The Use of the Esophageal Fistula for the Determination of Consumption and Digestibility of Pasture Forage by Sheep Donald L. Bath, William C. Weir and Donald T. Torell J ANIM SCI 1956, 15:1166-1171. The online version of this article, along with updated information and services, is located on the World Wide Web at: http://www.journalofanimalscience.org/content/15/ 4/1166 www.asas.org Downloaded from www.journalofanimalscience.org by guest on October 6, 2014 T H E USE OF T H E ESOPHAGEAL FISTULA FOR T H E DET E R M I N A T I O N OF CONSUMPTION AND D I G E S T I B I L I T Y OF PASTURE FORAGE BY SHEEP 1, 2 DONALD L. BATH, 3 WILLIAM C. W E I R 4 AND D O N A L D T . TORELL 5 University o] California, Davis M E T H O D of obtaining representative samples of forage a c t u a l l y eaten by grazing animals has long been a problem. The many methods previously proposed are time consuming and tedious. The use of the esophageal fistula in grazing animals offers a new approach to this problem (TorelI, 1954). This paper reports results obtained in testing this technique with these fistulated sheep. Once a representative sample of forage is obtained, several techniques are available for the determination of consumption and digestibility. Reid et al. (1950) have proposed the use of chromogens in the feces. Cook and Harris (1951) had difficulty in using this technique under range conditions. The lignin ratio method proposed by Forbes and Garrigus (1948) appears to be more applicable to all types of forage. Variation in the reported digestibility of lignin introduces some doubt in the accuracy obtained but most results indicate that lignin is only 0 to 5% digestible. Chromic oxide as an indicator substance has been used successfully in mixed rations but its effective use on pasture is limited because of the difficulty encountered in getting it uniformly mixed with the ingested forage. E x p e r i m e n t a l and Results Effect o] Collection on the Sample A study was conducted to test this technique on any change which might take place in forage while in the mouth before dropping out of the fistula. Chopped alfalfa hay was thoroughly mixed and divided into four lots by the quartering method. One lot was taken for chemical x This research was supported in part by Western Regional Project W-34. The authors wish to express their appreciation to G. P. Lofgreen and J. H. Meyer for their advice in connection with this research. s Present address: Santa Rosa High School, Santa Rosa, California. Associate Professor of Animal Husbandry, Davis. Associate Specialist in Animal Husbandry, Hopland Field Station. 1166 Downloaded from www.journalofanimalscience.org by guest on October 6, 2014 ESOPHAGEAL FISTULA FOR PASTURE STUDIES 1167 analyses and the other three lots were fed to a fistulated wether. The three samples collected from the fistulated wether were weighed and analyzed for comparison with the control sample. Results are shown in table 1. Examination of the analyses indicate that there was little change in the chemical composition of the material during the collection procedure. The ash content of the collected material appears to be somewhat higher than for the control sample. It is theoretically possible to explain this TABLE 1. COMPARISON OF COMPOSITION OF ALFALFA HAY BEFORE AND AFTER PASSING THROUGH T H E MOUTH AND AN ESOPHAGEAL FISTULA Dry matter composition Dry matter fed gm. Wet Dry collec- matter tion collected gm. gm. Control Fistula Collection I Collection I I Collection I I I 151.7 167.3 145.2 573 804 578 148 165 148 Ash Ether Protein extract Crude fiber Nitrogen free extract Lignln % % % % % % 12.0 27.8 1.3 22.4 36.5 6.8 12.3 12.9 12.8 27.4 27.5 27.4 1.3 1.2 1.2 22.2 22.2 22.5 36.8 36.2 36.1 6.4 6.4 6.3 on the basis of the mineral content of the saliva. The saliva excretion was estimated by the increase in weight of the material as fed and as collected. This increase is shown in table 1. If the saliva is assumed to contain 0.5% mineral, this amount of mineral would increase the ash content of Collection I by 1.4%, Collection II by 1.9%, and Collection III by 1.4%. The ash results would indicate that the effect is somewhat less than estimated by this method. The slightly lower lignin content of the collections compared to the control sample, while within the experimental error of the analyses, m a y also reflect some selection of the portion of the sample eaten by the wether as there was a small weighback in every case. This would not be a factor in pasture collections as only the part actually eaten is of interest. McDougall (1948) reported sheep saliva contained 0.7 to 0.9% ash. Consumption and Digestion Trials With the above test