Basson, W.D.

English

AJOL - African Journals Online

S. Afr. J. Anim. Scr. /, 45-47 (1971)A NOTE ON CONTAMINATION OF OESOPHAGEAL FISTULA SAMPLESWITH RUMEN INGESTAW.D. Basson*Department of Sheep ond Wool Science, University of PretoriaOf the numerous methods available for studyingthe diet of grazing animals, the oesophageal fistula hasmany advantages over other methods (McManus, 1961;van Dyne & Torell, 1964; van Dyne, 1968). One of themany factors affecting the validity of oesophageal fistulasamples is the occurrence of contamination of the samplesby regurgitated rumen ingesta. Although contaminationof oesophageal fistula samples has frequently been men-tioned (McManus, 1961; Cook, 1964), no information onthe frequency and extent of such contamination could befound in the literature reviewed.In a study of oesophageal f istula samples obtainedfrom pen-fed sheep, sample recoveries in excess of 100%were recorded. Three sheep, provided with oesophagealfistulas following the method of Hofmeyr & Vos ( 1964)were used to samples three pelleted rations. The rationswere lucerne huy, lucerne hay and maize (60:40) andEragrostis curvuln hay, and were all ground through amoderately-fine (6 mm) sieve prior to mixing and pelleting.The average dry weight, the percentage recovery and thesaliva content of the oesophageal fistula samples appearin Table l. These data represent three lS-minute collectionsby each of the sheep on each of the rations. The sheepwere not fasted prior to sampling and collections weremade at intervals of 2 to 3 davs.Variations in sample weight between animals andbetween collections have frequently been reported(Arnold,McManus, Bush & Ball, 1964.(Cook, 1964). The differ-ences in sample weight between rations (Table l) appearto be due to differences in palatabil ity. As a portion of thefeed consumed by oesophageal f istulated animals is normal-ly swallowed (i.e. escapes collection) and an unknownamount of rumen ingesta rnay be added to the sample byregurgitation, the values in Table 1 do not necessarilyrepresent the true recovery. The true recovery wil l, infact, be somewhat less than that indicated in Table l.The overall average apparent recovery of the samples con-*Present address: Research lnstituteScience, Irene.Table ISample weight, recovery and sliva added to rationsconsumed by oesophageol fistulated sheepRat ion Dry weight Apparent Apparentof sample sample re- saliva secre-(g) covery( fi\ tion (g) per100 sampleDMLucernehaymean 281 93range lll-432 58-1 I Is . D . *  ! 1 2 6  1 1 61 3 98G319t76Lucerne meanhay * maize range(60 :40 )  S .D . *3 1 990-s 39t  1 6 08853-99t 2 019499-575t  1 6 0Eragrostis meancurvula rangehay  S .D . *126 91 19979-2t7 66-113 42-399! 4 7  t l g  r  g g* S-D. = Standard deviationsumed was 9 | /, . The differences between rations for therecovery of samples l4/ere small and are probably due tothe fact that all rations were pelleted to the same sizepellet. The range of sample recovery was large and 5 out ofa total of 27 samples collected (19%) showed weightincreases. These weight increases were, however, smalland only exceeded 2% in 2 of the 5 samples. In most casesrecoveries exceeding lOOf, were associated with largesample weights. It may be assurned that these weight in-creases are mainly due to regurgitated material, althoughthe dry matter of the added saliva would make somecontribution (saliva contains l, l% dry matter accordingto Spector, l96l). Contamination of the samples by ru-men ingesta cannot always be determined, particularly wheresmall amounts are added or where the chewed sample andingesta have a similar appearance. The appearance of rumeningesta and chewed feed samples from ruminants on apelleted or finely-ground ration have a greater similaritythan those from grazing animals or animals fed coarseroughages. Although this suggests that contamination byrumen ingesta would be more easily detected in the graz-for Animal and Dairy45ing animal, the possible occurrence of contamination shouldnot be ignored.The moisture present in oesophageal fistula samplesmay originate from either the saliva or from regurgitatedrumen ingesta. The true saliva content of these samples cantherefore not be ascertained unless the degree of contamina-tion (if any) by rumen ingesta is known. It is, however,reasonable to assume that the greater percentage of thismoisture originates from saliva. The large variation in theapparent saliva secretion per unit feed consumed is note-worthy. This is due to the fact that one oi the oeso-phageal fistulated sheep often ate only a few mouth-fuls of feed at the beginning of the collection period andrefused to eat any more until its fistula plug u,as replaced,when it immediately