D. M. Allen2 and R. J. Grant Department of Animal Science University of Nebraska Lincoln 68583-0908
ABSTRACT Twelve early lactation Holstein cows (4 fistulated) were used in replicated 4 × 4 Latin squares with 4-wk periods to determine the effective neutral detergent fiber (NDF) content of wet corn gluten feed and to measure the effect of forage particle size on ruminal mat consistency and passage rate of wet corn gluten feed. Diets were 1) 23.3% NDF (17.4 percentage units of NDF from alfalfa silage), 2) diet 1 plus 11.1 additional percentage units of NDF from alfalfa silage, 3) diet 1 plus 10.7 percentage units of NDF from wet corn gluten feed, and 4) 8.6 percentage units of NDF from alfalfa silage plus 8.9 percentage units of NDF from coarsely chopped alfalfa hay and 10.7 percentage units of NDF from wet corn gluten feed. The calculated effective NDF factor for wet corn gluten feed, using change in milk fat concentration per unit change in NDF, was 0.74 compared with an assumed 1.0 for alfalfa silage. Rumination activity was measured to calculate a physically effective NDF factor for wet corn gluten feed, which was only 0.11 compared with 1.0 for alfalfa silage. Physically effective NDF also was determined for wet corn gluten feed by wet sieving; 22% of the particles were retained on the 3.35-mm screen or greater. Ruminal mat consistency increased and passage rate of wet corn gluten feed decreased with added hay. The inclusion of chopped alfalfa hay to a diet containing wet corn gluten feed increased ruminal mat consistency, rumination activity, and slowed passage rate, resulting in greater ruminal digestion of NDF from wet corn gluten feed. Depending on the response variable, the effectiveness of NDF from wet corn gluten feed varied from 0.11 to 0.74. (Key words: effective fiber, fibrous coproducts, corn gluten feed, rumination)
Received April 26, 1999. Accepted September 20, 1999. Corresponding author: R. J. Grant; e-mail:
[email protected]. 1 Published with the approval of the director as Paper Number 12,592, Journal Series, Nebraska Agricultural Research Division. 2 Present address: Department of Animal Sciences, University of Minnesota, St. Paul. 2000 J Dairy Sci 83:322–331
Abbreviation key: CGF = corn gluten feed, HF = high fiber, LF = low fiber, peNDF = physically effective neutral detergent fiber, WCGF = wet CGF. INTRODUCTION Because of low lignin content and a large proportion of potentially digestible fiber, nonforage sources of fiber supply energy needed for lactation without the ruminal acid load caused by rapidly fermented starchy concentrates. Nonforage sources of fiber also may serve as partial replacements for forage fiber in those situations where forage availability is limited. Compared with most forages, nonforage sources of fiber typically have a smaller particle size and relatively high specific gravity which promote particle passage from the rumen (9, 18). A coproduct of wet milling of corn, wet corn gluten feed (WCGF) is primarily a mixture of corn bran and fermented corn extractives (steep liquor). Although WCGF contains 40 to 45% NDF, it only contains 3% lignin and is a source of highly digestible fiber. When incorporating nonforage sources of fiber, such as WCGF, into rations for lactating dairy cows, at least two major considerations are 1) the interaction between forage and nonforage fiber for ruminal passage and digestion, and 2) the effective NDF content of the nonforage source of fiber. Sutherland (26) described the ruminal mat as a highly effective first-stage separator. Through the processes of filtration and mechanical entanglement, the mat selectively retains potentially escapable fiber particles, thereby increasing the time allowed for fermentation (11). Welch (31) predicted that the consistency of the ruminal mat (hard or soft packed) would either promote or retard particle passage from the reticulorumen. In the only previous study with lactating dairy cows, Weidner and Grant (30) observed a 16% decrease in the fractional passage rate of soybean hulls from the rumens of cows fed coarsely chopped hay to increase ruminal mat consistency of an alfalfa and corn silage blend. Nonforage sources of fiber do not stimulate rumination activity as effectively as dietary forage because of their small particle size (20). Therefore, it is important
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FORAGE AND NONFORAGE SOURCES OF FIBER Table 1. Chemical composition and particle distribution of alfalfa silage, alfalfa hay, and wet corn gluten feed. Fiber Source (% of DM) Item
