A note on the manipulation of sodium and potassium concentrations in the rumen of reindeer and the possible effect on digestibility

Rumen N a + and K + concentrations in reindeer were manipulated by introducing 4 M KC1 or 4 M NaCl into the reindeer rumen. A positive correlation was found between salivary and ruminal concentrations of N a + and K + . Decreased ruminal Na + concentrations seemed to decrease dry matter digestibility in nylon bags incubated in the rumen. Keyword: Rumen, Na + , K + , Dry matter digestibility Rangifer, 7(2): 33-36 Staaland, H. & Garmo, T. 1987. Om manipulering av natrium og kalium konsentrasjoner i vomma hos rein og om de mulige effekter på fordøyeligheten. Sammendrag: N a + og K + konsentrasjoner i vomma hos rein ble regulert ved å gi reinen 4 M KC1 eller 4 M NaCl direkte i vomma. Det ble funnet en positiv korrelasjon mellom spytt og vomkonsentrasjoner av N a + og K + . Redusert N a + konsentrasjon i vomma synes å redusere tørrstoff-fordøyelighet i nylonposer plassert i vomma. _ Rangifer, 7(2): 33-36 Staaland, H. & Garmo, T. 1987. Poron potsin natriumja kaliumkonsentraation kokeellisesta muuttamisesta ja tåmån mahdollisesta vaikutuksesta sulavuuteen. Yhteenveto: Poron potsin natriumja kaliumkonsentraatioita muutettiin antamalla 4 M KC1 tai 4 M NaCl suoraan potsiin. Syljen ja potsin Na ja K -konsentraatioiden vålillå todettiin positiivinen korrelaatio. Alentunut Na -konsentraatio potsisså nåyttåå våhentåvån kuiva-aineen sulavuutta potsiin sijoitetuissa nailonpusseissa. Rangifer, 7(2): 33-36 Material and methods Two male reindeer Calves, 7-10 months old and weighing about 50 kg were used in this study. The animals were purchased from domestic stocks and kept in indoor stalls at about 10°C. As basic food they were fed a commercial pellet diet, RF-71 (Jacobsen et al. 1977) for maintenance, but were adapted to the experimental diets for at least two weeks before trials. Both animals had rumen cannulae. Ruminal sodium and potassium were manipulated by introducing 100 ml 4 M KCL/day (4.8 M in the course of 15 days) or 100 ml 4 M NaCl/day (4 M in the course of 20 days) through the cannulae. Samples of rumen Rangifer, 7(2), 1987 33 Table 1. Dry matter disappearance (% disappearance ± S. D. , n=4) from nylon bags incubated for different periods in the rumen of reindeer with different N a + and K + concentrations and fed pure lichen of RF 71 diets. Diets fed to reindeer and N a + and K + cone, in rumen liquor mMoles/l±S.D. (n=6) Plant Incub. Lichens Lichens RF71 material in period Na: 121 ± 6 Na: 24 ± 8 Na: 114 ± 3 6 nylon bags (hrs) K: 38 ± 4 K:122 ± 1 8 K: 50 ± 7 RF71 48 78.2 ±4.7 74.3 ±2.4 77.8 ±3.9 24 67.6 ±5 .3 67.1 ±2.9 71.2 ±6 .4 6 59.7 ±1.4 57.0 ±0.7 61.9 ±3 .8 Hay 48 52.1 ±3.2 48.3 ±2 .8 53.3 ±1 .8 (Phleum 24 42.7 ±2 .1 40.9 ± 3.9 49.1 ±5 .8 pratense) 6 34.2 ±1 .3 29.2 ± 2.7 34.5 ± 1.2 Aspen 48 79.3 ±7.0 68.3 ± 2.0 74.3 ±3 .2 (leaves) 24 65.4 ±3.6 56.6 ± 6.4 67.5 ±4 .8 (Populus tremulus) 6 46.1 ±3.2 39.3 ±2.9 43.8 ±0 .7 Moss 48 22.3 ± 3.0 22.5 ± 2.6 23.2 ±1 .2 (Pleurozium 24 25.3 ±1 .3 18.2 ±1 .6 23.0 ± 1.5 schreberi) 6 22.4 ±3 .8 16.0 ±3 .0 18.9 ±0 .5 Mixed lichens 48 46.5 ± 1.5 38.8 ±3 .8 40.6 ± 6.4 (Cladonia 24 36.9 ±0.9 34.6 ±1 .2 36.2 ± 6.9 rangiferina & Cetraria nivalis) 6 27.7 ±1 .3 22.6 ± 2.9 23.7 ±0 .7 Lichens 48 51.4 ±3 .8 38.8 ±6.5 58.1 ±3.5 (Stereo24 40.8 ± 4.5 27.4 ± 2.5 38.4 ±13.6 caulon sp.) 6 19.2 ±3 .1 15.3 ±1 .6 14.0 ±1 .6 Mean (n=24) 48 55.0 48.5 54.6 24 46.5 40.8 47.6 6* 34.9 29.9 32.8 * Mean disappearance of dry matter after 6 hrs of incubation was significantly lower (P<0.002) for all diets than disappearance after 24 and 48 hrs (Duncan test, Ray 1982). content, saliva and blood for chemical analyses were obtained prior to the administration of minerals. The rumen samples were centrifuged at 15 000 rpm for 15 minutes to obtain rumen liquor for chemical analyses. Samples of saliva were collected by the method of Staaland et al. (1980). Blood samples were drawn from the jugular vein into Li-heparinized vacuum tubes. Sodium and potassium were determined by flame photometry. Rumen liquor Cl-concentrations were measured by titration (Schales and Schales 1941). Dry matter digestibility was determined by the nylon bag method (see Person et al. 1980). Nylon bags, pore size 32 /xm with 1.0 g dried plant material, were introduced into the rumen through