THE EFFECT OF A GRADUAL INCREASE OR DECREASE OF DAILY HAY INTAKE ON EATING AND RUMINATING BEHAVIOUR IN SHEEP

Summary In the present experiment, the relationship between rumination and the amount of roughage eaten by sheep was investigated in detail. Daily time spent eating was obviously changed along with an in ­ crease or decrease in daily hay intake. Daily time spent ruminating and daily number of boli regur ­ gitated was also linearly increased or decreased with an increase or decrease of daily hay intake, and there were regression lines between daily amount of hay eaten and daily ruminating time or daily number of boli with statistical significant coefficients. Cyclic rate (total rumination tiine(s)/number of boli regurgitated) and daily number of rumination periods did not change in an outline along with the changes in daily hay intake. From these results, it can be suggested that daily dry matter intake by sheep could be presumed by measuring daily time spent ruminating when they were fed only roughage feed.


Introduction g/d in continuous feeding experiment produced
It is obvious that the roughage utilization in ruminants would be influenced by an extent of ruminal fermentation, and the act of chewing during eating and ruminating has an important role to reduce the particle size of ingested rough age feed, which could facilitate microbial fermen tation in the rumen (Gordon, 1958).The eating and ruminating behaviour appears to be influenced clearly by physical property and chemical compo sition of feed eaten (Campling et al., 1962;Morgan and Campling, 1978;Qrskov et al., 1974;Fujihara, 1980).There is also another factor affecting the rumination behaviour in rough age feeding, which is the amount of feed eaten (Hancock, 1954;Gordon, 1965;Welch and Smith, 1969;Harumoto and Kato, 1978).Hancock (1954) has reported formerly that daily time spent ruminating was greatly changed with the changes of quality and quantity of ingested forage ration, and there were also quite big variation among individuals.Welch and Smith (1969) have reported with rams that progressing from 250 g/d offerings of hay to 1,800 a curvilinear increase in rumination time with a maximum in the range between 500 to 600 minutes per day.Gordon (1965) has also reported w辻h sheep that daily ruminating time might be periodically increased with an increase of hay intake, i.e., the typical curve of increasing rumina tion appears to be in three or possibly four parts, and then, something approaching a plateau occurr ing at certain daily hay intake, when each sheep was additionally fed a total of 300 g of grain mixture per day.There are also some observations on the changes of eating and ruminating behaviour with an increase of forage intake by sheep (Okamoto, 1979) and cattle (Harumoto and Kato, 1978).These observations would show that daily rumination time appears to be increased curvili nearly with an increase of roughage intake.Rela tively little work has been done on the relation ship between rumination and the amount of roughage intake, in which the range of daily change in roughage intake was relatively small (Gordon, 1965).
On the other hand, there is no correct and simple method for measuring the forage intake by grazing animals in the existing circumstances.If there is a relatively positive relationship between rumination and the amount of forage eaten, it could be useful method for estimating the amount of forages ingested by grazing ruminants.
In the present study, the eating and ruminating behaviour in sheep fed only forage ration were investigated in detail, when the amount of daily intake was increased or decreased gradually at a level of small amount.
The sun-cured hay was made from the herbage harvested at heading stage from a predominantly Italian ryegrass or cocksfoot pasture (1st cut), and the chemical composition (% of D.M.) of each hay, determined by the methods of AOAC (Hoitz,I960) and Van Soest and Wine (1971), is shown in table 1.

Experiment I
The experimental animals were kept in the metabolism crates throughout the experimental period of 21 days.During the initial 7 days of experimental period, each animal was offered 600 g (about 2.0% D.M. of body weight) of hay per day to roughly equalize the ruminal contents, and then the daily amount of hay offered was gradual ly increased (50 to 700 g/head) during 14 days (8th-21st day).One-half of the daily ration was given at 09:00 h and another half at 17:00 h.
Fresh water and salt licks containing trace minerals were freely available at all time.

Experiment II
After the experiment (A) as same as experi ment I except animals and hay used, during 7 days each animals was daily offered 600 g of hay, and daily amount of hay offered was gradually decreased (700 to 50 g) during 14 days (8th-21st day) (B).The other experimental pro cedures were similar to that of experiment I mentioned above.
In both experiments, during 14-day sampling period the time spent chewing during eating and ruminating was measured daily from records of jaw movement using a wire strain gauge held against the under-jaw of each animal according to the procedure described by Harumoto and Kato (1979).The statistical analysis of the data was made by t-test (Yoshida, 1975).