Alfalfa silage
Alfalfa hay
WCGF1
DM, % CP ADF NDF NEL, Mcal/kg Particle distribution2 % ≥ 9.5 mm 3.35 mm ≤ % < 9.5 mm 1.18 mm ≤ % < 3.35 mm 0.3 mm ≤ % < 1.18 mm 0.053 mm ≤ % < 0.3 mm % < 0.053 mm Physically effective NDF3, % ≥ 1.18 mm ≥ 3.35 mm
46.3 21.2 31.6 43.4 1.52
88.9 17.6 34.7 47.3 1.19
62.5 23.4 11.7 43.9 1.98
27.0 22.0 8.0 3.0 3.0 37.0
44.0 24.0 15.0 3.5 1.0 12.5
1.0 21.0 10.0 8.0 6.5 53.5
57.0 49.0
83.0 68.0
32.0 22.0
1
Wet corn gluten feed. Determined by wet sieving. 3 Physically effective NDF calculated according to Mertens (20). Neutral detergent fiber content of particles retained on 1.18-mm screen and greater was: alfalfa silage, 53.5%; alfalfa hay, 66.5%; and WCGF, 76.5%. 2
The WCGF was delivered and stored in a plastic silage bag prior to the start of this experiment. There was no visual evidence of molding during feeding. Dietary treatments were 1) basal low-fiber alfalfa silage diet (LF) formulated to contain 23.3% NDF (17.4 percentage units of NDF from alfalfa silage), 2) highfiber alfalfa silage diet (HF) formulated to contain 31.9% NDF (LF diet plus an additional 11.1 percentage units of NDF from alfalfa silage), 3) WCGF diet formulated to contain 31.6% NDF (LF diet plus 10.7 percentage units of NDF from WCGF), and 4) WCGF diet plus coarsely chopped alfalfa hay formulated to contain 32.0% NDF (8.6 percentage units of NDF from alfalfa silage plus 8.9 percentage units of NDF from alfalfa hay and 10.7 percentage units of NDF from WCGF). Diets were formulated to be similar in CP (18% CP, DM basis). The calculated RUP requirements (21) were met by adding Soy Pass (a nonenzymatically browned soybean meal containing 70% RUP manufactured by Lignotech USA, Rothschild, WI) to the diet to achieve 5.6 to 6.3% RUP (DM basis, Table 2). With these diets, Table 2. Ingredient and chemical composition of dietary treatments.
to consider the effective NDF content of these fiber sources. Effective NDF has been estimated with three approaches 1) change in milk fat concentration (2), 2) change in rumination activity (1), and 3) sieving and particle size analysis (20). Ration formulation requires that accurate effective NDF values be determined for nonforage sources of fiber, but various methods of determining effective NDF have resulted in inconsistent values for the same feed. For example, Swain and Armentano (27) measured effective NDF of corn gluten feed (CGF), using milk fat percentage as the response variable, and found that in two separate trials the values differed by 56%. The objectives of this research were 1) to evaluate the effect of altering forage particle size on ruminal mat consistency, rumination activity, passage rate of WCGF, and milk production, and 2) to determine the effective NDF content of WCGF relative to a high-fiber control diet based on response in milk fat concentration, rumination activity, and particle size distributions. MATERIALS AND METHODS Cows and Diets Twelve Holstein dairy cows (8 multiparous including four ruminally fistulated) were used in a replicated 4 × 4 Latin square design with 4-wk periods. Cows averaged 71 ± 25 DIM when they were assigned to diets. Fiber sources compared were alfalfa silage, alfalfa hay, and WCGF. Chemical composition and particle distribution of dietary fiber sources are shown in Table 1.
Diet1 (% of DM) Item Ingredient Alfalfa silage Alfalfa hay WCGF Ground corn Soybean meal Soy Pass2 Mineral and vitamin mix3 Composition DM, % NDF NDF from Alfalfa silage NDF from Alfalfa hay NDF from WCGF ADF CP RUP NEL, Mcal/kg4 Particle distribution5 (% of DM retained on screen) % ≥ 9.5 mm % ≥ 3.35 mm % ≥ 1.18 mm 0.053 mm ≤ % < 1.18 mm % < 0.053 mm
LF
HF
WCGF
WCGFH
40.0 ... ... 46.3 6.5 3.7 3.5
65.7 ... ... 29.2 1.7 ... 3.5
39.8 ... 24.4 28.6 2.1 1.7 3.5
19.9 18.8 24.4 26.9 4.8 1.7 3.5
66.0 23.3 17.4 ... ... 15.8 18.1 6.3 1.78
56.3 31.9 28.5 ... ... 22.4 18.0 5.6 1.67
62.0 31.6 17.3 ... 10.7 17.3 18.4 5.7 1.78
70.1 32.0 8.6 8.9 10.7 17.5 18.5 6.1 1.73
10.0 58.2 72.3 9.8 17.9
9.8 52.2 66.4 12.8 21.1
7.3 47.4 60.1 14.0 25.9
11.6 45.2 60.3 14.1 25.6
1 LF = Low fiber, HF = high fiber, WCGF = wet corn gluten feed, WCGFH = WCGF plus hay. 2 Nonenzymatically browned soybean meal (Lignotech USA, Rothschild, WI). 3 Supplement contained 7.9% Ca, 2.6% P, 1.8% Mg, 2.2% Na, 1,026 mg/kg of Zn, 718 mg/kg of Mn, 128 mg/kg of Cu, and 15,358, 3,072, and 94,270 IU per kilogram of Vitamin A, D, and E, respectively. 4 Estimated using values for individual ingredients given by NRC (21). 5 Determined by wet sieving.
