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ANIMAL PRODUCTION |
Department of Animal and Range Sciences, North Dakota State University, Fargo 58105
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Key Words: Cattle • Digestibility • Fermentation • Field Pea • Forage • Supplement
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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). Until recently, there has been a lack of information available on various aspects of feeding peas to ruminants. Recent research has focused on feeding field peas in growing and finishing rations (Birkelo et al., 2000; Flatt and Stanton, 2000). Most reports indicate similar DMI, feed conversion efficiencies, and weight gains when comparing field peas to cereal grains in growing and finishing diets (Poland and Landblom, 1996; Anderson, 1999; Birkelo et al., 2000). Encinias et al. (2000) evaluated the feeding value of field peas as a protein source in forage-based diets fed to beef cows. Field peas were supplemented at 0, 0.68, 1.36, and 2.04 kg daily. Forage intake of cows decreased linearly with increasing field pea supplementation; however, total intake (forage plus field pea) increased linearly with increasing supplementation. Cow body condition score was positively influenced by field pea supplementation. Limited data evaluating the effects of field peas on intake, fermentation, and digestion characteristics in ruminants consuming forage-based diets are available in the literature. Therefore, the objectives of this study were to determine the effects of increasing field pea supplementation on intake, digestion, microbial efficiency, ruminal fermentation, and in situ disappearance in steers fed grass hay–based diets. |
Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Four ruminally and duodenally cannulated beef steers (397 ± 55 kg initial BW) were used in a 4 x 4 Latin square design. All surgical procedures, animal care, and animal handling protocols were approved by the North Dakota State University Institutional Animal Care and Use Committee. Steers were housed in an enclosed barn in individual tie stalls (1.5 x 2.5 m). Animals were allowed ad libitum access to grass hay (predominately mature, cool-season, prairie hay harvested in northern Barnes County, ND), water, and trace-mineralized salt blocks (minimum 4.0 g Zn, 1.6 g Fe, 1.2 g Mn, 0.33 g Cu, 0.10 g I, and 0.04 g of Co/kg; North American Salt Company, Overland Park, KS). Steers were supplemented with one of four levels of rolled field peas (0, 0.81, 1.62, and 2.43 kg DM per steer daily; 2,623-µm particle size). The nutrient content of the grass hay and the field peas used in this experiment is provided in Table 1. Steers were fed forage and supplement twice daily at 12-h intervals.
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Each experimental period was 14 d in length, with a 9-d adaptation period. Feed and orts samples were collected on d 10 through 14 and composited. Steers were weighed at the beginning and end of each period. Chromic oxide (8 g) was dosed ruminally twice daily via gelatin capsules (Torpac Inc., Fairfield, NJ) at 0700 and 1900 on d 4 through 12. Duodenal fluid samples (200 mL) were collected on d 9 through 13. Samples were composited within steer for each period. Samples were collected in a manner that allowed for a collection to take place every other hour over a 24-h period. On d 10, duodenal fluid sampling took place at 0700, 1300, and 1900. On d 11, sampling took place at 0100, 0900, 1500, and 2100. Sampling took place at 0300, 1100, 1700, and 2300 on d 12, and at 0500 on d 13. Steers were fitted with fecal collection bags on d 10 to 14. Fecal bags were emptied and weighed twice daily at 12-h intervals. Fecal samples (10% of output) were composited across days and within steer for each period. Samples were stored frozen (–20°C) until analyses.
