Tall fescue (Festuca arundinacea Schreb.) infected with an endophyte that does not produce ergot‐like alkaloids (nontoxic endophyte) has not been evaluated for herbage mass, nutritive value, and ergovaline concentration when stockpiled during winter. Our objective was to quantify these responses for tall fescue infected with a native endophyte (K31 E+), a nontoxic endophyte (HiMag NTE), and with no endophyte (HiMag E−). Responses were measured on a fine, mixed, active, mesic Oxyaquic Fragiudalfs soil monthly from mid‐December through mid‐March in 1999‐2000 (Year 1) and 2000‐2001 (Year 2) in southern Missouri. Herbage mass for K31 E+ averaged 2370 kg ha−1, which was ≈20% greater than HiMag E− or HiMag NTE. Herbage mass did not change from mid‐December through mid‐March for any entry. The nutritive value of all entries was equal on comparable dates with acid detergent fiber (ADF) ranging from 285 to 338 g kg−1 during the winter. Nutritive value was highest in mid‐December of each year and then declined slowly after that. Neither HiMag E− nor HiMag NTE contained ergovaline, but K31 E+ had substantial concentrations of ergovaline in both years. The ergovaline concentration of K31 E+ was 454 μg kg−1 in December of Year 1 and 175 μg kg−1 in December of Year 2, but declined by ≈85% by March each year. The stable herbage mass, slowly declining nutritive value, and absence of ergovaline in HiMag E− and HiMag NTE suggest that livestock producers could eliminate toxicosis problems by stockpiling these forages for winter grazing.

Literature Summary Study Description Applied QuestionsFull scientific article from which this summary was written begins on page 491 of this issue.Grass tetany (hypomagnesemia) causes economic losses from death or reduced performance of livestock throughout the world. Attempts to reduce the incidence of grass tetany through application of fertilizer Mg have not generally been successful. Dietary Mg supplementation adds to the annual labor and cost of production and does not always ensure all animals receive adequate amounts of the mineral. Selective breeding of forages for higher levels of Mg and lower tetany ratio may offer a long-term solution to the grass tetany problem.Objectives of this study were to evaluate an experimental selection of tall fescue, HiMag, for its ability to reduce the risk of grass tetany through higher Mg concentration and lower tetany ratio of forage, and higher blood serum Mg concentrations of beef cattle under grazing conditions. Twenty, 1-acre pastures on a predominantly Creldon silt loam soil at the Southwest Research Center near Mt. Vernon, MO, were planted to four endophyte-free tall fescue cultivars, AU Triumph, Kentucky-31, Martin, and Mozark, and the experimental cultivar, HiMag. The study consisted of five individual grazing trials using cross-bred beef steers, dry cows, or cow/calf pairs during three autumn and two spring seasons between 1993 and 1995.Forages were sampled each season and analyzed for Mg, Ca, K, and P concentration, and the tetany ratio was calculated. Cattle were weighed at the beginning, middle, and end of each trial to determine average change in weight. Blood serum was collected at each weighing for determination of Mg, Ca, K, and P status of the cattle.Can cool-season forage grasses be selectively bred to reduce the risk of grass tetany?Forage from HiMag tall fescue consistently had higher Mg (22%), Ca (18%), and P (9%) concentration than other tall fescue cultivars. Potassium levels were not different among cultivars. This resulted in a lower tetany ratio for HiMag compared with the other cultivars. Higher Mg concentration (>0.20%) and lower tetany ratio (<2.2) suggest that HiMag tall fescue can reduce risk of occurrence of grass tetany.

Pasture growth, and thus forage supply, fluctuates throughout the year because of variable growing condi-Livestock operations, particularly pasture-based dairies in the tions (Fales et al., 1993; Matches and Burns, 1995). This lower Midwest, are interested in stockpiling annual ryegrass (Lolium multiflorum Lam.) as a source of high-quality winter forage. Almost creates an uneven forage supply and an intermittent no information exists about stockpiling annual ryegrass in this region.failure of the pasture system to meet livestock require-Our objective was to determine the yield and forage quality of stockments (Fales et al., 1993; Matches and Burns, 1995). In piled annual ryegrass compared with cereal rye during winter in the the lower Midwest, the longest period of inadequate lower Midwest. 'Barmultra' and 'Marshall' annual ryegrass were evalforage supply is from mid-December through miduated at two locations (Columbia and Mt. Vernon, MO) during the March (Matches and Burns, 1995; Kallenbach et al., winters of 1998-1999 (Year 1) and 1999-2000 (Year 2). 'Forage Master' 2001) and livestock producers in this region are searchcereal rye (Secale cereale L.) was included as a comparison. Uncut ing for high quality forage for winter grazing. strips (subplots) were harvested monthly from mid-December through One forage species attracting the attention of livemid-March each year. Stockpiled annual ryegrass yields ranged from stock producers in the lower Midwest is annual ryegrass. 825 to 2356 kg ha Ϫ1 , with Marshall yielding more than Barmultra on all but one harvest date during the 2 yr. Forage quality of stockpiled Producers establish annual ryegrass in the late summer, annual ryegrass typically declined from mid-December through mid-then allow it to accumulate growth for deferred or stock-February, with a larger decline in a normal winter (Year 1) than in pile grazing in the winter. For pasture-based dairy and a mild winter (Year 2). Although forage quality tended to decline beef stocker operations in the lower Midwest, stockpiled during winter, acid detergent fiber (ADF) never exceeded 252 g kg Ϫ1 ,annual ryegrass has become a popular forage for winand neutral detergent fiber (NDF) never exceeded 455 g kg Ϫ1 . This ter grazing. suggests that stockpiled annual ryegrass could be used in the lower Despite its popularity, stockpiling annual ryegrass hasMidwest as a source of high-quality winter forage for grazing livestock.

Grass tetany is a nutritional disease of ruminants caused by low dietary Mg.Previous research has shown that early spring P‐fertilization increases the leafMg concentration of tall fescue (Festuca arundinacea Schreb.) hay.However, little is known about how P‐fertilization alters the mineralconcentration of tall fescue under grazing. Our objective was to compare, undergrazing, the Mg, K, Ca, and P concentration of tall fescue when soil P wasconsidered either adequate or low. The treatments were tall fescue grown on soilfertilized to achieve 30 lb/acre P (P‐fertilized) or left unfertilized at 6 lb/acre P(Control). Three cow/calf pairs grazed each pasture from 15 February to 11April, 2000, and 6 March to 1 May, 2001. Forage samples were collected at thestart of grazing and at 14 day intervals thereafter. Under grazing, fertilization with P increased tall fescue forage Mg, K, and Ca concentrationonce spring growth started. However, the ratio of K/(Ca+Mg) never approached thecritical level thought to induce grass tetany. These results suggest thatfertilizing tall fescue pastures to an adequate soil P level improves the amountof dietary Mg available to ruminants during early spring and decreases the grasstetany potential of the forage.