Neither native nor popped cornmeal in the ration of dry cows affects magnesium absorption

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1 Livestock Production Science 63 (2000) locte/ livprodsci Neither ntive nor popped cornmel in the rtion of dry cows ffects mgnesium bsorption, b J.Th. Schonewille *, A.Th. Vn t Klooster, J.W. Cone, H.J. Klsbeek-Vn der Vlk, H. Wouterse, A.C. Beynen Deprtment of Nutrition, Fculty of Veterinry Medicine, Utrecht University, P.O. Box , 3508 TD Utrecht, The Netherlnds b DLO-Institute for Animl Science nd Helth, Deprtment of Ruminnt Nutrition, P.O. Box 65, 8200 AB Lelystd, The Netherlnds Received 16 November 1998; received in revised form 19 My 1999; ccepted 1 June 1999 Abstrct The hypothesis tested ws tht ddition of strch to the rtion of cows would stimulte mgnesium (Mg) bsorption becuse of lowering of ruminl ph, which renders Mg more soluble nd thus more vilble for trnsport cross the epithelium of the rumen, which is the mjor site of Mg bsorption in ruminnts. The tril hd Ltin-squre design in which five non-pregnnt, non-lctting multiprous cows were fed rtions contining either mix of cellulose nd mizeglutenfeed or ntive or popped cornmel ech t two levels (equivlent to 11 or 20% strch in the dry mtter). The dietry periods lsted 28 dys. The mount nd type of dietry strch did not significntly ffect totl gstro-intestinl trct Mg bsorption, post-prndil ruminl ph, rumen fluid concentrtions of Mg, K nd totl voltile ftty cids; for ll five tretments combined, the mesured vlues were % of intke, , mmol/ l, mmol/ l, nd mmol/ l (mens6s.e., n 5 5), respectively. For ll cows nd tretments combined, there ws significnt, negtive reltionship between ruminl ph nd Mg concentrtion in rumen fluid. The ruminl Mg concentrtions were low when compred with erlier work. On the bsis of published in-vitro studies showing tht concentrtions of soluble Mg fll to more or less constnt, low vlues when ph vlues re bove 6, it is suggested tht the high bseline vlues of ruminl ph in this study, hd prevented sttisticlly significnt effect of strch intke, if ny, on Mg bsorption Elsevier Science B.V. All rights reserved. Keywords: Mgnesium; Strch; Rumen; Fermenttion; Absorption 1. Introduction (Schonewille et l., 1997). In ruminnts, high K intkes inhibit mgnesium (Mg) bsorption which Grss silges from res with intensive livestock enhnces the risk of hypomgnesemi (Fontenot et production re generlly high in potssium (K) l., 1989). To sfegurd the Mg sttus of diry cows fed grss silges rich in K, it seems more pproprite to improve Mg bsorption from the diet rther thn *Corresponding uthor. Tel.: ; fx: to supplement the rtion with Mg becuse high Mg intkes by ruminnts my cuse depressed nutrient E-mil ddress: J.Schonewille@vet.uu.nl (J.Th. Schonewille) utilistion (Chester-Jones et l., 1989) / 00/ $ see front mtter 2000 Elsevier Science B.V. All rights reserved. PII: S (99)

2 18 J.Th. Schonewille et l. / Livestock Production Science 63 (2000) In study with dry gots the replcement of 2. Mterils nd methods dietry cellulose, t concentrtion of 342 g/kg dry mtter, by n equl mount of ntive corn strch hd 2.1. Animls nd experimentl design mrked stimultory effect on Mg bsorption (Schonewille et l., 1997b). It is not known whether Five non-pregnnt, non-lctting multiprous cows this observtion extends to diry cttle. In ny event, (ge y; men6s.e.), fitted with rumen the use of high mounts of strch in the rtion of cnnuls, were used. The cows were of Friesin diry cows entils the risk of ruminl cidosis nd Holstein 3 Holstein Friesin cross. During the exincreses feed costs to prcticlly uncceptble periment, they were housed in stnchion brn. level. Thus, to test whether consumption of corn The tril hd Ltin-squre design nd ws strch rises Mg bsorption in cows, we used in the preceded