Effects of fatty acids and acetone infusions on the
ruminating behavior of goats
S. Oshiro
a,*, Or-rashid Mamun
b, Shalla Wadud
b, Ryoji Onodera
b,
T. Hirayama
a, M. Hirakawa
a, H. Higoshi
aaFaculty of Agriculture, University of the Ryukyus, Senbaru, Nishihara-cho, Okinawa-Pre 903-0213, Japan
bFaculty of Agriculture, Miyazaki University, Miyazaki 889-2192, Japan
Accepted 1 June 1999
Abstract
Metabolites, such as volatile fatty acids (VFA: acetic acid, propionic acid, butyric acid) and acetone produced by rumen fermentation, were intravenously infused into the jugular vein of goats during feeding to explore the mechanism and roles of these compounds in ruminating behavior (number of boli and ruminating time). Four female goats were con®ned in metabolism cages with a stanchion. The ruminating behavior, measured by the number of ruminations, ruminating time, and number of remastications, decreased (P< 0.05) with an infusion of acetic acid and butyric acid. Propionic acid and acetone infusion, however, increased (P< 0.05) the ruminating behavior. Acetic acid, butyric acid, propionic acid and acetone in¯uenced ruminating behavior signi®cantly, and therefore, the data suggest that rumination receptors sensitive to VFA and acetone are more likely to be in an area such as the brain stem where they can respond to blood metabolite levels.#2000 Elsevier Science B.V. All rights reserved.
Keywords:Volatile fatty acid; Acetone; Goats; Rumination; Intravenous infusion
1. Introduction
The role of rumination in ruminant animals is to reduce the particle size of ®brous material of feed and thus to allow the feed to pass from the rumen (Pearce and Moir, 1964; Kennedy, 1985). The ruminating time is in¯uenced by diet (Kick et al., 1937; Balch, 1952; Oltjen et al., 1962; Pearce, 1965). The ruminating behavior of goats (Bell and Lawn, 1957; Oshiro et al., 1988; Oshiro, 1991), sheep (Gordon, 1958; Gordon and McAllister, 1970; Harumoto and Kato, 1979;
Murphy et al., 1983), and cattle (Suzuki et al., 1967) is in¯uenced by diet. The masticating behavior in¯uenced by room lighting is important to determine the ruminating behavior (Oshiro et al., 1996b). Light-ing is also important to determine the rumination circadian rhythm during 24 h (Gordon and McAllister, 1970; Oshiro, 1985a, b; Oshiro and Katayama, 1987; Oshiro and Koja, 1987; Oshiro, 1992; Oshiro et al., 1996b).
Ruminants adjust voluntary food intake in relation to the physiological demand for energy (Bail and Mayer, 1968; Bail, 1971). The effect of intraruminal infusion of acetic, propionic and butyric acid on the
Small Ruminant Research 35 (2000) 117±122
*Corresponding author. Tel.: +98-895-8734; fax: +98-895-8734.
masticating time of sheep and cattle was reported by Ulyatt (1965) and Simkins et al. (1967), respectively. Intravenous volatile fatty acid (VFA) infusions have no effect on the food intake of sheep (Forbes, 1986). We showed previously that the number of ruminations in goats increase in two days in fasting (Oshiro et al., 1992, 1996a), but the ruminating time (remasticating time per bolus) decreases from the second day after fasting (Oshiro et al., 1992) and the VFA production in the rumen decreases after fasting (Pothoven and Beitz, 1975; Murray et al., 1990). Feeding increases the VFA in the rumen and the blood (Pothoven and Beitz, 1975; Murray et al., 1990), and reduces the ruminating behavior immediately after feeding (Oshiro, 1985a, b; Oshiro and Katayama, 1987).
This study examined the effects of intravenous infusion of acetic, propionic, butyric acid and acetone on the ruminating behavior of goats.
2. Materials and methods
Four goats (Saanen X Native Okinawan goats cross-breeds, BW: Mean 35.5 kg, SD 2.3 kg) were offered
free choice alfalfa hay cubes (3 cm3 cm1.7 cm)
and water at 12:00 h every day. Each goat was ®tted with a jugular vein cannula and was locked in a stanchion of a raised (1 m) metabolism cage in an experimental room where the temperature and the
relative humidity were maintained at 20.41.58C
and 662%, respectively. The test room (10.4 m2)
was continuously lit by ¯uorescent electric bulbs (4
bulbs40 W). Goats used were accustomed for
4 weeks to the experimental room and handling situa-tion.
