Subtropical perennial grasses make important contributions to productive, season-long grazing systems in the USA. The perennial bermudagrasses, particularly 'Coastal' bermudagrass (C}'nodon dac-t}'lon (L.) Pers.), are extremely productive, but high fiber allows only poor to moderate animal performance. Steer average daily gains (ADG) and productivity estimates of the subtropical perennials Oaccidgrass (Penni.retum flaccidum Griseb.), P. orientak Rich., and switchgrass (Panicum virgatum L.) were obtained. Sequential grazing of tall fescue (Festuca arundinacea Schreb.) and Coastal as a system (F + C) served as the standard for comparison. The grazing experiment with yearling steers was conducted on a Typic Hapludult soil for 3 years. Calendar days grazed, ADG (kg) and steers ha-1 , respectively, from initiation of grazing until Coastal was stocked (period 1) averaged 53, 0.93, and 15.1 for tall fescue; 20, 1.35 and 11.1 for Oaccidgrass and 40, 1.07, and 8.9 for switchgrass. Number of steers ha-1 was greatest on tall fescue and ADG lowest (P ::5 0.06). Flaccidgrass supported significantly more animals than switchgrass. Summer (period 2) results (avg. 98 days) for ADG and steers ha-1 , respectively, were 0.43 and 25.1 for Coastal; 0.78 and 9.1 for Oaccidgrass (P. orientak was similar), and 0.92 and 7.9 for switchgrass. Steer ADG was lowest and steers ha-1 highest on Coastal, while the other grasses were similar for both. Tall fescue made little contribution because rainfall was below normal all 3 years. Seasonal results from the F + C showed most calendar days (160), lowest ADG (0.59) but similar numbers of steers ha-1 (9.5) compared with respective values of 130, 0.90, and 9.6 for Oaccidgrass and 140, 0.96 and 8.2 for switchgrass. Flaccidgrass averaged significantly more steers ha -I than switchgrass. Gain ha -I from tall fescue in period 1 (792 kg) and Coastal in period 2 (1160 kg) was greater than the average for the other grasses, 349 and 559 kg, respectively. However, seasonal computations based on combined land areas for the F + C system yielded 1010 kg of gain ha-1 • That gain did not difl'er from the 930 kg ha-1 for the other grasses, even though the F + C system averaged 25 more calendar days. Flaccidgrass and switchgrass have quality attributes and a sufficiently long growing season to make an important contribution to an animal enterprise that values large daily animal responses. Coastal is more appropriately used in enterprises for an animal class, or portion of the season, where only moderate to low response animai-1 is required.AdditioiUil index words: Forage quality, Available forage, Stand persistence, Gain ha-1 , Total digestible nutrients ha-I, Panicum virgatum L., Penniaetum flaccidum Grise b., Penniaetum orientale Rich.

In traditional grazing trials, per animal and per hectare productivity are determined, but pasture and animal measurements are generally inadequate to address reasons for different treatment responses. This 2-yr study examined the diet and diet characteristics of steers grazing tall fescue (Festuca arundinacea Schreb.), switchgrass (Panicum virgatum L.), flaccidgrass (Pennisetum flaccidum Griseb.), and bermudagrass (Cynodon dactylon [L.] Pers.) pastures. A randomized complete block design was used with two agronomic replicates. In vitro DM disappearance (IVDMD) of masticates from tall fescue (TF), switchgrass (SG), and flaccidgrass (FG) generally were similar; all exceeded 70% (70.3 to 79.9%), except for bermudagrass (BG), which was lowest (63.5 to 65.0%). Sieving the masticate DM showed BG to contain the highest proportion (20 to 29%) of particles passing a .5-mm sieve and the lowest proportion (6 to 8%) of particles retained on a 2.8-mm sieve. This resulted in BG having the smallest mean (1.29 mm) and median (1.08 mm) particle sizes in yr 1 and a mean (1.10 mm) and median (.91 mm) particle size smaller than SG in yr 2. Except for BG, the IVDMD of the masticate DM was lowest for small particles. Canopies showed BG and SG to have the highest proportion of stem (47 and 52%, respectively); the BG canopy was composed of fractions that were consistently lowest in IVDMD. In general, BG offered the grazing animal a canopy inferior in IVDMD concentration and had canopy characteristics that limited the animals' selection of a diet with quality as high as that of TF, SG, or FG.

Effects of potential stress encountered by two Holstein herds relocated into a new double-six herringbone parlor and free-stall facility were studied by evaluating alterations of milk yield and fat percentage, mastitis status, corticosteroids, and heat detection. One-half of one herd (18 cows) was moved 100 m to new facilities (Merged), and the remaining 18 cows were maintained in their original tie-stall barn (Control). The same day, the second herd of 50 cows (Moved) was transported via stock trailer 7 km to new facilities. Milk yield by Merged and Moved cows was decreased at first milking, but subsequent milk yields were similar to yields prerelocation. Milk fat percentage was decreased for only 3 days for Moved cows but was unchanged for Merged cows. Across groups, older cows and cows in late lactation tended to have greatest decreases in milk yield. Corticosteroids in serum were increased in Merged cows for only 2 days after relocation. No changes in milk somatic cell count or percentage heats detected were associated with relocation. Detrimental effects of herd relocation were slight and indicate that dairy herds can be moved without adversely affecting production traits.

Pasture experiments may be grazed using either variable (put-and-take) or fixed stocking rates. Considerations such as the risks of introducing bias, the reliability of the data, and the resources required for these methods of grazing are discussed, and criteria are described for choosing between the methods.

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