Since the discovery of fescue toxicosis, several attempts have been made to treat cattle directly to reduce the negative effects of N. coenophialum. Smith et al. (1986) reported animals recovered faster from exposure to E+ tall fescue when supplemented with thiamin. Lauriault et al. (1990) reported similar results for cattle consuming E+ tall fescue during heat stress. Additionally, Dougherty et al. (1991) reported cattle fed E+ tall fescue seed had a thiamin deficiency. As a result of these combined findings, some feed manufacturers have increased the thiamin content of cattle supplements for the tall fescue growing region.
Aiken et al. (2001) compared protein supplementation, estrogenic implants, and removal from E+ tall fescue pastures. The most notable response was that removal of stocker calves from E+ tall fescue pastures for 3 to 4 d alleviated signs of tall fescue toxicosis. Aiken et al. (2006) found that Synovex-S estrogen implants in steers grazing E+ tall fescue resulted in enhanced ADG of 0.25 kg/d at low stocking rates, but this difference was not realized at higher stocking rates. Findings suggested that implants did not reduce the severity of toxicosis and may have caused more stress on the animals because the implanted steers had higher rectal temperatures than non-implanted steers.
Copper is an important mineral in cattle diets. Deficiencies of Cu have been linked to rough haircoat, similar to that reported on cattle grazing E+, and to reduced immune responses. Saker et al. (1998) reported lower plasma or serum Cu in steers grazing E+ tall fescue than in those grazing E- tall fescue. They also found that cattle grazing E+ tall fescue had compromised immune function when compared with those grazing E- tall fescue. Dennis et al. (1998) found that Cu concentrations were higher in E- than in E+ tall fescues and increased linearly in response to N fertilization. These lower Cu concentrations possibly could have contributed to lowered Cu status in animals. Steers grazing E+ tall fescue had a serum Cu level below the generally accepted norm for cattle, but steers grazing E- tall fescue had serum Cu at the commonly accepted level (Oliver et al., 2000). Fisher et al. (2003) found that Cu was marginally deficient in nearly all of the 800 tall fescue pasture samples collected over a 3-yr period. In addition, the S level in many of these samples was high enough to cause concern that S would act as an antagonist to Cu utilization. Based on these results, many of the mineral supplements in the tall fescue growing region have been reformulated to contain more Cu than before. Nevertheless, supplementation with newly formulated Cu levels has not consistently improved haircoats of cattle grazing E+ tall fescue.
Jones et al. (2003) treated heifers consuming a diet of E+ tall fescue with domperidone to determine whether the effects would be similar to the beneficial responses obtained in horses (see Chapter 17). Studies evaluating gene expression of luteal tissue of heifers fed E+ tall fescue diets indicated that domperidone may be beneficial in treating reproductive problems in cattle (Jones et al., 2004).
Supplementing cattle grazing E+ tall fescue pastures with glucomannans, a yeast cell wall component that has absorptive capability, has been inconsistent in alleviating the signs of fescue toxicosis. Ely et al. (2004) reported improved animal performance when cattle grazing E+ tall fescue were supplemented with a modified glucomannan (FEB-200). However, even though Mills (2007) reported no improvement in animal performance when a similar glucomannan (MTB-100) was fed to grazing steers and heifers in a 2-yr study, Merrill et al. (2007) found that the same product alleviated prolactin depression and improved performance.
A seaweed [Ascophyllum nodosum (L.) Le Jolis] has been investigated as a product to alleviate some of the negative effects of tall fescue toxicosis on cattle (Allen et al., 2001; Fike et al., 2001; Montgomery et al., 2001; Saker et al., 2001). Feeding A. nodosum to cattle before grazing E+ tall fescue reduced core temperature during heat stress and therefore may have helped performance (Spiers et al., 2004). Reduction in hyperthermia associated with fescue toxicosis was reduced in cattle fed A. nodosum under increased heat stress (Spiers et al., 2004). The mode of action of seaweed in cattle nutrition has not been determined yet, although some interest remains in its use.
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