The prediction of grass silage intake by beef cattle receiving barley-based supplements

Transcription

1 Livestock Production Science 68 (001) locte/ livprodsci The prediction of grss silge intke by beef cttle receiving brley-bsed supplements, b,b,b B.F. McNmee *, D.J. Kilptrick, R.W.J. Steen, F.J. Gordon Agriculturl Reserch Institute of Northern Irelnd, Hillsborough, Co. Down, BT6 6DP, UK b Deprtment of Agriculture for Northern Irelnd nd the Queen s University, Belfst, UK Received 1 July 1999; received in revised form 9 My 000; ccepted 8 June 000 Abstrct Dt on the intke by beef cttle of 11 silges either unsupplemented or supplemented with brley-bsed concentrtes were provided from six studies crried out t the Institute. An empiricl model ws developed from these dt which described n exponentil decrese in silge intke s concentrte intke ws incresed, with y-xis intercepts corresponding to unsupplemented silge intkes nd common x-xis intercept of 73. (S.E. 5.00) g/ kg W corresponding to concentrte intke when offered s sole feed. The model curvture (r prmeter) ws lso shown to be constnt for ll silges (1.05 (S.E )). When the model ws vlidted ginst externl dt (11 published studies), the reltionship between ctul nd predicted silge DMI gve n R of 0.89 with n intercept nd slope not significntly different from 0 nd 1, respectively. Seventy-six percent of silge DMIs predicted using the developed model were within 0.5 kg DM of the observed intkes in the vlidtion dt. The developed model showed n improvement over previously published model, s indicted by significnt reduction in the men squred prediction error. 001 Elsevier Science B.V. All rights reserved. Keywords: Beef cttle; Predicted grss silge d libitum intke; Concentrte supplementtion; Empiricl model; Substitution rte 1. Introduction diry systems. While some models im to directly predict the totl intke in mixed diets (Vdiveloo nd Estimtes of voluntry intke form n importnt Holmes, 1979; Agriculturl Reserch Council, 1980; prt of feed rtioning systems for ruminnts nd Rook nd Gill, 1990), Lewis (1981) hs rgued tht mny pproches hve been dopted for the develop- more logicl pproch in mixed grss silge/ conment of empiricl models to predict the d libitum dry mtter intke of grss silge (SDMI) in beef nd *Corresponding uthor. Present ddress: Glen Ltd, Segoe Industril Estte, Crigvon, BT63 5UA, Northern Irelnd, UK. Tel.: ; fx: E-mil ddress: bmcnmee@glen.co.uk (B.F. McNmee) / 01/ $ see front mtter 001 Elsevier Science B.V. All rights reserved. PII: S (00)0013-X centrte diets my be to dopt two-stge prediction. The first stge being to derive model to predict the intke potentil of silge when given s the sole feed, nd the second to correct this model for the substitution effect of concentrtes. This concept is supported by recognition tht the extent to which the intke of grss silge is reduced by supplementry concentrtes depends, to lrge extent, on the intke

