Steer responses to feeding soybean hulls and steroid hormone implantation on toxic tall fescue pasture.

Crossbred steers were grazed in the spring and early summer on endophyte-infected (Neotyphodium coenophialum), Kentucky-31 tall fescue (Lolium arundinaceum) pastures to evaluate effects and interactions of feeding pelleted soybean hulls (PSBH) and steroid hormone implants (SHI) on steer performance, serum prolactin, and hair coat ratings (HCR). Steers were stratified by BW for assignment to six 3.0-ha toxic tall fescue pastures. With or without daily PSBH feeding, treatments were assigned randomly to pastures as the main plot treatment in a split-plot design. Pelleted soybean hulls were group-fed to provide 2.3 kg(steer·d(-1)) (as fed). With or without SHI (200 mg of progesterone and 20 mg of estradiol) treatments were randomly assigned as the subplot treatment to 2 steer subgroups within each pasture. Sixty-four steers were grazed for 77 d in 2007, and 60 steers were grazed for 86 d in 2008. Pasture forage mass declined linearly over time, but the rate of decline was greater (P = 0.001) in 2007 than in 2008. Pasture forage mass was never below 2,300 kg of DM/ha in either year. Average daily gain for steers on the combined PSBH and SHI treatments was greater (P < 0.01) than for those on the PSBH-only, SHI-only, and control (no SHI, no PSBH) treatments. Average daily gain for the PSBH-only steers was greater (P < 0.01) than for SHI-only and control steers and tended (P = 0.063) to be greater for SHI-only than for control steers. Steroid implants did not affect (P = 0.826) serum prolactin concentrations; however, prolactin concentrations in PSBH steers, with or without SHI, were increased (P = 0.01) 2-fold over SHI-only and control steers. Feeding PSBH and SHI treatments both reduced (P < 0.05) the percentage of steers with rough HCR, and a greater percentage of steers fed PSBH tended (P < 0.076) to have sleek hair coats. An economic analysis was conducted, which determined that costs of additional ADG with PSBH feeding were below breakeven costs over a wide range of PSBH costs and cattle prices. Breakeven costs for PSBH-only treatment for a range of cattle prices of $1.80 to $2.40/kg of BW were less than $120/t, whereas with PSBH feeding combined with SHI the breakeven cost was less than $240/t. Results indicate that steers grazing endophyte-infected tall fescue can be fed PSBH and implanted with steroid hormones to cost effectively increase ADG and that feeding PSBH can increase serum prolactin concentrations and induce some shedding of rough hair coats.

Mortality of horn fly larvae (Diptera: Muscidae) in bovine dung supplemented with ergotamine and N-formyl loline.

Dung-dwelling larvae of ectoparasites of livestock such as the horn fly, Hematobia irritans (L.), may be exposed to > or = 1 different alkaloid species in dung from animals ingesting herbage of the tall fescue (Festuca arundinacea Schreb.)--endophyte association (Neotyphodium coenophialum (Morgan-Jones & W. Gams) Glenn, Bacon & Hanlin comb. nov.). First-instar horn flies were exposed to bovine dung supplemented with up to 50 microM each of N-formyl loline and ergotamine tartrate in factorial combination. In the absence of ergotamine tartrate, N-formyl loline caused a linear decline in the number of pupae recovered, and probit analysis indicated an LC50 of 36 microM. In the absence of N-formyl loline, significant quadratic responses of larvae to ergotamine tartrate were established, and probit analysis indicated a LC50 of 34 microM. An interaction (P < 0.001) was found between the 2 alkaloids for larval survival. This interaction showed that ergotamine tartrate moderated the toxicity of N-formyl loline and indicates that a membrane-bound receptor may be involved. There was no evidence of carryover of effects of alkaloids on subsequent stages of development or expressed as abnormalities of pupae or adults. Interactions between alkaloids probably are involved in other plant-herbivore relationships of endophyte-infected grasses.

Mortality of horn fly (Diptera: Muscidae) larvae in bovine dung supplemented with loline alkaloids from tall fescue.

