Voluntary intake and ingestive behavior of steers grazing Johnstone or endophyte-infected Kentucky-31 tall fescue

Abstract

Effects of grazing low-endophyte (Acremonium coenophialum Morgan-Jones and Gams, less than 1% infection) Johnstone (J) or high-endophyte (60% infection) Kentucky-31 (K) tall fescue (Festuca arundinacea Schreb.) on grazing behavior and voluntary intake were studied. Six Angus steers (average initial BW = 326 kg) grazed 1.21-ha plots of each forage cultivar (three steers per cultivar) in four 28-d periods beginning May 27. Daytime observations (0630 until 2130) revealed that J steers spent more (P less than .10) time grazing and lying down and took more (P less than .05) prehensile bites than K steers did; conversely, steers grazing K spent more (P less than .10) time standing and idling than J steers did. Idling time showed a forage x period interaction (P less than .10). Mean OM bite size (grams per bite) was not affected (P greater than .10) by forage but differed (P less than .10) among periods. Limited nighttime observations (2130 until 0630) revealed no effects (P greater than .10) of forage on grazing time or number of prehensile bites taken. Voluntary intakes of OM and NDF did not differ (P greater than .10) between steers grazing J and K; however, a forage x period interaction (P less than .10) existed such that, during Period 1, steers grazing J had greater (P less than .01) OM and NDF intakes than did steers grazing K. These data suggest that cattle grazing endophyte-infected tall fescue display altered daytime grazing behavior and that reduction of voluntary intake attributable to endophyte infection may be less severe under free-grazing than has been reported for controlled environmental conditions.

Growth and subsequent feedlot performance of estradiol-implanted vs nonimplanted steers grazing fall-accumulated endophyte-infested or low-endophyte tall fescue

“…Contrary t o previous reports of decreased intake of endophyte-infested hay, seed, or green-chop diets compared with LE or endophyte-free diets under thermal stress conditions (Schmidt et al, 1982;Jackson et al, 1984;Strahan et al, 19871, we observed no decrease in DM1 of HE KY-31 relative to Johnstone. Data from our study are in agreement with those from other cattle grazing studies (Howard et al, 1992;Peters et al, 1992). Hemken et al (1981) reported no differences in voluntary intake among tall fescue cultivars at moderate ambient temperatures ( 10 to 18°C).…”

“…Forage mass ranged from 3,215 to 5,272 k g h a (data not shown) and was not expected to be limiting to DM1 or animal performance (Allden and Whittaker, 1970;Jamieson and Hodgson, 1979). The results of the present study, in conjunction with other pasture studies (Howard et al, 1992;Peters et al, 19921, suggest that previous reports of decreased voluntary intake with conserved endophyte-infested tall fescue forage under controlled environmental conditions may not be readily applicable to free-grazing cattle under pasture conditions. Forage DMD coefficients (Table 5) were not different ( P > .…”

Utilizing laboratory and field studies to determine physiological responses of cattle to multiple environmental stressors

“…This may be attributed to cattle grazing patterns with Eþ animals tending to shift their grazing time to cooler periods of the day or at night (Bond et al, 1984;Stuedemann et al, 1985), whereas E À animals graze throughout the day. Also, Eþ animals spend more time idling and standing under shade (Howard et al, 1992). Even with differences during peak hours, the relationship between T rum and T a or T bg was the same for both treatments.…”

A fungal endophyte of a palatable grass affects preference of large herbivores

“…Approximately 20-30% of C3 pooid grasses harbour asymptomatic and vertically transmitted fungal endophytes which may confer defences against herbivores by the synthesis of harmful alkaloids, concentrating the alkaloids in sheaths, developing inflorescences, and mature seeds (Leuchtmann 1992;Clay 1996;Schardl et al 2012;Saikkonen et al 2013;Young et al 2013). These endophytes are responsible for producing four alkaloid typesergots, lolitrem, lolines and peraminesand some of them have severe effects on animal performance, grazing behaviour or voluntary intake (Howard et al 1992;Porter & Thompson 1992;Jones et al 2000;Leuchtmann et al 2000;Schardl et al 2013).…”