2 6 B.F. McNmee et l. / Livestock Production Science 68 (001) 5 30 of the forge given s sole feed (Wilkinson, 1985; Irwin, 1970; Forbes nd Jckson, 1971; Steen nd Thoms, 1987). McIlmoyle, 198; Steen nd Kilptrick, 1999; Steen A number of models for predicting the intke of nd Kilptrick, unpublished; Ptterson et l., unsilge s sole feed re vilble in the literture. published). In the studies, 11 silges ( g/kg Such models hve included the independent vrites DM) were offered to totl of 681 heifers, bulls nd of silge digestibility nd dry mtter concentrtion steers of mixed breeds (initil liveweight (Bumgrdt et l., 1976; Lewis, 1981), whole diet kg) for periods rnging from 8 to 30 dys. Of the gross energy concentrtion nd metbolisbility (Ag- 11 silges exmined, eight were offered s sole riculturl Reserch Council, 1980), silge mmoni feed nd with, 3 or 4 levels of concentrte nitrogen concentrtion (Lewis, 1981), silge neutrl supplementtion. The other three silges were only detergent fibre concentrtion (Bumgrdt et l., offered to the nimls supplemented with 3, 4 or ) nd ner infrred reflectnce spectroscopy levels of concentrtes. The concentrte supplements (NIRS) (Steen et l., 1998). The ltter pproch hs offered in the studies were mostly brley bsed proved to be both ccurte nd simple nd pr- ( g/ kg brley) nd in ll cses were offered ticulrly suitble for use within technicl support seprtely to the silge portion of the diet. In ll role for the griculturl industry. The objective of studies the nimls were housed in open pens nd this pper is to develop this pproch further by were offered silge through brrier. Silge ws providing prediction model tht will djust d refreshed twice dily. libitum silge intke for the effect of level of The SDMIs (g/ kg W ) were nlysed using supplementry concentrtes offered in the diet of the Genstt nlysis of vrince procedures (Genstt 5 beef niml. If this cn be ccurtely chieved then Committee, 1989). Silge 3 concentrte mens from the combined prediction of silge intke s sole the nlysis of vrince were used in regression feed nd the effect of concentrte level on tht intke nlysis to investigte the reltionship between y 5 would enble more ccurte feed rtioning systems silge intke nd x 5 concentrte intke on g/kg to be developed. While Lewis (1981) hs followed W bsis. An exponentil reltionship of the form similr pproch, this hs proved to hve limited x y 5 1 br ws exmined, where ( 1 b) repreccurcy in previous independent vlidtions (Ag- sented silge intke, when silge ws offered s riculturl nd Food Reserch Council, 1991). sole feed. Three sets of models were fitted: 1. with seprte, b nd r prmeters for ech of. Mterils nd methods the 11 silges;. s (1) but with common r prmeter; The pproch dopted in the present study ws to 3. s () but extending to tke ccount of the develop n empiricl model from dt obtined from constrint tht the intercept of the eqution on the six studies crried out with growing cttle t this x-xis, equting to the concentrte intke t which Institute nd to vlidte the model ginst 11 pub- the silge intke ws zero, should be constnt for lished studies crried out outside the Institute. Be- ll silges i.e. the concentrte intke when concuse of the effect of liveweight on feed intke, ll centrte s the sole feed ws independent of dt were expressed in the form (kg silge DM silge type. This introduced the following con- intke/kg liveweight ) nd (kg supplement strint nd modified eqution: log ( /b )/log k x i e i i e DM intke/kg liveweight ) (r) 5 k giving y 5b (r r ) where k is constnt nd is equl to concentrte intke for zero silge intke nd i is silge type for i Model development The dt used to develop the model were derived from six studies crried out t the Agriculturl Reserch Institute of Northern Irelnd (Forbes nd Sttisticl tests, bsed on comprison of residul sum of squres, were crried out to compre the goodness of fit of the three sets of models.

3 B.F. McNmee et l. / Livestock Production Science 68 (001) Model vlidtion the model in estblishing the reltionship between silge nd concentrte DMI. A strong exponentil The developed model ws vlidted ginst dt reltionship ws identified, which when fitted in its from 11 published studies, crried out t vrious unconstrined form, showed n R vlue of loctions outside this Institute (Lever, 1973; Dren- Sttisticl tests used to compre the prmeters for nn nd Lwlor, 1976; Flynn, 1978; Drennn, 1979; the individul silges showed tht common r-vlue Aston nd Tyler, 1980; Petchey nd Brodbent, of 1.05 (S.E ) could be ssumed for the 1980; Veir et l., 1983, 1985, 1990; Drennn nd exponentil reltionship. Kene, 1987,b). These studies incorported 15 grss When fitted in its constrined form, the R vlue silges ( g/kg DM) offered to totl of 919 ws 0.98, with corresponding estimte for k of 73. steers, bulls nd wenlings of mixed breeds nd (S.E.5.00) g concentrte DM/ kg W. The differrnging from 93 to 491 kg liveweight for periods of ence in goodness of fit between the unconstrined dys. Silges were offered either unsup- nd constrined forms ws non-significnt (P.0.05). plemented or with brley-bsed supplements (.875 The SDMIs for the 11 silges used to develop the g/ kg fresh brley) t 1,, 3 or 4 levels ( g/ kg model re presented in Fig. 1. The plotted points W / dy). represent the observed SDMIs t the rnge of CDMIs In the vlidtion exercise, predicted silge intkes for the 11 silges while the plotted curves represent (P) in supplemented diets, using the developed the predicted SDMIs for the sme 11 silges in model, were compred ginst ctul observed silge ccordnce with the bove constrined eqution. intkes (A), using the men-squre prediction error (MSPE) defined s 3.. Model vlidtion 1 MSPE 5] O sa Pd In order to pply the developed model to the dt n vlidtion set, it ws necessry to evlute the silgewhere n is the number of pirs of vlues of A nd P specific prmeters in the model using the silge dry being compred. The MSPE cn be regrded s the mtter intke when silge i ws offered s the sole sum of the men bis, the line bis nd the rndom feed (SDMImx), thus: vrition bout the regression line (Rook et l., k 1990). Results re presented in terms of the proportionl SDMImxi5 b i(r 1) contribution of ech of these three components giving the eqution: to the MSPE. The squre root of the MSPE is the k x k men prediction error (MPE) nd is reported s y 5 SDMImx(r r )/(r 1). proportion of the men observed silge intke. Finlly the predicted silge intkes using the present This eqution ws pplied to clculte the premodel were compred ginst silge intkes predicted silge intkes for the vlidtion dt using the dicted using the Lewis (1981) model. Agin the SDMImx for the prticulr silges nd the vlues MSPE ws used s the prmeter of ccurcy. for k, the concentrte intke for zero silge intke estimted from the development dt set, nd the estimted vlue for r. This gives the eqution 3. Results nd discussion (ARINI model): x y 5 SDMImx i( ) Model development The reltionship between ctul nd predicted The wide rnge of SDMIs recorded for the 11 silge intkes ws found to be liner with intercepts silges when offered s the sole feed (50.6 to 88.8 g non-significntly (P.0.05) different from zero nd DM/ kg W ), together with the rnge of concen- regression coefficients non-significntly (P.0.05) trte supplementtion offered to the nimls (8.8 to different from unity i.e. 458 lines through the origin g DM/kg W ) fcilitted the development of This is shown in Fig..

