| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
ANIMAL NUTRITION |
* Departament de Ciència Animal i dels Aliments, and
and
Departament de Biologia Cellular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
 |
Abstract |
|---|
 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
|---|
0.06) for corn- than barley-based diets. Ammonia N concentration was lower in vitro (P = 0.006) and tended to be lower in vivo (P = 0.07) for corn- than barley-based diets. In vitro, pH could be reduced from 6.4 to 5.8 for 12 h/d without any effect on ruminal fermentation or microbial protein synthesis. In summary, ruminal synchronization seemed to have positive effects on in vitro fermentation, but in vivo recycling of endogenous N or intake differences could compensate for these effects.
Key Words: bovine • high-concentrate diet • nonstructural carbohydrates • protein synchrony • ruminal fermentation
|
INTRODUCTION |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
|---|
). Corn and barley are the main cereal grains used in high-concentrate beef cattle diets. Barley has a lower content of NSC but a greater rate and extent of ruminal degradation than corn (Herrera-Saldana et al., 1990b). Although there is extensive research on the effects of these NSC sources on microbial fermentation and animal performance using dairy cattle diets (Nocek and Russell, 1988; Herrera-Saldana et al., 1990a; Casper et al., 1999), few efforts have been made with high-concentrate beef cattle diets to improve ruminal fermentation by synchronizing these energy sources with protein supplements having similar degradation characteristics. High-concentrate diets are rapidly fermented in the rumen, leading to high concentrations of VFA in ruminal fluid and relatively low ruminal pH (Beauchemin et al., 2001). Low ruminal pH may affect fiber and protein degradation (Hoover, 1986; Shriver et al., 1986) and the efficiency of microbial protein synthesis (Strobel and Russell, 1986). The objectives of this work were to examine the effects of synchrony of nutrient release from NSC and protein sources, with different rates and extents of ruminal degradation, on: 1) ruminal fermentation and N metabolism studied in vivo and in vitro; and 2) intake and apparent total tract digestibility for heifers fed high-concentrate diets. We hypothesized that synchronizing energy and protein release from cereal grains and protein sources would improve ruminal fermentation and microbial protein synthesis. Moreover, these effects could vary in different ruminal pH conditions; thus, in the in vitro trial, we tested 2 pH: a constant pH of 6.2 and a variable pH, with 12 h at pH 6.4 and 12 h at pH 5.8.
|
MATERIALS AND METHODS |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
|---|
), and SFM has a greater rate of protein degradation in the rumen than SBM (28.3 vs. 8.1%/h, respectively; Rotger et al., 2006a). Barley and SFM were mixed to synchronize rapid fermentation, and corn and SBM to synchronize slow fermentation. Two unsynchronized diets with a rapidly and a slowly fermenting component were formulated by mixing barley with SBM or corn with SFM. From these combinations, 4 complete mixed diets were formulated according to NRC (1996), with a forage to concentrate ratio of approximately 10:90 (Table 1). Barley straw, chopped coarsely to approximately 7 cm in length, was the forage source. The proportion of total dietary CP supplied by SBM or SFM was 32% in the diets based on barley and 57% in the diets based on corn. Concentrate and straw were manually mixed before feeding once daily (at 0830).
|
The ruminal fistulation was performed, under local anesthesia and with full aseptic precautions, 3 wk before the beginning of the experiment. The research protocol was approved by the Institutional Animal Care and Use Committee of the Universitat Autònoma de Barcelona.
Sample Collection and Analyses.