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an increase in milk fat concentration or rumination activity for cows fed the LF versus the HF diet would be attributable to additional NDF from alfalfa silage. Similarly, an increase in milk fat concentration or rumination activity for cows fed the LF versus the WCGF diet would be attributable to additional NDF from WCGF. The effect of increasing dietary forage particle length on ruminal mat consistency and passage kinetics of WCGF would be determined by comparing responses to the WCGF diet with or without added chopped hay. Experimental periods were 28 d; the last 7 d were used for sample and data collection. Diets were fed once daily in amounts to ensure 10% orts. Amounts offered and orts were recorded daily. Body weight was measured each week immediately after a.m. milking. Daily milk production was recorded electronically for all cows. Composite a.m. and p.m. milk samples were collected twice during wk 4 of each period and analyzed for percentage of milk fat, protein, and lactose (3; Milko-Scan Fossomatic; Foss Food Technology Corp., Eden Prairie, MN). Calculation of milk composition was weighted according to a.m. and p.m. milk production. Cows were fistulated and housed under conditions described in animal use protocols approved by the Institutional Animal Care and Use Committee at the University of Nebraska. Sample Collection and Analysis Forage, concentrate, and TMR samples were composited daily during the last 7 d of each collection period for chemical analysis. Samples were oven-dried (60°C), ground through a Wiley mill (1-mm screen; Arthur H. Thomas Co., Philadelphia, PA), and analyzed for CP (3), amylase-modified (heat stable α-amylase; ANKOM Tech. Corp., Fairport, NY), ash-free NDF (28), and ADF (28). Sodium sulfite (0.5 g/sample) was added to SoyPass samples in an attempt to adequately solubilize all protein complexes, resulting in a more accurate determination of NDF content (15). Particle size was determined on masticate, ruminal digesta, and fecal samples collected at approximately 4 h postfeeding on the last day of each period. Collection procedures for masticate, dorsal rumen, ventral rumen, reticulum, and fecal samples were as described by Weidner and Grant (30). Two representative subsamples of each sample type were processed and wet sieved in duplicate for 15 min with a vibrational sieve shaker (Fritsch Analysette; Worthington, OH) utilizing a continuous water spray on the top and middle sieves as described by Shaver et al. (25). Sieves were chosen to ensure that less than 2% of the sample was retained on the top screen (with the exception of the hay samples) and less than 20% on each of the subsequent screens. Nine 20-cm diameter sieves from the US Standard SeJournal of Dairy Science Vol. 83, No. 2, 2000
ries were used for masticate, digesta, and fecal samples with screen apertures of 12.5, 9.5, 6.3, 3.35, 1.18, 0.6, 0.3, 0.150, and 0.053 mm. The same technique was used to determine particle size distributions for composite TMR, forage, and WCGF samples during each period. Additionally, rumens were emptied, and digesta was weighed and sampled for DM and NDF analyses to determine ruminal fill. Total chewing, eating, and ruminating times were determined during the last week of each collection period. The chewing action of individual cows was recorded every 5 min for 24 h. Ruminal fluid samples were collected via ruminal fistula immediately beneath the ruminal mat at 4-h intervals for 24 h during the last day of each period. Ruminal pH was determined immediately with a portable pH meter. Samples were frozen until analysis for VFA by GLC with run conditions described by Weidner and Grant (30). The fractional passage rate of WCGF fiber from the rumen was determined with Er as a rare earth marker. Some evidence exists that rare earth markers may migrate, but this movement would likely occur postruminally and not affect the ruminal passage kinetics reported. Wet corn gluten feed NDF was soaked in a solution containing 87 mg of Er-acetate/g of DM in 7.5 ml of distilled water for 24 h and then soaked in 10 ml of 0.1 M acetic acid/g of DM for 6 h. Each fistulated cow was dosed with 100 g (DM basis) of