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Effects of feeding Fermenten on ruminal fermentation in lactating Holstein cows fed two dietary sugar concentrations

Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada

¹ Corresponding author: masahito.oba{at}ualberta.ca

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGMENTS REFERENCES

 
This study was conducted to determine the effects of feeding Fermenten (Church and Dwight Co., Princeton, NJ) with or without dietary sucrose on ruminal fermentation, apparent total-tract nutrient digestibility, and nutrient utilization. Eight ruminally cannulated Holstein cows (163 ± 55 d in milk; mean ± standard deviation) were used in a replicated 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. Experimental diets were formulated with and without Fermenten (0 vs. 3.3% of dietary DM) at 2 dietary sugar concentrations (2.8 vs. 5.7%). Dietary treatment did not affect dry matter intake or apparent total-tract nutrient digestibility. Feeding Fermenten did not affect ruminal pH, but high-sugar diets tended to increase the daily minimum pH (5.61 vs. 5.42) and mean pH (6.17 vs. 6.30) compared with low-sugar diets. Ruminal ammonia concentration tended to be greater for cows fed Fermenten compared with control (18.1 vs. 15.9 mg/dL), but was not affected by dietary sugar concentration. Significant interactions between Fermenten and dietary sugar concentration were detected for some milk production responses. Fermenten treatment numerically increased milk fat yield (0.92 vs. 0.82 kg/d), 4% fat-corrected milk yield (24.3 vs. 21.9 kg/d), and milk energy output (18.2 vs. 16.4 Mcal/d) compared with control for cows fed low-sugar diets, but not for cows fed high-sugar diets. Increasing dietary sugar concentration did not enhance the effects of Fermenten, providing no support for the theory that synchronizing the availability of N and fermentable energy in the rumen improves nutrient utilization in lactating dairy cows.

Key Words: Fermenten • rumen pH • sucrose • sugar

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGMENTS REFERENCES

 
Rumen pH is determined by the balance between fermentation acid production in the rumen and its removal primarily by neutralization, absorption, and passage (Allen, 1997). Efficiency of microbial protein production, defined as microbial N production per unit of ruminally degraded OM, can be a factor affecting rumen pH as the OM degraded in the rumen is not available for fermentation acid production if it is utilized to yield microbial cells. According to the calculation shown by Allen (1997), increasing microbial efficiency from 20 to 30 g of microbial N/kg of ruminally degraded OM would decrease fermentation acid production by 12.5%. As microbial efficiency ranges from 10 to 50 g of microbial N/kg of ruminally degraded OM (Clark et al., 1992), alteration of microbial efficiency can be a factor affecting fermentation acid production and consequently rumen pH. However, little in vivo data are available in the literature to support this theory.

Microbial efficiency is affected by many factors including rumen pH (Strobel and Russell, 1986), rate of passage (Oba and Allen, 2000), and availability of N (Ricke and Schaefer, 1996). Argyle and Baldwin (1989) showed that addition of amino acids and peptides increases microbial efficiency in vitro. Fermenten (Church and Dwight Inc., Princeton, NJ) is a byproduct of fermentation that contains a high proportion of amino acids and short peptides (Lean et al. 2005). Previous in vitro studies have demonstrated that Fermenten increased the efficiency of microbial N production, nutrient digestibility, and the acetate to propionate ratio (Lean et al., 2005). Thus, it is hypothesized that feeding Fermenten to lactating dairy cows would increase ruminal pH. However, effects of Fermenten on in vivo ruminal fermentation have not been investigated extensively.

The rate of fermentation in the rumen is greater for sugar compared with other carbohydrate fractions (Sniffen et al., 1992), and Lean et al. (2005) showed that Fermenten increased in vitro microbial efficiency to a greater extent with additional dietary sugar. Therefore, the objective of this study was to determine the effects of dietary inclusion of Fermenten on ruminal fermentation, apparent total-tract nutrient digestibility, and nutrient utilization in lactating dairy cows fed 2 dietary sugar concentrations.