In situ disappearance measurements were taken on d 10 to 13. For in situ analysis, grass hay was ground in a Wiley mill (2-mm screen, model 3; Arthur H. Thomas, Philadelphia, PA), and field peas were coarsely rolled in a roller mill (2,623-µm mean particle size, model K; Roskamp Mfg. Inc., Cedar Falls, IA). Rolled field peas (5 g) and grass hay (5 g) were placed in Dacron bags (10 x 20 cm, 50 ± 15-µm pore size; Ankom, Fairport, NY) and ruminally incubated for 0, 2, 4, 8, 16, 24, 36, 48, 72, and 96 h. Bags were inserted in reverse order, and all bags were removed at 0 h and rinsed with a hose to remove large particulate matter. In situ bags were then rinsed in a top-loading washing machine (model WJXR2080TSWW; General Electric, Louisville, KY). The machine was filled with 45 L of cold water. The bags were agitated (using the delicate cycle) for 1 min, drained, and spun for 2 min. This cycle was repeated five times. Bags were dried in a forced-air oven (50°C, model SB-350; Grieve Corp., Round Lake, IL) and stored at room temperature until analysis.
On d 13 of each period, ruminal fluid samples were collected at –2, 0, 2, 4, 6, 8, 10, and 12 h after feeding. Ruminal fluid was collected with a suction strainer, and pH was recorded using a pH meter and a combination electrode (model 2000; Beckman Instruments Inc., Fullerton, CA). A 4-mL sample of ruminal fluid was retained, and 1 mL of 25% HPO3 (wt/vol) was added to the fluid. Samples were frozen (–20°C) for later analysis of NH3-N and VFA.
Rumen evacuations were performed on d 14 of each period to determine DM fill. Ruminal contents of each steer were removed, weighed, mixed, and subsampled for DM, OM, ADF, and NDF analysis. A 4-kg sample of ruminal contents was taken, and 2 L of formalin/saline solution (3.7% formaldehyde/0.9% [wt/vol] NaCl) was added (Zinn and Owens, 1986) for isolation of bacterial cells and analysis for DM, OM, N, and purines. Samples were stored frozen (–20°C) until analysis.
Laboratory Analysis
Dietary, orts, ruminal content, and fecal samples were dried at 5°C in a forced-air oven (5°C, model SB-350, Grieve Corp.) for 48 h. Dried samples were ground with a Wiley mill (2 mm, model 3; Arthur H. Thomas). Duodenal samples were lyophilized (Virtis Genesis 25LL; Virtis Co. Inc., Gardiner, NY) and ground with a blender (Osterizer Galaxie Pulse Matic I6; Sunbeam, Purvis, MS).
Dietary, orts, fecal, and duodenal samples were analyzed for DM, OM, ADF, N (AOAC, 1990), and NDF (Robertson and Van Soest, 1991). Ruminal samples were analyzed for DM, OM, ADF (AOAC, 1990), and NDF (Robertson and Van Soest, 1991). Duodenal samples were analyzed for Cr (Czarnocki et al., 1961) by the spectrophotometric method of Fenton and Fenton (1979). Chromium concentrations were used to calculate digesta flow. Digestibility was calculated by subtracting flow rate from intake and dividing by intake. Feed samples were analyzed for in vitro organic matter digestibility (IVOMD) using a modified procedure of Tilley and Terry (1963), in which samples were centrifuged and the supernatant fluid discarded before adding pepsin. In situ forage residue was analyzed for DM, NDF, N (AOAC, 1990), and purines (Zinn and Owens, 1986). In situ pea residue was analyzed for DM (AOAC, 1990).
Ruminal fluid was thawed and centrifuged (20,000 x g, 10 min). Liquid was filtered through a 0.45-µm filter and placed in storage tubes. Ruminal VFA concentrations were determined by gas chromatography (model GC 9A; Shimadzu, Kyoto, Japan) and separated on a packed column (model SP-1200; Supelco, Bellefonte, PA) using 2-ethyl butyric acid as the internal standard (Goetsch and Galyean, 1983).
Bacterial cells were isolated from ruminal contents that contained 2 L of formalin/saline solution. Ruminal contents were blended (model 37Bl19, Waring, New Hartford, CT), and the mixture was strained through two layers of cheesecloth. Feed particles and protozoa in ruminal samples were removed via centrifugation at 500 x g for 20 min. The sample was then centrifuged 30,000 x g for 20 min to collect the bacteria from the supernatant. Isolated bacteria were frozen, lyophilized, and analyzed for DM, ash, N (AOAC, 1990), and purines (Zinn and Owens, 1986).
