Fecal bacteria in Hokkaido native horses were enumerated by their morphology and Gram staining, and then three major cellulolytic species were quantitated by recently developed competitive polymerase chain reaction (cPCR) assays. Fecal bacterial flora in horses showed drastic change between grazing on summer grassland pasture and grazing on winter woodland pasture mainly consisting of bamboo grass (Sasa nipponica). The number of total bacteria was decreased in winter samples, accompanied with a higher proportion of Gram negative rods and lower proportions of Gram negative cocci, Gram positive rods and cocci than those in summer. This high proportion of Gram negative rods was partly explained by the high cPCR-assay values for Fibrobacter succinogenes (a highly cellulolytic Gram negative rod) in winter samples. Of three major cellulolytic bacterial species, F. succinogenes was dominant in feces of

Hokkaido native horses (HH) were compared with light half-bred horses (LH) for digestibility and the number of bites and chews when fed non-chopped timothy hay at 90% of the maintenance level in the pen. Apparent digestibility of nutrient and energy in HH were similar to those in LH. The time budget of eating by HH per day was shorter than that by LH (P<0.05, 403.3 vs 557.5 min), while there was no difference between HH and LH in the eating rate. The rate of biting, bite size, chewing rate per a minute and the number of chews per 1 g DM intake in HH were similar to those in LH. Ingestion by HH was indicated to be more efficient than that by LH.

In this study, grazing behavior of mares and cows was compared on woodland pastures, in the context of foraging hierarchy. A horse-group (12 native Hokkaido horses) and a cattle-group (5 Hereford cows) were grazed on the woodland pastures of 13.3 ha and 5.8 ha, respectively. They grazed mainly on Sasa nipponica. Grazing behavior at a feeding station (FS) scale was recorded for three focal animals in each group. Mares took one bite per FS at a high percentage of FSs (24.3%) and cows took one, two and three bites per FS at high percentage (20.3%, 19.2% and 15.4%, respectively). Although feeding patch (FP) scale for both animals could be defined as a group of FSs, the length of FP and grazing behavior at FP scale were similar for both animals. The number of steps taken between two adjacent FSs or FPs for mares was larger than that for cows. The results suggested that both horses and cattle had similar foraging hierarchy from bite to FP scale but grazing behavior of horses at the FS scale was different from that of cattle, suggesting that grazing behavior of large herbivores has greater similarity in larger foraging hierarchies.

To study the differences between Hokkaido native horses and light half-bred horses on woodland pasture from the nutritional and behavioral viewpoint, feed intake, grazing time, moving distance, daily staying area and distance to the nearest neighbor were measured. Voluntary dry matter intake per body weight and metabolic body weight of Hokkaido native horses were higher than those of light half-bred horses (2.0 vs 1.8%, 88 vs 86 gDM/kgMBW), and the body weight loss of Hokkaido native horses during the experimental period was smaller than that of light half-bred horses. Grazing time, total moving distance, especially the moving distance with grazing were longer for Hokkaido native horses than for light half-bred horses. The distributions of distance between the nearest neighbor horses of the same breed for both breeds were similar. The distance from the one breed to the nearest neighbor of the other breed was greater than that within the same breed (P<0.01). The mean distance from the first position of a horse to its position at 1 hr intervals for Hokkaido native horses was 162 m, which was greater than 65 m for light half-bred horses. The daily staying area of Hokkaido native horses throughout the period of observation was larger than that of light half-bred horses. The differences between the two breeds in voluntary intake and behavior seemed to be large, but these differences were not significant.

In this study, effects of grazing-experienced heifer presence on foraging behavior development at the feeding station (FS) scale for first-grazing season calves were determined. A group of four calves grazing alone (C), and another comprising four calves (Wc) and three grazing-experienced heifers (Wh), were alternately stocked every day for 2 h on the same pasture for 26 days. The foraging time budget for Wc was significantly longer than that for C (P < 0.05) on day 7, and was similar to that for Wh on all days. Bite rate per FS was significantly higher for Wc (15.5 bite/min) than for C (13.2 bite/min) from day 1 to 14 (33.4 vs. 29.0 bite/min, respectively; P < 0.01) and significantly lower than that for Wh on all days. The number of steps taken between adjacent FSs by Wc (4.7) was significantly lower than that for C (7.2) on days 1 and 14 (2.1 vs. 2.9 steps, respectively; P < 0.01) and was similar to Wh on all days. This suggests that grazing-experienced heifers have positive effects on the foraging behavior development of new-season grazing calves through 14 days after the start of stocking.