Animals were attached to chewing sensors to mea-sure the jaw movements. A polyethylene catheter was inserted toward the heart into a jugular vein. Meta-bolites were slowly infused into each goat using a peristaltic pump (micro tube pump: MP-3, Tokyo Rikakikai Co. Ltd.). Data were collected for 24 h from noon on day 1 until noon on day 2. All six experiments included a non-infusion experiment without intrave-nous infusions, Ringer' solution infusion (infusing at
the rate of 0.01 ml/kgbody weight/min): Ringer's
solution containing acetic acid, propionic acid, butyric acid and acetone. Acetic acid, propionic acid, butyric acid and acetone infusions were infused at the rate of
0.05, 0.03, 0.01, and 1 mmol/0.0l ml/kgbody weight/
min, respectively. Intravenous infusions of Ringer's solution started at 00:00 h (midnight) and continued until 12:00 h (noon) of the next day (day 2). The pH of the solution was adjusted to 7.0 with 0.1N NaOH solution. The infused volume in all infusion
experi-ments were at a rate of 0.01 ml/kgbody weight/min
using the peristaltic pump. Each metabolite dissolved in the Ringer's solution was given to four goats at 3-week intervals. Experiment was conducted twice, and on each experiment two animals were used, respec-tively, in 3-days interval. Blood was sampled at 12, 16, 20, 0, 1, 2, 3, 6, 9 and 12 h. The blood plasma was analyzed for VFA using a liquid chromatograph (model LC-10AS, Shimazu Corporation, Kyoto, Japan), for acetone using gas chromatograph (model GC-6A, Shimazu Corporation, Kyoto, Japan), for non-etheri®ed fatty acids (NEFA) using the Duncombe method (Duncombe, 1964), and for glucose using the glucose oxidase method (Trinder, 1969).
The animal's jaw movement was recorded continu-ously for 24 h from 12:00 h through to 12:00 h of the next day using an auto-counter system (LB-8801, TECMO Co. Ltd.). Goats were allowed a period to adapt to the system before the experiment.
The results were reported as ruminations (number of boli; boli/h and ruminating time; min/h), mastica-tions and rest. The ruminamastica-tions were further reported as number of remastications (chews/h), remasticating time (min/h), intermittent time (min/h), bolus forma-tion time (sec/bolus), number of remasticaforma-tions per bolus (chews/bolus), remasticating time (sec/bolus) and intermittent time per bolus (sec/bolus) in each rumination; the average of all these components in each hour of rumination and within each day was calculated.
Statistical analyses of all data were made between data collected before and after infusion using the method of TUKEY (Snedecor and Cochran, 1989).
3. Results
Table 1 shows the results of the ruminating beha-vior with acetic acid, propionic acid, butyric acid and acetone infusions into the jugular vein.
The ruminating behavior (number of boli, ruminat-ing time and number of remastications) was constant
Table 1
Ruminating behavior, eating behavior, and resting time before and after VFA and acetone infusion
Item Non-infusiona Ringer-infusion Acetate-infusion Propionate-infusion Butyrate-infusion Acetone-infusion
Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD
Number of boli (boli/l2 h) P-I 160.8 64.0 136.5 17.7 126.3 75.5 125.7 58.3 144.1 42.4 128.5 75.0 D-I 138.2 68.1 132.8 42.1 51.8 49.1b 162.5 44.5b 113.0 55.5b 175.0 40.0b