by 14-dy pre-experimentl period tht present study diets tht contined either 100 or 200 g llowed the cows to become dpted to rtions bsed strch/ kg dry mtter in the form of cornmel. primrily on rtificilly dried grss. Ech experimen- A possible mechnism by which strch could tl period lsted 28 dys. The nimls were rndomincrese Mg bsorption is lowering of ruminl ph ly ssigned to ech sequence of feeding on the five which renders Mg more soluble nd thus more experimentl rtions. vilble for trnsport cross the epithelium of the rumen, which is the mjor site of Mg bsorption in 2.2. Rtions ruminnts (Rogers nd Vn t Klooster, 1969; Toms nd Potter, 1976). Ntive corn strch is slowly During the pre-experimentl period the dily degrded by ruminl bcteri but popping of corn rtion of ll cows consisted of 4.5 kg rtificilly strch increses the rte of ruminl fermenttion dried grss, 0.2 kg brley strw nd 2.2 kg of (Cone et l., 1989; Cone nd Vlot, 1990) nd my commercilly vilble concentrte contining 9.0 g further lower ruminl ph (Mlestein et l., 1988). C, 4.9 g P nd 6.3 g Mg/kg. During the experimen- Thus, it could be suggested tht popped cornmel tl periods, the commercil concentrte ws replced enhnces Mg bsorption more thn would ntive by 0.1 kg of pelletted experimentl concentrte nd cornmel. This suggestion ws tested lso in this 2.1 kg powdered feed contining the dietry vrifeeding tril with dry cows. bles. The ingredient composition of the experimen- Tble 1 Ingredient composition of the experimentl rtions Control Ntive cornmel Popped cornmel 10% strch of dm 20% strch of dm 10% strch of dm 20% strch of dm Constnt components (kg/ d) b Control mix (kg/ d) c Ntive cornmel (kg/d) c Popped cornmel (kg/d) The constnt components consisted of 4.5 kg of rtificilly dried grss (924 dry mtter/kg), 0.2 kg of brley strw (930 g of dry mtter/ kg), nd 0.1 kg of experimentl concentrte (910 g of dry mtter/ kg). The experimentl concentrte consisted of 5.0 g of beet vinsses, 92.6 g of beetpulp, 1.4 g of MgO, nd 1.0 g premix. The premix consisted of mg of CCO 3, 3.0 mg of CoSO 4? 7H2O, 2.1 mg of N2SeO 3? 5H2O, 5.3 mg of KIO 3, 30.5 mg of MnSO 4? H2O, 27.5 mg of ZnSO 4? H2O, mg of CuSO 4? 5H2O, 17.2 mg of retinylcette (50,000 IU), 5.0 mg of choleclciferol ( IU), nd 150 mg DL--tocopherylcette (150 IU). b The control mix (917 g of dry mtter/kg) consisted of 63 g of distilled wter/kg, 639 g of cellulose/kg, nd 298 g of mizeglutenfeed/ kg. c The corn mel used in this study ws derived from one btch. One portion ws popped nd ground to pss 3 mm sieve. The dry mtter contents of the ntive cornmel nd the popped cornmel were 884 g/kg nd 881 g/kg, respectively nd the strch contents were 652 nd 668 g/ kg dry mtter, respectively.

3 J.Th. Schonewille et l. / Livestock Production Science 63 (2000) tl rtions is shown in Tble 1. The control rtion During the lst eight dys of ech experimentl contined cellulose nd mizeglutenfeed which ws period, urine nd feces were collected quntittively replced by either ntive or popped cornmel so s to from ech cow. Urine ws collected by using urinls formulte the experimentl rtions. In essence, this ttched to the cows with the use of lether hrnsreplcement involved n exchnge of cellulose ses. Urine coursed down into two vessels so tht (Arbocel, Interntio B.V., Rotterdm, The Nether- pproximtely 80% ws collected in one vessel. The lnds) nd corn strch. The ntive nd popped remining urine ws collected in the other vessel cornmel were from the sme btch nd were which contined N-zide s preservtive. Totl supplied by Presco Interntionl, Weert, The Nether- urine collections from ech 24-h period were lnds. The nlysed composition of the whole rtions weighed, nd 0.5% of the totl urine ws smpled is shown in Tble 2. from the preserved urine nd stored t 2 188C in The nimls were fed individully. On