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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 42 (1987), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Two experiments were carried out to examine the effects of grazing severity on the performance of January/February calved British Friesian dairy cows. In Experiment 1, three groups of cows were rotationally grazed across twenty-four one-day paddocks with high (H), medium (M) or low (L) herbage allowances. Cows on treatment M were offered a daily herbage allowance designed to achieve a residual sward height of 50 mm, assessed by a rising-plate sward stick. The daily herbage allowance (g organic matter (kg live-weight)-1 on treatments L and H were 0.30 below and above that for M, respectively, to give residual sward heights of 42 and 59 mm. In Experiment 2, three groups of cows were grazed across twenty-four one-day paddocks to obtain residual sward heights of 50 mm (severe), 60 mm (moderate) and 80 mm (lax).Average milk yields on the L, M and H treatments in Experiment 1 were 11.8, 14.6 and 14.5 kg d,-1 and in Experiment 2 they were 13.7, 16.0 and 17.0 kg d-1 on the severe, moderate and lax treatments, respectively. The results indicate that the critical herbage height below which milk production per cow declines may vary with the production potential of the animal. There were no significant treatment effects on milk composition.Milk output ha-1 and utilized metabolizable energy ha-1 were greatest with the low herbage allowance in Experiment I and the moderate treatment in Experiment 2. Net herbage accumulation on the severe treatment in Experiment 2 was 30% lower than that on the lax treatment, as a result of treading damage in early season.It is concluded that, in a rotational grazing system, a reasonable compromise between sward utilization and animal performance can be achieved by grazing January/February calved cows to a residual sward height of 60 mm as assessed by a rising-plate sward stick. This is equivalent to a sward surface height of about 80 mm.
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  • 2
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: An experiment was carried out during 1984 to examine the effects of three alternative grazing strategies for January/February calved British Friesian dairy eows on sward and animal production. Cows were rotationally grazed across 1 d paddocks without concentrate supplementation from 30 April to 1 October. A flexible grazing (EG) treatment involved manipulating residual herbage height, as assessed by a rising-plate sward stick, with cows initially grazing to 80 mm, reducing to 60 mm when milk yield declined below 20 kg d−1 and finally to 50 mm when milk yield declined below 15 kgd−1. Control (C) cows grazed to a constant residual herbage height of 60 mm throughout the season (a 60-inm rising-plate sward stick height is equivalent to a sward surface height of approximately 80 mm). On a further treatment a leader/follower (LF) approach was used, with cows paired for calving date and parity and within pairs allocated to either a high-(leader) or a low-yielding (follower) group, according to milk yield at turnout, with the leader group grazing 1 d ahead of the follower group. Overall stocking rates on C and LE treatments were identical but herbage allowances differed as a result of treatment effects.Animal performance data for the FG, C and LE treatments, respectively, were: milk yield (kg d−1) 14·5, 14·7 and 16·0 (s.e. 0·59); milk fat yield (g d−1) 577, 571 and 637 (s.e. 29); milk protein yield (g d−1) 528, 527 and 576 (s.e. 19); and liveweight gain (kg d−1) 0·09, 0·20 and 0·14 (s.e. 0·04).Overall, there was no benefit in animal production following lax grazing in spring even with high-yielding cows, and this approach resulted in the accumulation of stem and senescent material in the sward in mid-season. However, preferential treatment of high-yielding cows by grazing as a leader group in a leader-follower system resulted in higher milk production, particularly in late season, with an overall improvement in milk yield for the LF treatment of 9% relative to treatment C.
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  • 3
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Two systems of grazing management involving preferential treatment of high- yielding dairy cows were compared with a grazing system in which both high- and low-yielders received uniform treatment. Cows were rotationally grazed across I-day paddocks without concentrate supplementation from 23 April to 8 October 1985, with a mean stocking rate over the season of 5-4 cows ha−1. Preferential treatment of high-yielding cows was achieved either by using a leader/follower approach (LF) with high-yielding cows in the leader group, or by preferential forage feeding (PFF) where high-yielding cows were allowed access to grass silage for 1 -5 h daily and grazed alongside low-yielders. Control (C) cows grazed together as a single group. The high grazing stocking rates used on all three treatments resulted in good grass utilization with residual sward heights, assessed by a rising-plate sward stick, of 45, 50 and 48 mm for the LF, PFF and C treatments respectively. Animal performance data for the LF, PFF and C treatments respectively were: milk yield (kg d−1) 15middot;1, 15middot;6 and 14middot;7 (s.e. 0middot;78); milk fat yield (g d−1) 598, 606 and 567 (s.e. 34); milk protein yield (g d−1) 500, 519 and 480 (s.e. 31); and live weight gain (kg d−1) 0middot;12, 0middot;23 and 0middot;25 (s.e. 0·05). These results indicate that leader/follower grazing had little overall effect on animal performance when high grazing severity was imposed, with the improvement in animal performance of high-yielding cows in the leader group being offset by the reduced performance of the follower group. Buffer-feeding of high-yielding, rotationally-grazed cows with high-quality grass silage had little effect on animal performance and resulted in a decrease in the efficiency of grassland utilization. Silage appeared to substitute for herbage, with a reduction in herbage DM intake of 0middot;55 kg per kg silage DM consumed.
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