The experiment consisted of 4 periods of 28 d; 14 d for diet adaptation, and 14 d for sample collection. Body weight was recorded before feeding on 3 consecutive days at the beginning and at the end of the trial and on d 1 of each experimental period. To ensure ad libitum intake, refusals were weighed daily before feeding and the offered ration was 110% of the previous day’s intake. From d 1 through 3, the new experimental diet was introduced progressively. To calculate DM and nutrient intake, from d 15 through 19, feed and refusal samples were collected and composited within heifer and period. On d 17, a 500-mL sample of ruminal contents was collected with a vacuum pump from different locations in the rumen, before the morning feeding and at 2, 4, 8, 12, 16, and 24 h after feeding, and squeezed through 2 layers of cheesecloth. After sampling, extra ruminal fluid was returned to the rumen. The pH of the ruminal fluid was measured immediately and 2 subsamples were taken at each time. First, a 4-mL subsample of strained fluid was acidified with 4 mL of 0.2 N HCl, and frozen. Samples were later thawed in the refrigerator overnight, centrifuged at 25,000 x g for 20 min, and the supernatant analyzed for ammonia N by spectrophotometry (Chaney and Marbach, 1962). Second, 1 mL of a solution made up of 2 g/L of mercuric chloride (to impede microbial growth), 20 mL/L of orthophosphoric acid, and 2 g/L of 4-methylvaleric (internal standard) in distilled water was added to 4 mL of strained ruminal fluid, which was then frozen (Jouany, 1982). Volatile fatty acids were subsequently analyzed with a polyethylene glycol, nitroterephthalic acid-treated capillary column (BP21, SGE, Europe Ltd., Buckinghamshire, UK) by gas chromatography using the G1530A (6890) model of the Hewlett Packard gas chromatograph (Hewlett Packard GmbH Chemische Analysentechnik, Waldbronn, Germany).
To estimate fecal output and calculate the apparent total tract digestibility afterwards, from d 20 through 28 of each period (6 d of adjustment, 3 d of sampling) rations were thoroughly mixed with chromic oxide (1 g/kg of DM). Feed, refusals, and fecal samples were collected daily on the sampling days. Fecal grab samples (approximately 300 g on a wet weight basis) were collected twice a day (0900 and 1600), and dried at 103° C for 48 h. Chromium content of feed, refusals, and feces was determined according to the procedure of Le Du and Penning (1982) by atomic absorption spectrophotometry. For fecal chemical analysis, a portion of fecal samples was composited within heifer and period.
Feed, refusals, and fecal samples were analyzed for DM (24 h at 103° C) and ash (4 h at 550° C). Nitrogen content was determined using the Kjeldahl method (method 976.05; AOAC, 1990) with Se as catalyst. Neutral detergent fiber content of feed and refusals was determined according to the method of Van Soest et al. (1991) with sodium sulfite and heat stable 
-amylase, and was expressed without residual ash.
Calculations.
Total tract apparent digestibility was calculated as 1 minus the quotient between fecal output and intake. Ruminal fluid pH, ammonia N, and VFA measurements after feeding were averaged across time by calculating the area under the ruminal data vs. time curve and dividing by total time (Pitt and Pell, 1997). The same procedure was used to calculate mean daily hours and area under the curve at pH 5.8 (Nocek et al., 2002). The pH change was calculated as the difference between greatest and lowest pH for each heifer and period.
Statistical Analyses.
Data were analyzed using the PROC MIXED procedure (version 8.2, SAS Inst. Inc., Cary, NC) for a Latin square design with a 2 x 2 arrangement of treatments (Littell et al., 1996). The model accounted for the effect of protein source, NSC source, the interaction of protein x NSC sources, and period as fixed effects. Animal was considered a random effect. Effects were considered significant at P 0.05. When significant differences were detected, differences among means were tested using Tukey’s multiple comparison test.
Ruminal data collected at different times after feeding were analyzed using the PROC MIXED procedure for repeated measures. The model contained the same fixed effects as described before, except that time after feeding and its interaction with main factors were included. Time after feeding was the repeated factor, and the subject was the interaction of heifer x period, nested within treatment. For each variable analyzed, data were subjected to 4 covariance structures: variance components, compound symmetric, one-band unstructured, and autoregressive of order 1. The covariance structure that yielded the smaller Akaike and Schwarz’s Bayesian criterion was considered to be the most desirable for analysis.
In Vitro Trial
Apparatus and Experimental Design.
To study the effects of protein and NSC sources and pH on microbial fermentation and nutrient flow, eight 1,320-mL dual-flow continuous culture fermenters, as developed by Hoover et al. (1976), were used in 3 consecutive periods in a 2 x 2 x 2 arrangement of treatments.
