Feed additives have become an important part of rations for feedlot cattle during the past several years. They have been shown to being about improved performance in various ways such as stimulating growth, favorable alterations in fermentative and synthetic activity of the digestive tract and improvement in general health of the animals allowing more efficienct absorption and utilization of nutrients consumed

Embry, L. B.

Swan, W. S.

English

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South Dakota State UniversityOpen PRAIRIE: Open Public Research Access InstitutionalRepository and Information ExchangeSouth Dakota Cattle Feeders Field Day Proceedingsand Research Reports, 1974 Animal Science Reports1974Effects of Monensin on Feedlot Performance ofGrowing and Finishing SteersL. B. EmbrySouth Dakota State UniversityW. S. SwanFollow this and additional works at: http://openprairie.sdstate.edu/sd_cattlefeed_1974Part of the Animal Sciences CommonsThis Report is brought to you for free and open access by the Animal Science Reports at Open PRAIRIE: Open Public Research Access InstitutionalRepository and Information Exchange. It has been accepted for inclusion in South Dakota Cattle Feeders Field Day Proceedings and Research Reports,1974 by an authorized administrator of Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. For moreinformation, please contact michael.biondo@sdstate.edu.Recommended CitationEmbry, L. B. and Swan, W. S., "Effects of Monensin on Feedlot Performance of Growing and Finishing Steers" (1974). South DakotaCattle Feeders Field Day Proceedings and Research Reports, 1974. Paper 6.http://openprairie.sdstate.edu/sd_cattlefeed_1974/6South Dakota S tate University Brookings , South Dakota Department of Animal Science A gricultural Experiment S tation A . S .  S eries 74-5 Effects of Monensin on Feedlot P erformance o f  G rowing and Finishing Steersa L .  B .  Embry and W. S .  Swan Feed additives have become an important part o f  rations for feedlot cattle during the pas t  several years . They have been shown to bring about improved per­formance in various ways such as s timulating growth , favorable alterations in fermentative and synthetic activity of the diges tive tract and improvement in general health of the animals allowing more e fficient abs orption and utilization o f  nutrients consumed. Much research has been d evoted t o  the se arch for and study of compounds or products that may have important economic value as feed additives . Recent re­search has shown t hat monensin is such a compound . Monensin is a biologically active compound produced by streptomyces cinnamonensis and is used as an anticoc­cidial for poultry . It has been shown to favorably alter rumen fermentation resulting in an increase in propionic acid production which sh ould be expected to improve feed e fficiency . In the experiment reported , monensin was t es t ed at various levels as to e ffects on feedlo t  performance of steers during a growing phase with h�gh-roughage rations and during a finishing phase with high-concentrat e rations . Procedures The 128 Hereford stee rs used in the experiment were purchased in mid-May . They had been wintered as one group using a ration o f  alfalfa hay , corn silage and about 5 lb. of oats. Average weight at time o f  purchase .was 608 pounds . They had been t reat ed for control of internal and external parasites and had b een given the vaccinations commonly associated with preconditioning and no additional treatments were given af ter arrival . During a preliminary peri od of about 6 week s , the steers were fed once daily a ration of 5 lb . whole corn grain and a full feed o f  alfalfa-b romegrass hayl age (about 45% moisture) . High-Roughage Phase Following the preliminary period , the cat tle we re allotted on basis of weigh t into 16 pens of 8 head each . Ration treatments were monensin at O, 10, 20 o r  30 g 8Monensin used in th e experiment supplied by Eli Lilly and Company , G reen field , Indiana , through the courtesy o f  Dr . H .  