indicating that there was little change in forage during the esophageal fistula collection, trials were conducted on three types of irrigated pastures. Two esophageal fistulated ~wethers were used to make collections of the pasture forage. Since Collections and leakage Downloaded from www.journalofanimalscience.org by guest on October 6, 2014 1168 BATH, WEIR AND TORELL at the fistula decrease the a m o u n t of feed actually taken into the digestive tract b y the fistulated animals, it was thought desirable to take fecal collections from three normal non-fistulated wethers which had been fitted with fecal collection bags. This technique was therefore based on the assumption that all five sheep ate the same quality of forage from the pastures. T h e three wethers used for fecal collections weighed 84, 89, and 12 7 lb. at the conclusion of the trials. TABLE 2. CHEMICAL COMPOSITION ON ESOPHAGEAL FISTULA COLLECTIONS AND HAND CLIPPED FORAGE FROM THREE KINDS OF PASTURE % Dry basis Pasture Sheepno. Sudan Sudan Sudan Sudan Sudan Sudan 1 3 1 3 1 3 Sudan Sudan Trefoil Trefoil Trefoil Trefoil Trefoil Alfalfa Alfalfa Alfalfa Alfalfa Alfalfa Date August 12 August 12 August 14 August 14 August 17 August 17 Average6 collections Hand clipped August 17 3 3 3 3 August 27 August 29 August 30 August 30 Average 4 collections 1 3 1 September 13 September 13 September 16 Average 3 collections Hand clipped September 18 Ash Protein Lignin Ether extract 14.6 13.4 14.0 12.0 16.6 11.6 15.5 16.1 14.5 13.6 16.8 14.7 8.4 8.4 8.8 9.3 9.7 8.5 1.59 1.62 1.75 1.52 I. 74 1.30 13.7• 12.2 15.2• 8.1 8.85• 6.5 1.59• 1.61 13.0 11.9 11.9 11.2 25.8 28.2 26.8 27.2 6.9 7.1 5.9 6.4 2.60 2.88 2.37 2.47 12.0• 27.0• 6.6• 2.58• 10.8 14.8 10.5 27.3 24.5 22.2 6.6 5.6 7.4 1.63 1.89 1.86 12.0-----2.424.7~---2.9 6.5~---.9 1.79• 8.8 21.6 5.5 2.13 T h e five wethers were placed in each pasture one week before the actual trials were conducted in order that they might become accustomed to the forage a n d to allow time for previous feed' to clear the digestive tract of the wethers used for fecal collections. Fistula collections were attempted at the beginning, mid point, and near the end of each test period. Some difficulty was encountered in some of the collections so results are reported only where forage samples adequate for analyses and free of r u m e n contents were obtained. (An occasional collection was ruined b y regurgitation.) Downloaded from www.journalofanimalscience.org by guest on October 6, 2014 ESOPHAGEAL FISTULA FOR PASTURE STUDIES 1169 For comparative purposes, square-foot plots randomly located in the sudan and alfalfa pastures were hand clipped. The analyses of the esophageal fistula collections and the hand-clipped samples are shown in table 2. The sudan pasture tested was almost pure Sudan grass. The pasture had been previously grazed and clipped. Most of the plants were about six to eight inches high and in the vegetative stage during the test. A small amount of Sudan on the irrigation checks and near the fence was more mature with seed heads developing. The trefoil was a 91~o pure stand of narrowleaf birdsfoot trefoil (Lotus tenuis) with yellow star thistles and peaweed as impurities. When grazed it was about eight inches high with some blooms and some seed heads developing. The alfalfa field was a pure stand of alfalfa with a small amount of dry weedy material around the fences. The stage of maturity was somewhat variable due to some dry, sandy areas in the pasture, and varied from no bloom in some areas to 100~o bloom in others. The feces were collected from the three intact wethers twice daily, dried, weighed, and an aliquot taken for analyses for ash, lignin, and nitrogen. Using the lignin-rafio method of Forbes and Garrigus (1948) and the total digestible nutrients method of Lofgreen (1953), daily dry matter consumption, total digestible nutrients and percent digestible protein were calculated. (table 3). Discussion The use of fistulated wethers to collect representative samples of pasture or range forage and similar intact wethers to collect feces from such forage gives promise of a useful technique for measuring consumption and digestibility of such forage. Further refinements of the technique are needed for more precise results. The forage collections should precede the fecal collections by an interval equal to the time it takes the forage under study to pass through the digestive tract. This could be obtained by giving a marker to the intact sheep when turned into a study area. More data are needed to determine the variability between samples collected by the same fistulated sheep on the same pasture. Data are also needed on the variability of samples