Dietary treatments were the same as in vivo, and each diet was tested at constant (6.2) or variable pH (12 h at pH 6.4 and 12 h at pH 5.8). Variable pH was designed to simulate the subclinical acidosis frequently associated with the feeding of high-concentrate diets (Beauchemin and Rode, 1997). Schwartzkopf-Genswein et al. (2003) considered subclinical acidosis to be when ruminal pH was below 5.8 for 12 h/d. Consequently, 8 treatments were used: 1) Barley-SBM, pH 6.2; 2) Barley-SBM, pH 6.4 to 5.8; 3) Barley-SFM, pH 6.2; 4) Barley-SFM, pH 6.4 to 5.8; 5) Corn-SBM, pH 6.2; 6) Corn-SBM, pH 6.4 to 5.8; 7) Corn-SFM, pH 6.2; and 8) Corn-SFM, pH 6.4 to 5.8. The diets were ground through a 1.5-mm screen (hammer mill, P. Prats S. A., Sabadell, Spain), and 95 g (DM basis) was fed daily to each fermenter in 3 equal portions every 8 h. The temperature was maintained at 39° C, and the pH was maintained at the programmed level by infusion of 3 N HCl or 5 N NaOH solutions. Anaerobic conditions were maintained by infusion of N2 at a rate of 40 mL/min. Fermentation conditions were monitored and controlled by a computer and a Programmable Linear Controller (FieldPoint, National Instruments, Austin, TX). Artificial saliva (Weller and Pilgrim, 1974) was continuously infused into flasks and contained 0.4 g/L of urea to simulate recycled N. Liquid and solid dilution rates were maintained at 9 and 6%/h, respectively, similar to values previously observed in vivo with heifers fed high-concentrate diets (Devant et al., 2001; Rotger et al., 2005, 2006a).
The fermenters were inoculated with a composited ruminal fluid taken from 4 ruminally cannulated growing heifers (BW of 375 kg) fed ad libitum a high-concentrate diet (15.2% CP and 2.75 Mcal of ME/kg of DM), containing as the main ingredients: 34.0% corn, 40.0% barley, 11.8% soybean meal, and 11.8% barley straw.
Sample Collection and Analyses.
The experiment consisted of 3 experimental periods of 8 d (5 d for adaptation and 3 d for sampling). During the sampling days, effluent collection vessels were maintained in a 4° C bath. Solid and liquid effluents were mixed and homogenized for 1 min and a 600-mL sample was obtained by aspiration. At the end of each period, effluent samples from the 3 sampling days were composited and mixed within each fermenter, and were homogenized for 1 min. Subsamples were taken for total N, ammonia N, and VFA analyses, and analyzed as described for the samples obtained in vivo. The rest of the sample was lyophilized. Dry samples were analyzed for DM and ash (as described before), and for purine content (as described below).
Bacteria were isolated from the fermenter flasks on the last day of each period. Solid- and liquid-associated bacteria were isolated using a combination of several detachment procedures (Whitehouse et al., 1994), which were selected to obtain the maximum detachment without affecting cell integrity. To remove attached bacteria, small marbles (30 of 2-mm and 15 of 4-mm diameter) and a solution made with 0.2 g of methyl-cellulose in 100 mL of distilled water were added to each fermenter flask and mixed at 30° C for 1 h. After incubation, the fermenter flasks were refrigerated at 4° C for 24 h, and were subsequently agitated for 1 h to dislodge loosely attached bacteria. Finally, the fermenter content was filtered through 2 layers of cheesecloth and washed with saline solution (NaCl, 8.5 g/L). Bacterial cells were isolated within 4 h by differential centrifugation at 1,000 x g for 10 min to eliminate feed particles, and the supernatant was centrifuged at 20,000 x g for 20 min to isolate the bacterial pellet. Pellets were rinsed twice with saline solution, and re-centrifuged at 20,000 x g for 20 min. To prevent contamination of bacteria with ash, the final pellet was recovered with distilled water. Bacterial cells were lyophilized and analyzed for DM, ash, N, and purine contents. The purine content in bacteria and effluent samples was determined by HPLC (Balcells et al., 1992) using allopurinol as the internal standard. Organic matter digestion, and flows of nonammonia, microbial and non-ammonia-nonmicrobial N were calculated as described by Stern and Hoover (1990).