n energy plstic bottle which contined 100 ml 6 M HCl. The bsis, the rtions provided pproximtely the require- dily feces production of ech cow ws mixed ment for mintennce. The rtions were offered thoroughly, nd 3% of the wet weight ws stored t twice dily in two equl portions t 08:00 nd 17: C. At the end of ech collection period, the h. Feed refusls, if ny, were recorded. stored feces frctions of ech cow were combined, mixed thoroughly nd smpled. The smples were 2.3. Collection of smples dried t 608C for four dys, ground, nd stored in ir-dry form in seled jrs t room temperture until During the lst week of ech experimentl period, nlysis. the experimentl feedstuffs were smpled dily nd On dy 19, pproximtely 10 min prior to the then pooled, ground nd stored in seled jrs t room morning mel, 350 ml of Cr-EDTA solution (100 g temperture. Cr-EDTA/ l) ws injected into the rumen s mrker Blood smples were tken on dy 21 of ech for estimting the rumen volume nd pssge rtes of experimentl period. Between 16:00 nd 16:30 h, the liquid phse from the rumen. Rumen liquid before the fternoon mel, blood ws smpled from smples (pproximtely 30 ml) were tken t 07:45, the jugulr vein into evcuted heprinized tubes. 09:00, 10:00, 11:00, 13:00, 15:00 nd 17:00 h. The blood smples were centrifuged for 10 to 15 min Immeditely fter collection, ph of ruminl fluid ws t pproximtely 2700 g, nd the plsm ws col- recorded nd the rumen liquid smples were cenlected nd stored t 2 188C. trifuged t room temperture t 2700 g for 15 min, Tble 2 Anlysed composition of the experimentl rtions (g/ kg dry mtter) Control Ntive cornmel Popped cornmel 10% strch of dm 20% strch of dm 10% strch of dm 20% strch of dm Crude protein Crude ft Crude sh Crude fibre Neutrl detergent fibre Acid detergent fibre Acid detergent lignine Strch Mg K N C

4 20 J.Th. Schonewille et l. / Livestock Production Science 63 (2000) nd the superntnt ws stored in plstic tubes t stuffs nd feces ws estimted by tomic bsorption 2 188C. An liquot of the superntnt from the spectroscopy (Perkin-Elmer 3110; Perkin-Elmer, rumen liquid smples tken t 07:45, 09:00, 11:00, Norwlk, CT, USA). Clcium nd K in feedstuffs 13:00, 15:00 nd 17:00 h ws centrifuged t 208C t nd K in superntnt of rumen fluid were estimted 30,000 g for 30 min nd the superntnt ws stored by tomic bsorption spectroscopy nd N in feedin plstic tubes t 2 188C. From the rumen liquid stuffs by tomic emission spectroscopy (Perkin smples tken t 07:45, 09:00, 11:00, 13:00, 15:00 Elmer 3110). Mgnesium in plsm, urine, supernnd 17:00 h, 2 ml non-centrifuged fluid ws de- tnt of rumen fluid, nd chromium (III) in rumen proteinised ccording to the method of Bergmeyer fluid were mesured directly by tomic bsorption (1970). After 10 min, the de-proteinised rumen spectroscopy. The ccurcy of ech ssy run ws liquid smples were centrifuged t room temperture monitored using commercil reference smple (hy t 2700 g for 15 min nd the superntnt ws powder, CRM 129; Community Bureu of Refercollected nd stored in plstic tubes t 2 188C until ence, Brussels, Belgium) nd lbortory reference nlysis of voltile ftty cids (VFAs). smples, nd ws found to be within 5% devition from the trget vlues. The combined within nd 2.4. Chemicl nlyses between-run precision of the determintions ws # 3.0% (coefficient of vrition). Smples of the feedstuffs were subjected to the VFAs in rumen fluid were determined gs- Weende nlysis. Nitrogen contents were determined chromtogrphiclly (Perkin Elmer Autoscn) with by the mcro-kjeldhl method (IDF, 1986); fctor 2 m glss column (Chromosorb WAW DMCS; 17% of 6.25 ws used to convert g of N into crude neopentyl glycol dipte, 1% H3PO 4). Pivlic cid protein. Ether extrcts of the feedstuffs were pre- (0.045%, w/ v) ws dded to the de-proteinised pred ccording to the AOAC (1984); the solvent