Ruminating time (min/12 h) P-I 136.1 41.2 144.7 23.8 139.6 84.2 116.5 11.2 121.8 83.5 131.1 97.9 D-I 156.2 86.4 141.0 51.2 55.9 58.4b 153.6 31.2b 105.7 94.1b 191.9 66.4b
Number of remastications (chews/12 h) P-I 8908 1869 9419 1241 9485 751 4714 398 8877 892 8006 639 D-I 7919 1009 9641 2394 3719 416b 9068 1120b 7978 537b 11358 930b
Remasticating time (min/12 h) P-I 116.6 34.5 122.4 24.9 123.1 98.1 103.3 8.0 107.4 75.7 112.7 91.1 D-I 136.9 81.3 120.6 49.8 50.2 54.7 131.9 33.8 92.7 87.8 154.0 66.2
Intermittent time (min/12 h) P-I 19.8 7.8 22.1 2.6 16.4 7.6 13.2 3.5 16.1 8.5 18.4 7.6 D-I 18.7 6.3 20.4 4.6 5.8 4.3 21.7 2.7 13.0 6.4 23.3 5.4
Masticating time (min/12 h) P-I 57.9 28.3 40.1 14.2 56.5 8.7 39.7 9.0 46.0 12.1 48.2 8.8 D-I 56.7 13.2 42.9 20.9 43.1 12.4b 30.6 9.4b 33.4 8.6b 40.1 2.1b
Number of mastication (chews/12 h) P-I 6425 4393 5015 2161 4389 1157 3942 728 5130 922 5785 465 D-I 5123 1682 5235 3068 3357 1608b 2748 477b 4020 301b 5217 586b
Resting time (min/12 h) P-I 526.0 25.6 535.2 20.5 523.9 111.9 563.8 19.4 552.2 105.6 540.7 96.3 D-I 520.1 81.0 536.1 48.3 608.0 68.4 535.8 39.5 580.9 104.7 488.0 66.0
Bolus time (s/bolus) P-I 56.3 3.3 60.0 5.7 60.0 6.0 60.6 5.7 57.0 3.2 61.5 3.9 D-I 60.4 6.0 62.5 7.6 69.5 4.9 67.0 9.5 55.2 0.8 55.6 3.7
Remasticating time per bolus (s/bolus) P-I 46.7 2.9 49.2 1.9 53.2 6.2 51.8 6.9 48.8 4.2 50.2 2.8 D-I 52.5 5.4 54.8 8.2 61.9 4.8 58.5 8.9 47.7 0.8 47.1 4.9
Intermittent time per bolus (s/bolus) P-I 9.6 1.2 10.8 3.7 6.8 0.5 8.8 1.5 7.5 0.8 11.7 1.2 D-I 7.9 1.0 7.7 1.3 7.6 0.8 8.4 1.4 7.6 0.4 9.0 4.1
Number of remastication (chews/bolus) P-I 74.6 9.9 73.3 7.6 78.3 13.1 80.0 16.0 77.9 13.8 73.9 4.8 D-I 79.2 14.4 81.4 16.1 90.9 8.8 88.3 20.1 71.4 5.9 67.2 11.0
P-I: pre-infusion, D-I: during-infusion of metabolites.
aNon-infusion: was not infused during P-I and D-I.
bMeans(Means; SD) in the same row having the superscripts are significantly different (P< 0.05).
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Table 2
Blood composition of goats treated with non, saline, acetic acid, propionic acid, butyric acid, acetone infusion
Item Non-infusiona Ringer-infusion Acetate-infusion Propionate-infusion Butyrate-infusion Acetone-infusion
Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD
Acetic acid (mmol/l) P-I 0.85 0.04 0.89 0.07 0.97 0.15 0.82 0.12 1.05 0.10 0.92 0.07 D-I 0.91 0.06 0.90 0.12 2.09 0.17b 0.63 0.11 0.95 0.14 0.92 0.13
Propionic acid (mmol/l) P-I 0.08 0.03 0.10 0.04 0.13 0.09 0.08 0.02 0.18 0.06 0.11 0.01 D-I 0.12 0.09 0.12 0.06 0.21 0.07 0.13 0.03b 0.18 0.03 0.11 0.02
Butyric acid (g/day) P-I 0.12 0.02 0.09 0.03 0.15 0.11 0.12 0.02 0.18 0.06 0.11 0.03 D-I 0.11 0.05 0.11 0.04 0.21 0.12 0.11 0.03 0.23 0.05b 0.11 0.03
Acetone (mmol/dl) P-I 0.092 0.009 0.090 0.006 0.068 0.016 0.082 0.009 0.089 0.008 0.098 0.012 D-I 0.096 0.006 0.096 0.011 0.076 0.019b 0.086 0.009b 0.116 0.006b 5.432 4.833b
NEFA (mEq/dl) P-I 0.26 0.005 0.27 0.012 0.25 0.011 0.26 0.008 0.26 0.018 0.26 0.009 D-I 0.25 0.011 0.28 0.015 0.34 0.011b 0.36 0.023b 0.34 0.021b 0.36 0.013b
Glucose (mg/dl) P-I 55.6 1.2 56.2 1.24 53.2 1.04 54.6 1.28 53.5 1.23 55.0 1.44 D-I 56.0 1.46 53.7 1.28 60.4 1.83b 70.6 3.83b 63.4 1.88b 58.3 1.38
P-I: pre-infusion; D-I: during-infusion of metabolites.
aNon-infusion: was not infused during P-I and D-I.
bMeans in the same row having the superscripts and significantly different (P< 0.05).