Statistical Analyses.
Data were analyzed as a completely randomized design with a 2 x 2 x 2 arrangement of treatments, using the Proc Mixed procedure (Littell et al., 1996) of SAS (SAS Inst. Inc.). The model contained the effect of pH, protein source, NSC source, and the interaction of protein x NSC sources as fixed effects. Fermenter and period were considered random effects. Effects were considered significant at P 0.05. When significant differences were detected, differences among means were tested using the Tukey’s multiple comparison test.
|
RESULTS AND DISCUSSION |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
|---|
Intake of DM and OM tended to be greater (P 0.059) for the corn than for the barley-based diets (Table 2). This difference became significant (P 0.015; data not shown) when expressed as grams per kilogram of BW0.75. Previous studies with dairy cattle reported greater intake in corn- than barley-based diets, mainly due to greater palatability of corn (McCarthy et al., 1989; Casper et al., 1994, 1999). Despite the difference in DM and OM intake among diets, no differences were detected in CP intake due to lower than formulated CP content of the corn-based diets (13.1 vs. 14.1% for analyzed and formulated CP content of corn-based diets, respectively). Neutral detergent fiber intake tended to be greater for the SFM diet (P 0.052) when corn was the NSC source, but not when combined with barley (NSC x CP interaction, P 0.055). Conversely, intake of NDF from roughage was greater (P = 0.013) when SBM was the protein source. Because SFM has greater NDF content than SBM, a greater straw content was incorporated into SBM-based diets.
|
). Values of apparent total tract digestibility were slightly lower than values obtained by Herrera-Saldana et al. (1990a) with dairy cattle fed a 35:65 forage:concentrate diet. Boss and Bowman (1996a) and Surber and Bowman (1998) reported greater total tract DM and OM digestibility for barley- than corn-based diets fed to steers. However, McCarthy et al. (1989) and Khorasani et al. (2001) did not observe differences in the apparent total tract digestibility in dairy cows, arguing that the lower ruminal degradability of cornstarch could be compensated with greater postruminal digestion.
No differences were detected among treatments for average ruminal pH (6.5 ± 0.14; Table 3) and its daily postprandial evolution (NSC x CP x time, P = 0.32; Figure 1). The amount of time that pH was below pH 5.8 was not affected by NSC or protein source; and decreases in ruminal pH below pH 6 for less than 4 h may have negligible effects on ruminal fermentation (Sauvant et al., 1999). Khorasani et al. (2001) observed that the average pH was not affected by the grain source, but the rate of decrease of pH after feeding was faster for cows fed barley than for cows fed corn. In barley-based diets, the highest pH was greater (P = 0.041) when combined with SBM, and the pH change tended to be greater for the desynchronized diets (P = 0.10).
|
|
) tended to be lower (P = 0.075) for corn-based diets and below or at the lowest level of the ranges to maximize microbial protein synthesis (3.3 to 8.5 mg/100 mL; Kang-Meznarich and Broderick, 1981). Because of greater prefeeding values and greater diurnal fluctuation for the barley-than corn-based diets, a time after feeding x NSC x CP interaction (P < 0.001) was detected for postprandial evolution of NH3-N (Figure 1). Most studies in dairy cattle reported lower NH3-N concentration in barley- than corn-based diets, mainly due to the greater rate of NSC degradability of barley and the greater incorporation of NH3-N into microbial protein synthesis (Mc-Carthy et al., 1989; Casper et al., 1990, 1999). In contrast, Surber and Bowman (1998) reported a greater ruminal NH3-N concentration for steers fed barley than for steers fed corn.