4 8 B.F. McNmee et l. / Livestock Production Science 68 (001) 5 30 Fig. 1. The observed nd predicted silge DMI of 11 silges in supplemented diets with vrious levels of DMI when offered s sole feed. Fig.. Actul versus predicted silge DMI using the ARINI model from 11 published feeding studies crried out t vrious loctions outside the Institute. The SDMI predicted for the vlidtion set using the bove model, showed men difference between ctul nd predicted intke of 8.9%61.87 nd men bis of 1.0% Substitution rtes chrcteristic of the ARINI model re shown in Tble 1. A feture of this model is the incresing substitution rte s concentrte DMI is incresed nd s silge intke s sole feed is incresed. The ccurcy of the ARINI model ws compred with tht of the Lewis (1981) model

5 B.F. McNmee et l. / Livestock Production Science 68 (001) Tble 1 b Exmple substitution rtes (SR ) nd corresponding mrginl substitution rtes (MSR ) s determined by the ARINI model (ll intkes re expressed s g/kg W ) Concentrte DMI SDMI s sole feed SDMI SR SDMI SR MSR SDMI SR MSR SDMI SR MSR SDMI SR MSR SDMI SR MSR kg of silge DM reduced per kg of concentrte offered. b The difference in SR by incresing the concentrte intke by 10 g/kg W. which ws developed from similr stndpoint. The wide rnge of weights were used. This lrge vrivlidtion prmeters re shown in Tble, together tion necessittes ccurte correction of intkes for with the MSPE nd the proportion of MSPE ttribut- liveweight differences correction which is not ble to men bis, line bis nd rndom error. The tken into ccount in the Lewis (1981) model. In men bis nd the MPE re expressed s propor- ddition, the Lewis eqution is bsed on series of tion of the observed silge intke. The men pre- prllel curves, of SDMI versus concentrte DMI, dicted intke using the Lewis (1981) model ws for silges with differing intkes s sole feed considerbly lower thn the ctul men intke with wheres, the ARINI model uses series of con- bis of 4.9 g/kg W compred to 1.01 g/kg vergent curves. It is expected tht the use of con- W for the ARINI model. This lrge men bis vergent curves, to describe the decresing SDMI s ws responsible for the inccurcies encountered CDMI is incresed, is biologiclly more pproprite with the Lewis model when vlidted using these s it reflects the decresing significnce of the silge dt, with the men bis ccounting for 30% of the qulity (nd hence its intke s sole feed) s silge clculted MSPE. The result ws tht the MPE for represents decresing proportion of the totl diet. the Lewis model ws compred to for the ARINI model. Furthermore, the R of the predicted versus ctul SDMIs for the vlidtion dt 4. Conclusions set showed significnt improvement from 0.76 to 0.89 with the ARINI s compred to the Lewis A model hs been developed to predict the SDMI model indicting tht the new model ccounts for t given level of concentrte supplementtion more of the vrince. providing the intke of the silge when consumed s The poor reltive performnce of the Lewis sole feed is known or my be ccurtely predicted (1981) model in the present vlidtion exercise my from silge compositionl prmeters. Vlidtion of hve been due to the fct tht the vlidtion dt the model with independent dt reveled tht 76% were derived from experiments in which nimls of of SDMI predictions were within 8% of the ctul Tble Prediction precision of ARINI model s compred to the Lewis (1981) model (ctul men intke555.7 (S.E..71; n533) g DM/ kg W ) Model Predicted intke Proportion of MSPE b Men S.E. MSPE Bis Line Rndom Bis MPE ARINI Lewis gdm/kgw. (g DM/kg W ). b