ruminl fluid s n internl stndrd. ws evported nd the crude-ft residue weighed. The crude fibre contents of the feedstuffs were 2.5. Sttisticl nlyses estimted using the Fibertec System M2 (Tector, Stockholm, Sweden). The NDF, ADF nd ADL All dt were checked for norml distribution content of the feedstuffs were estimted ccording to using the Kolmogorov Smirnov test nd then were the methods described by Goering nd Vn Soest subjected to nlysis of vrince (ANOVA) with (1970). To determine the strch content of the niml, experimentl period nd dietry tretment s feedstuffs, they were enzymticlly treted with fctors (Wilkinson, 1990). Rumen-liquid minerl myloglucosidse from Aspergilles niger (EC dt were subjected to repeted mesurement nly ) to hydrolyse ll strch to glucose (Keppler ses with niml, experimentl period nd dietry nd Decker, 1974). Subsequently, glucose ws me- tretment s fctors (Wilkinson, 1990). When sured enzymticlly with test combintion (Boeh- dietry fctor hd sttisticlly significnt influence, ringer Mnnheim Dignostic, Mnnheim, Germny) Bonferroni s test ws used to identify the diets tht nd computerised utonlyser (Beckmn hd different effects on the vrible involved. Synchron CX Systems; Beckmn, Mijdrecht, The Throughout, the level of sttisticl significnce ws Netherlnds). The free glucose content of the feed- pre-set t P, stuffs ws mesured directly. Strch ws clculted s totl glucose minus free glucose. For the experimentl feedstuffs, i.e., the control mix nd the 3. Results two types of cornmel, the in-vitro rte of fermenttion ws determined ccording to the method 3.1. In-vitro fermenttion of the dietry vribles described by Cone et l. (1996). Prior to the determintion of the selected minerls in feedstuffs nd To check the fermenttion profiles of the dietry feces, the smples were shed (4808C for 6 h) nd vribles, the control mix, ntive nd popped cordissolved in 15 ml 4 M HCl. Mgnesium in feed- nmel were incubted with rumen culture nd totl

5 J.Th. Schonewille et l. / Livestock Production Science 63 (2000) gs production ws mesured (Cone et l., 1996) Mgnesium blnce nd plsm Mg The high rte nd subsequent decline in the rte of gs production during the first hour of the incub- Mgnesium intke ws similr for ll five dietry tions (Fig. 1) probbly represents the degrdtion of tretments (Tble 3). Upon ANOVA, fecl excrethe wter-soluble frction of the experimentl feed- tion of Mg ws found to be significntly ffected by stuffs (Cone et l., 1997). After 5 h of incubtion, the fctor diet (P ), but significnt differences the incubtion contining the popped cornmel hd between specific rtions could not be identified by the highest rte of gs production. After 10 h, the Bonferroni s t-test. Consequently, Mg bsorption nd rte hd fllen to pproximtely 20% of the pek urinry excretion were similr for the tretments. vlue, but now the control mix nd ntive cornmel The dietry tretments did not ffect (P ) produced their pek vlues. After 20 h the rte of plsm Mg. For ll tretments combined, men totl gs production hd returned to bseline vlues plsm Mg concentrtion ws 0.80 mmol/ l (S.E. for the three feedstuffs ; n 5 5) Feed intke nd body weight 3.4. Rumen liquid: Mg nd K concentrtion, ph nd VFAs Experimentl rtions were consumed completely throughout the experiment. Men body weight t the Mg nd K concentrtions in rumen liquid, before end of the experiment ws 746 kg (S.E. 16.0; n 5 5), the morning feed nd lso fter feeding, were not which ws lmost identicl (P ; pired t-test) significntly influenced by the dietry tretments to pre-experimentl vlues (744 kg, S.E. 14.0; n 5 (Tble 4). Post-prndil men Mg vlues were 5). highest fter feeding the rtions with either 20% Fig. 1. In-vitro gs production rtes fter incubtion of rumen culture with either the control mix (h), ntive cornmel (d) or popped cornmel (s).