The total VFA concentration (average of 116.4 ± 4.92 mM ) was similar to that of Rotger et al. (2005) for heifers of a similar age and fed high-concentrate diets. Total VFA concentration and postprandial evolution (Figure 1) were not affected by NSC or protein source (Table 3). Most research studies with dairy cattle reported a greater VFA concentration in barley-based diets, due to the greater rate of NSC degradability of barley (McCarthy et al., 1989; Khorasani et al., 2001); other studies reported no differences between barley-and corn-based diets (Casper and Schingoethe, 1989), or greater VFA concentration for corn-based diets (Casper et al., 1999). Surber and Bowman (1998) reported a greater VFA concentration in barley-based diets compared with corn-based diets with beef cattle. Molar proportions of individual VFA were not affected by NSC or protein source (Table 3) in agreement with Casper et al. (1999). Other studies with dairy cattle observed a greater concentration of propionate in barley-based diets, possibly because of greater degradation of starch in these diets (Casper and Schingoethe, 1989; McCarthy et al., 1989). Molar proportion of valerate was greater for the barley-based diets (P = 0.009), in agreement with Surber and Bowman (1998).
In Vitro Trial
The in vitro trial was designed to evaluate the effects of NSC and protein sources on microbial fermentation and nutrient flow maintained at a constant pH of 6.2, or 12 h at a pH of 6.4 and 12 h at a pH of 5.8, simulating subclinical acidosis. Significant interactions were found between NSC and protein sources, in disagreement with some in vitro (Newbold and Rust, 1992; Mansfield et al., 1994) and in vivo (Henning et al., 1993) studies that reported that ruminal fermentation was controlled by either availability of energy or protein and not by the interaction of these 2 nutrients.
True OM digestibility tended to be greater (NSC x CP interaction P = 0.072) for synchronized (barley-SFM and corn-SBM) than unsynchronized diets (barley-SBM and corn-SFM; Table 4). Although it is widely known that barley has a greater extent of ruminal degradation (Nocek and Russell, 1988; Herrera-Saldana et al., 1990b), some in vivo studies with steers fed high-concentrate diets based on barley or corn have failed to detect these differences in OM digestibility (Spicer et al., 1986; Surber and Bowman, 1998) or have observed a greater ruminal OM digestibility in corn-based diets (Boss and Bowman, 1996b).
|
) was lower (P = 0.006) in corn-based diets, in agreement with the in vivo trial. However, although the slightly lower CP content of corn-based diets could not have been the cause of the lower NH3-N concentration in the in vivo trial, because it was compensated for by a greater intake, it could be a valid argument in the in vitro trial, in which all diets had the same intake. The low NH3-N concentrations observed in corn-based diets did not seem to impair ruminal degradation of OM or microbial protein synthesis (Table 4). The high availability of energy from NSC may allow the incorporation of peptides and preformed AA into microbial cells, reducing the ruminal concentration of NH3-N without limiting microbial fermentation (Russell et al., 1983; Van Kessel and Russell, 1996; Russell, 1998). Barley protein is more degradable than corn protein (Spicer et al., 1986; Herrera-Saldana et al., 1990b), which most likely explains the greater NH3-N concentration in barley-based diets. Nonammonia N concentration was greater (P = 0.015) when SBM was the protein source. A trend in the NSC x CP interaction (P = 0.092) was detected for microbial protein flow (Table 4). Within each NSC source, microbial N tended to be greater (P = 0.092) in the synchronized diet. There is general agreement that energy source is the main factor determining microbial protein synthesis (Hoover and Stokes, 1991; Henning et al., 1993). Previous studies observed a greater flow of microbial N to the duodenum for barley-based than for corn-based diets fed to dairy cows (McCarthy et al., 1989) or steers (Spicer et al., 1986; Boss and Bowman, 1996b; Surber and Bowman, 1998). However, there is some disagreement whether synchronization between energy and protein sources would improve microbial growth. Some in vivo studies reported greater microbial protein synthesis for synchronized diets (Herrera-Saldana et al., 1990a; Casper et al., 1999), and others found no effect of synchronization (Henning et al., 1993; Mansfield et al., 1994; Richardson et al., 2003), concluding that ruminal fermentation may be limited by protein or energy availability rather than by lack of synchronization of release of these nutrients. Different NSC and protein sources may confound the effects of synchronization.