6 30 B.F. McNmee et l. / Livestock Production Science 68 (001) 5 30 intkes. The developed model hs been designed for Reference Mnul. Oxford Scientific Publictions, Clrendon use in nimls offered silge nd concentrtes of Press, Oxford. Lever, J.D., Rering of diry cttle 4. Effect of concentrte similr composition, nd in ccordnce with the supplementtion on the liveweight gin nd feed intke of feeding regimen, to tht dopted in the studies from clves offered roughges d libitum. Anim. Prod. 17, which the model ws derived, i.e. silge Lewis, M., Equtions predicting silge intke by beef nd g/kg DM, concentrtes g/kg brley nd diry cttle. In: Proceedings of the Sixth Silge Conference, silge provided d libitum, seprte to the concen- Edinburgh, pp Petchey, A.M., Brodbent, P.J., The performnce of fttentrte supplementtion. ing cttle offered brley nd grss silge in vrious proportions either s discrete feeds or s complete diet. Anim. Prod. 31, References Rook, A.J., Gill, M., Prediction of the voluntry intke of grss silges by beef cttle 1. Liner regression nlyses. Anim. Prod. 50, Agriculturl nd Food Reserch Council, AFRC Technicl Rook, A.J., Dhno, M.S., Gill, M., Prediction of the Committee on Responses to Nutrients. Report no. 8. Voluntry voluntry intke of grss silges by beef cttle 3. Precision of intke of cttle. Nutr. Abs. Rev. (Series B) 61, lterntive prediction models. Anim. Prod. 50, Agriculturl Reserch Council, The Nutrient Requirements Steen, R.W.J., Kilptrick, D.J., The reltive effects of grss of Ruminnt Livestock. Commonwelth Agriculturl Bureux, silge:concentrte rtio, metbolisbility of the diet nd d Slough. libitum versus restricted dry mtter intke t equivlent energy Aston, K., Tyler, J.C., Effects of supplementing mize nd intke on the performnce nd crcss composition of beef grss silges with brley, nd mize silge with ure or cttle. Livest. Prod. Sci., In press. mmoni, on the intke nd performnce of fttening bulls. Steen, R.W.J., McIlmoyle, W.A., 198. The effect of frequency of Anim. Prod. 31, hrvesting grss for silge nd level of concentrte supple- Bumgrdt, B.R., Crbill, L.F., Gobble, J.L., Wngness, J., menttion on the intke nd performnce of beef cttle. Anim. In: Proceedings 1st Interntionl Symposium on Feed Com- Prod. 35, position, Animl Nutrient Requirements nd Computeristion Steen, R.W.J., Gordon, F.J., Dwson, L.E.R., Prk, R.S., Myne, of Diets, pp C.S., Agnew, R.E. et l., Fctors ffecting the intke of Drennn, M.J., Compenstory growth in cttle 1. Influence grss silge by cttle nd prediction of silge intke. Anim. Sci. of feeding level during the first winter (9 to 14 months of ge) 66, on subsequent performnce nd crcss composition. Ir. J. Thoms, C., Fctors ffecting substitution rtes in diry Agric. Res. 18, cows on silge bsed rtions. In: Hrseign, W., Cole, D.J.A. Drennn, M.J., Kene, M.G., Concentrte feeding levels (Eds.), Recent Advnces in Animl Nutrition, pp for unimplnted nd implnted finishing steers fed silge. Ir. J. Vdiveloo, J., Holmes, W., The prediction of the voluntry Agric. Res. 6, feed intke of diry cows. J. Agric. Sci. Cmbr. 93, Drennn, M.J., Kene, M.G., 1987b. Responses to supplementry Veir, D.M., Butler, G., Ivn, M., Proulx, J.G., Utilistion of concentrtes for finishing steers fed silge. Ir. J. Agric. Res. 6, grss silge by cttle: effect of brley nd fishmel supple ments. Cn. J. Anim. Sci. 65, Drennn, M.J., Lwlor, M.J., Evlution of pelletted dried Veir, D.M., Fortin, A., Ivn, M., Butler, G., Proulx, J.G., grss s supplement to grss silge for fttening steers. Anim. Performnce of Hereford3Shorthorn bulls nd steers rised in Prod., Northern Ontrio nd fed different levels of grss silge nd Flynn, A.V., Supplementing erly nd lte cut silges with high moisture brley. Cn. J. Anim. Sci. 63, brley for store cttle. An Fors Tluntis. Anim. Prod. Res. Veir, D.M., Proulx, J.G., Seone, J.R., Performnce of beef Rep., steers fed grss silge with or without supplements of soyben Forbes, T.J., Irwin, J.H.D., Silge for winter fttening. J. Br. mel, fish mel nd brley. Cn. J. Anim. Sci. 70, Grssld. Soc. 5, Wilkinson, J.M., Evlution of conserved forges. In: Forbes, T.J., Jckson, N., A study of the utiliztion of Whittemore, C.T., Simpson, K. (Eds.), Beef Production from silges of different dry-mtter content by young beef cttle Silge nd Other Conserved Forges. Longmn, London, pp. with or without supplementry brley. J. Br. Grssld. Soc. 6, Genstt 5 Committee, In: Pyne, R.W. et l. (Ed.), Genstt 5