6 22 J.Th. Schonewille et l. / Livestock Production Science 63 (2000) Tble 3 Mgnesium blnce fter the feeding of the experimentl rtions Control Ntive cornmel Popped cornmel Pooled S.E.M. P 10% strch 20% strch 10% strch 20% strch of dm of dm of dm of dm Intke (g/ d) nd nd Feces (g/ d) Absorption (g/ d) (% of intke) Urine (g/ d) Blnce (g/ d) nd 5 Not determined becuse the cows were offered restricted mount of feed. Tble 4 Concentrtions of Mg nd K in rumen liquid (mmol/l), totl voltile ftty cids (VFAs in mmol/l) nd ruminl ph in cows fed the experimentl rtions Control Ntive cornmel Popped cornmel Pooled S.E.M. P 10% strch 20% strch 10% strch 20% strch of dm of dm of dm of dm Ruminl Mg concentrtion Post prndil Ruminl K concentrtion Post prndil Ruminl VFA concentrtion Post prndil Ruminl ph Post prndil 6.49 b 6.52 b c Post-prndil vlues re geometricl mens for five vlues; i.e., these vlues cn be considered s n estimtion of the re under the curve (Wolever nd Jenkins, 1986). Cows were given restricted mount of feed t 08:00 nd 17:00 h. b,c Vlues in the sme row with different superscript were borderline significntly different (P, 0.10), Bonferroni test). ntive or popped cornmel. The ruminl ph de- men post-prndil concentrtions of totl VFAs cresed significntly (P, 0.05) fter feeding, irre- were highest fter feeding the rtion with 20% spective of dietry tretment. Post-prndil ruminl popped cornmel, but the increse versus tht for the ph ws borderline significntly lower fter feeding other tretments ws not sttisticlly significnt. of the rtion with 20% popped cornmel insted of Post-prndil concentrtions (mm) of totl VFAs, ntive cornmel. cette, nd propionte, nd the cette-to-propionte Before the morning feed, concentrtions of totl rtio were similr (P ) for the five rtions; for VFAs were similr for ll dietry tretments. After ll tretments combined (n 5 5), the men vlues feeding, totl VFA concentrtions were significntly were (S.E ), 72.5 (S.E ), 15.1 (P, 0.05) incresed when either the control rtion or (S.E ) nd 4.8 (S.E ), respectively. Upon the rtion with 20% popped cornmel ws fed. The ANOVA, post-prndil concentrtions of butyrte in

7 J.Th. Schonewille et l. / Livestock Production Science 63 (2000) ruminl fluid were found to be significntly ffected 1987) is not yet fully understood. A possibility is by the fctor diet (P ), but Bonferroni s t-test tht the ddition of strch to the rtion my stimulte did not identify specific rtions tht produced differ- Mg bsorption by incresing the rte of ruminl ent vlues. The butyrte concentrtion for ll tret- fermenttion nd decresing ruminl ph. A lowering ments combined ws 13.8 mm (S.E ) of ruminl ph renders Mg more soluble nd thus more vilble for trnsport cross the epithelium of 3.5. Rumen volume nd pssge rte the rumen which is the mjor site of Mg bsorption in ruminnts (Rogers nd Vn t Klooster, 1969; Rumen volume, bsolute nd frctionl outflow of Toms nd Potter, 1976). The discrepncy between the liquid phse were not ffected (P ) by the outcome of our study nd tht of Wilson et l. ny dietry tretment, the combined vlues for ll (1969) might be relted to difference in strchtretments (n 5 5) being 70 l (S.E. 1.4), 5.9 l/h (S.E. induced chnge of ruminl ph. Feed intke in our 0.07) nd 8.7%/ h (S.E ), respectively. study ws pproximtely three-times lower thn tht in the study of Wilson et l. (1969). The level of feed intke is negtively ssocited with the buffer- 4. Discussion ing cpcity of ruminl fluid (Robinson et l., 1986). Thus, the ph-lowering effect of supplementl strch In this feeding tril, Mg bsorption ws not might hve been greter in the study of Wilson et l. significntly ffected by the strch content of the (1969) so tht Mg bsorption ws effectively inrtion. In studies with gots (Schonewille et l., cresed which in turn llowed the cows to mintin 1997b) nd sheep (Pfeffer et l., 1970; Giduck nd their plsm Mg vlues. Fontenot, 1987) rtions with strch content of t For ll dietry tretments combined, significnt