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Fibrozyme, the First Protected Enzyme for Ruminants: Improving Fiber Digestion and Animal Performance |
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Author: D. HOWES, J. M. TRICARICO, K. DAWSON and P. KARNEZOS (Courtesy of Alltech Inc.)
The enhancement of the natural capability of the ruminant digestive tract to extract nutrients from the feed has been an important goal for nutritionists for well over half a century. It is not too surprising that the main focus has primarily been on feeds of lower digestibility. However, rising feed prices have increased the need for producers of ruminant livestock to look at new biotechnological feeding programs that will maximize the utilization of nutrients from feedstuffs.
One approach has been an attempt to increase the rumen digestive capacity by stimulating an increase in rumen microflora with the supplementation of specific strains of live viable yeast cultures that stimulate the production of a major fiber digesting bacterium, Ruminococcus albus (Dawson and Girard, 1997).
Another approach has been an attempt to modify feed materials themselves to render them more readily digestible with enzymes. Recently, attempts have been made to define the conditions under which exogenous enzymes are most able to elicit a positive production response in ruminants (Feng et al., 1996; Sanchez et al., 1996). In comparison with use in monogastrics, research into the application of enzyme technology for use in ruminant production is in its infancy. This paper will suggest how enzymes might be useful in ruminant diets and describe both performance and rumen function studies on a new fibrolytic enzyme supplement, Fibrozyme.
STABILITY OF ENZYMES IN THE RUMEN
When considering the exceptional fiber-digesting capacity of the rumen, it is difficult to see how fibrolytic enzymes added to forages prior to consumption could further improve the utilization of forages by ruminants. On the other hand, digestion of forages in ruminants is considerably less than complete; and fiber digestion rate has a large impact on intake, especially where tropical forages are concerned. Supplemental fibrolytic enzymes may act by initiating degradation of plant structural polysaccharides prior to ingestion and ruminal digestion, or by complementing the fibrolytic enzymes produced by ruminal microorganisms.
Until recently, it was taken for granted that supplemental enzymes not binding to their target substate would be rapidly degraded by microbial or host proteolytic enzymes in the digestive tract. However, these concerns may prove to be unfounded. The extensive glycosylation of fungal enzymes is now known to protect them against proteolytic attack in monogastric animals (Chesson, 1993). Recent improvements in enzyme technology have allowed selection of better strains of organisms and identification of enzymes with more clearly defined main and partial activities. Commercial enzyme products marketed as feed additives are produced from fermentation extracts of bacterial (Bacillus spp.) or fungal (e.g., Aspergillus, Trichoderma spp.) origin.
An excellent review by Beauchemin and Rode (1996) discussed the problems of comparing and evaluating some of the older studies with enzymes in ruminant rations. We would refer the reader to this review for a better understanding of enzymes for ruminants. It should be considered that at present, virtually all our experience with enzymes comes from relatively crude bacterial and fungal preparations. The normal commercial preparation of a ‘cellulase’enzyme may contain a wide variety of activities in addition to cellulase. Some of these separate activities may play an important role in the final true digestibility of a substrate. The natural hesitancy of enzyme producers to reveal precise details of activity profiles of products and the unhelpful situation regarding assay analysis makes the comparison of different enzymes only really possible with animal production and cost-benefit data.
ENZYMES IN ACTION
It is not clear whether the major benefit of enzyme application occurs in prefeeding treatment or after the feed enters the rumen. The benefit may also involve some degree of protection of the enzyme from rumen microbial breakdown. The conditions in the rumen may be more constant for pH and temperature and, therefore, more ideal for enzyme activity. However, there is also evidence that when enzymes are added directly to grass and silages they have a definite benefit in improving digestibility of forages. Therefore, it may be useful to consider the action of enzymes with regard to both pretreatment and ruminal or direct-fed applications.
PRE-TREATMENT/STORAGE APPLICATION
Treatment of feed or forage well ahead of feeding such as in silage inoculant applications, allows the potential for increased rumen enzymatic activity.An increase of up to 10% in digestibility of straw was reported by Nakashima and Orskov (1989). More recently, it was reported by Beauchemin et al. (1995) that enzyme treatment of high-quality forages such as alfalfa and timothy grass during the cubing process could significantly increase nutrient value for steers by increasing average daily gain (ADG) by 30% and dry matter intake (DMI) by 10%.
Enzyme treatment of feed within a short time (a few minutes to an hour) of feeding is described as ‘direct fed’. In contrast to enzymatic pre-treatment, direct-fed enzymes rely on response within a quicker time frame and would be expected to act during digesta transit. This approach offers greater on-farm flexibility of enzyme use and will allow the farmer to maximize nutritive value of the cheaper home-grown forage crops and, therefore, reduce the costs of production much as the poultry or pig feed manufacture currently uses enzyme supplements.
There is still a major question as to the possibility of enzymes surviving in the rumen for sufficient time and at a sufficient activity to give a consistent effect on fiber digestibility. The levels of fibrolytic enzymes in the rumen are reported to be low (Vandevoorde and Verstaete, 1987). It was reported by Kopecny et al. (1987) that cellulase stability in the rumen is low. However, Forwood et al. (1990) found that when liquid enzymes were sprayed directly onto tall fescue a 5% increase in in vitro dry matter digestibility was found. Lewis et al. (1996) also showed a positive effect of adding enzymes to foragebased diets prior to feeding. This study, investigating effects of treating forage with enzyme 16 h before feeding, showed an increase in volatile fatty acid (VFA) production of 30%; but little effect on forage digestibility was noted when the enzyme was infused into the rumen directly. Therefore, it would appear that the means of delivering the enzyme into the rumen and the time allowed between treatment and feeding may be crucial.
DOSE/RESPONSE
Recent studies have reported performance differences from supplementing various levels of enzymes. This may partially help explain some of the variations that are shown in the literature. Beauchemin et al. (1995) have demonstrated that it is possible to over-treat as well as under-treat with enzymes when treating forage for beef animals. In a recent study Beauchemin and Rode (1996) made the point that many experiments showing the effects of enzymes have shown both positive and negative results. These same authors reported in this study that when an enzyme was sprayed onto forage, they found an increase inADG of 13% but no difference in feed intake. An addition to this study, with a second enzyme preparation of xylanase and cellulase activities, gave a positive dose response inADG and also showed no enzyme effect on feed intake (Table 1). It is possible that the improved nutrient utilization observed at the higher enzyme supplementation supported higher VFAproduction, which would promote more gain with less or equal feed intake.
Atrial investigating enzyme dose level by Sanchez et al. (1996) with highproducing dairy cows fed alfalfa haylage used three levels of fibrolytic enzymes (1.25, 2.5 and 5 l/ton dry matter) as part of a total mixed ration (TMR). These researchers did not show a dose response when higher levels of enzymes were fed. The positive enzyme response was not linear and was more effective for the intermediate level of enzyme application compared to the control animals which were fed the untreated ration (Table 2). In contrast, DMI was increased by all levels of enzyme addition. The authors felt that the explanation for the lower milk production and higher feed intake in the highest level of enzyme application could be explained by increased body condition score indicating cows were using nutrients for weight gain instead of milk production. However, the difference in milk production could also be due to unequal pairing of cows with the cows in the high-enzyme treatment group having longer average days in milk (DIM). Differences in expected intake patterns as well as milk production would account in part for an inconsistent dose response to treatment.
Table 1. Effect of enzyme dosage on response to fibrolytic enzymes in corn silage diets fed to cattle.*
Table 2. Performance effects from cows fed forage treated with three levels of enzymes.*
The difference in paired lactating cow production may account for a good deal of the inconsistent enzyme dose response for this trial as well as a good deal of the data reported in the literature, especially when numbers of cattle are small. It is for this reason that we wanted to look at a large group of high-producing cows to be able to compare cows with similar DIM and production history to determine if we could measure an effective treatment difference on a new fungal extract preparation for ruminants (Fibrozyme).
EFFECTS OF FIBROZYME ON PERFORMANCE OF HIGH-PRODUCING COWS
DIETS AND PROCEDURES
Over 400 high-producing Holstein cows were used in a lactation trial to evaluate effects of Fibrozyme. The cows were fed the same TMR in six separate pens that contained approximately 100 animals per pen. Three of the pens were designated as controls and three pens received the Fibrozyme supplement at 15 g/day. The composition of the TMR is given in Table 3.
Table 3. Ration ingredients and analysis.
Cows were paired based on parity, production, stage of lactation and use of bovine somatotropin (bST). Four separate sub-groups of pairs were established with respect to bST treatment. Cows which received no bST for the entire test period were designated ‘no-bST’ and cows that received bST for the entire test period were termed ‘bST’. Cows originally assigned to bST that were taken off bST before the end of the experiment were termed ‘early bST’. Similarly, cows assigned to the ‘no-bST’group that subsequently received bST were designated the ‘late bST’ group. Adjustments were made for pen effect, DIM, and lactation number or similar history. The data were collected from October 5 to December 7 (63 days) and were statistically analyzed for differences in milk yield, milk fat, fat corrected milk (3.5%) yield and milk protein.
The milk production and milk component samples for the individual cow data were taken with Afikim milk samplers to allow collection of milk from start to finish at each milking unit. Milk samples were taken from individual cows at the morning and afternoon milking (6:30 AM and at 2:30 PM) and composited for analysis for milk components (fat and protein) as well as total milk weight. The milk samples were sent to the DHIA lab in Ithaca, New York, and the statistical analysis was done at the University of Florida Dairy Science Center.
RESULTS
Fibrozyme tended to increase milk yield while bST increased milk protein (Table 4). As cows are not placed on bST until after 100 to 120 days in milk, what appears to be no effect of bST on milk production is not the case. The cows were paired on similar bST treatment effects, so milk production traits could be measured. The cows that were paired with the shortest average DIM (108) received no bST, and the cows that received bST late in the test period had the longest average DIM (215). Historically, this herd has reported a 15% increase in milk production for cows receiving bST in late lactation when they would normally show a drop in milk production.
Table 4. Effect of Fibrozyme on cows receiving different treatments of bST.
Fibrozyme tended to increase milk yield regardless of bST assignment (P< 0.08). The lowest milk production was experienced by the control/late bST group, although differences were not significant among bST assignments. The data indicated that bST increased protein percentage (P<0.01), when administered throughout the trial. Fibrozyme increased milk yield over the 63-day period by 7.04% compared to the control.
EFFECTS OF FIBROZYME ON RUMINAL DIGESTION OF FIBER
Enzyme treatment of forages could beneficially affect both rate and extent of digestion. In order to examine dynamics of digestion of enzyme-treated forages, a series of in vitro studies was conducted at the University of Kentucky.
Four fistulated steers were fed either a 100% grass hay or 50% concentrate ration supplemented with or without Fibrozyme (15 g/day). Rumen fluid from these steers was used in the in vitro studies described below. Each animal received a different diet during each of four sampling periods. The four treatment periods consisted of 8-day enzyme supplementation periods in which the animals received either an enzyme supplemented or unsupplemented diet followed by a 7-day resting period when no supplements were given. Midway through the trial the dietary treatments were switched. The change in diet was accompanied by a 14-day adaptation period for the animals to adjust to the new diets before initiating the succession of enzyme supplementation.
Rumen fluid collected from each animal once in each supplementation period was used to evaluate the in vitro degradation of a fescue based reference diet. The rumen fluid was strained through four layers of cheesecloth into two 250 ml bottles and it was immediately taken to the laboratory. The bottles were introduced in an anaerobic chamber (10% hydrogen, 20% CO2, 70% nitrogen) where the rumen fluid was mixed with an equal volume of McDougall’s artificial saliva (McDougall, 1948). The mixture was blended at high speed for 2 min and the resulting cell suspension was used as inoculum for the serum bottle cultures. All cultures were prepared under a CO2 gas phase in 100 ml serum bottles.
Approximately 0.5 g of a ground reference diet was weighed into each of 36 bottles. The other 36 did not receive feed and served as substrate-free controls. A 60 ml syringe flushed with CO2 was used to inoculate 50 ml of cell suspension into nine bottles containing substrate and nine substrate-free controls. This procedure was repeated with the remaining three cell suspensions to a total of 72 cultures. The cultures were sealed with a rubber septum and an aluminum seal to maintain anaerobic conditions. They were incubated in a water bath with agitation at 39°C. Three replicate cultures containing substrate, and three substrate-free controls from each treatment group were removed after 0, 12, and 24 h incubations. Final dry weights were corrected for dry matter carry over from rumen fluid inocula using the values estimated from substrate-free controls at each incubation time.
VOLATILE FATTYACID PRODUCTION
VFAconcentrations were determined by gas chromatography. Samples were taken from the supernatant and frozen until preparation. They were clarified with 25% metaphosphoric acid, and 1 ml was injected on a Hewlett-Packard model 5890 series II gas chromatograph equipped with a 6 ft x 4 mm glass column packed with 10% SP-1000/1% H3PO4 on 100/120 ChromosorbWAW. The oven temperature was held constant at 135°C and the flow rate was 32 ml/min. VFA produced by each culture were determined by subtracting the average VFA concentrations at 0 h from the VFA concentrations at 12, 18, and 24 h. Hexose utilization was estimated stoichiometrically from VFAproduction by calculating the theoretical fermentation balance.
IN VITRO DRYMATTER DISAPPEARANCE DETERMINATION
Dry matter disappearance was determined for each culture using a centrifugation technique. Material from sampled cultures was washed with 50 ml deonized distilled water into 250 ml centrifugation bottles. These were centrifuged at 4,000 x g for 10 min and the supernatant was discarded.
The resulting pellet was resuspended in approximately 5–10 ml deonized distilled water and transferred to pre-weighed, aluminum dishes. These were placed in the drying oven at 98°C overnight. Dishes were equilibrated at room temperature in a desiccator and dry weights were recorded. To estimate dry matter carry over from rumen fluid inocula, the amount of reference diet added to each serum bottle was subtracted from the final dry weights obtained at 0 h. The difference in weight observed was attributed to incoming dry matter from rumen contents used to inoculate the serum bottle cultures. This value was used to correct the final dry weights for carry over at all incubation times. The amount of dry matter digested after 12 and 24 h was estimated for each treatment culture by subtracting the corrected final dry weights from the amount of reference diet weighed into each culture. In vitro dry matter disappearance was expressed as a percentage and was calculated by dividing the estimated dry matter digested by the amount of reference diet added to each serum bottle culture.
RESULTS
The effects of Fibrozyme supplementation on in vitro fiber digestion of the 100% grass hay diet demonstrated that at 12 h, in vitro dry matter disappearance was 44% greater in cultures receiving Fibrozyme compared to the unsupplemented control (Table 5). Estimated hexose utilization and net VFA production in Fibrozyme supplemented cultures also tended to be greater than those in unsupplemented cultures after 12 h of incubation.
Addition of Fibrozyme to the diets of steers consuming a 50% concentrate ration with grass hay did not alter patterns of in vitro dry matter disappearance (Table 6). However, VFAproduction and carbohydrate utilization were greater in cultures derived from Fibrozyme supplemented animals than in animals receiving unsupplemented rations. This suggests that Fibrozyme had a significant impact on the digestibility of soluble components found in these high-concentrate diets.
CONCLUSIONS
For commercial success enzymes for ruminants are going to have to compete with or complement an ever increasing variety of feed additives as well as bST. The technology will have to deliver consistency of performance at a very minimum for on-farm return.We are learning more regarding how fungal fermentation extracts can modify rumen microorganism production and how we can use enzymes to produce more positive changes in short chain fatty acids and improved milk production.
Table 5. In vitro dry matter disappearance, estimated hexose utilization, and net VFA production from a hay based reference ration by batch cultures inoculated with rumen contents from animals fed a 100% grass hay diet with or without Fibrozyme at 12 and 24 h.
Table 6. In vitro dry matter disappearance, hexose utilization, and net VFA production from a hay based reference ration by batch cultures inoculated with rumen contents from animals fed a 50% concentrate diet with or without Fibrozyme at 12 and 24 h.
Response to Fibrozyme supplementation under commercial conditions indicated that adding enzymes to increase fiber digestion had a positive impact on milk yield of high-producing cows. In vitro studies indicate that additions of Fibrozyme to ruminant diets enhanced digestion of particulate material and carbohydrate metabolism in a fescue hay diet during the short incubation period (first 12 h after addition), but had little consistent long-term effects on digestion when examined over a longer period (18–24 h after addition). The increase in 12-h digestion rate may help explain the increase in intake seen in response to Fibrozyme in field trials.
The ability of the enzyme supplement to enhance digestive processes appears to be dependent on the source microbial population and the nature of the diet. Maximal effects on substrate utilization and fermentation end product formation were observed when microbial populations obtained from grain fed animals were tested for their ability to utilize carbohydrates in forage-based rations. The enzyme also appears to enhance the ability of ruminal microbial populations to degrade soluble carbohydrates in animals fed concentrate-containing diets and may have important special applications in systems where mixtures of concentrates and forages are used.
REFERENCES
Beauchemin, K.A. and L.M. Rode. 1996. Use of feed enzymes in ruminant nutrition. Proceedings of the Canadian Society of Animal Sciences Annual Meeting, Lethbridge, Alberta, 7–11 July. pp. 103–130.
Beauchemin, K.A., L.M. Rode and V.J.H. Sewalt. 1995. Fibrolytic enzymes increase fibre digestibility and growth rate of steers fed dry forages. Can. J. Anim. Sci. 75:641–644.
Chesson, A. 1993. Feed enzymes. Animal Feed Science Technology 45:65–79.
Dawson, K.A. and I.D. Girard. 1997. Stimulatory effects of yeast culture on rumen bacteria. In: Biotechnology in The Feed Industry. Proceedings of the 13th Annual Symposium (T.P. Lyons & K.A. Jacques, eds), Nottingham University Press, Loughborough, Leics, UK.
Feng, P., C.W. Hunt, G.T. Pritchard and W.E. Julien. 1996. Effects of enzyme preparations on in situ and in vitro digestive characteristics of mature coolseason grass forage in beef steers. J. Anim. Sci. 74:1349–1357.
Forwood, J.R., D.A. Sleper and J.A. Henning. 1990. Topical cellulase application effects on tall fescue digestibility. Agron. Journal 82:909–913.
Kopecny, J., M. Marounek and K. Houb. 1987. Overenf vhodnosti aplikace celulaz Trichoderma viride do krmnych davek prezvykavcu [Testing the suitability of the addition of Trichoderma viride cellulases to feed rations for rations for ruminants]. Zivocisna Vyroba 32:587–592.
Lewis, G.E., C.W. Hunt, W.K. Sanchez, R. Treacher, G.T. Pritchard and P. Feng. 1996. Effect of direct fed fibrolytic enzymes on the digestive characteristics of a forage-based diet fed to beef steers. J. Anim. Sci. 74:3020–3028.
McDougall, E.I. 1948. Studies on ruminant saliva. I. The composition and output of sheep’s saliva. Biochem. J. 43:99.
Nakashima,Y. and E.R. Orskov. 1989. Rumen degradation of straw – 7. Effects of chemical pre-treatment and addition of propionic acid on degradation characteristics of botanical fractions of barley straw treated with a cellulase preparation. Animal Production 48:543–551.
Sanchez,W.K., C.W. Hunt, M.A. Guy, G.T. Pritchard, B. Swanson, T.Warner and R.J. Treacher. 1996. Effect of fibrolytic enzymes on lactational performance of dairy cows. Proceedings of American Dairy Science Association. Corvallis, Oregon. July 14–17. (Poster).
Vandevoorde, L. andW. Verstaete. 1987. Anaerobic solid state fermentation with possible application to cellulase production. J. Appl. Micro. Biotech. 26:479–484.
Authors: DEAN HOWES1, JUAN MARCELO TRICARICO2, KARL DAWSON2 and PETER KARNEZOS1
1 Alltech, Inc., Nicholasville, Kentucky, USA
2 Department of Animal Sciences, University of Kentucky, Lexington, Kentucky, USA
Author: D. HOWES, J. M. TRICARICO, K. DAWSON and P. KARNEZOS (Courtesy of Alltech Inc.)
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