	MATERIALS AND METHODS

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Experimental Design
All experimental procedures used in this study were approved by the Faculty Animal Policy and Welfare Committee at the University of Alberta and were performed according to the guidelines of the Canadian Council of Animal Care (Ottawa, Ontario, Canada). Eight ruminally cannulated lactating Holstein cows from the Dairy Research and Technology Center (Edmonton, Alberta, Canada) were used in this study. This study was conducted from October 2006 to January 2007. At the start of the study, the mean ± SD for BW, BCS, and DIM were 616 ± 38 kg, 2.64 ± 0.32, and 163 ± 55, respectively. Throughout the study cows were housed in individual tie stalls and offered 2 h of exercise daily. Cows were fed a TMR ad libitum once daily at 0900 h and milked twice daily at 0400 and 1500 h.

Cows were randomly assigned to treatments in a replicated 4 x 4 Latin square design balanced for carry-over effects with a 2 x 2 factorial arrangement of treatments. Each 21-d period consisted of a 14-d diet adaptation period and 7-d collection period. Treatments were dietary inclusion of Fermenten (0 vs. 3.3% of dietary DM) and dietary sugar concentration (2.8 vs. 5.7%). Fermenten was included by replacing canola meal and urea, and sucrose was included by replacing cracked corn grain to prepare high-sugar diets (Table 1). Diets were formulated using the Cornell-Penn-Miner System (CPM Dairy, Version 3.0.8; Cornell University, Ithaca, NY; University of Pennsylvania, Kennett Square, PA; and William H. Miner Agricultural Research Institute, Chazy, NY) to supply adequate NE_L and MP for a 650-kg cow producing 35 kg of milk with a fat concentration of 3.5%. All diets were formulated to contain similar CP and forage NDF concentrations.

Body weight was measured on 2 consecutive days immediately before the start of the study and on the last 2 d of each period. Body condition score was determined using a 5-point scale (Wildman et al., 1982) immediately before the start of the study and on the last day of each period by 2 experienced technicians. Milk yield was recorded on d 15, 16, and 17 of each period, and milk samples were collected for the corresponding 6 consecutive milkings.

Ruminal pH was measured every 30 s continuously for 72 h starting d 15 of each period using the Lethbridge Research Center pH monitoring system (Dascor, Escondido, CA) as described by Penner et al. (2006). Daily minimum, mean, and maximum pH as well as the duration and area that ruminal pH was below 5.8 were determined as described by Penner et al. (2007).

Blood, rumen fluid, and fecal samples were collected every 9 h over a 72-h duration starting on d 18 of each experimental period. Blood was sampled from the coccygeal vessel into a vacutainer tube containing Na heparin (Fisher Scientific Company, Nepean, Ontario, Canada) and was immediately placed on ice until centrifugation at 2,500 x g for 20 min. Harvested plasma was stored at –20°C. Ruminal digesta were collected via the ruminal cannula from the cranial sac, ventral sac, and caudal dorsal sac and strained through a perforated material (Peetex, pore size = 355 µm; Sefar Canada Inc., Scarborough, Ontario, Canada) immediately after collection. Samples were placed on ice until being stored at –20°C. Fecal samples were collected manually from the rectum and stored at –20°C. Plasma, rumen fluid, and fecal samples were composited to yield one sample per cow per period for further analysis.

An additional sample of ruminal contents was collected from the rumen fluid and rumen mat interface at 1200 h (3 h after feeding) on d 20 of period 4. Protective gloves were replaced before sampling from each cow, and rumen contents were collected into sterile 140-mL vials, immediately placed on dry ice, and stored at –80°C until bacterial profile analysis.

Chemical Analysis
Period composites of feed ingredients, refusals, and feces were dried in a forced-air oven for 48 h at 55°C to determine DM concentrations. Dried samples were ground to pass through a 1-mm screen using a Wiley mill (Thomas-Wiley, Philadelphia, PA). Samples were analyzed for concentrations of DM, ash, NDF, indigestible NDF, CP, crude fat, and total ethanol-soluble carbohydrates. Dry matter concentration was determined after drying samples at 135°C for 2 h (AOAC, 2002; method 930.15). Ash concentration was determined after placing the samples in a muffle furnace for 5 h at 550°C (AOAC, 2002; method 942.05). Neutral detergent fiber concentration was determined using amylase and sodium sulfite (Van Soest et al., 1991). Indigestible NDF was used as an internal marker to determine the apparent total-tract digestibility (Cochran et al., 1986). The indigestible NDF concentration was determined for ingredient, refusal, and fecal samples by placing 2 g of each sample into a nitrogen free polyester bag (5 x 10 cm, pore size = 50 µm; R510, Ankom Technology, Macedon, NY). Bags were incubated in triplicate in the rumen of a lactating cow for 120 h. Crude protein concentration was quantified by flash combustion with gas chromatography and thermal conductivity detection (Carlo Erba Instruments, Milan, Italy; Rhee, 2005). Crude fat was determined using the Ankom^XT15 Extractor (Ankom Technology). Total ethanol-soluble carbohydrates were determined according to Hall et al. (1999) and Dubois et al. (1956) using sucrose as a standard carbohydrate.