lest 298 g/ kg dry mtter significntly incresed Mg (P ), negtive reltionship ws found bebsorption. The difference between the outcome of tween ruminl ph nd the Mg concentrtion in this study nd those with gots nd sheep my be ultrcentrifuged ruminl fluid (Fig. 2). On verge, cused by the difference in ruminnt species used. the rtion contining 20% popped cornmel pro- However, it seems more obvious tht the strch duced the lowest ph nd highest Mg concentrtions content of the rtions used in this study ws too low (Tble 4). However, the Mg concentrtions were still to exert n effect on Mg bsorption, but there is lower thn those previously found in cows some evidence tht this ws not the cse. Wilson et (Schonewille et l., 1992), which cnnot be esily l. (1969) demonstrted tht plsm Mg concen- explined. The Mg concentrtion in ultrcentrifuged trtion ws low in Jersey cows when grzing on ruminl fluid cn be determined by vrious fctors, tetny-prone psture, wheres plsm Mg ws min- including Mg intke, dietry Mg source, Mg solutined within the norml rnge when the cows were bility nd rumen outflow (Vn t Klooster, 1967). offered supplementl strch (900 g/ dy). Assuming The observed low vlues might hve been cused by mximum grss intke of 2.6 kg dry mtter/ 100 kg the rumen volume, the observed volume being live weight (CVB, 1997) nd live weight of 350 reltively high (Schonewille et l., unpublished kg, the strch content of the whole rtion my hve results), which could relte to the strw component been in the order of 90 g/ kg dry mtter. This of the rtion. The dietry Mg concentrtion used in clcultion indictes tht in our study the strch this study cn be considered norml while the dded content of the experimentl rtions should hve been Mg in the form of MgO is well vilble high enough to stimulte Mg bsorption if this were (Schonewille et l., 1992). From in-vitro studies by the ction by which the Jersey cows studied by Dlley et l. (1997) it followed tht the solubility of Wilson et l. (1969) mintined norml plsm Mg Mg in ruminl fluid decreses bruptly when the concentrtions fter feeding supplementl strch. ruminl ph hs vlues higher thn 6. Thus, the The mechnism by which strch stimultes Mg impct of ingested strch on ruminl fermenttion, bsorption in gots (Schonewille et l., 1997b) nd nd consequently on lowering ruminl ph, ws sheep (Pfeffer et l., 1970; Giduck nd Fontenot, probbly not sufficient to increse the solubility of

8 24 J.Th. Schonewille et l. / Livestock Production Science 63 (2000) Fig. 2. Reltionship between ph of ruminl fluid nd Mg concentrtion in ultrcentrifuged rumen fluid [j control, n ntive cornmel (10%), m ntive cornmel (20%), s popped cornmel (10%), d popped cornmel (20%)]. Dt correspond with nte- nd postfeeding 2 rumen smples (6 time points/ dietry tretment) The solid line represents the regression line; y x (R dj %; Pmodel,pH , Pconstnt ). Mg in the rumen nd thereby increse Mg bsorp- nd K-insensitive mechnism (Leonhrd et l., tion. This resoning would imply tht bseline vlues 1989). An increse in ruminl K concentrtions is of ruminl ph re crucil s to the effect of dietry ccompnied by n increse in the trnsmurl postrch on Mg bsorption. Furthermore, if rumen ph tentil difference (Mrtens nd Blume, 1986; Mrindeed determines Mg bsorption then the rte of tens et l., 1987) s cused by depolristion of the fermentbility of the diet components other thn picl membrne potentil of rumen epithelil cells, strch, will lso ffect the mount of mgnesium thereby reducing the driving force for Mg uptke by bsorbed. these cells (Leonhrd-Mrek nd Mrtens, 1996). The level of Mg bsorption found in this study cn The trnsport component tht is insensitive to K is be considered very low (Schonewille et l., 1994), crrier-medited process tht is bsed on exchnging but comprble vlues hve been reported erlier one Mg ion for two H ions (Schrrer nd Lutz, 1990; (Kemp et l., 1961). Bsed on the observed rumen Mrtens et l., 1991). The K-insensitive component volume, Mg