Experiment I
The hay used in expt.I was somewhat low quality as shown in table 1, as compared with that used in expt.II, i.e., the protein content was relatively lower and the crude fibre content was contrariwise relatively higher in the former than in the latter.
Figure 1(a) shows the changes in daily time spent eating, daily rumination time and daily number of boli regurgitated in sheep, when daily amount of hay was gradually increased from 50 g to 700 g/head.The time spent eating hay was almost linearly increased with an increase of daily hay intake, and there was a regression line between the eating time (Y) and daily amount of hay eaten (X) as follows; Y = 49.86 + 0.27X,

Experiment
Organic  and the coefficient of correlation (r = 0.865) was significant statistically (p < 0.01).Daily time spent ruminating and daily number of boli regurgi tated were also increased linearly with an increase of daily hay intake, and there were also regression lines between the rumination time (Ya) or daily number of boli (Yb) and daily hay intake (X) as follows; Ya = 229.96+ 0.75X (r = 0.898) and Yb = 286.28+ 0.63X (r = 0.806), respectively.The both coefficients of correlations were also significant statistically (p < 0.01).As shown in figure 1(b), rumination periods and cyclic rate (total rumination time(s)/number of boli regur gitated) were not changed largely with an increase of daily hay intake, although rumination periods was a little b辻 more in feeding of small amount hay (50-150 g/d).Therefore, time spent ruminat ing per rumination period was gradually, but slightly, increased with an increase of daily hay intake as same as daily time spent ruminating.
Figure 1(c) shows the time spent eating, rumi nation time and the number of boli regurgitated per 100 g dry matter eaten, when daily hay intake by sheep was gradually increased from 50 g to 700 g.The time spent eating was almost similar when daily hay intake was in a range between 100 g to 700 g, and the time spent ruminating and the number of boli were also similar in a range of daily hay intake between 200 g to 700 g per head.

Experiment II
The hay used in expt.II was slightly high quality as compared with that used in expt.I, as mentioned above.As shown in figure 2(a), daily time spent eating hay was linearly increased with an increase of daily hay intake, and there was a regression line between daily time spent eating (Y) and daily hay intake (X) as follows; Y = 9.45 + 0.18X, and a coefficient of correlation (r = 0.987) was significant statistically (p < 0.01).Daily time spent ruminating and the number of boli regurgi tated were also linearly increased with an increase of daily hay intake, and there was also regression line between daily time spent ruminating (Y) and daily hay intake (X) as follows; Y = 146.59+ 0.53X, and a coefficient of correlation (r = 0.985) was statistically significant (p < 0.01).As shown in figure 2(b), the number of rumination periods and cyclic rate did not change markedly with an increase of daily hay intake, and therefore, the rumination time during a rumination period resulted in increase slightly.Figure 2(c) shows the time spent eating, time spent ruminating and the number of boli regurgi tated per 100 g dry matter eaten by sheep when they were fed a hay diet at daily level of 50 g to 700 g.The time spent eating 100g dry matter did not change with an increase of daily hay intake.The time spent ruminating and the number of boli regurgitated also did not change with an increase of daily hay intake, when sheep were fed daily in a range between 200 g to 700 g hay.
Figure 3(a) shows the changes in daily time spent eating, daily time spent ruminating and daily number of boli regurg辻ated in sheep when daily amount of hay offered was gradually de creased from 700 g to 50 g during 14 days.Daily time spent eating diet was decreased with a de crease of daily hay intake, and there was a re gression line between the eating time (Y) and daily amount of hay eaten (X) as follows; Y = 10.28 + 0.18X, and the correlation coefficient (r = 0.978) was significant statistically (p < 0.01).Daily time spent ruminating and daily number of boli regurg辻ated were also linearly decreased with a decrease of daily hay intake.There was also regression line between daily time spent ruminating (Y) and daily hay intake (X) as follows; Y = 166.01+ 0.47X, and the coefficient of correlation (r = 0.974) was significant statisti cally (p < 0.01).
As shown in figure 3(b), daily number of rumi nation periods and cyclic rate were not changed with a decrease of daily hay intake, and as a result, the rumination time per rumination period resulted in a slight decrease with a decrease of daily hay intake.
Figure 3(c) shows the eating time, rumination time and the number of boli regurgitated per 100 g dry matter eaten by sheep.The eating time did slightly increase when the amount of hay offered daily was quite small (150-50 g), and the rumina tion time and number of boli did rapidly increase with small amount of hay offered daily in a range between 100 g to 50 g.