Milk samples were analyzed for milk fat, CP, lactose, and MUN by infrared spectroscopy (MilkoScan 605, Foss Electric, Hillerød, Denmark; AOAC, 1996) at the Alberta Central Milk Testing Laboratory (Edmonton, Alberta, Canada). Period composite samples, prepared based on the yield of milk fat from each milking, were also analyzed to determine milk fatty acid profile. Milk fatty acids were extracted and, after esterification, fatty acid profiles were determined using gas chromatography (Khorasani et al., 1991).

Plasma samples were analyzed for glucose, insulin, BHBA, and plasma urea nitrogen concentrations. Plasma glucose concentration was measured using a glucose oxidase/peroxidase enzyme (P7119, Sigma, St. Louis, MO) and dianisidine dihydrochloride (F5803, Sigma). Absorbance was determined with a plate reader (SpectraMax 190, Molecular Devices Corp., Sunnyvale, CA). A commercial kit was used to determine the plasma concentration of insulin (Coat-A-Count, Diagnostic Products Corporation, Los Angeles, CA). Plasma BHBA concentration was determined using the enzymatic oxidation of BHBA to acetoacetate using 3-hydroxybutrate dehydrogenase (H6501, Roche, Mississauga, Ontario, Canada), and the concomitant reduction of NAD to NADH was determined using a plate reader at the wavelength of 340 nm. The concentration of plasma urea N was determined according to Fawcett and Scott (1960) with modifications for use with a plate reader.

Rumen fluid samples were centrifuged at 26,000 x g for 15 min, and supernatants were collected. The centrifuged supernatant was analyzed for VFA concentration by gas chromatography according to the method described by Khorasani et al. (1996). Rumen NH₃-N was determined colorimetrically as described by Fawcett and Scott (1960). Rumen digesta samples collected for bacterial profiling were analyzed using PCR-coupled denaturing gradient gel electrophoresis technique (Guan et al., 2008).

Statistical Analysis
Data were summarized by cow and period and analyzed using the PROC MIXED procedure of SAS (version 9.1; SAS Institute Inc., Cary, NC). The model included the random effect of cow nested in square and the fixed effects of square, period, and treatment. Preplanned orthogonal contrasts were made to determine the effects of dietary sugar concentration, dietary inclusion of Fermenten, and their interactions. For response variables with a significant sugar x Fermenten interaction, a Bonferroni test was used to separate treatment means. Significance was declared when P < 0.05 and tendencies were discussed when P < 0.10.

	RESULTS

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DMI and Ruminal Fermentation
Dietary treatment did not affect DMI, averaging 21.7 kg/d (Table 2). Feeding Fermenten did not affect any ruminal pH measurements, but high-sugar diets tended to increase (P = 0.09) the daily minimum (5.61 vs. 5.42) and mean pH (6.17 vs. 6.30) compared with low-sugar diets. In addition, cows fed high-sugar diets tended to have a shorter duration that rumen pH was below 5.8 compared with cows fed low-sugar diets (139 vs. 283 min/d; P = 0.08), but the area that ruminal pH was below 5.8 was not affected by dietary treatment.

There were no detectable treatment effects on the bacterial profile as determined through PCR-coupled denaturing gradient gel electrophoresis analysis (Figure 1). Overall, there was greater than 78% similarity between band patterns across treatments.

View larger version (40K): [in this window] [in a new window]   Figure 1. The PCR-coupled denaturing gradient gel electrophoresis for ruminal bacteria profile 3 h after feeding for cows fed Fermenten (Church & Dwight Inc., Princeton, NJ) with 2 dietary sugar concentrations; LSNF = low sugar, no Fermenten; LSWF = low sugar with Fermenten; HSNF = high sugar, no Fermenten; HSWF = high sugar with Fermenten.

