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AAES Research Series 488
of the nine paddocks (no shade) had three crossbred steers
randomly assigned. Forage availability was maintained in the
vegetative state by grazing additional animals.
At both locations, steers had ad libitum access to mineral
supplement and water during the grazing season which
was approximately 150 days, initiated in June and concluded
in October. Steers were weighed and blood collected at 28
day intervals throughout the grazing season. Blood was used
to prepare serum which was analyzed for prolactin concentrations.
In addition, steer body temperature and respiration
rates were determined on days when daytime temperatures
exceeded 90°F. At Mount Vernon, steer hair coat was scored
based on the following system: 1 = slick, short-haired animal
(less than 1/2” in length); 2 = has some medium length hair
(1/2” to 1”); 3 = medium length hair coat covers most of the
body; 4 = medium hair plus some rough, long, dead hair; 5 =
hair coat consists primarily of rough, long, and dead hair.
Within each location data from both years were combined
and least squares means ± standard error are presented.
Analysis was conducted using a general linear model (SAS
Institute, Inc. Cary, NC). In the model, forage variety and
year were treated as class variables.
Implications
Both novel endophtye varieties (HiMag 4 and HiMag
9) of tall fescue survived the hot and dry summers during this
grazing trial. In addition, those varieties produced animal
gains and physiological responses similar to the endophytefree
control steers. These forages could be very useful for
profitable production of livestock.
Literature Cited
Bouton, J., et al. 2000. Alleviating tall fescue toxicosis problems
with non-toxic endophytes. Proc. Tall Fescue
Toxicosis Workshop. October 16-17. Chapell Hill, TN
p 9-15.
Hoveland, C.S. 1993. Ecosystems. Environ. 44:3.
Results and Discussion
Fayetteville results: Values shown in Table 1 represent
the mean for the combined year effect for each item. Steers
grazing E+ had a lower (P < 0.05) ADG (0.93 lb/d) than steers
grazing HiMag 4, HiMag 9, and E- (1.43, 1.36, and 1.61 lb/d,
respectively). Mean respiration rates were higher (P < 0.05)
in cattle grazing E+ (91.3 breaths/min) compared to those
steers grazing HiMag 4, HiMag 9, and E- (59.8, 62.3, and
63.3, respectively). Mean rectal temperatures for steers grazing
E+ pastures (105.3°F) were higher (P < 0.05) than in cattle
grazing HiMag 4, HiMag 9, and E- pastures (103.6, 103.8,
and 103.5°F, respectively). Mean prolactin concentrations
were higher (P < 0.05) in cattle grazing E+ pastures (42.48
ng/ml), compared to the cattle grazing E-, HiMag 4, and
HiMag 9 (152.46, 146.82, and 165.32 ng/ml, respectively).
Mount Vernon results: Table 2 presents the combined
year means for each item. Average daily gain (ADG) was
decreased (P < 0.05) in steers grazing E+ (0.55 lb/d), compared
to that of steers grazing E- (1.21 lb/d) and HiMag 4
(1.21 lb/d). Mean hair score for cattle grazing E+ (3.96) was
higher (P < 0.05) than those grazing HiMag 4 (2.46) and E-
(2.13) pastures. Cattle grazing E+ pastures had higher (P <
0.05) respiration rates (122.8 breaths/minute), compared to
those grazing E- and HiMag 4, which were 93.2 and 103.6,
respectively. Mean rectal temperature for steers grazing E+
was 106.3°F. This was higher (P < 0.05) than for steers grazing
E- (104.3°F) and HiMag 4 (104.9°F), which were different
from each other (P < 0.05). Mean prolactin concentrations
were lower (P < 0.05) in cattle grazing E+ pastures (16.46
ng/ml), compared to cattle grazing E- and HiMag 4 (108.27
and 154.63 ng/ml, respectively). The results of this study confirm
other studies (Bouton et al., 2000) that indicate that tall
fescue can be inoculated with non-toxic endophytic fungus.
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