The contribution of N flow to the duodenum from field peas was calculated by the following equation: nonbacterial nitrogen (NBN) flow – (hay UIP x N supplied by hay). Hay UIP was calculated using data from the 0-kg treatment. Hay UIP was calculated by dividing NBN flow to the duodenum by N intake from hay.
Statistical Analysis
Data were analyzed as a 4 x 4 Latin square using the GLM procedure of SAS (SAS Inst. Inc., Cary, NC). The model contained effects for period, animal, and diet. Ruminal data over time were analyzed as a repeated measures design (Gill and Hafs, 1971). The model included effects for period, animal, treatment, sampling time, treatment x sampling time, and animal x period x treatment. The three-way interaction was used in the error term to test for treatment effects. Treatment means were separated using linear, quadratic, and cubic contrasts. In situ forage DM and NDF disappearance were calculated using a model developed by Mertens and Loften (1980). The equation used for the model was as follows: residual = b x e–k(t–lag) + i, where b = the slowly degraded fraction, k = rate, t = time, and i = the indigestible fraction. The Ørskov and McDonald (1979) digestion model was used to calculate in situ forage N disappearance and field pea DM disappearance. The equation used for the model was a + b (1 – e–kt), where a = the fraction degraded at time 0, b = the slowly degraded fraction, k = rate, and t = time.
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Results and Discussion |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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). Forage DMI (kg/d) decreased quadratically (P = 0.09), whereas forage DMI relative to BW was not affected (P = 0.15) by level of field pea supplementation. Similar results were reported by Encinias et al. (2000), who supplemented 0, 0.68, 1.36, or 2.04 kg/d field peas in forage-based diets fed to beef cows. In their study, forage intake of cows decreased linearly and total intake increased linearly with increasing supplementation. Similar to our work with field peas (Table 1
), supplementing forage-based diets with cereal grains has often reduced forage intake (Chase and Hibberd, 1987; Galloway et al., 1993; Pordomingo et al., 1991). Garcés-Yépez et al. (1997) also reported higher total intake in supplemented vs. unsupplemented cattle when supplementing corn/soybean meal, wheat middlings, or soybean hulls. In contrast, Pordomingo et al. (1991) reported no differences in total intake when supplementing 0, 0.2, 0.4, or 0.6% BW corn to steers grazing native rangeland.
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). Similarly, Vanzant et al. (1990) and Sunvold et al. (1991) reported no differences in ruminal DM fill for cereal grain supplemented and unsupplemented steers consuming range forage. Heldt et al. (1999) supplemented a carbohydrate source (cornstarch grits, glucose, and alkaline hydrogen peroxide-treated oat fiber) and degradable intake protein (DIP) to steers consuming prairie hay, and reported a 14.6% decrease in ruminal DM fill with increased supplemental DIP. The decrease in ruminal DM fill with supplementation was a function of increased liquid and solid passage rates and increased organic matter digestibility. Supplementation may have had a larger effect on ruminal DM fill in the work of Heldt et al. (1999) compared with our study because they used lower-quality hay (5.7% CP, 74.9% NDF). In contrast, Sunvold et al. (1991) reported a linear increase in DM fill when supplemental CP concentration was increased from 15 to 25% when fed with 2.4% CP dormant bluestem hay.
Total organic matter intake (OMI) increased quadratically (P = 0.09) with increasing level of supplementation (Table 3). However, forage OMI decreased quadratically (P = 0.09). Previous studies have reported increases in total OMI and forage OMI when supplementing low-quality hay diets with a carbohydrate source and increasing levels of DIP (Heldt et al., 1999; Olson et al., 1999; Bodine et al., 2000). The difference between our study and these studies likely reflects differences in forage quality. The forages used in the above-mentioned studies were between 4.9 and 6.0% CP, whereas the forage used in our study was 8.0% CP. Differences in forage CP likely caused differences in forage OMI. In addition, the lower level of starch and greater level of CP in field peas compared with other cereal grains may have caused differences (Bodine et al., 2000).