P .  G rueter. P repared for the Eight eenth Annual Bee f Cattle Feeders Day , November 1, 1974. 19 - 2 -per ton of air-dry ration. Each level of monensin was administered to four pens of cattle, two of which were fed alfalfa-bromegrass hay and two alfalfa-bromegrass haylage. Rations during the high-roughage phase contained 75% alfalfa-bromegrass forage (hay or haylage) and 25% concentrates (corn and supplements) on an air-dry basis (90% dry matter). No supplemental protein was considered necessary with the high level of forage. However, a supplement was prepared to provide supplemental minerals, vitamin A and the test levels of monensin. These were mixed with ground corn and was supplemented at 5% of the air-dry ration. The control supplement contained 84% ground corn, 10% dicalcium phosphate and 6% trace mineral salt. Vitamin A was added to furnish 1,000 IU per pound of ration. A monensin premix was used to provide the test levels of the compound and replaced an equal weight of corn in the supplement. The final air-dry ration was 75% alfalfa­bromegrass forage, 20% ground corn and 5% supplement. The ratio of 75% roughage to 25% concentrates on an air-dry basis was computed to the equivalent ratio as fed from moisture contents of feed determined periodically during the experiment. The concentrate mixture (corn and supplement) was also computed to an as-fed basis from moisture contents of the feeds. It was batch mixed daily with the roughage but not mixed together prior to feeding. The cattle were fed in outside, paved pens without shade or shelter. This phase of the experiment was terminated after 111 days. High-Concentrate Finishing Phase Following termination of the high-roughage phase of the experiment, the steers were changed to high-concentrate rations. There were no changes in loca­tion or pen allotment. Final weights for the previous phase were used as the initial weights for this phase of the experiment. Experimental treatments for each pen of cattle were the same as during the high-roughage phase except for changes in the ratio of concentrates to roughage. Rations contained 90% concentrates and 10% roughage (alfalfa-bromegrass hay or haylage) on an air-dry basis (90% dry matter). The cattle were changed from the previous high-roughage rations to the high-concentrate ones over a period of about 10 days. A supplement to provide 10% of the air-dry ration was mixed with the corn in the same manner as for the previous phase. Ingredient composition of the control supplement was 83% ground corn, 4% urea (45% N), 5% dicalcium phosphate, 5% limestone and 3% trace mineral salt. Vitamin A was added to provide 1, 500 IU per pound of air-dry ration. A monensin premix was used to provide the test levels (0, 10, 20 or 30 g/ton of air-dry ration) of the compound and replaced an equal weight of corn. Appropriate levels of feeds as fed were computed from moisture contents of feed as during the previous phase of the experiment. Concentrates and roughage were fed separately once daily in amounts to be nearly consumed by the next feeding. The experiment was terminated after 106 days of the finishing phase and the cattle marketed. Carcass data were obtained upon slaughter. 20 - 3 -Results High-Roughage Growing Phase Results of the 111-day high-roughage phase of the experiment are presented in table 1. Rates of gain were high for the type of diet fed but with only small differences between treatment groups (2. 48 to 2. 53 lb. daily) . Therefore, monensin appeared to have no effect on weight gains of the cattle. Table 1. Monensin for Growing and Finishing Cattle for High-Roughage Phase (June 21 to Oct. 10--111 days) Monensin, g/ton air-dry feed No. of animals !nit. shrunk wt. , lb. Final shrunk wt. , lb. Avg. daily gain, lb. 0 32 636. 4 911. 4 2. 48 Avg. daily feed {air-dry) , lb. Hay or haylage Suppl. Corn Total Feed/100 lb. gain {air-dry) , Hay or Suppl. Corn Total haylage 19. 93 1. 32 5. 36 26. 61 lb. 808 53 217 1078 10 20 32 634. 