Discussion
Daily time spent eating hay diet in average was slightly longer in experiment I than that in experi ment II, and this would be due to the differences of kind and quality of hay used in both experi- merits.In our previous results (Fujihara, 1981;Fujihara and Nakao, 1982), it was also shown that some differences in eating time in sheep fed various roughages were obviously due to the differences in physical form and/or quantity of dietary fibre drived from some differences in the original plants.
Daily time spent eating hay diet almost linearly increased with an increase of daily hay intake (figures 1(a) and 2(a)), and also decreased linearly with a decrease of daily hay intake (figure 3(a)).Daily time spent eating per 100 g dry matter of hay was relatively longer when daily hay intake was quite small (50-150 g) than when daily hay intake was in a range between 200 g to 700 g .This finding did not always agree with that reported by other workers (Freer and Campling, 1965), in which the rate of eating diet was faster with small amount than that with large amount of ration.Freer and Campling (1965) have described that the complementary relationship between the time spent eating and the time spent ruminating was observed with diets of hay and dried grass, that is, the rate of eating roughage was fast with small amounts of food, and the rumination per unit (pound) food high; with large amounts of food opposite trends occurred so that the total amount of chewing per unit (pound) food was about the same.In the present study, however, any complementary relationship between the eating time and ruminating time was not found when daily amount of hay eaten was increased or decreased gradually.
In the present study, there was a regression line between daily time spent ruminating and daily amount of hay eaten, and this do not agree with the results obtained by other workers (Hancock, 1954;-Welch and Smith, 1969;Harumoto and Kato, 1979;Okamoto, 1979), in which there were quadratic regression between the daily rumination time and daily hay intake in sheep or cattle.The differences in both experiments would be clue to the differences in the rate of daily change of hay eaten.Then, in the present study, if the data was summarized according to the rate of 200 g hay intake per day, the regression between the rumina tion time and daily hay intake also obviously showed a quadratic.
According to Gordon (1965), the typical curve of increasing rumination with an increase of hay intake appeared to be in three or four parts, i.e., the first of all there was rapid rise from minimum FUJJHARA ET AL.
hay intake, then something approaching a plateau occurring at a daily hay intake range 200-300 g.In the present experiment, however, we could not find any 'plateau' phenomenon in all sheep when either the daily hay intake was gradually increased or it was decreased gradually.It may be a reason that the feeding level before experiment should obviously affect the rumination behaviour i.e., in the present study, daily feeding level of hay during the preliminary period (7-day) was about 2.0 % D.M. of body weight to equalize the rumen volume at the opening of experiment, and in Gordon's experiment, the sheep had been eaten daily 300 g of hay during the preliminary period.
On the receptor of a reflex to ruminate, it is generally accepted that there is a organ obviously which may be an end of the exciter (Hill, 1957(Hill, , 1958)).It has been also recognized that the rumina tion can be originally induced by some elongative stimuli to the cardia, the reticulo-rumen wall and/or the reticular wall, and mainly a rumination seems to be clearly induced with stimulation of a tactile receptor in the reticular wall induced by tactile stimuli of some coarse particles of food eaten (Schalk and Amadon, 1928;Ash andKay, 1957, 1959).It may be also assumed that some other tactile stimuli to another digestive organs except the reticulo-rumen is another important factors stimulating the rumination activity (Hard ing and Leek, 1973).Therefore, the results obtained in the present study, in which the rumi nation activity was markedly stimulated or suppressed with an increase or a decrease of daily hay intake by sheep, would have been occurred with an increase or a decrease of tactile stimuli to the reticulo-rumen wall as a receptor related to rumination in changing the amount of roughage eaten day to day.
In the present study, the body weight of ex perimental animal was slightly different in each experiment, and that was not always similar in both experiments I and II.Therefore, to standar dize the result with the relationship between the daily hay intake and daily time spent ruminating, the rumination time was shown in relation to the changes of dry matter intake per metabolic body size (B.W.。")each animal (see figure 4).There was also a regression line between daily time spent ruminating (Y) and daily intake of dry matter per kg B.W.0-75 (X) as follows; Y = 207.48+ 113.5X (figure 4 It is considered in ruminants that the boli re gurgitation during ruminating will be occurred in concert w辻h a contraction of the reticulum, and that a contraction of the reticulum do not change with the change of quantity or quality of food eaten (Balch, 1952).According to Campling (1966)> the daily number of rumination periods did not change with the change in dietary charac teristics and/or the daily time spent ruminating, though there were obvious differences among individuals.The results obtained in this study confirm the facts mentioned above in an outline, though there were slower cyclic rate and slight increase of the daily number of rumination periods during the period which the daily amount of hay intake was relatively small (50-150 g).From these facts, it can be concluded that cyclic rate and daily number of rumination periods as mechanical fac tors induced in the rumination activity can not be influenced by the change in amounts of food eaten.

Figure 1 .
Figure 1.The eating and rumination behaviour in sheep with the increase of daily hay in take (Experiment I), (a) Time spent eating (히, rumination time (o) and the number of boli reg니rgitated (X); (b) Rumination period (®), rumination time/rumination period (X) and cyclic rate (o)； (c) Time spent eating (®), rumination time (o) and the number of boli regurgitated (X) per 100g dry matter eaten.

Figure 2 .
Figure 2. The eating and rumination behaviour in sheep with the increase of daily hay intake (Experiment II).(a) Time spent eating (♦), rumination time (o) and the number of boli reg니rgitated (X); (b) Rumination period (®), rumination time/rumination period (X) and cyclic rate (o)； (c) Time spent eating (®), rumination time (o) and the number of boli regurgitated (X) per 100 g dry matter eaten.

Figure 3 .
Figure 3.The eating and rumination behaviour in sheep with the decrease of daily hay in take (Experiment II).(a) Time spent eating (♦), rumination time (o) and the number of boli regurgitated (X); (b) Ru mination period (히, rumination time/ rumination period (X) and cyclic rate (。)；(c) Time spent eating (®), rumina tion time (o) and the number of boli regurgitated (X) per 100 g dry matter eaten.