| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2000: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1999: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
Ruminants degenerate upper front teeth. This study was carried out in order to clarify an advantage of this degeneration of upper front teeth at grass foraging, compared with horse. The experiments were carried out using three thoroughbred horses and three cows of dry Holstein in July 1999, and three castrated Suffolk sheep in July and August 2000. Grass species used were perennial ryegrass leaves (PRG), tall fesue leaves (TF) and reedcanary culms (RCG) in 1999, and orchardgrass leaves (OG) applied with 0, 10 and 20 kg/10a of nitrogen. These grasses were fixed on 15 one-way loadcells in 1999 and 5 three-way loadcells in 2000, and were grazed by animals. At prehending bite, break-down strength of grasses was measured by loadcells.
Prehending load per 1g DM was 22.9-27.9 kg in cow 17.7-23.6 kg in horse when PRG and TF leaves were given, and 75.2 kg at low leaf density and 41.2 kg at high leaf density in sheep. Mean load per 1 bite was 12.5 kg in cow and 19.4 kg in horse at grazing of PRG
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and TF leaves, and 2.8-3.3 kg in sheep. These values were correspondent to 1.9% in cow, 3.6% in horse and 8.7% of body weights. Sheep used 2.01-2.26 kg of total load at forward movement and 2.63-2.65 kg kg of total load at buckward movement when maximum values of total loads observed at each point were used. This result suggests that sheep can effectively sever grasses by a lower front teeth at forward movement, resulted in lower total load.
Cow wrap their tongues around grass and pull to pregend it. In a mixture of hard culms of RCG and soft PRG/TF leaves, cow could selectively shear soft leaves without upper front theeth, because hard culms were avoided for their higher tensile strength. Hoese use strong, mobile and sensitive upper lip to collect grass and shear off it by both upper and lower front teeth. At grazing, horse sheared both leaves and culms together. Therefore, "comb-out" strategy of ruminant foraging is made a proposal concerning an avoidance of hard culms. This term was brought from the same behavior of combing out a hair. The result will be published soon. Less
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