the cannulae and incubated for 6, 24 or 48 hrs before removed. A l l trials were dublicated (/. e. two nylon bags were used in each of the two animals used). Dry matter disappearance in different trials was compared using paired t-tests (Ray 1982). Furthermore linear regretion between salivary and ruminal N a + and K + concentrations were calculated as well as standard deviations from mean values. Results and discussion The concentration of potassium in the rumen increased after adding KC1 through the cannulae and the sodium concentrations decreased. This could be reversed by feeding the animals sodium-rich food like RF-71 or by introducing NaCl into the rumen. Rumen K + and Na + concentrations were inversely related (Eq. 1). 34 Rangifer, 7(2), 1987 Eq. 1. K(rumen) = -0.71 xNa(rumen) + 128.64 n=42,r=-0.88,P>0.01 Irrespective of large quantities of CI" accompanying the K + or Na + doses, ruminal Cl~ concentrations remained within the range of 2 8 mmole/1 rumen liquor (mean value 4.2 ± 1.5 mmole/l,n=43). Salivary concentrations of K + and Na + were directly proportional to rumen concentrations (Eqs. 2 and 3). Eq. 2. K(rumen) = 1.30x K(saliva) + 15.34 n=29,r=0.87,P<0.01 Eq. 3. Na(rumen) = 1.05 xNa(saliva) + 2.95 n=29,r=0.81,P<0.01 Thus, the concentrations of K + and Na + in the saliva give good predictions also of ruminal concentrations. Plasma concentrations of K + and Na + were 4.2±0.7 and 135.5±7.4 mmol/1 respectively (n=30) and did not vary significantly with treatment. Disappearance of dry matter in the nylon bags increased with time of incubation (P<0.002). There was no significant difference in dry matter disappearance in the reindeer fed only lichens or only RF-71 diet, provided the K + and Na + concentrations were the same (Table 1). Dry matter disappearence from the nylon bags were significantly reduced at low Na + and high K + concentrations (Table 2). The influence of Na + and K + on microbial growth and digestive processes in the rumen are not well understood (Thomson et al. 1978, Duran and Kawashia 1980). It is assumed that N a H C 0 3 added to the diet may improve utilization of nitrogene and increase ruminal digestibility (Phillip 1983, Hubbert et al. 1958, Wede¬ kind et al. 1986). Addition of sodium improve growth in cattle fed low sodium diets (Horrocks 1964). However, sodium and potassium may influence the metabolism of other minerals (see e.g. Rogers et al. 1982, Mees et al. 1985, Greene et al. 1986,Staalandeffl/. 1986). Sodium deficiency is common among northern herbivores in spring and summer (Weeks and Kirkpatrick 1976, Staaland and Sæbø 1986). One possible cause, besides low levels of this mineral in the forage, is high levels of potassium in the vegetation. Where no extra sodium is available, e.g. from salt licks, sea water or aquatic vegetation (see e.g. Fraser et al. 1984, Staaland et al. 1986), shifts in ruminal sodium/potassium concentrations may occur. Such shifts might therefore also influence on energy metabolism of wild ruminants like the reindeer. It is evident from this study that salivary concentrations of Na + and K + can be used to predict rumen values of these ions. In reindeer, like sheep (Warner and Stacy 1972), intake of forage with a high K + concentration can alter salivary and ruminal concentrations of Na + and K + . Table 2. Paired comparison t-test between differences in dry matter disappearance from nylon bags incubated for different periods in the rumen of reindeer with different N a + and K + concentrations and for animals fed pure lichen of RF71 diets (n=6). See table 1 for further explanations. Differences between mean dry matter disappearance Periods of incubations (hrs) N a + and K + concentrations and diets compared 6 24 48 Lieh, (high Na) Lieh, (low Na) 5.0 5.7 6.5 ± 1 . 5 ± 5 . 0 ± 4 . 9 P<0.01 P<0.05 P<0.05 RF 71 (high Na) Lieh, (low Na) 2.9 6.8 6.1 ± 2 . 6 ± 3 . 8 ± 6 . 8 P<0.05 P<0.01 P̂ =0.08 RF 71 (high Na) Lieh, (high Na) -2.1 1.1 -0.4 ± 2 . 8 ± 3 . 5 ± 4 . 6 n.s. n.s. n.s. Rangiter, 7(2), 1987 35 Change in ruminal concentrations of these ions may affect the energy metabolism of reindeer. However, it should be kept in mind that the method used for measuring digestion in this study (the nylon bag technique) indicates only what happens with forage in the rumen and does not measure digestion further down in the alimentary tract.

