On the Diurnal Pattern of Weight Change of Heifers as a Characteristic of the Grazing Behaviour under Rotational Grazing

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  • 体重の日内変動からみた輪換放牧牛の採食行動
  • タイジュウ ノ ニチナイ ヘンドウ カラ ミタ リンカン ホウボク ウシ ノ

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Abstract

In order to make clear the diurnal pattern of the grazing behaviour of dairy heifers under rotational grazing condition, their weights were measured at intervals of three hours from the day they were transferred to a new paddock to the following day. In experiment 1, the first group was moved to a new paddock at 1000 hours and the second group was moved at 1300 hours to the same paddock. In experiment 2, the first group and the second group were moved at 1000 and 1600 hours, respectively. The research was conducted for 6 periods in experiment 1 and for 3 periods in experiment 2 on the orchardgrass-dominant sward. In experiment 1, the behaviour of heifers was observed and the numbers of heifers grazing, ruminating (standing and lying), resting (standing and lying) and loafing were recorded every 10 minutes. The mean liveweights of heifers were 200-240kg. 1. Heifers grazed most intensively during the first three hours after the moving time and increased 10-16kg in their during these hours. They gained 2-3kg in weight during the second or third three hours after the moving time, but they lost 8-10kg in weight in the night time between 1900 and 0400 hours. However, heifers moved at 1600 hours extended their grazing time after sunset and their weights increased between 1900 and 2200 hours. 2. There were two peaks of grazing which occurred just after the moving time and in the late afternoon till just after sunset. But, there was a remarkable difference between two peaks from the view point of weight increase. It was supposed that heifers grazed less amount of herbage at the peak of grazing in the late afternoon than at the peak immediately after the moving time. 3. On the following day, there was no hasty increase in weight as was seen after moving time and weights of heifers did not reach to the maximum weight on the first day, although they kept still the higher weights than those of heifers before the moving time. It was concluded that from the pattern of weight change grazing behaviour of heifers on the following day was less active compared with that on the first day. 4. Ruminating behaviour was scarecely observed till the night on the first day, but on the following day there was a considerable time for ruminating behaviour during daytime. As above results, behaviour of heifers under rotational grazing was so strongly influenced by the transfer to a new paddock that they did not show such a normal pattern of behaviour as regular repetition of grazing, resting and ruminating on the first day. The diurnal pattern of grazing behaviour of heifers on the first day differed makedly from those on the second day.

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