Effects of endophyte-infected tall fescue seed and red clover isoflavones on rumen microbial populations and physiological parameters of beef cattle1,2

Lolium arundinaceum [(Darbyshire) tall fescue] toxicosis is responsible for substantial beef production losses in the United States, due to its negative effects on reproduction, growth, and feed efficiency. These effects are consequences of toxic alkaloids within tall fescue. Interseeding legumes, such as Trifolium pratense (red clover), into pastures has been shown to mitigate a portion of these effects. Clovers contain isoflavones, which may play a role in tall fescue toxicosis mitigation. The present study utilized 36 Angus steers to determine the effects of daily supplementation with a red clover-isolated isoflavone feed additive on physiological symptoms of tall fescue toxicosis and the rumen microbial environment over a 21-d period. Angus steers were initially stratified based upon their single nucleotide polymorphism genotype at the DRD2 receptor. Treatments were then randomly assigned in a 2 × 2 factorial arrangement within a completely randomized design, where treatment factors consisted of tall fescue seed type (endophyte-infected tall fescue seed vs. endophyte-free tall fescue seed) supplemented with and without the isoflavone additive. Steers that consumed endophyte-infected tall fescue seed had lower serum prolactin concentrations (P = 0.0007), average daily gain (ADG; P = 0.003), final body weight (BW; P = 0.004), and feed efficiency (P = 0.018) when compared with steers that consumed endophyte-free tall fescue seed. Serum insulin-like growth factor-1 (IGF-1) tended to be reduced with supplementation of isoflavones (P = 0.06) but was unaffected by seed type (P ≥ 0.10) and seed by treatment interaction (P ≥ 0.10). Isoflavones reduced serum glucose levels (P = 0.023), but neither seed type, isoflavones, or their interaction affected serum urea nitrogen (SUN), nonesterified fatty acids (NEFA), or insulin (P ≥ 0.10). Volatile fatty acid concentrations, dry matter intake (DMI), ruminal pH, and overall feeding behaviors were also unaffected by seed type or isoflavone treatments (P ≥ 0.10). Twenty-eight ruminal bacteria taxa shifted as a result of seed type or isoflavone treatment (P < 0.05). In this experiment, feeding isoflavones to Angus cattle did not completely mitigate all symptoms of fescue toxicosis. However, dose–response trials may aid future research to determine if dietary supplementation with isoflavones alleviates fescue toxicosis symptoms and promotes livestock growth and performance.

Tall Fescue Toxicosis Mitigation Strategies: Comparisons of Cow-Calf Returns in Spring- and Fall-Calving Herds

Tall fescue toxicosis adversely affects calving rate and weight gains reducing returns to cow-calf producers in the south–central United States. This grazing study estimated animal and economic performance implications of endophyte-infected fescue and calving season. Establishing novel endophyte-infected tall fescue on 25% of pasture acres resulted in improved calving rates (87% vs. 70%), weaning weights (532 lbs vs. 513 lbs), and partial returns per acre ($257 vs. $217). Additionally, fall-calving cows had higher calving rates (91% vs. 67%), weaning weights (550 lbs vs. 496 lbs), and partial returns per acre ($269 vs. $199) than spring calving cows.

Clinical manifestations of tall fescue (Festuca arundinacea) and perennial ryegrass (lolium perenne) toxicosis in Oregon and Japan

There are multiple vehicles for endophyte toxicosis in animals including exposure from pasture, straw residues and seed screenings. This report discusses the clinical cases typically seen with tall fescue and perennial ryegrass toxicosis in Oregon and Japan. Case I involves a herd of 330 Black Angus cattle. Before the March calving season the owner wished to increase the protein content of the feed ration by feeding pellets made of seed screenings and grass hay. Forty two animals were lost to tall fescue toxicosis and dry gangrene of the feet and legs. Case II involves 1300 beef cows in Eastern Oregon fed grass straw; 485 animals were lost due to dry gangrene characteristic of tall fescue toxicosis. Case III describes 4 of 15 cases of both tall fescue and perennial ryegrass toxicosis in Japanese black cattle. Case IV involves llamas and alpacas on pasture and lawn paddocks where some animals were affected by tall fescue and some by perennial ryegrass. Keywords: tall fescue, Festuca arundinacea L., perennial ryegrass, Lolium perenne, endophyte, Neotyphodium coenophialum, Neotyphodium lolii

Transferring endophyte technology to North American farmers

Bacon and others discovered the tall fescue endophyte in 1977. Since that time, North American researchers have developed several endophyte-based technologies to reduce fescue toxicosis. The most recent has been the release of MaxQ, a novel endophyte that enhances persistence but does not cause fescue toxicosis. Despite its advantages, MaxQ has been adopted slowly across the fescue belt of the US. This paper presents possible social and managerial reasons for this slow adoption. It closes by offering some possible solutions. Keywords: MaxQ, novel endophyte, tall fescue toxicosis, pasture renovation, educational efforts