Two male reindeer Calves, 7-10 months old and weighing about 50 kg were used in this study.The animals were purchased from domestic stocks and kept in indoor stalls at about 10°C.As basic food they were fed a commercial pellet diet, RF-71 (Jacobsen et al. 1977) for mainte-nance, but were adapted to the experimental diets for at least two weeks before trials.Both animals had rumen cannulae.Ruminal sodium and potassium were manipulated by introducing 100 ml 4 M KCL/day (4.8 M in the course of 15 days) or 100 ml 4 M NaCl/day (4 M in the course of 20 days) through the cannulae.Samples of rumen content, saliva and blood for chemical analyses were obtained prior to the administration of minerals.The rumen samples were centrifuged at 15 000 rpm for 15 minutes to obtain rumen liquor for chemical analyses.Samples of saliva were collected by the method of Staaland et al. (1980).Blood samples were drawn from the jugular vein into Li-heparinized vacuum tubes.Sodium and potassium were determined by flame photometry.Rumen liquor Cl-concentrations were measured by titration (Schales and Schales 1941).Dry matter digestibility was determined by the nylon bag method (see Person et al. 1980).Nylon bags, pore size 32 /xm with 1.0 g dried plant material, were introduced into the rumen through the cannulae and incubated for 6, 24 or 48 hrs before removed.All trials were dublicated (/.e. two nylon bags were used in each of the two animals used).Dry matter disappearance in different trials was compared using paired t-tests (Ray 1982).Furthermore linear regretion between salivary and ruminal Na + and K + concentrations were calculated as well as standard deviations from mean values.

Results and discussion
The concentration of potassium in the rumen increased after adding KC1 through the cannulae and the sodium concentrations decreased.This could be reversed by feeding the animals sodium-rich food like RF-71 or by introducing NaCl into the rumen.Rumen K + and Na + concentrations were inversely related (Eq. 1).
Salivary concentrations of K + and Na + were directly proportional to rumen concentrations (Eqs. 2 and 3).
Disappearance of dry matter in the nylon bags increased with time of incubation (P<0.002).There was no significant difference in dry matter disappearance in the reindeer fed only lichens or only RF-71 diet, provided the K + and Na + concentrations were the same (Table 1).Dry matter disappearence from the nylon bags were significantly reduced at low Na + and high K + concentrations (Table 2).
The influence of Na + and K + on microbial growth and digestive processes in the rumen are not well understood (Thomson et al. 1978, Duran andKawashia 1980).It is assumed that NaHC0 3 added to the diet may improve utilization of nitrogene and increase ruminal digestibility (Phillip 1983, Hubbert et al. 1958, Wede¬ kind et al. 1986).Addition of sodium improve growth in cattle fed low sodium diets (Horrocks 1964).However, sodium and potassium may influence the metabolism of other minerals (see e.g.Rogers et al. 1982, Mees et al. 1985, Greene et al. 1986,Staalandeffl/. 1986).Sodium deficiency is common among northern herbivores in spring and summer (Weeks andKirkpatrick 1976, Staaland andSaebø 1986).One possible cause, besides low levels of this mineral in the forage, is high levels of potassium in the vegetation.Where no extra sodium is available, e.g. from salt licks, sea water or aquatic vegetation (see e.g.Fraser et al. 1984, Staaland et al. 1986), shifts in ruminal sodium/potassium concentrations may occur.Such shifts might therefore also influence on energy metabolism of wild ruminants like the reindeer.
It is evident from this study that salivary concentrations of Na + and K + can be used to predict rumen values of these ions.In reindeer, like sheep (Warner and Stacy 1972), intake of forage with a high K + concentration can alter salivary and ruminal concentrations of Na + and K + .Change in ruminal concentrations of these ions may affect the energy metabolism of reindeer.However, it should be kept in mind that the method used for measuring digestion in this study (the nylon bag technique) indicates only what happens with forage in the rumen and does not measure digestion further down in the alimentary tract.

Table 1 . Dry matter disappearance (% disappearance ± S. D., n=4) from nylon bags incubated for different periods in the rumen of reindeer with different Na + and K + concentrations and fed pure lichen of RF 71 diets.
Ray 1982isappearance of dry matter after 6 hrs of incubation was significantly lower (P<0.002)foralldiets than disappearance after 24 and 48 hrs (Duncan test,Ray 1982).

Table 2 . Paired comparison t-test between differences in dry matter disappearance from nylon bags incuba- ted for different periods in the rumen of reindeer with different Na + and K + concentrations and for animals fed pure lichen of RF71 diets (n=6). See table 1 for further explanations. Differences between mean dry matter disappearance
RF 71 (high Na) -Lieh, (high Na) n.s.n.s.