solubility s estimted ccording to of trnsepithelil Mg movement my become stu- Dlley et l. (1997) nd Mg intke per mel, the rted t Mg concentrtions bove 4 mm (Mrtens mximum rumen concentrtion of soluble Mg ws nd Hrmeyer, 1978; Mrtens, 1979; Cre et l., clculted to be 1.08 mm, which more or less 1984), wheres the K-sensitive trnsport component corresponds with the mesured postprndil vlues. remins function of the Mg concentrtion (Rm et At these low Mg concentrtions there will be net l., 1998). In our study, the feeding of strch did not ruminl Mg bsorption s predicted on the bsis of ffect the Mg nd K concentrtions of the ultrcenstudies by Cre et l. (1984). The process of Mg trifuged rumen fluid. Thus, it seems tht the K- trnsport cross the picl membrne of the rumen sensitive trnsport component ws not ffected by epithelium involves two mechnisms: K-sensitive the feeding of strch. It could be suggested tht

9 J.Th. Schonewille et l. / Livestock Production Science 63 (2000) short-chin ftty cids produced during ruminl fermenttion kinetics mesured with fully utomted time relted gs production pprtus. Anim. Feed Sci. Technol. 61, fermenttion of dietry crbohydrtes my stimulte Mg bsorption by the delivery of protons to the CVB (Centrl Veevoeder Bureu), Voedernormen Lnd Mg / 2 H exchngers locted in the picl mem- bouwhuisdieren en Voederwrde Veevoeders, CVB, Lelystd. brne of the epithelium. However, totl VFA con- Dlley, D.E., Isherwood, P., Sykes, A.R., Robson, A.B., centrtions were not significntly ltered by the Effect of in vitro mnipultion of ph on mgnesium solubility in ruminl nd cecl digest in sheep. J. Agric. Sci. Cmb. feeding of strch. Since ruminl Mg concentrtions 129, were very low in our study, both the K-sensitive nd Fontenot, J.P., Allen, V.G., Bunce, G.E., Goff, J.P., Fctors the K-insensitive trnsport component fcilitted influencing mgnesium bsorption nd metbolism in rumin- only low rtes of ruminl Mg bsorption. These nts. J. Anim. Sci. 67, Giduck, S.A., Fontenot, J.P., Utiliztion of mgnesium nd considertions explin why the observed percentges other mcrominerls in sheep supplemented with different of pprent Mg bsorption were reltively low nd redily-fermentble crbohydrtes. J. Anim. Sci. 65, 1667 why no effect of strch feeding ws observed In conclusion, this study shows tht the ddition of Goering, H.K., Vn Soest, P.J., Forge fiber nlyses cornmel to the rtion of dry cows did not sig- (pprtus, procedures nd some pplictions). In: Agric. Hndbook No. 379, ARS-USDA, Wshington, DC. nificntly influence Mg bsorption. It is suggested IDF (Interntionl Diry Federtion), Interntionl IDF tht the high bseline vlues of ruminl ph nd high Stndrd 20A, Interntionl Diry Federtion, Brussels. buffering cpcity of ruminl fluid hd prevented n Kemp, A., Deijs, W.B., Hemkes, O.J., Vn Es, A.J.H., effect of strch intke, if ny, on Mg bsorption. Hypomgnesemi in milking cows:intke nd utiliztion of mgnesium from herbge by lctting cows. Neth. J. Agric. Sci. 9, Acknowledgements Keppler, D., Decker, K., In: Bergmeyer, H.U. (Ed.), Methods of Enzymtic Anlysis, 2nd ed, Acdemic Press, New York. This study ws supported by the Product Bord Leonhrd, S., Mrtens, H., Gbel, G., New spects of Animl Feed (Produktschp Diervoeder), The Hgue, mgnesium trnsport in ruminnts. Act Vet. Scnd. 86 (Suppl.), The Netherlnds. Wim Lensink is thnked for his Leonhrd-Mrek, S., Mrtens, H., Effects of potssium on biotechnicl ssistnce s is Jn Vn Der Kuilen for mgnesium trnsport cross rumen epithelium. Am. J. Physiol. chemicl nlysis. 271, G1034 G1038. Mlestein, A., Vn t Klooster, A.Th., Cone, J.W., Degrdbility of vrious types of strch by incubtion with rumen References fluid or bcteril -mylse. J. Anim. Physiol. Anim. Nutr. 59, Mrtens, H., In vivo untersuchungen uber die bsorption Assocition of Officil Anlyticl Chemists, Officil Meth- von mgnesium us dem pnsen von schfen. Eine bschtzung ods of Anlysis, 14th ed., AOAC, Arlington, VA. der mximlen bsorptionskpzitt des pnsens. Berl. Munch. Cre, A.D., Brown, R.C., Frrr, A.R., Pickrd, D.W., Tierrzl. Wchr. 92, Mgnesium bsorption from the digestive trct of sheep. Q. J. Mrtens, H., Blume, I., Effect of intrruminl sodium nd Exp. Physiol. 