Larvae of arthropod ectoparasites of livestock, such as the horn fly, Haematobia irritans (L.), may be exposed to acyl-loline alkaloids in dung of ruminant livestock ingesting herbage of the tall fescue (Festuca arundinacea Schreb.)-endophyte association [Neotyphodium coenophialum (Morgan-Jones & W. Gams) Glenn, Bacon & Hanlin comb. nov.]. Biological activity of alkaloid-supplemented bovine dung was assayed by growth, development, and survival of 1st instars of horn fly. An extract from tall fescue seed, containing N-formyl loline (NFL), N-acetyl loline (NAL), and loline (59:21:20 by mass, respectively) caused 100% mortality of horn fly larvae when dung was supplemented at > or = 100 micrograms/g. Probit analysis of data corrected for natural mortality indicated a LD50 of 30 micrograms/g (95% fidicial limits: 20-49 micrograms/g). When horn fly larvae were introduced to dung supplemented with up to 50 microM of acyl-loline derivatives, mortality of larvae varied significantly between alkaloids (P < 0.0001). Probit analysis indicated that NFL [LD50: 34 microM (95% fidicial limits: 3-53 microM)] was more toxic than NAL [LD50: 46 microM (0-83 microM)], and that loline hydrochloride was not toxic.

Oviposition and development of face flies in dung from cattle on herbage and supplemented herbage diets.

Dung was collected from Angus cattle (Bos taurus L.) fed (ad libitum) hays of endophyte-free (EF) and endophyte (Acremonium coenophialum Morgan-Jones and Gams) infected (EI) tall fescue (Festuca arundinacea Schreb.), smooth bromegrass (Bromus inermis Leyss.), red clover (Trifolium pratense L.), alfalfa (Medicago sativa L.), and alfalfa-smooth bromegrass (1:1 w/w) and green-chopped Kentucky bluegrass (Poa pratensis L.). Samples of dung were subsequently collected from the same animals offered the same herbage diets supplemented each day with ground maize (Zea mays L.) kernels at 0.35 kg per body weight. Dung from both sources were used in bioassays to establish oviposition preferences of face flies (Musca autumnalis De Geer). When offered dung from herbage diets, face flies deposited 38.3% of their eggs on dung derived from EF tall fescue diets, 9.9% on dung from EI tall fescue diets, 21.0% on dung from alfalfa diets, 7.4% on dung from red clover diets and 22.8% on dung from alfalfa-bromegrass diets. Face flies avoided ovipositing in dung from cattle ingesting bromegrass hay and Kentucky bluegrass green-chop. Supplements increased oviposition preference of face flies for dung from cattle ingesting Kentucky bluegrass greenchop to 19.1% at the expense of oviposition on dung from cattle ingesting alfalfa hay diets (4.5%), otherwise, they had little effect on oviposition preference ranking. Growth and development of first instar larvae of face flies was also measured in bioassays of dung from cattle on herbage and supplemented herbage diets. The presence of endophyte reduced pupation in dung from cattle on tall fescue hay diets from 86.3 to 79.8% and from 90.1 to 73.2% in dung from cattle on supplemented tall fescue hay diets. Pupal liveweights averaged 27.5 mg on dung from cattle on EF tall fescue diets, 22.1 mg from dung of cattle on EI tall fescue diets, 22.2 mg from dung of cattle on supplemented EF tall fescue diets and 24.0 mg from dung of cattle on supplemented EI tall fescue diets. Eclosion and the sex ratio of adults were not affected by dung from cattle on different source diets.

Induction of tall fescue toxicosis in heat-stressed cattle and its alleviation with thiamin.

Livestock grazing endophyte (Acremonium coenophialum)-infected tall fescue (Festuca arundinacea Schreb. cv. Kentucky 31) at high ambient temperatures may suffer from fescue toxicosis. Adult Angus cows (Bos taurus) were fed 0 to 1 kg/d of 70% infected tall fescue seed containing about 4.4 g of loline alkaloids in factorial combination with thiamin at 0 or 1 g/d. Cows assigned to the zero level of tall fescue seed received a supplement of equivalent energy and protein. Ingestive behavior was measured at 1330 to 1430 EDT during two 4-d periods in two consecutive weeks in August on alfalfa (Medicago sativa L.) pastures using a tethered grazing system. Alfalfa intake per measured grazing session of cows given tall fescue seed declined linearly (P less than .01) as air temperatures during grazing increased above 25 degrees C, largely because of shorter grazing meals. Thiamin increased alfalfa intake per measured grazing session by extending grazing time. Alkaloids in ingested endophyte-infected tall fescue induce thiamin deficiencies in cattle that result in symptoms of tall fescue toxicosis.

Forage composition and intake by steers grazing vegetative regrowth in low endophyte tall fescue pasture.

A grazing trial was conducted with six half-sib yearling Angus steers (average initial weight 281 kg) to quantitate nutrient composition and voluntary intake of vegetative regrowth forage in low-endophyte (Acremonium coenophialum Morgan-Jones and Gams) Kentucky-31 tall fescue (Festuca arundinacea Schreb.) pasture. A new .6-ha section in each of two 3.0-ha pastures (three steers/pasture) was clipped to a 5-cm height on five consecutive days to establish a series of plots that could be grazed continuously during 5-d test periods at uniform stages of vegetative regrowth; each period represented a specific regrowth stage (7, 14, 21, 28 and 35 d). Steers were conditioned by training them to graze to satiety while tethered with an adjustable-length rope to a 1-m galvanized steel post. Grazing time was limited to two sessions daily beginning at 0800 and 1400, and satiety was achieved after no more than 2.5 h of continuous grazing in each session. Forage DM availability was controlled by adjusting tether length and was set each day at 4% of steer BW. Fecal DM output was measured by chromic oxide dilution. A quadratic (P less than .05) effect of regrowth stage was observed for forage contents of NDF and ADF due to abrupt increases in both fractions at wk 5; values for ADL were unaffected by stage of forage regrowth. Forage contents of CP and ash showed a cubic (P less than .05) response to advancing stage of regrowth, with highest (23.6 and 11.0%, respectively) and lowest (14.7 and 9.1%, respectively) values for both fractions occurring at wk 1 and 5, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Thiamin supplementation and the ingestive behavior of beef cattle grazing endophyte-infected tall fescue.

Livestock grazing endophyte (Acremonium coenophialum Morgan-Jones and Gams)-infected tall fescue (Festuca arundinacea Schreb.) perform poorly due to tall fescue toxicosis, especially when animals are under heat stress. In order to determine whether thiamin promotes recovery from tall fescue toxicosis, 1 or 0 g of thiamin per day, as mononitrate, was fed orally to adult Angus (Bos taurus) cows (380 +/- 8 kg) grazing either tall fescue pasture with and without endophyte or alfalfa (Medicago sativa L.). A tethered grazing system employing a split-plot design was used to estimate intake and components of ingestive behavior. No significant differences attributable to thiamin supplements were seen in rates of intake and biting, grazing time and intake per bite when cows grazed endophyte-infected tall fescue during the first 4 d of exposure. When cows grazed endophyte-infected (greater than 95%) tall fescue with 2,091 micrograms/g loline alkaloids after 4 d of exposure, the untreated animals ingested herbage dry matter (DM) at 1.19 kg/h, whereas the cows receiving thiamin ate 1.57 kg/h (P less than .05). Cattle achieved these rates of DM intake by forming bites of 1.0 and 1.2 g DM at 24 and 26 bites/min when treated with 0 and 1 g of thiamin per day, respectively. Thiamin supplements had no effect on ingestive behavior of cows grazing endophyte-free tall fescue or alfalfa after exposure to these forages for 4 d. Responses to thiamin generally were greater when cattle grazing endophyte-infected tall fescue were exposed to heat stress. Oral thiamin supplementation may alleviate tall fescue toxicosis of beef cattle during warm weather.