van der Merwe, FJ

van Rooyen, P

English

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2 t lS.Afr .  J .  An im.  Sc i .  1983,  13(3)Digestibility of the samediet in cattle and sheepP. van Rooyen* and F.J.  van der  MerweDepartment of Animal Science, University of Stellenbosch,Stellenbosch 7600, Republic of South Africa*To whom correspondence should be addressedThe question is posed of the applicability to cattle feeding, ofdigestibility data obtained with sheep. An experiment isdescribed where the same high concentrate diet was fed atthree levels, equalised per kg body mass between species. Inenergy and crude fibre cattle showed consistently lowerdigestibil i t ies than sheep, The difference is probably due tolonger rumen retention time in sheep.Die vraag word gestel of verteerbaarheidsgegewens wat metskape verkry is in beesvoeding toegepas kan word. 'n Proefword beskryf waarin dieselfde hodkragvoerdieet op drievoedingspeile wat op 'n per kg l iggaamsmassabasis tussenspesies gelyk gestel is aan beeste en skape gevoer is. Beeste hetdeurlopend energie en vesel swakker verteer as skape. Dieverskil word toegeskryf aan die waarskynlike langerru menretensietyd by skape.Keywords: Feed evaluation, digestibility, sheep, cattleIntroductionIn many laboratories, especially in Europe, sheep areused as 'instruments' for determining the digestibility offeeds and mixed diets. The most obvious reason for this isthat sheep are smaller than cattle and hence costs aremuch lower. Blaxter and Wainman (1961) could find nosignificant differences between sheep and cattle in thedigestion of different feeds over a range of levels. Theexception was a diet of low protein content, where theprotein was better digested by sheep than cattle. Schie-mann, Jentsch and Wittenburg (I97I) found that di-gestibility figures in cattle and sheep correlate well, anassumption that was also prevalent in the Netherlands fora number of years. Therefore it is no surprise that the newenergy feeding system which was introduced in the Nether-lands and other European countries in 1978, derives theME-contents of feed from digestibility data obtainedusing sheep (Van Es, Vermorel and Bickel, 1978). On theother hand, in the USA, data on digestibility or metab-olizability of feeds from sheep trials are not considered tobe of great value for cattle (Moe, Tyrell and Flatt, L974).There are indications that sheep ruminate more effectivelyand therefore digest grain more efficiently than cattle,while cattle are more efficient in digesting long roughages.In their comprehensive overview of the subject Schneiderand Flatt (1975) found published data with significantresults to prove both similarit ies and differences.If there is a difference in digestive capacity betweencattle and sheep it could quite possibly be related to thedifference in size of the reticulo-omasal orif ice, throughwhich digesta has to enter the lower digestive tract. Insheep it is so small that it is difficult for larger foodparticles to pass. The result is that these particles areregurgitated, resulting in a higher digestibil i ty after ru-mination. This may be true of whole grains but it sti l lleaves open the question of the relative digestibil i ty of afinely-ground, high-grain, complete diet in cattle andsheep.Materials and MethodsIn a recent experiment the digestibil i ty of such a dietcontainin 930% hay ground though a 6.25 mm screen andwhich analysed 145 gcrude protein (CP) , L24 gcrude fibre(CF) and 18,7 MJ gross energy (GE) per kg DM, wasdetermined with both steers and wethers fed at threecomparable levels in terms of feed DM per kg body massper day.Both the wethers and the steers were penned individuallyand adapted to the experimental diet for a period of 28days at an estimated maintenence level of feeding, followedby ten days at the appropriate experimental feeding level.The three levels tested were lI, 16 and 2l g per kg livebody mass per day. Faeces were collected over a ten dayperiod following the 38 day adaptation period (28 atmaintenance plus 10 at experimental level). The sheepwere fitted with harnesses and faeces bags. With