To allow improved prediction of daily herbage intake of dairy cows in rotational grazing systems, intake behaviour was assessed throughout the day in 24-h paddocks. Herbage intake in 16 lactating Holstein±Friesian cows was assessed using the short-term (1-h) weight gain method at four predetermined natural meal times throughout the day (early morning, T1; late morning, T2; mid-afternoon, T3; and early evening, T4). The study comprised two 4-day experiments, each with a cross-over design of four blocks. In both experiments, cows grazed a 24-h paddock daily, and the effect of the immediately previous grazing experience on intake behaviour was investigated throughout the day, taking account of daily¯uctuations in the short-term physiological condition of the cows. Experiment 1 was carried out to investigate overall grazing behaviour during meals as a sward is progressively depleted during the day, with intake being assessed within the paddock and, hence, on a depleted sward. Experiment 2 similarly investigated the effect of sward depletion and physiological condition throughout the day on intake, but cows were removed to fresh, undefoliated swards during intake measurement periods; thus, intake rate was not in¯uenced by differences in sward condition. Intake behaviour from both experiments was compared to establish the effect on herbage intake of changes in sward state and non-sward factors. In Experiment 1, sward surface height, available herbage mass, proportion of leaf and green leaf mass declined as the day progressed. Bite mass declined with sward depletion, and mean intake rate was 1á64 kg dry matter (DM) h ±1 , which was signi®cantly lower at T3 (P < 0á01) than during other meals. In Experiment 2, plot sward conditions did not change throughout the day, and intake behaviour also remained constant, with a mean intake rate of 2á11 kg DM h ±1 . Mean bite depth as a proportion of pregrazing extended tiller height was constant throughout the day (mean 0á32). The results show that, although cows grazed throughout the day on progressively depleted swards, indicative of rotationally grazed paddocks (Experiment 1), bite mass declined linearly and intake behaviour was variable. However, where intake was assessed on high-quality, undefoliated swards (Experiment 2), intake behaviour was similar regardless of the time of day and the immediately previous experience. There was some indication of an interaction between the effects of the sward and the physiological condition of the animal on herbage intake.

Growth of grass herbage in Ireland is highly seasonal with little or no net growth from November to February. As a result, feed demand exceeds grass supply during late autumn, winter and early spring. At low stocking rates [£2 livestock units (LU) ha )1 ], there is potential to defer some of the herbage grown in autumn to support winter grazing. This study examined the effects of four autumn-closing dates and four wintergrazing dates in successive years on the accumulation of herbage mass and on tiller density in winter and subsequent herbage production at two sites in Ireland, one in the south and one in the north-east. Closing swards from grazing in early and mid-September (north-east and south of Ireland respectively) provided swards with >2 t DM ha )1 and a proportion of green leaf >0AE65-0AE70 of the herbage mass above 4 cm, with a crude protein (CP) concentration of >230 g kg )1 DM and dry matter digestibility (DMD) of >0AE700. The effects of autumn-closing date and winter-grazing date on herbage production in the subsequent year varied between the two sites. There was no significant effect of autumn-closing date in the north-eastern site whereas in the south earlier autumn closing reduced the herbage mass in late March by up to 0AE34 t DM ha )1 and delaying winter grazing reduced the herbage mass in late March by up to 0AE85 t DM ha )1 . The effects of later grazing dates in winter on herbage mass continued into the summer at the southern site, reducing the herbage mass for the period from late March to July by up to 2 t DM ha )1 . The effects of imposing treatments in successive years did not follow a consistent pattern and year-to-year variation was most likely linked to meteorological conditions.

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1998). Effect of duration of fasting period on short-term intake rates of lactating dairy cows. AbstractThe effects of duration of fasting on the short-term feeding behaviour of 12 grazing and 12 silage-fed lactating Holstein-Friesian dairy cows were examined. Four groups of three cows were rotated around fasting treatments of 1, 3, 6 or 13 h following a balanced Latin-square design. Herbage intakes for each treatment group were assessed over al-h period. As intended there were no significant differences in sward characteristics between the experimental plots grazed by cows from different treatment groups. However, total dry-matter (DM) intake, biting rate and DM intake per bite, measured over the 1-h grazing period, increased significantly when the duration of fasting was extended from 1 to 6 or 13 h (P < 0-05). There were only minor differences in grazing behaviour following fasting durations ofl and 3, or 6 and 13 h. In a parallel study, undertaken to assess the influence of fasting duration on appetite independently of grazing, four groups of three cows were housed indoors and offered 30 kg of a high quality grass silage. Silage DM intakes, measured over a 1-h period, increased significantly with extended fasting periods (P < 0-01), though silage DM intake was considerably lower than that of grazing cows for each fasting treatment. These results suggest that dairy cows grazing on good quality swards may be able to compensate for increased degree of hunger by increasing both biting rate and DM intake per bite to increase DM intake rate. Although the DM intakes of silage and grazed grass followed similar patterns of increasing intake with extended fasting duration, DM intake rates were considerably higher in grazing cows for each fasting treatment.

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