The efficiency of microbial protein synthesis, expressed as grams of microbial N per kilogram of OM truly digested in the rumen, tended to be greater (P = 0.077) when barley was the NSC source, in agreement with results reported by Boss and Bowman (1996b) with beef cattle. However, the present values were greater than those reviewed by Oldham (1984) for dairy cows. The high incorporation of peptides and preformed AA into microbial protein in high-concentrate diets might increase the efficiency of microbial protein synthesis (Russell, 1998).
Similar to true OM digestibility, a trend in the NSC x CP interaction (P = 0.067) was detected for total VFA concentration (Table 5), being greater for synchronized (barley-SFM and corn-SBM) than unsynchronized diets (barley-SBM and corn-SFM). The molar proportion of acetate tended to be greater (P = 0.055) and molar proportion of propionate tended to be lower (P = 0.068) in barley-based diets than in corn-based diets. Consequently, the acetate:propionate ratio was greater (P = 0.029) in the barley-based diets.
|
and Boss and Bowman (1996b), with steers limit-fed high-concentrate diets based on barley or corn, also reported a greater acetate:propionate ratio for barley-based diets. The molar proportion of valerate was affected by the protein source and was greater (P = 0.042) in SBM-based diets.
The fluctuation of pH studied in vitro simulated the subclinical acidosis frequently observed in feedlot cattle fed high-concentrate diets (Owens et al., 1998), even though it was not detected in the in vivo trial. Ruminal OM digestibility, microbial fermentation, and N metabolism were not affected by the simulated ruminal subclinical acidosis. In agreement with the results of Calsamiglia et al. (2002), pH could be reduced from 6.4 to 5.8 for 12 h/d with small effects on ruminal fermentation and microbial protein synthesis. Continuous pH of 5.8 for 12 h/d may not be critical for amylolytic bacteria.
In summary, synchronization of NSC and protein sources for rapid or slow fermentation tended to result in greater OM digestion, VFA production, and flow of microbial N in a dual-flow continuous culture, but in vivo, synchronization had no effect on ruminal fermentation. Recycling of endogenous N or intake differences could compensate for the effects of synchronization observed in vitro. Moreover, heifers ate an average of 9 meals per day (Rotger et al., 2006b), which might have negated the effects of synchronization observed in vitro with 3 meals per day. The low ruminal NH3-N concentration observed in vivo and in vitro did not seem to impair ruminal fermentation, possibly because in high-concentrate diets there may be a high incorporation of peptides and preformed AA directly into microbial protein synthesis. Fluctuation of pH over a 12-h period had no effect on ruminal fermentation or microbial protein synthesis, and may not be critical for amylolytic bacteria. Barley-based diets resulted in a lower feed intake in vivo and in a greater efficiency of microbial synthesis estimated in vitro than did corn-based diets.
|
Footnotes |
|---|
2 Corresponding author: Alfred.Ferret{at}uab.es
Received for publication June 17, 2005. Accepted for publication November 17, 2005.
|
LITERATURE CITED |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
|---|
This article has been cited by other articles:
|
|
 |
|
  V. Fellner, J. C. Burns, and D. S. Marshall Effect of Feeding Corn, Hull-Less or Hulled Barley on Fermentation by Mixed Cultures of Ruminal Microorganisms J Dairy Sci, May 1, 2008; 91(5): 1936 - 1941. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. A. Cole and R. W. Todd Opportunities to enhance performance and efficiency through nutrient synchrony in concentrate-fed ruminants J Anim Sci, April 1, 2008; 86(14_suppl): E318 - E333. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Calsamiglia, P. W. Cardozo, A. Ferret, and A. Bach Changes in rumen microbial fermentation are due to a combined effect of type of diet and pH J Anim Sci, March 1, 2008; 86(3): 702 - 711. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Rotger, A. Ferret, X. Manteca, J. L. R. de la Torre, and S. Calsamiglia Effects of dietary nonstructural carbohydrates and protein sources on feeding behavior of tethered heifers fed high-concentrate diets J Anim Sci, May 1, 2006; 84(5): 1197 - 1204. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
); barley-sunflower meal (
); corn-soybean meal (
); and corn-sunflower meal (
). Diet x time after feeding interactions were P = 0.316 for ruminal pH; P = 0.860 for total VFA concentration; and P < 0.001 for ammonia N concentration.