Cows fed high-sugar diets had a greater BW gain compared with cows fed low-sugar diets (1.08 vs. 0.60 kg/d; P = 0.05). A sugar x Fermenten interaction was detected for BCS change/21 d (P = 0.03) where cows fed Fermenten in the high-sugar diet numerically gained more BCS than cows fed Fermenten in the low-sugar diet (0.25 vs. 0.06 /21 d); but not in the high-sugar diet.

Dietary treatment did not affect the concentrations of short- or mid-chain fatty acids in milk although Fermenten increased the concentration of C22:5 (Table 6). Interactions between Fermenten and dietary sugar concentration were detected for the concentrations of oleic (C18:1 cis), linoleic (C18:2), and linolenic (C18:3) acids; feeding Fermenten numerically increased concentration of these unsaturated fatty acids compared with controls for cows fed low-sugar diets, but apparently did not affect the concentration in high-sugar diets.

	DISCUSSION

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The tendency of higher ruminal pH for cows fed high-sugar diets may indicate that the disappearance of sugars from the rumen does not necessarily increase fermentation acid production in the rumen. Ribeiro et al. (2005) showed that bacterial OM production in continuous culture increased linearly from 12.3 to 14.4 g/d as the concentration of sucrose increased from 0 to 8%. If sucrose supplementation increased microbial cell yield, ruminally degraded OM available for fermentation acid production would be reduced (Allen, 1997). However, ruminal ammonia concentration was not affected by dietary sugar concentration, providing no support for this speculation. Alternatively, sucrose may have provided less carbon than starch as sucrose hydrolysis yields fewer monomers compared with starch hydrolysis (x 1.05 vs. x 1.11; Hall and Herejk, 2001). Although the rate of fermentation is greater for sugar than for other carbohydrate fractions (Sniffen et al., 1992), overall fermentation and microbial protein production may not be maximized from sugar fermentation compared with starch or pectin fermentation (Hall and Herejk, 2001). However, cows fed high-sugar diets gained more BW than cows fed low-sugar diets, whereas milk energy output was not affected by dietary sugar concentration. Thus, it is not likely that energy intake is reduced by the replacement of cracked corn grain by sucrose.

It is also possible that bacteria convert soluble dietary sugars to glycogen as a short-term storage of energy that can be utilized later, thereby temporarily reducing fermentation acid production. For example, Hall and Weimer (2007) demonstrated in vitro that the addition of 65, 130, or 195 mg of sucrose to 130 mg of isolated NDF resulted in increased glycogen concentration at 0 and 4 h but found that glycogen concentration decreased thereafter. Other studies have demonstrated that inclusion of sugar may result in increased solid or liquid passage rate from the rumen (Rooke et al., 1987; Sutoh et al., 1996). If feeding sucrose increased the passage rate, it may also have decreased the amount of carbohydrate fermented in the rumen and thereby reduced fermentation acid accumulation. Another possible explanation is monosaccharide transport across the ruminal epithelial cells. Ruminal epithelial cells have both sodium-glucose linked glucose transporters (Aschenbach et al., 2000) and facilitated glucose transporters (Aschenbach et al., 2005), which allow for monosaccharide transport such as glucose to be absorbed without being fermented to VFA in the rumen. However, the quantitative significance of glucose transport across ruminal epithelia is not known. Further research is warranted to understand the metabolism of sugar in the rumen.

In the current study, Fermenten inclusion had minimal effects on ruminal fermentation. However, a tendency for greater ammonia concentration was observed when cows were fed diets containing Fermenten. Previous in vitro studies showed that Fermenten increased CP digestibility and ammonia concentration (Lean et al., 2005). In addition, Broderick et al. (2000) reported that cows fed Fermenten had greater ruminal ammonia concentration compared with cows fed soybean meal. However, the tendency for elevated ammonia concentration cannot be fully attributed to the direct effect of Fermenten, but in part to greater dietary CP concentration for Fermenten treatments. Although all experimental diets were formulated to contain similar dietary CP concentration, analysis of feed ingredients that were collected during the study revealed that dietary CP content was slightly higher for Fermenten treatment compared with control.