resumed normal eating. The amountof saliva (apparent) added per 100 g dry matter collectedby this animal was almost twice that added by theother two sheep.Table 2Dry matter composition of feed and oesophagealfistuh samplesRation sampledCrude*Protein%Crude+Fibreo//0Ashol/0oesophageal fistula samples found in this study can, there-fore, be almost entirely attributed to salivary astr contami-nation. The low nitrogen content of saliva (0,014% accord-ing to Marshall, Torell & Bredon, 1967) would not beexpected to increase the protein content of the fistulasamples to any marked degree. The relatively small increasein the protein content of the fistula samples is not regardedas particularly significant.Van Dyne & Torell (1964) have drawn attention toa non-enzymatic browning reaction in which carbohy-drate degradation products may condense with protein.This type of reaction appears to be favoured by thepresence of water (e.9. a high saliva content) and dryingat high temperature. The samples used in this study weredried at 75oC and this type of reaction could have occur-red in a number of samples which showed browning.It is therefore possible that this could have had someeffect on the chemical composition of the fistula samples.The results obtained in this study suggest hat con-tamination of oesophageal fistula samples with rumeningesta does occur, even though relatively short collectionperiods were used. The effect of this contamination on thechemical composition of the sampled feed appears tobe relatively small. Contamination by rumen ingesta is,however, not necessarily confined to samples with re-coveries in excess of 100ff. It is suggested that samplecontamination by rumen ingesta could be prevented byplacing a small inflatable baloon in the oesophagus belowthe fistula during collection periods. Although the pre-starving of oesophageal fistulated animals prior to samplingwould also reduce the possibility of contamination of thisnature, Arnold et al. (1964) have indicated that thisprocedure could affect grazing selection on natural pasture.From this and other studies (cf. van Dyne &Torell, 1964) it is clear that considerable variance occursin the sampling performance of oesophageal fistulatedanimals. Samping errors due to animals which for variousreasons may be "poor" samplers could be minimized byperformance testing of oesophageal fistulated animals bothprior to and during the course of diet sampling experiments.AcknowledgementsThe author wishes to thank Professor D.M. Joubertand Dr. B.D.H. van Niekerk for constructive criticism ofthe manuscript and Dr. H.C. Voss for advice in planningthe experiment.ReferencesARNOLD, G.W.,  McMANUS, W.R.,  BUSH, I .G. & BALL,JUDITH, 1964. Aust. J. exp. Agric. Anim. Husb.4 , 7 1 .Lucerne luyFeed sampleFistula sampleDifference ( %\18 ,419 ,3+4,533,734,9+3 ,510 ,5I  l , g+t2,4Lucerne hay * maizeFeed sampleFistula sampleDifference ( /)15 ,4t6,7+9,02 l , 822,1+  1 , 56,58 ,3+27,7E. curvula luyFeed sampleIristula sampleDifferencet t ,21 2 , l+ 7 , 124.524,50.08 , 19 ,7+  1 9 , 7* Fixpressed on an ash-free basis.The protein and fibre content (on an ash-iree basis)and the ash content of the feed and oesophageal fistulasamples are presented in Table 2. The difference in thefibre content of the feed and fistula samples is relativelysmall and pr<lbably insignificant. The increase of approxim-ately 2O /' in the ash content is slightly higher than thatreported by Lombard & van Schalkwyk (1963) for apelleted ration. Ruminant saliva contains 0,7 to 0,9%ash (McDougal l .  1948) and with an average of  l l7g ofsaliva added per 100 g of sample collected in this study.the increase in ash content would be expected to beapproximately 15'/ ' . The increase in ash content of the46COOK, C.W., 1964. J. Anim. Sci. 23, 265.HOFMEYR, C.F.B. & VOSS, H.C., 1964. Jl. S. Afr. vet.med. Ass. 35, 579.LOMBARD, P.E. & VAN SCHALKWYK, A., 1963. S.Afr. Tyd*r. Landbouwet. 6,205.MARSHALL, B., TORELL, D.T. & BREDON, R.M.,1967. J. Range Mgmt.20, 310.McDOUGALL, E.1., 1948. Biochem. I . 43,99.McMANUS, W.R., 1961, Aust. J. exp. Agric. Anim.Husb.  l ,  159 .SPECTOR, W.S., 1961. Handbook of biological data.Philadelphia: Saunders.VAN DYNE, G.M., 1968. Measuring quality and quantityof the diet of large herbivores. Int. Bbl. ProgrammeHandbook No. 7, eds. F.B. Golley & H.K. Buechner.Oxford: Blackwell.VAN DYNE, G.M. & TORELL, D.T., 1964.J. Range Mgmt.1 7 , 7 .47

A note on contamination of oesophageal fistula samples with rumen ingesta

https://www.ajol.info/index.php/sajas/article/download/140424/130174

A note on contamination of oesophageal fistula samples with rumen ingesta

Abstract

Similar works

Full text

Available Versions

AJOL - African Journals Online