labeled, undried WCGF. Ruminal digesta samples were collected at 0, 6, 12, 24, 36, 48, 72, and 96 h postdosing. Samples were dried in a forced-air oven at 60°C for 48 h and ground through a 1-mm screen (Wiley mill). Erbium was extracted from the samples by 0.1 M diethylenetriaminepentaacetic acid solution (17). Erbium concentrations were determined by atomic absorption spectroscopy with an air-acetylene flame. Techniques described by Llamas-Lama and Combs (19) were used to calculate the ruminal escape rate of WCGF. To determine the fractional rate of ruminal NDF digestion of WCGF, 5-g samples of dried, unground WCGF (60°C, forced-air oven) were measured into Dacron bags by the in situ bag technique. Samples were incubated in duplicate for 0, 6, 12, 24, 36, 48, 72, and 96 h. Dacron bags were 10 × 20 cm with a mean pore size of 53 µm (ANKOM Tech. Corp., Fairport, NY). Upon removal from the rumen, bags were rinsed and dried at 60°C in a forced-air oven for 48 h (32). Bags were weighed and the residue was analyzed for amylasemodified, ash-free NDF. Kinetics of NDF digestion and apparent extent of ruminal fiber digestion, using measured rates of passage and digestion, were calculated as described by Grant (13). The specific gravity of WCGF was determined by a flotation technique described by Weidner and Grant
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(30). Duplicate samples of four treatments were analyzed: WCGF (0 h of ruminal incubation), Er-labeled WCGF (0 h of ruminal incubation), WCGF (3 h of ruminal incubation), and Er-labeled WCGF (3 h of ruminal incubation). Four solutions with specific gravities of 1.0, 1.1, 1.2, and 1.4 at room temperature (23°C) were prepared according to Hooper and Welch (16). The percentage of particles within each specific gravity fraction (DM basis) was calculated. The effect of increasing dietary particle size on ruminal mat consistency was determined with a technique adapted from Welch (31) as described by Weidner and Grant (30). Ruminal mat consistency was measured at 3 h postfeeding. A 454-g weight was placed in the ventral rumen 1 h prior to measurement to ensure normal mat reformation. Upon release of an exterior 1500-g weight, ascension of the 454-g weight through the ruminal contents was recorded every 10 s for 120 s. The ascension rate, in centimeters per second, was considered to be an indication of ruminal mat consistency. Data were analyzed as a replicated 4 × 4 Latin square design with model effects for square, cow within square, period, treatment, and square × treatment using the GLM procedure of SAS (24). A multiple t-test was used to determine significance among means for significant main effects (24). Significance was declared at P < 0.10 unless otherwise noted. RESULTS AND DISCUSSION Dietary Chemical Composition and Particle Size Chemical composition and particle distribution of fiber sources is presented in Table 1. Although our goal was to have alfalfa hay and silage of similar quality, as sampled and analyzed the quality of the hay was slightly lower than the silage. The NDF of WCGF was similar to alfalfa silage, but ADF was distinctly lower at 11.7 versus 31.6%, respectively. Particle distributions from wet sieving showed that the coarsely chopped alfalfa hay had the greatest particle length; 44% of the particles were retained on the 9.5-mm screen, whereas over 50% of WCGF passed through the 0.053-mm screen. The alfalfa hay contained 63% more large particles (≥9.5-mm screen) than the alfalfa silage. The physically effective NDF (peNDF) for the fiber sources, as measured by wet sieving, was greatest for the alfalfa hay and least for the WCGF. Our goals were to manipulate TMR particle size by partially substituting longer particle length hay for silage and to compare the effectiveness of NDF from alfalfa and WCGF that differed substantially in particle size. Diets LF, HF, and WCGF without hay were formulated by an approach similar to Clark and Armentano (6, 7, 8; Table 2). The LF diet contained 17.4 percentage
Table 3. Consumption of DM, NDF, and ADF by cows fed experimental diets. Diet1 Item DMI kg/d % of BW NDF kg/d % of BW ADF kg/d % of BW
LF
HF
WCGF
WCGFH
SE
24.2ab 4.2ab
22.4b 3.9b
25.1a 4.4a
26.1a 4.5a
1.1