Although ruminal pH and VFA concentrations were not altered by feeding Fermenten, it is apparent that Fermenten modified ruminal fermentation in relation to biohydrogenation of unsaturated fatty acids for cows fed low-sugar diets. Linoleic and linolenic acids in milk are derived from dietary lipids that escape biohydrogenation by ruminal microbes as mammals are unable to synthesize them. Thus, greater concentrations of linoleic and linolenic acids in milk indicate less biohydrogenation of fatty acids in the rumen. Fermenten treatment had numerically greater concentrations of linoleic and linolenic acids in milk fat than control for cows fed low-sugar diets, and overall, cows fed low-sugar diets had tendencies for lower ruminal pH than cows fed high-sugar diets. However, there were no interactions between sugar and Fermenten detected for ruminal pH; thus, it is unclear why the inclusion of Fermenten is associated with the inhibition of biohydrogenation in low sugar diets. Previously, the inclusion of sucrose has been shown to linearly reduce biohydrogenation of linoleic and linolenic acids in continuous culture (Ribeiro et al., 2005). But, in our study, the concentrations of linoleic and linolenic acids in milk fat were not affected by dietary sugar concentration.

Nutrient Utilization
Previous in vitro studies showed that Fermenten increased the efficiency of microbial N production (Lean et al., 2005). Although greater microbial N production potentially contributes to greater milk production by increasing the supply of true protein available for absorption and metabolism, the current study was not designed to evaluate treatment effects on milk or milk protein yield. Cows used in this study were in mid to late lactation and had a low level of milk production (average milk yield during the study was 25.3 kg/d). Thus, all experimental diets were expected to provide sufficient energy and MP to meet their requirements, and it is not likely that the CP contents of the dietary treatments would affect milk or milk protein yield in this study. The primary objective of the current study was to determine whether feeding Fermenten affects ruminal fermentation. The use of cows in late lactation for this study was expected to allow us to evaluate treatment effects on milk fat concentration and energy partitioning because rumen fermentation affects milk fat concentration of low-yielding cows to a greater extent than that of high-yielding cows (Bradford and Allen, 2004).

We observed that cows fed Fermenten in the low-sugar diet numerically increased the yields of milk fat and FCM, and milk energy output, but we had not expected to observe these responses. In previous in vitro studies, Fermenten has been shown to modify rumen fermentation by mixed ruminal microbes, resulting in improvements in the efficiency of microbial nitrogen production, increases in CP, OM, and DM digestibility, and an increase in the acetate to propionate ratio (Lean et al., 2005). In general, providing additional sugar, which ferments rapidly in the rumen, enhanced the previously mentioned effects (Lean et al., 2005). As such, we hypothesized that feeding Fermenten would improve nutrient utilization to a greater extent with the dietary inclusion of sucrose. However, feeding Fermenten in a high-sugar diet did not improve lactation performance in the current study. Although feeding Fermenten in the high-sugar diet numerically increased milk CP concentration, the physiological implication of this observation is not clear because milk yield was numerically lower for this dietary treatment and as a result, milk CP yield was not affected by treatment. Synchronizing ruminal availability of N and energy is expected to improve efficiency of nutrient utilization and animal performance in theory, but this concept has not been supported by data in the literature (Hall and Huntington, 2008). Our results suggest that the combination of Fermenten and additional dietary sucrose do not improve nutrient utilization and further question the theory of synchronizing ruminal N and energy fermentation.

	CONCLUSIONS

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Contrary to the pretrial hypothesis, replacing canola meal and urea with Fermenten did not increase ruminal pH or nutrient digestibility although it may decrease biohydrogenation of unsaturated fatty acids in the rumen. In addition, feeding Fermenten increased milk energy output for cows fed low-sugar diets, but not for cows fed high-sugar diets in the present study. These data indicate that the combination of Fermenten and supplemental sucrose do not improve the efficiency of nutrient utilization and therefore, do not provide support for the theory that synchronizing the availability of N and fermentable energy in the rumen improves nutrient utilization in lactating dairy cows, at least with this combination of substrates. Increasing dietary sugar concentration by replacing cracked corn grain with sucrose increased ruminal pH, but for reasons that cannot be explained with the data obtained from the current study. Ruminal fermentation and metabolism of sugars warrant further investigation.

	ACKNOWLEDGMENTS

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The authors acknowledge the financial support of Church & Dwight Co. Inc. (Princeton, NJ), Alberta Livestock Industry Development Fund, and Agriculture and Food Council. The authors also thank the Dairy Research and Technology Centre staff for general animal husbandry, and C. Silveira, M. Bal, P. Regmi, L. Chow, and S. Vishantha-Patabendi for technical assistance.

Received for publication September 12, 2008. Accepted for publication November 15, 2008.

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