collected by different fistulated sheep on the same pasture. Studies currently underway on this subject will be published in a later paper. Downloaded from www.journalofanimalscience.org by guest on October 6, 2014 1170 B A T H , W E I R AND TORELL T A B L E 3. R E S U L T S C A L C U L A T E D F R O M F E C A L C O L L E C T I O N S Daily Daily fecal wt. feed intake dry matter dry matter Pasture Sheep no. gm. gm. % % % Sudan Sudan Sudan 13 32 65 412 366 345 828.7 653.4 643.2 48.0 45.3 46.7 56.8 44.5 44.7 8.6 6.8 6.8 Trefoil Trefoil Trefoil 13 32 65 381 309 350 1166.1 997.3 1145.5 63.4 64.7 64.9 78.7 76.3 78.1 21.2 20.6 21.1 Alfalfa Alfalfa Alfalfa 13 32 439 411 339 1350.8 1138,2 964.8 62.4 59.7 59.8 76.5 71.7 75.2 18.9 17.7 18.6 65 T.D.N dry-basis Protein Digestible digestibility protein The most difficult task in connection with this procedure was keeping the fistulated sheep in good health and in condition to make the collections. Experience t o date indicates that the fistulated sheep require careful daily attention. The fistula may be kept closed with double layers of plastic--one layer in the esophagus and a second on the outside of the skin---and the two laced together with heavy nylon fishline. Two of the wethers used for these studies (No. 1 and 3) were operated on in ~[une, 1954, and were in thrifty condition 20 months later. Collection periods should not exceed 30 minutes or the sample may be lost by regurgitation and contamination with rumen contents. Larger collections can usually be obtained by keeping the fistulated wethers off feed the night preceding the collection period. T A B L E 4. C O M P A R I S O N OF T E S T R E S U L T S W I T H M O R R I S O N ' S R E QUIREMENTS FOR "GROWING EWE LAMBS AND YEARLINGS" IN THREE WEIGHT CLASSIFICATIONS 80-lb. lambs 90-lb. lambs 120-lb. lambs lb. lb. lb. Dry matter Required a Sudan test Trefoil test Alfalfa test 2.2-2.7 1.4 2,5 2.1 2.3-2.8 1.4 2.2 2.5 2.6-3. 1.8 2.6 3.0 Total digestible nutrients Required a Sudan test Trefoil test Alfalfa test 1.4-1.7 .7 1.6 1.3 1.5-1.8 .6 1.4 1.5 1.8-2. .9 1.6 1.9 a Morrison's table III. Downloaded from www.journalofanimalscience.org by guest on October 6, 2014 ESOPHAGEAL FISTULA FOR PASTURE STUDIES 1171 A comparison of the results obtained from this test with Morrison's (1948) requirements for l a m b s is shown in table 4. T h e low intake on the Sudan p a s t u r e m a y in p a r t be due to the fact t h a t the intact lambs were not accustomed to the fecal collection bags. T h e values obtained on the trefoil and the alfalfa compare rather favorably with Morrison's tables. F u r t h e r trims are needed to determine the gain of lambs on pasture and determine the actual intake of d r y m a t t e r and T . D . N . of such lambs on the pasture. Summary A test conducted to s t u d y the change in chemical compositio~ of forage during the process of passing through the mouth and out an esophageal fistula indicated that there was little difference between the sample fed and t h a t collected from the fistula. A technique is described in which esophageal fistulated wethers were used to collect samples of Sudan grass, trefoil, and alfalfa pasture as consmned b y grazing sheep and normal wethers equipped with f e c a l collection harnesses were used to collect feces. Assuming that all sheep are eating the same quality forage and using the lignin-ratio procedure, d r y m a t t e r consumption, total digestible nutrients, and digestible protein of the pasture forage were calculated. I m p r o v e m e n t s and possible use of this technique are discussed. Literature Cited Cook, C. Wayne and Lorin E. Harris. 1951. A comparison of the lignin ratio technique and the chromogen method of determining digestibility and forage consumption of desert range plants by sheep. J. Animal Sci. 10:565. Forbes, R. M. and W. P. Garrigus. 1948. Application of a lignin ratio technique to the determination of the nutrient intake of grazing animals. J. Animal Sci. 7:373. Lofgreen, G. P. 1953. The estimation of total digestible nutrients from digestible organic matter. J. Animal Sci. 12:359. McDougall, E. I. 1948. Studies on ruminant saliva I. The composition and output of sheep's saliva. Biochem. J. 43:99. Morrison, F. B. 1948. Feeds and Feeding. The Morrison Publishing Company, Ithaca, New York. Reid, J. T., P. G. Woolfold, C. R. Richards, R. W. Kaufmann, J. K. Loosli, K. L. Turk, J. I. Miller and R. E. Blaser. 1950. A new indicator method for determination of digestibility and consumption of forages by ruminants. J. Dairy Sci. 1:60. Torell, D. T. 1954. An esophageal fistula for animal nutrition studies. J. 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