8 911. 1 2. 49 19. 26 1. 28 5. 17 25. 71 774 52 208 1034 32 634. 8 915. 9 2.53 18. 81 1. 25 5. 05 25. 11 743 49 199 991 30 32 635. 0 909. 7 2. 48 17. 83 1. 19 4. 79 23. 81 723 49 194 966 Feed consumption decreased with increasing levels of monensin in the rations. The decrease in feed consumption but with similar rates of gain resulted in an improvement in feed efficiency with increasing levels of the compound. The im­provement amounted to 4. 1, 8. 1 and 10. 4%, respectively, for the 10, 20 and 30 g per ton levels. There were no evident differences in eating patterns of cattle in the various treatment groups. The reduction in feed intake but with similar rates of gain and a resulting improvement in feed efficiency were consistent throughout the high-roughage phase of the experiment. High-Concentrate Finishing Phase Results of the high-concentrate finishing phase of the experiment are pre­sented in table 2. Rates of gain were about the same between treatment groups except slightly lower for the highest level of monensin. Feed intake was reduced with increasing levels of the compound as occurred with the high-roughage rations. Feed efficiency was improved but slightly less than in the high-roughage phase. In this phase of the experiment, the improvement in feed efficiency for 10, 20 and 30 g per ton of monensin amounted to 1. 7, 7. 4 and 6. 8%, respectively. 21 - 4 -There were only small differences between treatment groups in the carcass characteristics measured except for a slight lower dressing percent and fat depth for cattle fed the highest level of monensin and making the lowest rate of gain. Abscessed livers were not reduced by the compound. Table 2. Monensin for Growing and Finishing Cattle High-Concentrate Finishing Phase (Oct. 10, 1973 to Jan. 24, 1974--106 days) Monensin, g/ton air-dry feed 0 10 20 30 No. of animals Avg. init. shrunk wt., lb. Avg. final shrunk wt., lb. Avg. daily gain, lb. Avg. daily ration (air-dry), lb. Hay or haylage Suppl. Corn Total Feed/100 lb. gain (air-dry), lb. Hay or haylage Suppl. Corn Total Carcass data Number Carcass wt. , lb • Dressing percent Conformafiiona Marbling Carcass gradea Maturityc Colo rd Firmnesse % kidney fat Loin eye area, sq. Fat depth, in.f Condemned livers . f in. 31 909.9 1193. 6 2.68 3.15 1. 29 17. 84 22.28 118 48 668 834 30 710.2 59. 35 21.2 5. 3 19 .o 23.0 4.7 5.4 3.3 11.57 (30) o .  72 6 :Prime= 23, choice= 20, good= 17. 32 911. 1 1190 .4 2.64 3.07 1. 22 17.24 21.53 117 46 657 820 30 712. l 59 .91 21.4 5. 4 19 .1 23.0 4. 6 5. 1 3.6 11.62 (29) 0. 78 11 31 914.9 1195. 3 2.65 2.93 1. 09 16.26 20. 28 111 42 619 772 31 707.4 59.21 20. 9 5.4 19. 3 23.l 4.8 5.3 3.6 11. 61 (28) 0.73 1 32 909.7 1180 .o 2. 55 2.87 1.04 15 .81 19. 72 113 41 623 771 30 694.1 58.87 21. 0 5. 2 18.9 23.0 4. 6 5.2 3.5 11. 71 (24) 0. 61 13 Modest amount = 6, small amount = S. cA maturity = 23, B maturity • 22. dLight cherry red= 5, cherry red • 4. eFirm = 6, moderately firm= 5. fsome losses in carcass identification occurred in coolers. Values in paren­thesis are number of carcasses for these characteristics. 22 - 5 -Summary Results of the experiment indicate that monensin reduces feed intake with either high-roughage or high-concentrate rations with little, if any, e ffect on rate of gain when fed at levels up to 30 g per ton of air-dry ration. These effects resulted in improved feed efficiency of 4.1, 8. 1 and 10.4% with high-roughage rations and 1.7, 7. 4 and 6. 8% with high-concentrate rations for 10, 20 and 30 g of monensin per ton of air-dry ration. The effects appeared to be rather consistent throughout the two phases of the experiment. Levels of the compound used in the experiment appeared to have no important e ffects on carcass characteristics. 23 

Effects of Monensin on Feedlot Performance of Growing and Finishing Steers

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Effects of Monensin on Feedlot Performance of Growing and Finishing Steers

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