Studies were made on the resting gas metabolism and the cardio-respiratory functions of 4 adult Wagyu (Japanese Black Breed of Cattle) in grazing.
The principal results obtained were as follows :
(1) Both O_2 consumption and CO_2 production gradually increased with grazing, and reached obout 165% of their initialresting value. On the 7 or 10th day after grazing was started, the excess metabolism was observed.
(2) The averege output of heat in grazing cattle at rest was 1.33～1.78 Cal. per Kg. B.W. per hour. This value seemed to be nearly equal to that produced by mild work. The changing curves of heat production in grazing cattle consisted of 3 parts : early rapid rising, next gradual rising and rapid falling immediately after grazing was over. And the resting value immediately after grazing was ended did not completely recover its initial level for about half a month afterwards.
(3) The respiratory quotient in resting metabolism of grazing cattle was high and remained virtually unchanged through the experiment. This suggests that the energy source of the grazing cattle mostly came from carbohydrate.
(4) The pulse rate, respiration rate and pulmonary ventilation rate gradually increased about 35%, 50% and 70% respec tively on the 40th day after grazing was started.
(5) The oxygen pulse per 1 Kg.B.W. differed a little individually, but its considerable increase was seen in all of the cattle during the grazing period. From this fact, it seemed that the oxygen-transport capacity of cattle's heart was improved by grazing. And this experiment seems to show that fatigue, if considered from the oxygen pulse, did not occur.
(6) The tidal air increased in the early 10 days of the grazing period, but then gradually decreased. Accordingly it follows that the increment of pulmonary ventilation rate in the grazing period should be attributed to that of raspiration rate.
In conclusion, the energy expenditure of grazing cattle is considerably high, and a ramarkably rapid rise of metabolic level appears during the early 10 days of the grazing period. When cattle are pastured on poor grasslands, the stress of grazing on the cattle is so severe that they may possibly have various kinds of accidents or disorders. And the early stage of grazing period is most dangeraous.