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). There were no differences in apparent (P = 0.29) or true ruminal OM (P = 0.38) disappearance relative to intake. Also, there were no differences in intestinal OM disappearance as a percentage of entering (P = 0.42) or relative to intake (P = 0.50). Apparent total-tract OM disappearance was not affected (P = 0.13) by increasing supplementation. Apparent total-tract digestion of NDF and ADF follow a similar pattern as OM and were not altered by treatment (data not shown). Numerous studies have found that cereal grain supplementation decreases OM digestibility (Vanzant et al., 1990; Pordomingo et al. 1991). Pordomingo et al. (1991) reported that in situ forage OM disappearance was greatest for steers fed corn at 0.2% of BW and least for those fed corn at 0.4 and 0.6% of BW. Field pea supplementation does not seem to decrease OM digestion, perhaps because of lower starch and higher DIP levels (78%; NRC, 1989) than cereal grains. Degradable intake protein supplementation of low-quality forage-based diets generally increases OM digestion (Köster et al., 1996; Bodine et al., 2000; Bandyk et al., 2001).
Nitrogen intake increased linearly (P < 0.001) with increasing supplementation (Table 4). The increase in N intake reflects an increase in dietary N with increasing field pea level. Krysl et al. (1989) reported greater N intakes in steers supplemented with SBM than in unsupplemented steers or sorghum-supplemented steers. Total N (P < 0.001), bacterial N (P = 0.002), and NBN (P = 0.001) flow to the duodenum increased linearly with increasing level of field pea supplementation. The contribution of N flow to the duodenum from field peas was 0, 7.97, 14.83, and 23.25 g/d for the treatments, which partially explains the increase in NBN flow to the duodenum.
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reported that cracked corn and corn gluten feed supplementation to steers grazing tall fescue did not affect net ruminal microbial protein synthesis and suggested that energy was likely not limiting microbial protein synthesis. In contrast, Köster et al. (1996) reported that efficiency of microbial growth increased linearly as supplemental DIP increased when low-quality (1.9% CP) hay diets were fed to beef cows. Bodine et al. (2000) reported that, as DIP was added to prairie hay (6.1% CP) diets, ruminal NH3-N increased linearly, suggesting that the increased DIP supply increased available N for microbial protein synthesis. Cattle consuming lower-quality forages may have been deficient in ruminal NH3-N, which could limit microbial CP synthesis and growth, and lead to decreased microbial degradation of fiber. Degradable intake protein supplementation can correct a rumimal NH3-N deficiency, leading to increased microbial fiber digestion and increased forage OMI.
Apparent ruminal N disappearance (% of intake; P = 0.07) and apparent total-tract N disappearance (P = 0.09) increased quadratically with increasing field pea supplementation. Also, true ruminal N disappearance (% of intake) increased linearly (P = 0.003) with increasing field pea supplementation. Köster et al. (1996) reported a quadratic increase in apparent ruminal N digestibility with the addition of DIP to low-quality hay diets.
There were no time x treatment interactions for ruminal pH (P = 0.51; Table 5). There was a cubic effect (P < 0.001) for ruminal pH (Table 5). Several studies have reported reductions in ruminal pH resulting from cereal grain supplementation (Funk et al., 1987; Leventini et al., 1990; Sanson et al., 1990). However, some studies report no effect on ruminal pH with cereal grain supplementation (Pordomingo et al., 1991; Krysl et al., 1989). Guthrie and Wagner (1988) and Köster et al. (1996) reported decreased pH as the level of protein supplement increased.