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during the non-infusion and Ringer's solution infusion experiments.
The number of boli, ruminating time and number of remastications were signi®cantly different between the periods before and after infusion in the acetic acid, propionic acid, butyric acid and acetone infusion
experiments (P< 0.05). The number of boli,
ruminat-ing time and number of remastications tended to be lower during the acetic acid and butyric acid infusions than before the infusions, although they tended to be higher during the propionic acid and acetone infusions than before the infusions. The remasticating time, intermittent time and resting time were the same before and after the infusions.
The number of mastications and the masticating time decreased more after infusing with acetic acid, propionic acid, butyric acid, and acetone than before
their infusions (P< 0.05).
The bolus formation time, remasticating time per bolus, intermittent time per bolus and number of remastications per bolus were constant during the infusion periods in the non-infusion, Ringer's solu-tion, acetic acid, propionic acid, butyric acid, and acetone infusion experiments.
Table 2 shows plasma VFA, acetone, NEFA, and glucose concentrations after acetic acid, propionic acid, butyric acid, and acetone were infused into the jugular vein. The plasma concentrations of acetic, propionic, butyric acid were higher than the pre-infu-sion levels after acetic, propionic acid, butyric acid infusion. Plasma acetone and NEFA concentrations after acetic acid, propionic acid, butyric acid and acetone infusions were higher than before the
infu-sions (P< 0.05). Acetic acid, propionic acid, and
butyric acid infusions signi®cantly (P< 0.05)
increased the plasma glucose concentration, although non-infusion, Ringer's solution infusion and acetone infusions did not change it.
4. Discussion
Feeding affects mastication and rumination at the same time (Gordon and McAllister, 1970; Oshiro, 1985a; Oshiro and Katayama, 1987; Oshiro and Koja, 1987). The ruminating behavior during and after feeding in continuous light either stays the same or decreases (Oshiro et al., 1987, 1988). Therefore, we
believe that decrease in the ruminating behavior after feeding (Oshiro, 1985a, b) is related to the increase in rumen acetic acid and plasma acetic acid after feeding (Pothoven and Beitz, 1975).
In this study, an acetic acid infusion into a jugular vein decreased the ruminating behavior, suggesting that the ruminating behavior decreases during and after feeding because of the increase in acetic acid during and after feeding, and that the ruminating behavior increases after fasting because of the decrease in acetic acid after fasting (Oshiro et al., 1992). The results of this study may indicate an effect of acetic acid, propionic acid, butyric acid and acetone infusion on masticating behavior, because masticating behavior was reduced by the acetic acid infusion into the jugular vein of goats during spontaneous meals, suggesting that ruminants adjust their ruminating and masticating behavior according to the VFA concen-tration in the rumen and plasma. Montgomery and Baumgardt (1965) supported the hypothesis that rumi-nants adjust voluntary food intake in relation to the physiological demand for energy if rumen ®ll or the rumen load does not limit their consumption. The results of this study showed strong evidence that VFA concentrations in the jugular vein decrease mas-ticating behavior, although Bail and Mayer (1968) reported that the food intake of goats does not decrease with acetic acid infusion into the jugular vein during spontaneous meals.
We conclude that the immediate reduction of the ruminating behavior after feeding occurred not by the increase in masticating behavior itself during feeding, but to the increasing blood acetic acid and butyric acid after feeding. Our data suggest that rumination recep-tors sensitive to VFA are more likely to be in an area such as the brain stem (Anderson, 1951), where they can respond to blood levels.
Acknowledgements
This work was supported by a Grant-aid for ti®c Research from the Ministry of Education, Scien-ti®c and Culture of Japan (no. 62480072).
O.M. Mamun and S. Wadud are students of the United Graduate School of Agricultural Science, Kagoshima University (three-year doctoral course). O.M. Mamun would like to thank the Ministry of
Education, Science, Sports and Culture of Japan for the award of a research scholarship since 1996.
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