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Effects of supplemental amylase and roughage source on performance and carcass characteristics of finishing beef cattle |
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Author: J.D. RIVERA, M.D. ABNEY, N.A. ELAM, J.F. GLEGHORN, J.T. RICHESON, J.J. CRANSTON, and M.L. GALYEAN – Texas Tech University (Courtesy of Alltech Inc.)
The use of enzymes in feedlot diets has not been evaluated extensively, and most of the research with high concentrate diets has been done with barley.
Beauchemin et al. (1997) evaluated the addition of two enzyme mixtures that varied in the proportion of xylanase and cellulase activity to 95.1% concentrate feedlot diets based on either barley or corn. Feed efficiency for the overall finishing period was improved approximately 11% with a highxylanase activity enzyme treatment of barley compared with untreated steam-rolled barley. With corn, however, the addition of the high cellulase activity enzyme improved feed efficiency compared with no enzyme addition.
Less research has been done with the addition of enzyme preparations that contain amylase activity to cattle diets. Hristov et al. (2000) dosed 0, 100, 200, or 400 g/d of an enzyme preparation that contained carboxymethylcellulase, xylanase, ß-glucanase, and amylase into the rumen of cannulated heifers fed an 85.5% rolled barley diet. Enzyme treatment linearly decreased ruminal pH and quadratically increased in situ effective degradability of the diet. Ruminal amylase activity was not increased by dosing the enzyme, but duodenal amylase activity increased quadratically with enzyme addition. J.M Tricarico (Alltech Inc., Nicholasville, KY, unpublished data) dosed 0, 12, 24, or 36 g/day of an amylase preparation to 24 Holstein cows fed a corn silage-ground corn diet.
The addition of 12 g/day of amylase increased ground corn digestibility after 24 hrs, increased milk fat yield, and increased milk protein yield. Although these data suggest potentially positive effects on cattle performance with addition of enzymes to feedlot diets, performance results for enzyme preparations with high amylase activity are not available in the literature.
Dry matter intake (DMI) by beef cattle fed high concentrate, grain-based diets is likely controlled by metabolic factors and not limited by bulk fill. Small changes (e.g. 5% of DM or less) in the level of bulky roughage and changing from less fibrous to more fibrous sources of roughage typically increase DMI by feedlot cattle. Galyean and Defoor (2003) hypothesized that much of the effect of roughage source and level on DMI by feedlot cattle could be accounted for by changes in dietary NDF supplied by roughage.
The objectives of our experiment were twofold: first, to determine whether the addition of supplemental amylase to a finishing diet affects performance and carcass characteristics of beef cattle, and second, to evaluate whether differences in performance exist when diets are formulated to supply the same percentage of dietary NDF from different roughage sources.
Experimental procedures
One hundred twenty steers were blocked by body weight (BW) to six blocks, implanted with Ralgro (Schering-Plough Animal Health, Union, NJ) in the right ear, and sorted to their assigned Texas Tech University (TTU) Burnett Center pens. These steers had been previously vaccinated with Vision 7 Somnus (Intervet, Millsboro, DE) and with Bovishield 4 + Lepto (Pfizer Animal Heatlh, Lee’s Summit, MO), and had been administered Cydectin (Fort Dodge Animal Health, Overland Park, KS).
Five days after the cattle were implanted and sorted to pens, each pen of cattle was brought through the working chute to determine an individual starting BW for the experiment.
Four dietary treatments were arranged in a 2 x 2 factorial in a randomized complete block design. Pen was the experimental unit (six pens per treatment with five steers per pen for a total of 120 steers). The four treatments were as follows: 1) ALF-, 88% concentrate diet with alfalfa as the roughage source and no supplemental amylase; 2) CSH-, 93.5% concentrate diet with cottonseed hulls as the roughage source and no supplemental amylase; 3) ALF+, 88% concentrate diet with alfalfa as the roughage source plus supplemental amylase; and 4) CSH+, 93.5% concentrate diet with cottonseed hulls as the roughage source plus supplemental amylase. The enzyme preparation used in this study contained amylase activity (Alltech Inc., Nicholasville, KY) and was added as a premix.
The premix was (DM basis) 46.07% ground corn and 53.93% amylase enzyme preparation. Ingredient composition of the diets fed during the experiment is shown in Table 1. Each diet contained the same intermediate premix (Table 2), which supplied protein, various minerals and vitamins, Rumensin (33 mg/kg, DM basis), and Tylan (8.8 mg/kg, DM basis). Additionally, each of the diets was formulated to contain the same percentage of NDF from roughage (approximately 6%).
Table 1. Ingredient composition (% DM basis) of the experimental diets.
a Composition of the supplement is shown in Table 2.
b Control premix was composed of ground corn only.
c Amylase enzyme (Alltech Inc., Nicholasville, KY) premix was composed (DM basis) of 46.07% ground corn and 53.93% amylase enzyme.
Table 2. Composition of the TTU 2.5 supplement used in experimental diets.
a Concentrations noted by the ingredient are on a 90% DM basis.
Samples of mixed feed delivered to feed bunks were taken weekly throughout the experiment. Samples of feed taken from the bunk were composited for each period of the experiment and analyzed for DM, ash, CP, acid detergent fiber, Ca, and P (Table 3) using AOAC (1990) procedures. Bunk sample DM values were used to compute average DMI by the cattle in each pen. Alfalfa hay and cottonseed hull samples were analyzed for NDF using procedures described by Goering and Van Soest (1970).
Feed bunks were evaluated visually at approximately 0700 to 0730 daily. The quantity of feed remaining in each bunk was estimated, and the suggested daily allotment of feed for each pen was recorded. This bunk-reading process was designed to allow little or no accumulation of unconsumed feed (0 to 0.45 kg per pen). Feed bunks were cleaned, and unconsumed feed was weighed and dried at intervals (corresponding to intermediate weigh dates) throughout the trial. Feed bunk DM weighed back from the pen was used along with DM of feed delivered to calculate DMI by each pen.
After 28, 84, and 112 days on feed, cattle were weighed on a pen basis using a platform scale (+2.27 kg). On day 56 and just before shipment to slaughter, BW measurements (+0.45 kg) were obtained for individual animals using a single-animal scale (C & S Single-Animal Squeeze Chute [Garden City, KS] set on four load cells). Both scales were calibrated with 454 kg of certified weights (Texas Dept. of Agric.) on the day before each scheduled weigh day. On day 56, at the time of the scheduled BW measurement, each steer was implanted with Revalor S (Intervet). On day 112, it was visually estimated that steers in Blocks 5 and 6 would have sufficient finish to grade USDA Choice in approximately two weeks, and those steers were scheduled to ship to slaughter on day 133 of the experiment. Steers in blocks 3 and 4 were weighed individually and shipped to slaughter on day 154 of the experiment, whereas steers in blocks 1 and 2 were weighed individually on day 168 and shipped to slaughter. All cattle were slaughtered at the Excel Corp. facility in Plainview, TX.
Carcass collection. Carcass data were collected by personnel of TTU Department of Animal and Food Sciences. Data included hot carcass weight, fat thickness at the 12th rib, longissimus muscle area, percentage of kidney, pelvic, and heart fat, liver score, marbling score, quality grade, and yield grade.
Statistical analyses. Performance data and carcass data were analyzed as a randomized complete block design, with a 2 x 2 factorial arrangement of treatments. The fixed effects of the model included roughage source, amylase addition, and the interaction of roughage source x amylase addition. Block was a random effect. Data were analyzed using PROC MIXED of SAS (SAS Inst. Inc., Cary, NC). Percentage of abscessed livers and carcasses grading USDA Choice were analyzed using a non-parametric model (PROC GENMOD of SAS).
Table 3. Chemical composition of the experimental diets.
a All values except dry matter (%) are expressed on a DM basis.
b Calculated based on chemically analyzed values of 52.08% neutral detergent fiber (NDF) for alfalfa hay and 89.69% NDF for cottonseed hulls.
Results and discussion
PERFORMANCE DATA
Performance data are presented in Table 4. An interaction between amylase and roughage source was detected for day 0 to 28 ADG (P=0.02). Cattle fed CSH+ had greater ADG than those fed ALF+, ALF-, or CSH-. Similarly, for ADG from day 0 to 112, an amylase x roughage source interaction was observed (P=0.04); cattle fed CSH+ had greater gains than those fed CSH-. However, for day 0 to 56, d 0 to 84, and overall ADG, no effects (P>0.10) of roughage source, amylase, or the interaction of roughage source and amylase were detected.
An amylase x roughage source interaction (P<0.10) was observed for DMI on day 0 to 56 and on day 0 to 112. Cattle fed the CSH+ had greater DMI than in the other three treatments. In contrast, J.M. Tricarico (Alltech Inc., Nicholasville, KY, unpublished data) noted no difference in DMI by Holstein cows fed graded levels of amylase. In the present study, no differences (P>0.10) were noted among treatments for feed efficiency at any period during the finishing phase.
Although differences were not significant, there were strong trends for a roughage source x amylase interaction for overall ADG (P<0.12), DMI (P<0.20), and feed:gain (P<0.18). These trends were largely the result of the increased ADG and DMI and improved feed:gain when amylase was supplemented to cattle fed cottonseed hulls as the roughage source. It is unclear, however, why cattle fed amylase enzyme and cottonseed hulls had greater DMI and ADG at various periods of the study. Perhaps differences in ruminal digesta kinetics between alfalfa and cottonseed hulls affected the need for supplemental amylase either in the rumen or intestines. Additionally, diets containing cottonseed hulls had a higher concentration of cottonseed meal than diets with alfalfa as the roughage source. Possibly different protein sources altered the need for additional amylase or the effect of amylase on ruminal fermentation. Effects of supplemental amylase on ruminal fermentation and on digestion of starch in the rumen and intestines are largely unknown and merit further study.
Table 4. Effects of roughage source and the addition of supplemental amylase on feedlot performance by finishing beef steers.
To enlarge the image, click here
a Observed significance level for the effect. A x R = amylase x roughage interaction.
b Standard error of the treatment means, n = six pens per treatment.
c Adjusted final BW = hot carcass weight divided by a common dressing percent of 62.84%.
d Blocks 5 and 6 were fed for 133 days, blocks 3 and 4 were fed for 154 days and blocks 1 and 2 were fed for 168 days.
e Calculated using adjusted final BW.
Percentage of NDF from roughage source for the diets (6.32% for ALF+ and ALF-, and 5.86 for CSH+ and CSH-) was determined using chemically measured values for alfalfa and cottonseed hulls. Roughage source did not affect DMI, ADG, or feed:gain at any point in the feeding period. Based on these data, it seems that performance by finishing cattle is not affected by roughage source when the percentage of NDF supplied by the roughage source is similar, which agrees with the recent findings of Galyean and Defoor (2003).
CARCASS DATA
Carcass data are presented in Table 5. Neither roughage source, addition of amylase, nor the interaction affected (P>0.10) carcass weight, dressing percent, fat thickness, percentage of kidney, pelvic, and heart fat, marbling score, yield grade, or percentage of cattle grading USDA Choice or better. The addition of amylase increased longissimus muscle area (P=0.05), but it is unclear why this happened. No effect (P>0.10) of amylase, roughage, or amylase x roughage was noted for liver score data.
Table 5. Effects of roughage source and the addition of amylase supplemental enzyme on carcass characteristics of beef steers.
To enlarge the image click here
a Observed significance level for the effect. A x R = amylase x roughage interaction.
b Standard error of the treatment means, n= six pens per treatment.
c Blocks 5 and 6 were fed for 133 days, blocks 3 and 4 were fed for 154 days and blocks 1 and 2 were fed for 168 days. d Adjusted final BW = hot carcass weight divided by a common dressing percent of 62.84%.
e Hot carcass weight.
f Dressing percent = (carcass weight/final weight) x 100. g Back fat thickness at the 12th rib.
h Longissimus muscle area.
i Percentage of kidney, pelvic, and heart fat.
j Marbling score: 400 = Small, 500 = Modest.
k Percentage of A-, A, and A+ abscessed livers.
Summary and conclusions
Based on the results of this study, roughage source did not affect performance when diets were balanced for the percentage of NDF supplied by roughage. The addition of supplemental amylase to a diet containing cottonseed hulls, but not alfalfa, as the roughage source, increased ADG and DMI at various times during the feeding period. Perhaps the dynamics of ruminal digesta differed between the two diets, which might have increased the need for amylase at various times during the feeding period. Further research is required to determine the need for amylase in diets containing cottonseed hulls as the roughage source, potential effects of amylase on ruminal fermentation, and the role that protein source might play in response to amylase.
References
AOAC. 1990. Official Methods of Analysis (15th Ed.). Association of Official Analytical Chemists, Washington, DC.
Beauchemin, K.A., S.D.M. Jones, L.M. Rode and V.J.H. Sewalt. 1997. Effects of fibrolytic enzymes in corn or barley diets on performance and carcass characteristics of feedlot cattle. Can. J. Anim. Sci. 77:645-653.
Galyean, M.L., and P.J. Defoor. 2003. Effects of roughage source and level on intake by feedlot cattle. J. Anim. Sci. (In press).
Goering, H.K. and P.J. Van Soest. 1970. Forage fiber analyses. Agric. Handbook No. 379. ARS, USDA.
Hristov, A.N., T.A. McAllister, and K.J. Cheng. 2000. Intraruminal supplementation with increasing levels of exogenous polysaccharidedegrading enzymes: Effects on nutrient digestion in cattle fed a barley grain diet. J. Anim. Sci. 78:477-487.
Authors: J.D. RIVERA, M.D. ABNEY, N.A. ELAM, J.F. GLEGHORN, J.T. RICHESON, J.J. CRANSTON, and M.L. GALYEAN
Texas Tech University, Lubbock, TX, USA
Author: J.D. RIVERA, M.D. ABNEY, N.A. ELAM, J.F. GLEGHORN, J.T. RICHESON, J.J. CRANSTON, and M.L. GALYEAN – Texas Tech University (Courtesy of Alltech Inc.)
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