69, potssium concentrtions nd of the trnsmurl potentil Chester-Jones, H., Fontenot, J.P., Veit, H.P., Webb, Jr. K.E., difference on mgnesium bsorption from the temporrily Physiologicl effects of feeding high levels of mgnesium to isolted rumen of sheep. Qurt. J. Exp. Physiol. 71, sheep. J. Anim. Sci. 67, Mrtens, H., Gbel, G., Strozyk, H., The effect of potssium Cone, J.W., Vlot, M., Comprison of degrdbility of strch nd the trnsmurl potentil difference on mgnesium trnsport in concentrtes by enzymes nd rumen fluid. J. Anim. Physiol. cross n isolted preprtion of sheep rumen epithelium. Anim. Nutr. 63, Qurt. J. Exp. Physiol. 72, Cone, J.W., Cline-Theil, W., Mlestein, A., Vn t Klooster, A.Th., Mrtens, H., Hrmeyer, J., Mgnesium trnsport by isolted Degrdtion of strch with rumen fluid. A comprison of rumen epithelium of sheep. Res. Vet. Sci. 24, different strch sources. J. Sci. Food Agric. 49, Mrtens, H., Leonrd, S., Gbel, G., Minerls nd digestion: Cone, J.W., Vn Gelder, A.H., Driehuis, F., Description of exchnges in the digestive trct. In: Jouny, J.P. (Ed.), Rumen gs production profiles with three-phsic model. Anim. Feed Microbil Metbolism nd Ruminnt Digestion, Inst. Ntl. Sci. Technol. 66, Rech. Agron, Pris, pp Cone, J.W., Vn Gelder, A.H., Visscher, G.J.W., Oudshoorn, L., Pfeffer, E., Thompson, A., Armstrong, D.G., Studies on Influence of rumen fluid nd substrte concentrtion on intestinl digestion in the sheep. 3. Net movement of certin

10 26 J.Th. Schonewille et l. / Livestock Production Science 63 (2000) inorgnic elements in the digestive trct on rtions contining or glucose in the diet nd the effects on pprent mgnesium different proportions of hy nd rolled brley. Br. J. Nutr. 24, bsorption in gots. J. Diry Sci. 80, Schonewille, J.Th., Vn t Klooster, A.Th., Vn Mosel, M., A Rm, L., Schonewille, J.T., Mrtens, H., Vn t Klooster, A.T., comprtive study of the in vitro solubility nd vilbility of Beynen, A.C., Mgnesium bsorption by whethers fed mgnesium from different sources. Tijdschr. Diergeneesk. 117, potssium bicrbonte in combintion with different dietry mgnesium concentrtions. J. Diry Sci. 81, Schonewille, J.Th., Vn t Klooster, A.Th., Beynen, A.C., Robinson, P.H., Tmming, S., Vn Vuuren, A.M., Influence High phosphorus intke depresses pprent mgnesium bsorpof declining level of feed intke nd vrying proportion of tion in pregnnt heifers. J. Anim. Physiol. Anim. Nutr. 71, strch in the concentrte on rumen fermenttion in diry cows Livest. Prod. Sci. 15, Toms, F.M., Potter, B.J., The site of mgnesium bsorption Rogers, P.A.M., Vn t Klooster, A.Th., Observtions on from the ruminnt stomch. Br. J. Nutr. 36, digestion nd bsorption of food long the gstrointestinl trct Vn t Klooster, A.Th., De toestnd vn clcium, mgof fistulled cows. 3 The fte of N, K, C, Mg nd P in the nesium en enkele ndere minerlen in drminhoud en mest vn digest. Meded. LndbHogesch. Wgeningen 69 11, herkuwers in verbnd met hun resorptie. Thesis, Meded. Schrrer, E., Lutz, T., Effects of short chin ftty cids nd LndbHogesch. Wgeningen, p K on bsorption of Mg nd other ctions by the colon nd Wilkinson, L., Systt: the System For Sttistics, SYSTAT cecum. Z. Ernehrwiss. 29, Inc, Evnston. Schonewille, J.Th., Rm, L., Vn t Klooster, A.Th., Wouterse, H., Wilson, G.F., Reid, C.S.W., Metson, A.J., Butler, G.W., Beynen, A.C., Intrinsic potssium in grss silge nd Influence of strch nd penut oil on plsm mgnesium in mgnesium bsorption in dry cows. Livest. Prod. Sci. 48, grzing diry cows. NZ J. Agric. Res. 12, Wolever, T.M.S., Jenkins, D.J.A., The use of the glycemic Schonewille, J.Th., Rm, L., Vn t Klooster, A.Th., Wouterse, H., index in predicting the blood glucose response to mixed mels. Beynen, A.C., 1997b. Ntive corn strch versus either cellulose Am. J. Clin. Nutr. 43,