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). There was a cubic response (P < 0.001) in ruminal NH3-N concentration with increasing supplementation. The cubic effects were likely caused by the magnitude of change between the treatments. In contrast, Heldt et al. (1999) reported decreased ruminal NH3-N concentrations with increasing supplemental carbohydrate (starch, glucose, and fiber). However, when DIP was supplemented, ruminal NH3-N concentrations increased (Heldt et al., 1999). Low ruminal NH3-N concentrations were also reported by Chase and Hibberd (1987) when using corn as a supplement for low-quality (4.2% CP), forage-based diets. Similar to our study, many studies have reported increased ruminal NH3-N with an increasing level of supplemental DIP (Krysl et al., 1989; Heldt et al., 1999; Bodine et al., 2000).
There were no time x treatment interactions for ruminal VFA concentrations (P > 0.20; Table 5). There was a cubic effect (P = 0.008) for total VFA concentrations with increasing field pea supplementation. Leventini et al. (1990) and Pordomingo et al. (1991) reported no effects of increasing supplemental cereal grain (barley and corn, respectively) on total VFA concentration. Olson et al. (1999) reported that the addition of supplemental starch had no effect on total VFA concentration, but total VFA increased linearly as supplemental DIP increased. Similarly, Köster et al. (1996) reported that total ruminal VFA increased dramatically in response to supplemental DIP.
There was a cubic effect (P = 0.04) for molar proportions of acetate with increasing field pea supplementation. There were no differences (P = 0.69) in molar proportions of propionate. The acetate:propionate ratio was not affected (P = 0.43) by supplementation. Feeding higher levels of concentrates in ruminant diets can increase propionate levels and decrease the acetate:propionate ratio (Bauman et al., 1971; Herbein et al., 1978). Köster et al. (1996) reported a linear decrease in acetate portion, whereas propionate increased and the acetate:propionate ratio decreased in a quadratic manner with supplemental DIP in steers fed low-quality hay. These results are in agreement with those of McCollum and Galyean (1985), who supplemented prairie hay with cottonseed meal and reported decreased molar proportions of acetate and increased molar proportions of propionate with supplementation. Leventini et al. (1990) reported decreased acetate and propionate portions as barley supplementation increased, whereas Pordomingo et al. (1991) reported no differences in acetate and propionate portions with increasing level of supplemental corn.
There was a cubic effect (P < 0.001) for butyrate with increasing field pea supplementation. Isobutyrate (P = 0.01) and isovalerate (P = 0.02) portions increased quadratically, whereas valerate increased linearly (P < 0.001) with increasing field pea supplementation. Olson et al. (1999) and McCollum and Galyean (1985) reported increases in butyrate with DIP supplementation; other studies have reported little effect on butyrate with DIP supplementation (DelCurto et al., 1990; Köster et al., 1996). Similar to our study, Olson et al. (1999) and Köster et al. (1996) reported that isobutyrate, valerate, and isovalerate increased linearly as supplemental DIP was increased.
No differences (P = 0.33) were detected for rate of in situ DM disappearance of forage (Table 6). Energy supplementation in low-quality, forage-based diets often decreases forage digestibility (Caton and Dhuyvetter, 1997), and DIP supplementation in low-quality, forage-based diets often increases forage digestion (Köster et al., 1996; Bodine et al., 2000; Bandyk et al., 2001). Field pea supplementation does not seem to decrease forage digestion, perhaps because of lower starch and higher DIP levels than cereal grains. No differences were detected for rate of in situ forage NDF (P = 0.52) and N (P = 0.12) disappearance. Krysl et al. (1989) reported no differences in in situ NDF disappearance of forage with SBM and sorghum supplementation. There were no differences (P = 0.32) in rate of field pea in situ DM disappearance with an increasing level of supplementation.
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Implications |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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1 Correspondence: 177 Hultz Hall (phone: 701-231-7660; fax: 701-231-7590; e-mail: glardy{at}ndsuext.nodak.edu).
Received for publication April 2, 2003. Accepted for publication April 5, 2004.
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Literature Cited |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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