The mutagenic activity of the major DNA adduct formed by liver carcinogen aflatoxin B1 (AFB1) was investigated in vivo. An oligonucleotide containing a single 8,9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin (AFB1-N7-Gua) inserted into single-stranded genome bacteriophage M13. Replication SOS-induced Escherichia coli yielded mutation frequency for AFB1-N7-Gua 4%. predominant G --> T, identical to principal human tumors believed be induced aflatoxin. T mutations AFB1-N7-Gua, unlike those (if...

Effects of supplemental energy sources on nutrient digestion and urea kinetics at 2 levels degradable intake protein were evaluated in cattle (Bos taurus). Six ruminally duodenally cannulated steers (208 ± 17 kg) used a 6 × