Effect of Parotid Saliva Secretion on Dry Forage Intake in Goats

Transcription

1 1118 Effect of Protid Sliv Secretion on Dry Forge Intke in Gots Ktsunori Sungw*, Yoshifumi Nktsu, Yoriko Nishikuo, Tkeshi Ooshiro, Kout Nitou nd Itsuki Ngmine Fculty of Agriculture, University of the Ryukyus, 1 Senru, Nishihr-cho, Okinw , Jpn ABSTRACT : Reserch ws crried out to clrify whether suppression of dry forge intke during the erly stges of feeding in ruminnts is cused y feeding induced hypovolemi which is produced y the ccelerted secretion of protid sliv. Gots with protid fistul were fed roughly crushed lflf hy cues, commercil ground concentrte feed nd NHCO 3 twice dily (1:-12:, 16:-18:). The nimls were free ccess to drinking wter ll dy prior to, during nd fter experiments. The nimls were intrruminlly infused every dy prior to the morning feeding period with protid sliv collected from the protid fistul over 24 h period. The present experiment consisted of two tretments, non-infusion () nd intrruminl infusion of protid sliv (RSF). In the RSF tretment, 4-5 kg of protid sliv (28-29 mosm/l) collected over 24 h period ws intrruminlly infused 1 h prior to the commencement of the morning feeding. During feeding, eting nd protid sliv secretion rtes were mesured. Blood smples were lso periodiclly collected from the jugulr vein. During nd fter 2 h feeding, wter intkes were mesured, respectively. These mesurements were used to define thirst levels. It is thought tht rumen fill in the RSF tretment ws higher thn the tretment. Plsm osmollity in the RSF tretment incresed in the first hlf of the 2 h feeding period due to the intrruminl infusion of protid sliv. Therefore, protid sliv secretion rtes in the RSF tretment were lower thn the tretment for 3 min period from 3 to 6 min fter the commencement of feeding. On the other hnd, plsm totl protein concentrtion nd hemtocrit in the RSF tretment decresed y 3.2 nd 3.3% prior to the commencement of feeding due to the intrruminl infusion of protid sliv. In the first hlf of the 2 h feeding period, plsm totl protein concentrtion nd hemtocrit in the RSF tretment showed tendency to decrese compred to the tretment. Thirst level in the RSF tretment during feeding ws pproximtely 31.3% less thn the tretment. Upon the completion of the 2 h feeding period, cumultive feed intke in the RSF tretment ws significntly lrger (19.7%) thn the tretment. The results suggest tht suppression of dry forge intke during the erly stges of feeding in gots is prtly cused y feeding induced hypovolemi, which is produced y the ccelerted secretion of protid sliv. (Asin-Aust. J. Anim. Sci. 23. Vol 16, No. 8 : ) Key Words :Protid Sliv Secretion, Thirst Senstion, Dry Forge Intke, Gots INTRODUCTION Ruminnts consume n enormous mount of hy (lower energy content) in short time. Sliv in sheep is secreted in lrge volumes during the first hour fter the commencement of dry forge intke (Sto, 1975). Sliv cts s luricnt in the mouth nd esophgus, nd ssists in the mstiction, re-mstiction, swllowing nd reswllowing of dry forge. Sliv lso cts s n lkline nd serves to uffer the decrese in the ph of rumen fluid due to the voltile ftty cid production of microil fermenttion in the rumen. In this wy, sliv plys n importnt role in eting nd homeosttic regultion of the cid-se lnce in rumen fluid. Dily sliv secretion volumes were 6 to 16 L in sheep (Ky, 196), nd 98 to 19 L in cttle (Biley, 1961). The ilterl glnds contriuting to the totl sliv secretion volumes re the protid, sumndiulr, inferior molr, sulingul, uccl, lil, phryngel nd pltine glnds (Crter nd Grovum, 199). Protid sliv secretion * Corresponding Author: K. Sungw. Tel: , Fx: , E-mil: 98694@gr.u-ryukyu.c.jp Received Novemer 14, 22; Accepted Mrch 17, 23 contriutes 5 to 6% of the totl sliv secretion volumes. Protid sliv is considered to e the fluid supply for the non-secretory rumino-reticulum (Ky, 1966). Secretion rtes of protid sliv in gots fed lflf hy cues twice dy peked immeditely following the strt of feeding, ut decresed shrply 3 min following the strt of feeding (Sungw et l., 22). Eting rtes in gots fed lflf hy cues lso rpidly decresed in the first 4 min of feeding. Sungw et l. (22) reported tht intrruminl infusion of protid sliv incresed dry forge intke in gots deprived of wter during feeding. From these reports, it is thought tht protid sliv secretion volume is regulting fctor in dry forge intke. Until now, experiments investigting the physiologicl reltionship etween protid sliv secretion volume nd dry forge intke hve not een conducted. In the present experiment, the nimls were prepred with protid fistul. Protid sliv from the fistul ws collected nd infused into the rumen once ech dy prior to morning feeding. The present experiment ws conducted to clrify whether rpid decrese in eting rtes with feeding is prtly cused y decrese in secretion rtes of protid sliv in gots with free ccess to wter.

2 PAROTID SALIVA SECRETION AND DRY FORAGE INTAKE 1119 MATERIALS AND METHODS Animls Five gots (1 Jpnese Snen got, ged 4 yr, weighing 72.5 kg; 4 crossred Jpnese Snen/Nuin gots, ged 3-5 yr, weighing 72, 83, 9, 97 kg) were used in this experiment. In order to collect protid sliv, the pertur of one of the protid ducts ws surgiclly prepred to exteriorize it vi the cheek of the niml more thn 6 month prior to experimenttion. Either n Atom Disposle Multiple Purposes Tue (o.d mm, 8 Fr, Atom, Tokyo) pproximtely 1 cm in length or depending on the niml, fluid infusion tue (o.d. 4. mm, Terumo, Tokyo) ws inserted into the protid duct nd fixed to the cheek. Furthermore, to enle the return of sliv collected from the protid fistul, n extension tue (X3-25, Top, Tokyo) ws inserted into the dorsl sc of the rumen. The other end of the tue ws fixed to the skin. Protid sliv flowing from the protid fistul ws collected in plstic ucket. The sheep were mintined in metolism cges tht llowed for the seprte collection of urine, feces nd sliv. The nimls were fed twice dy t 1: m nd gin t 4: pm for 2 h ech time. Prior to the morning feeding, the collected sliv (3-5 kg) ws infused into the rumen vi the extension tue using thtu pump (Minipndy, KP- 3F, Koshin, Tokyo). Following this, 2-3 kg of roughly crushed lflf hy cues, 2 g of NHCO 3 nd 2 g of commercil ground concentrte feed were fed to the nimls for 2 h. Animls were given free ccess to wter throughout the dy. The lflf hy cues (83.4% dry mtter) contined, on dry mtter sis, 18.7% crude protein, 2.4% crude ft, 29.7% crude fier, 39.7% nitrogen free extrcts (NFE), 45.9% neutrl detergent fier (NDF) nd 36.6% cid detergent fier (ADF). The proportion of ech ingredient in the ground concentrte feed ws 48% mize, 24% sorghum, 1% rley, 5.% rice polishing,.5% sodium chloride,.5% diclcium phosphte nd.5% vitmin-trce minerls premix. The concentrte feed (86.9% dry mtter) contined, on dry mtter sis, 13.4% crude protein, 3.6% crude ft, 3.7% crude fier, 71% NFE, 14.6% NDF nd 5.4% ADF. Alflf hy cues were ground with willey mill (Type 4-525P, Ikemoto Rik Kougyou, Tokyo, Jpn). The chemicl components of their feeds were quntified using the procedures descried y Nihon Shiryo Kyouki (Kto, 1988). Experiment The experiment ws crried out in lortory with room temperture of C nd reltive humidity of 74-84%. Before morning feeding, protid sliv ws infused intrruminlly to clrify whether mrked decrese in protid sliv secretion during the erly stges of feeding depresses feed intke in gots with free ccess to wter. The control tretment monitored cumultive feed intke nd eting rtes in the sence of infusion. Tretments in this experiment were crried out in order, eginning with the no infusion control () followed y the protid sliv intrruminl infusion tretment (RSF). The gots used in this experiment hd free ccess to wter during feeding. The tretments were crried out on 2-3 nimls t one-week intervls to ensure tht nimls recovered nd to minimize the compounding effects of the previous tretments. Respirtion frequency, hert rte nd rectl temperture were mesured every dy prior to the morning feeding period. The vlues of these physiologicl prmeters indicted whether n individul ws in good helth nd hd no mesurle crry-over effects from the previous tretments. In order to tke lood smples during the course of the experiment, polyethylene tue (o.d. 1.5 mm, No. 5, Immur Gomu, Tokyo) ws inserted into the jugulr vein of the nimls on the dy prior to the commencement of experimenttion. This tue ws fixed in plce nd filled with heprine-sline solution (5 i.u./ml) to prevent cogultion of the lood. On the dy of the experiment, depending on the niml, either n extension tue (o.d. 2. mm, X-1, Top, Tokyo) or polyethylene tue (o.d. 2.2 mm, No. 7, Immur Gomu, Tokyo) ws connected to the tue inserted into the protid fistul. From the open end of the tue, protid sliv ws collected in grduted mesuring cylinder (1 ml). On the dy of the RSF tretment, kg of sliv ws infused into the rumen using th tu pump (Minipondy, KP-3F, Koshinsh) 1 h prior to the commencement of the morning feeding period. The infusion volume for nimls weighing 72.5, 83., 9. nd 97. kg ws 5. kg, while the niml weighing 72. kg ws infused with 4. kg. Feeding ws egun t 1:3 m nd the nimls were fed roughly crushed lflf hy cues for 2 h. Eting rtes were determined using mesuring scle. The lflf hy cues (2.-3. kg) were plced in feed ox ttched to 6 kg mesuring scle. The weight of the remining feed ws mesured every 1 min for the durtion of the 2 h feeding period. The rte of sliv secretion ws mesured in grduted cylinder. Mesurements egn 1 min prior to feeding commencement nd continued every 1 min for the durtion of the feeding period nd concluded with the lst mesurement eing tken t the end of the 2 h feeding period. To mesure the osmollity of sliv, smple of the collected protid sliv ws tken. This smple ws plced in test tue nd refrigerted until mesuring. Wter intke ws mesured t the end of the 2 h feeding period nd gin 3 min following the completion of the feeding period. Fluid intke is regulted y the thirst mechnisms (Guyton nd Hll, 1996, Prsetiyono et l., 2). In the present experiment, the level of thirst (wter ppetite) ws evluted quntittively using wter intke.

3 112 SUNAGAWA ET AL. Rte of eting (g DM/1min) Cumultive feed intke (gdm) ,5 2, 1,5 1, 5 RSF Time fter feeding (min) Time fter feeding (min) Figure 1. The effect of intrruminl infusion of protid sliv (RSF) on rte of eting nd cumultive feed intke in gots with free ccess to wter. Vlues re men±s.e. (n=5) of five gots., Mens with different superscripts re significntly different from no infusion tretment (, p<.5). A totl of 1 lood smples were tken, 2 ech prior to nd fter the feeding period, nd 6 during feeding fter 1, 3, 45, 6, 9, 12 min hd elpsed. Blood smples (5 ml ech) were tken from the jugulr vein. Smples were collected in heprinized tues to prevent cogultion nd were susequently refrigerted. Blood plsm ws otined y centrifugtion (16,26 g, 1 min, 5 C). Biochemicl nlysis Alflf hy cues were ground with Willey mill (Type P, Ikemoto Rik Kougyou, Tokyo, Jpn). The chemicl components of their feeds were quntified using the procedures descried y Nihon Shiryo Kyouki (Kto, 1988). Sliv osmollity ws mesured ccording to the principle of freezing-point method using n osmometer (Model OM-61, Kyoto Diichi Kgku, Kyoto). Blood smples were plced in hemtocrit cpillry tues nd centrifuged using hemtocrit centrifuge (HC-12 A, Tomy Seiko, Tokyo, 16,26 g 5 min) to seprte plsm nd red lood corpuscle. A hemtocrit reder determined hemtocrit. Plsm protein nd osmollity were mesured y refrctometer (Atgo, Tokyo) nd y n osmometer, respectively. Plsm N, K nd Cl were mesured with Spotchem EL (SE-152, Arkly, Kyoto). Sttisticl nlysis The experiments in this reserch were conducted ccording to switchck design. A two-wy nlysis (niml, tretment) of vrince ws performed. Following Thirst level (g) 8, 7, 6, 5, 4, 3, 2, 1, 1:3-12:3 12:3-13: (12 min) (3 min) tht n F-test ws used to compre the tretments. For sttisticl nlysis, GLM procedures (SAS, 199) were dopted. Dt re presented s mens±se (n=5) of five sheep. RESULTS RSF Figure 2. The effect of intrruminl infusion of protid sliv (RSF) on thirst levels during nd fter feeding in gots with free ccess to wter. Vlues re mens±s.e. (n=5) of five gots., Mens with different superscripts re significntly different from no infusion tretment (, p<.5). Physiologicl responses The men vlues of respirtion frequency, hert rte nd rectl temperture efore infusion in the two tretments were 31±2.9 reths/min, 83±3. ets/min nd 38.9±.4 C, respectively. The rte of eting nd cumultive feed intke The rte of eting nd cumultive feed intke is shown in Figure 1. Eting rtes in the tretment rpidly decresed in the first 4 min of the feeding period ( to 1 min 455 g/1 min, 3 to 4 min 11 g/1 min). However, eting rtes in the RSF tretment decresed slowly until 6 min of the feeding period hd elpsed. Eting rtes in the RSF tretment during the first 6 min of feeding were higher thn those in the tretment. After 6 min of the feeding period hd elpsed, there were no significnt differences etween two tretments. The cumultive feed intke of oth tretments upon the conclusion of the 2 h feeding period ws : 1,597±137.7 g/2h nd RSF: 1,912±131.6 g/2h. Compred with the tretment, cumultive feed intke in the RSF tretment ws 19.7% lrger upon conclusion of the 2 h feeding period. Thirst level The thirst levels clculted using the wter intke of the 2 h feeding period nd the wter intke of the 3 min period following the conclusion of feeding re shown in Figure 2. Thirst levels during feeding were : 5,23±1,188 g/2h, RSF: 4,15±1,19 g/2h. Compred to the tretment,

4 PAROTID SALIVA SECRETION AND DRY FORAGE INTAKE 1121 Plsm osmollity (mosm/l) Plsm totl protein concentrtion (g/dl) Hemtocrit (%) RSF thirst level in the RSF tretment decresed y pproximtely 2.7% due to the infusion of protid sliv. Thirst levels in the nd RSF tretments following the conclusion of feeding were 2,3±86 g/2h nd 2,6±572 g/2h respectively. Thirst level in the RSF tretment showed only 1% decrese nd ws not significntly different from the level in the tretment. Plsm concentrtions of osmollity, totl protein, hemtocrit, N, K nd Cl Plsm concentrtions of osmollity, totl protein, hemtocrit, N, K nd Cl re shown in Figure 3 nd 4. Plsm osmollity in the tretment incresed very slowly with feeding, while tht in the RSF tretment incresed more rpidly. In comprison with the tretment, plsm osmollity in the RSF tretment ws significntly (p<.5) higher throughout the entire period fter infusion. Plsm concentrtions of N nd Cl in oth tretments incresed slowly with feeding, ut the plsm K concentrtions remined un-chnged. In comprison with the tretment, plsm N concentrtions in the RSF Time fter feeding (min) Infusion Feeding, Drinking Drinking Figure 3. The effect of intrruminl infusion of protid sliv (RSF) on plsm osmollity, plsm totl protein concentrtion nd hemtocrit in gots with free ccess to wter.vlues re mens±s.e. (n=5) of five gots. Significnce differences etween RSF nd no infusion tretment () re indicted y p<.5. Plsm N (mmol/l) Plsm K (mmol/l) Plsm Cl (mmol/l) RSF Time fter feeding (min) Infusion Feeding, Drinking Drinking Figure 4. The effect of intrruminl infusion of protid sliv (RSF) on plsm N, K nd Cl concentrtions in gots with free ccess to wter. Vlues re mens±s.e. (n=5) of five gots. Significnce difference etween RSF nd no infusion tretment () re indicted y p<.5. tretment were higher fter 3 min of the feeding period hd elpsed. On the other hnd, plsm Cl concentrtions in the RSF tretment during the first 6 min of feeding were significntly lower thn those in the tretment. Plsm K concentrtions in the RSF tretment were similr to those in the tretment. In oth tretments, totl protein concentrtions prior to feeding (: 7.3±.29, RSF: 7.2±.28 g/dl) hd incresed 15 min fter the commencement of feeding (: 8.±.27, RSF: 8.±.34 g/dl). After 15 min of the feeding period hd elpsed, plsm totl protein concentrtions grdully decresed in oth tretments. Plsm totl protein concentrtion in the tretment prior to infusion (7.3±.35 g/dl), nd 6 min fter infusion (7.3±.29 g/dl), were similr. On the other hnd, due to the intrruminl infusion of protid sliv, plsm totl protein concentrtion in the RSF tretment decresed pproximtely 4.% from pre-infusion level of 7.5±.31 g/dl to level of 7.2±.28 g/dl 6 min fter infusion. Plsm totl protein concentrtions in the RSF tretment showed tendency to decrese compred to those of the tretment for the first hour of the feeding period. The

5 1122 SUNAGAWA ET AL. Rte of sliv secretion (ml/1min) Cumultive sliv secretion volumes (ml) RSI RSF , Time fter feeding (min) Figure 5. The effect of intrruminl infusion of protid sliv (RSF) on sliv secrtion nd cumultive sliv secrtion in gots with free ccess to wter. Vlues re mens±s.e. (n=5) of five gots., Mens with different superscripts re significntly different from no infusion tretment (, p<.5). vlues in the RSF tretment decresed significntly (p<.5) in the second hour. In oth tretments, hemtocrit prior to feeding (: 3.±.89, RSF: 29.2±.73%) hd mrkedly incresed 15 min fter the commencement of feeding (: 35.2±.49, RSF: 34.2±.97%). However, hemtocrit grdully decresed in oth tretments for the reminder of the feeding. Hemtocrit in the tretment prior to infusion (29.8±.86%), nd 6 min fter infusion (3.±.89%), were similr. On the other hnd, due to the intrruminl infusion of protid sliv, hemtocrit in the RSF tretment decresed pproximtely 3.3 % from pre-infusion level of 3.2±1.24% to level of 29.2±.73% 6 min fter infusion. Hemtocrit vlues in the RSF tretment showed tendency to decrese compred to those of the tretment for the first hour of the feeding period. The vlues in the RSF tretment were significntly (p<.5) lower in the second hour. Sliv secretion rtes nd cumultive protid sliv secretion Secretion rtes of protid sliv nd cumultive protid sliv secretion re shown in Figure 5. The rtes of protid sliv secretion in oth tretments peked for the first 1 min fter feeding ws commenced (: efore feeding 65±11 ml/1 min, to 1 min 136±1 ml/1 min, RSF: Sliv osmollity (mosm/l) RSF Time fter feeding (min) Figure 6. The effect of intrruminl infusion of protid sliv (RSF) on sliv osmollity during feeding in gots with free ccess to wter. Vlues re mens±s.e. (n=5) of five gots. Significnce differences etween RSF nd no infusion tretment (NI) re indicted y p<.5. efore feeding 45±7 ml/1 min, to 1 min 127±16 ml/1 min). These rtes then decresed s the feeding progressed. Sliv secretion rtes in the tretment slowly decresed until 5 min of the feeding period hd elpsed, while the rtes oserved in the RSF tretment decresed more rpidly. The sliv secretion rtes in the RSF tretment were lower thn those in the tretment during the time period etween 3 nd 6 min of the 2 h feeding period. Cumultive sliv secretion volumes upon conclusion of the 2 h feeding period were 76±64 in tretment, nd 537±52 ml/2h in the RSF tretment. Cumultive sliv secretion volume in the RSF tretment showed significnt 29.3% decrese when compred to the tretment. Sliv osmollity Sliv osmollity is shown in Figure 6. Sliv osmollity prior to feeding commencement nd in the first 1 min of the feeding period ws similr in oth nd RSF tretments. However, fter the first 1 min of the feeding period hd elpsed, sliv osmollity in the RSF tretment ws significntly (p<.5) higher thn tht in the tretment throughout the entire period of feeding. Levels in protid sliv osmollity prior to, during nd fter feeding were lower thn those in plsm osmollity. DISCUSSION Sto (1975) reported tht when sheep were intrruminlly loded with wter prior to feeding, increses in plsm osmollity were impeded nd the mrked suppression of protid sliv secretion fter the conclusion of the 2 h feeding period did not occur. Furthermore, when plsm osmollity ws experimentlly incresed through n intrvenous infusion of hyper-osmotic mnnitol solution

6 PAROTID SALIVA SECRETION AND DRY FORAGE INTAKE 1123 nd hyper-osmotic NCl solution, sliv secretion ws suppressed. In the present experiment, sliv secretion rtes etween 3 min nd 6 min of the feeding period in the RSF tretment were lower thn the rte oserved in the tretment over the sme time period (Figure 5). Wrner nd Stcy (1977) reported tht there ws negtive correltion mong sliv secretion rtes, ruminl fluid osmollity nd plsm osmollity through intrruminl or intrvenous infusion of hyper-osmotic solutions. Sto (1975), Wrner nd Stcy (1977) indicted tht when plsm osmollity incresed to phrmcologicl level through intrruminl or intrvenous infusion of hyper-osmotic solution, protid sliv secretion volumes were suppressed in sheep. In the present experiment, we found tht when plsm osmollity incresed to physiologicl level through intrruminl infusion of protid sliv, protid sliv secretion during feeding ws suppressed in gots. From these results, it is thought tht the suppression of protid sliv secretion during feeding ws the result of n increse in plsm osmollity rought out y the incresed intrruminl sliv flow. It ws reported tht the feed intke of lflf pellets ws regulted y chnges in ruminl fluid osmollity (Bile et l. 1969; Kto et l. 1979; Grovum, 1995). The sme sized dose of hyper-osmotic NCl, polyethylene glycol-4 (PEG), sodium cette or sodium propionte produced the sme increses in rumen fluid osmollity when intrruminlly infused. These increses in rumen fluid osmollity resulted in the sme sized decrese in feed intke (Grovum, 1995). On the other hnd, when the ruminl fluid osmollity ws decresed y the intrruminl infusion of n excessive mount of wrm wter (39.8 C) in sheep fed on lflf hy cues, feed intke incresed y 3% (Sungw et l., 22). It ws thought tht the chnges in ruminl fluid osmollity were sensed y the osmoreceptors in the rumen wll nd these signls were then trnsported to the centrl nervous system (Leek nd Hrding, 1975). However, the effect of internl humorl fctors on the intke of grss hs not een investigted under these experimentl conditions. Cmpling nd Blch (1961), nd Anil et l. (1993) reported tht when lloon ws inserted into the rumen to restrict rumen cpcity of cows fed on hy nd silge, feed intke decresed. Hidri (1987) reported tht when sheep free ccess to hy reched certin level of rumen fill, they stopped feeding. On the other hnd, Kto (1977) compred feeding times nd feed intke in sheep with n esophgus fistul under norml feeding nd shm feeding conditions. The nimls were fed fresh grss, hy nd concentrted feed. Feeding time nd feed intke under shm feeding conditions tended to e slightly greter thn norml feeding conditions wherey ingested mtter is llowed to enter the rumen. This difference however, ws not significnt. This result suggests tht despite the consumed feed not entering the rumen, some extrruminl mechnism exists to suppress grss intke. In the present experiment, gots eting crushed lflf hy cues secreted lrge volumes of protid sliv during the first 4 min fter the commencement of feeding (Figure 5). Protid sliv hs rich NHCO 3 nd fluid, nd its secretion volumes re lrgest in the slivry glnds. Protid sliv secreted in lrge quntities hs een considered to e the fluid supply for the non-secretory rumino-reticulum (Ky, 1966) nd crete n environment of microil fermenttion in the rumen. However, protid sliv secreted in lrge volumes during the erly stges of feeding must mke severe demnds on the sodium nd wter in the circultion. In the intr-ruminl iso-osmotic sline-loding experiment, Mthi et l. (21) recorded n incresed plsm nd cererospinl fluid sodium concentrtion during feeding, yet wter intke ws reduced in comprison with untreted control group. The senstion of thirst is produced in the rin s result of the integrtion of neuronl nd humorl informtion (Fitzsimons, 1979). Neuronl informtion is trnsported vi the utonomic nerves (especilly the vgus) from chemoreceptors in the internl viscerl orgns. A rod rnge of internl humorl informtion is trnsported vi the lood nd cererospinl fluid. Incresed extrcelluer fluid osmollity, decreses in extrcelluer fluid volume nd rteril pressure, ngiotensin II, nd dryness of the mouth stimulte the secretion of thirst (Guyton nd Hll, 1996). Plsm osmollity in the RSF tretment incresed y pproximtely 3.2% with intrruminl infusion of protid sliv prior to the commencement of feeding. The increses in plsm osmollity of the RSF tretment were rought out y increses in plsm N concentrtion tht ws sored vi rumen fter intrruminl infusion of protid sliv (Figure 4). However, in the RSF tretment, hemtocrit nd plsm totl protein concentrtion decresed y 3.3 nd 3.2%, respectively (Figure 3). Plsm totl protein consists of lumin (4-5%), α-gloulin (12-17%), β-gloulin (8-12%), γ-gloulin (25-33%) nd firinogen (3-8%) in dult cow (Tsud, 1994). Diurnl chnges of oth plsm totl protein concentrtions nd hemtocrit vlues reflect vritions in the circulting plsm volume (Blir-West et l., 1988). These results indicte tht centrl receptors for plsm osmollity did not completely determine thirst levels in response to feeding ecuse nimls intrruminlly infused with protid sliv did not drink more wter despite hving higher plsm osmollity thn tht in the noninfusion tretment. Sungw et l. (21, 22) intrvenously infused in gots fed lflf hy cues twice dy with n iso-osmotic mnnitol solution. The infusions were conducted from 1 h prior to feeding nd continued

7 1124 SUNAGAWA ET AL. Tle 1. The reltionships mong feed intke, thirst levels nd exogenous intrruminl fluid flow in gots Cumultive sliv Exogenous intrruminl Cumultive feed intke secretion from unilterl Tretments fluid flow during feeding (g DM/2h) protid slivry duct (ml/2h) (ml/2h) until 1 h of 2 h feeding period hd elpsed. This infusion supplements the fluid in the lood lost through ccelerted sliv secretion during the erly stges of dry forge feeding. It ws reported tht thirst levels decresed pproximtely 13% while ccumulted feed intke incresed 43% with iso-osmotic mnnitol solution. From these results, it is thought tht the suppression of feed intke of dry forge in gots is not simply result of rumen fill ut lso the result of thirst senstions tht re produced in the rin through hypovolemi cused y the ccelerted secretion of protid sliv during the initil stges of feeding. Sungw et l. (22) used the sme nimls nd experimentl methods to investigte the effects of intrruminl infusion of protid sliv nd wrm wter (36 C) on feed intke in wter-deprived gots during feeding. The results of tht experiment nd of the present experiment hve een grouped nd re shown Tle 1. Cumultive feed intke (Y) ws linerly nd positively correlted to the increse in exogenous intrruminl fluid flow (X 1 ), Y= X 1, r=.99. However, the cumultive feed intke ws lso linerly nd negtively correlted to the increse in thirst levels (X 2 ), Y= X 2, r=.86. Additionlly, etween exogenous intrruminl fluid flow (X 1 ) nd thirst levels (X 2 ), the correltion eqution X 1 = X 2, r=.82 ws otined. From these results, it is thought tht exogenous intrruminl fluid flow decresed thirst levels cused y feeding induced hypovolemi in gots fed on dry forge, nd relieved suppression of feed intke during the erly stges of feeding. The results of the present experiment suggest tht suppression of dry forge intke during the erly stges of feeding in gots is prtly cused y feeding induced hypovolemi, which is produced y the ccelerted secretion of protid sliv. ACKNOWLEDGMENT We thnk G. McIlvride for help in prepring the mnuscript. This reserch ws prtly supported y Grntin-Aid for Explortory Reserch of the Ministry of Eduction, Science, Sports nd Culture in Jpn (No ). REFERENCES Thirst levels (wter ppetite) upon the conclusion of feeding(g/3min) NI 1,1± ±59 6,4±1,17 RSI 1,532±29 531±32 5, 5,76±7 RWI 1,65± ±39 5, 3,21±5 1,596±376 75±64 6,262 2,875±651 RSF 1,912±352 c 537±52 9,3 2,6±572 c Gots with protid fistul were used in these experiments. Protid sliv from the fistul ws collected over 24 h, nd infused into the rumen ech dy prior to mornig feeding. NI, RSI nd RWI tretments were non-infusion, intrruminl infusion of protid sliv or wrm wter (36 C), respectively (Sungw et l., 22). Gots in these tretments were deprived of wter during morning feeding on the dy of experimenttion. nd RSF tretments were non-infusion nd intrruminl infusion of protid sliv in gots with free ccess to wter throughout ll dy.,,c Mens wih different superscripts re significntly different mong ech tretments (p<.5). Anil, M. H., J. N. Mny, H. W. Symonds nd J. M. Fores Responses in the voluntry intke of hy or silge y lctting cows to intrruminl infusions of sodium cette, sodium propionte or rumen distension. Br. J. Nutr. 69: Bile, C. A., J. Myer nd C. L. McLughlin Feeding ehvior of gots: ruminl distension, ingest dilution nd cette concentrtion. Amer. J. Physiol. 217: Biley, C. B Sliv secretion nd its reltion to feeding in cttle. 3. The rte of secretion of mixed sliv in the cow during eting, with n estimte of the mgnitude of the totl dily secretion of mixed sliv. Br. J. Nutr. 15: Blir-West, J. R. nd A. H. Brook Circultory chnges nd rennin secretion in sheep in response to feeding. J. Physiol. 24: Cmpling, R. C. nd C. C. Blch Fctors ffecting the voluntry feed intke of the cow. 1. Preliminry oservtions on the effect, on the voluntry intke of hy, of chnges in the mount of the reticulo-ruminl contents. Br. J. Nutr. 15: Crter, R. R. nd W. L. Grovum A review of the physiologicl significnce of hypertonic ody fluids on feed intke nd ruminl function: slivtion, motility nd microes. J. Anim. Sci. 68: Fitzsimons, J. T The physiology of thirst nd sodium ppetite. Cmridge University Press. Cmridge. UK. Grovum, W. L Mechnisms explining the effects of short chin ftty cids on feed intke in ruminnts-osmotic pressure, insulin nd glucgons. In: Ruminnt Physiology: Digestion, Metolism, Growth nd Reproduction. Proceedings of the Eighth Interntionl Syposium on Ruminnt Physiology (Ed. W. V. Engelhrdt, S. Leonhrd-Mrek, G. Breves nd D. Giesecke). Ferdinnd Enke Verlg. Stuttgrt. pp Guyton, A. C. nd J. E. Hll Centrl nervous system centers for thirst. In: Textook of Medicl Physiology. W. B. Sunders Compny. Phildelphi. Pensylvni. pp Hidri, H Control of food intke. In: Shin Nyuugyuu no

8 PAROTID SALIVA SECRETION AND DRY FORAGE INTAKE 1125 kgku (Ed. A. Shit). Nouunkyou. Tokyo. pp Kto, S Experimentl studies with regrd to fctors controlling feed intke in sheep. Ph.D. Thesis. Tohoku University, Sendi, Jpn. Kto, S., Y. Sski nd T. Tsud Food intke nd rumen osmollity in the sheep. Annles de Recherches Veterinire. 1: Kto, Y Anlysis of chemicl components of feed. In: Shiryo Bunseki Kijun Kyouki). Tokyo. pp Ky, R. N. B The rte of flow nd composition of vrious slivry secretions in sheep nd clves. J. Physiol. (Lond.) 15: Ky, R. N. B The influence of sliv on digestion in ruminnts. World Rev. Nutr. Diet. 6: Leek, B. F. nd R. H. Hrding Sensory nervous receptors in the ruminnt stomch nd the reflex control of reticulo-ruminl motility. In: Digestion nd Metolism in the Ruminnt Stomch (Ed. I. W. McDonld nd A. C. I. Wrner). University of New Englnd Pulishing Unit. Armidle. Austrli. pp Mthi, M. L., C. E. Thomson nd M. J. McKinley. 21. Influence of ruminl wter-loding on renl sodium excretion nd wter intke following feeding in sheep. Act. Phsiol. Scnd. 172: Prsetiyono, B. W. H., K. Sungw, A. Shinjo nd S. Shirom. 2. Physiologicl reltionship etween thirst level nd feed intke in gots fed on lflf hy cues. Asin-Aust. J. Anim. Sci. 13: SAS SAS/STAT User's Guide. Volume 2, Version 6, Fourth Edition. SAS Institute Inc., SAS Cmpus Drive, Cry, NC Sto, Y., The reltionship etween sliv secretion nd ody fluid lnce during feeding. Ph. D. Thesis. Tohoku University, Sendi, Jpn. Sungw, K., B. W. H. E. Prsetiyono nd A. Shinjo. 21. Significnce of hypovolemi in feed intke control of gots fed on dry feed. Asin-Aust. J. Anim. Sci. 14: Sungw, K., B. W. H. E Prsetiyono nd I. Ngmine. 22. Significnce of feeding induced hypovolemi in feed intke control of gots fed on lflf hy. Asin-Aust. J. Anim. Sci. 15: Sungw, K., Y. Nktsu, Y. Nishikuo, K. Nitou nd I. Ngmine. 22. Effects of intrruminl sliv flow on feed intke in gots fed on lflf hy cues. Asin-Aust. J. Anim. Sci. 15: Tsud, T Blood. In: Animl Physiology. (Ed. T. Tsud). Youkendo. Tokyo. pp. 49. Wrner, A. C. nd B. D. Stcy Influence of ruminl nd plsm osmotic pressure on slivry secretion in sheep. Q. J. Exp. Physiol. 62: