Abstract: Thousands of hectares of timothy (Phleum pretense L.) grown in the Mid-Atlantic region are infected by cereal rust mite (Abacarus hysterix) that causes discoloration and curling of leaves, decreased nutritional quality, and substantial decreases in yield. A decline in production of timothy hay can lower income for hay producers and cause horse owners to search for alternative hays. Low alkaloid reed canarygrass (Phalaris arundinacea L.) hay has potential as an alternative to timothy hay because it grows well in the Mid-Atlantic region, is believed to have a similar nutrient quality to timothy, and is not as susceptible to cereal rust mite. Eleven mature, stalled Thoroughbred geldings (549 +/- 12.1 kg) that were exercised daily were used to compare voluntary DMI and apparent nutrient DM digestibility of timothy and low-alkaloid Chiefton variety reed canarygrass hay. Horses were paired by age and BW and randomly assigned to timothy or reed canarygrass hay during a 14-d period to measure voluntary DMI followed by a 4-d period to measure apparent DM digestibility. Both hays met the minimum requirements for DE, CP, Ca, P, K, Fe, and Mn, but they did not meet the minimum requirements for Cu, Zn, and Na for horses at maintenance and averaging 550 kg of BW. Timothy hay seemed to have a lower CP concentration (14.4%) compared with reed canarygrass hay (17.1%) and a more desirable Ca:P ratio at 1.6:1 compared with 0.8:1 for reed canarygrass hay. Horses fed timothy consumed more hay (P <0.001) during the voluntary DMI period compared with horses fed reed canarygrass. Greater voluntary DMI of timothy occurred on d 1, 3, and 5 (P <0.05), but DMI was similar for other days. Apparent DM digestibility was greater in horses fed timothy hay by 9.6% compared with horses fed reed canarygrass hay (P <0.05). Horses fed timothy had greater DM digestibility of ADF (P = 0.001), NDF (P = 0.001), sugar (P = 0.05), and Ca (P = 0.001) but lower apparent DM digestibility of CP (P = 0.012) and crude fat (P = 0.004). Timothy hay was superior in voluntary DMI and apparent DM digestibility compared with low-alkaloid reed canarygrass hay fed to horses.

Abstract: Holstein steer calves (n = 25) were used to evaluate the effects of treadmill exercise (TME) on blood metabolite status and formation of dark-cutting beef. Calves were blocked by BW (156 {+/-} 33.2 kg) and assigned randomly within blocks to 1 of 5 TME treatments arranged in a 2 x 2 factorial design (4 or 8 km/h for a duration of 10 or 15 min) with a nonexercised control. Venous blood was collected via indwelling jugular catheters at 10, 2, and 0 min before TME and at 2-min intervals during exercise. Nonexercised steers were placed on the treadmill but stood still for 15 min. Serum cortisol levels, as well as plasma concentrations of glucose, lactate, and NEFA, were similar (P > 0.05) before TME. Serum cortisol concentrations were unaffected (P > 0.05) during the first 6 min of TME, but between 8 and 15 min of TME, cortisol concentrations were greater (P < 0.05) in steers exercised at 8 km/h than those exercised at 4 km/h or controls (speed x time, P < 0.001). Although TME did not affect (P > 0.05) plasma glucose levels, plasma lactate concentrations in steers exercised at 8 km/h increased (P < 0.05) sharply with the onset of the TME treatment and remained elevated compared with steers exercised at 4 km/h or unexercised controls (speed x time, P < 0.001). Exercised steers had the lowest (P < 0.05) plasma NEFA concentrations during the first 6 min of TME compared with unexercised steers; however, NEFA concentrations were similar after 10 and 12 min of TME, and by the end of TME, steers exercised at 8 km/h had greater (P < 0.05) NEFA levels than nonexercised controls or steers exercised at 4 km/h (speed x time, P < 0.001). Even though muscle glycogen levels and pH decreased (P < 0.001) and muscle lactate concentrations increased (P < 0.001) with increasing time postmortem, neither treadmill speed nor TME duration altered postmortem LM metabolism. Consequently, there were no (P > 0.05) differences in the color, water-holding capacity, shear force, or incidences of dark-cutting carcasses associated with preslaughter TME. It is apparent that preslaughter TME, at the speeds and durations employed in this study, failed to alter antemortem or postmortem muscle metabolism and would not be a suitable animal model for studying the formation of the dark-cutting condition in ruminants.

Abstract: Two studies were conducted to determine the relationship of feeding behavior to the phenotypic expression of feed efficiency. In Exp. 1, a feedlot diet containing roughage was fed (traditional). In Exp. 2, a no-roughage diet was fed. Residual feed intake (RFI), a measure of feed efficiency, was calculated for both studies. In Exp. 1, 6 feed efficient (low RFI) steers and 6 feed inefficient steers (high RFI) were selected from a contemporary group of 80 steers, and feeding behaviors were analyzed. In Exp. 2, 9 feed efficient and 8 feed inefficient steers were selected from a contemporary group of 40 steers. There were no differences (P > 0.13) in initial or final BW or ADG between efficient and inefficient groups in either Exp. 1 or 2. In Exp. 1 DMI and average eating bouts daily differed (P < 0.001) with efficient steers consuming less feed and eating fewer times per day. In Exp. 2, efficient steers consumed less (P < 0.001) feed, and average eating bouts daily tended (P = 0.07) to be fewer in efficient animals. Limited differences were noted in feeding behavior between groups, with inefficient steers from both studies having a more variable eating pattern throughout the day. The average daily eating rate did not differ (P > 0.20) between groups in either experiment. The average number of days comprising a feeding pattern for both feed efficiency groups in Exp. 1 and 2 was found to be 2 to 3 d and multiples of 2 to 3 d. In Exp. 1 the feed intake pattern of efficient and inefficient steers changed once they reached a BW of approximately 391 kg and 381 kg, respectively. This occurred near d 47 for the efficient steers and near d 32 for inefficient steers. In Exp. 2 the feed intake pattern of both efficient and inefficient steers changed once they reached a BW of approximately 399 kg, which occurred on d 31 for the efficient steers and on d 33 for the inefficient steers. From the measured variables there were no differences in growth and limited differences noted in feeding behavior between feed efficient and feed inefficient groups. The results of the trials suggest increased variability of feed intake throughout the day for feed inefficient animals.