steersfaeces were quantitatively collected immediately they werevoided on the concrete floor using the external markerchromic oxide to correct for recovery.Results and DiscussionThe apparent digestibility of the diet as fed at three levelsto cattle and sheep is presented in Table 1. The apparentdigestibility of CP corresponded fairly well in sheep andcattle with sheep showing slightly lower values except atthe highest feeding level. In apparent digestion of GE,sheep showed consistently higher values than cattle at alllevels. In apiparent digestion of CF it was interesting toTab le  1  Apparent  d iges t ib i l i t y  o f  energy ,  c rudepro te in  and c rude f ib re  o f  the  same d ie t  fed  a t  th reeleve ls  to  sheep and ca t t leDigestibi l i ty (%)Feeding levelGlke Bw/d) Energy Crude protein Crude fibreCattle Sheep Cattle Sheep Cattle Sheep Cattle Sheep1 1 , 376,927,371,2 70,r 7g,g g6,g g1,g76,7 69,0 79,2 g3,g gL,621,0 65,8 74,3 75,r 76,637,3 59.845,2 57 ,749,4 50,1note that sheep showed considerably higher values thancattle at the two lower feeding levels, while at the highestlevel digestibility of CF was almost equal in the twospecies. Another noticable aspect of CF digestion wasthat in cattle the apparent digestibility increased withincreasing level of feeding, while with sheep it declined,as was expected.If the ME~content of the diet is estimated for the twospecies at each level of feeding, the values in Table 2 areobtained (ME calculated as DE x 0,81). These dataindicate a consistent 10% difference between cattle andsheep.Table2 ME concentration of the diet incattle and sheep fed at three levelsME (MJ /kg DM)Feeding level Cattle/Sheep(g/kg BW/d) Cattle Sheep x 10011 10,9 11,9 91,616 10,7 11,8 90,721 10,2 11,2 91,1One of the unanswered questions iswhether these feed-ing levels were, in effect, comparable in the two speciesalthough the intakes were equal on a per kg live bodymass basis. However, since sheep have a significantlylowermaintenance energy requirement than cattle (Blaxter,1962) a difference in relative feeding level cannot beresponsible for the difference in energy digestibility foundbetween cattle and sheep in this experiment, because thesheep should then have shown lower values.The conceptual framework for understanding food in-take and relative digestive capacities of ruminants, haschanged over the past years. Much more light has beencast on fermentation rate and rumen retention time ofingesta. The fact that the reticulo-omasal orifice is physi-cally smaller in sheep than in cattle, would lead to a longerretention time in sheep than in cattle. Therefore, sheepare able to digest the slowlyfermented CF more efficientlythan cattle as shown in Table 1. This effect would decreaseas feeding level increased as shown, and thus rate ofpassage would be increased and retention time decreasedwith a consequent reduction in CF digestibility. Thisexplains the above finding that the sheep obtained moreME from the diet at each feeding level despite intakeswhich were equal on a per kg live body mass basis.BLAXTER, K.L., 1962. The energy metabolism of ruminants.London: Hutchinson Scientific and Technical.BLAXTER, K.L. & WAINMAN, F.W., 1961. The utilization offood by sheep and cattle J. Agric. Sci. Camb. 57, 419.MOE, P.W., TYRRELL, H.F. & FLATT, W.P., 1974. Predictionof the net energy value of feeds for lactation. Proc. 6th Symp.Energy Metab., EAAP, 210.SCHIEMANN, R.R., JENTSCH, W. & WITTENBURG, H., 1971.Zur Abhangingkeit der Verdau1ichkeit der Energie und derNahrstoff von der H6he der Futteraufnahme und derRationzussamensetzung. Arch, Tierem., 21, 223.SCHNEIDER, B.H. & FLATT, W.P., 1975. The evaluation offeeds through digestibility experiments Athens, USA: TheUniversity of Georgia Press.VAN ES, A.J.H., VERMOREL, M. & BICKEL, H., 1978. Feedevaluation for ruminants: New energy systems in the Netherlands,France and Switzerland Livestock Prod. Sci. 5,326.

Digestibility of the same diet in cattle and sheep

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Digestibility of the same diet in cattle and sheep

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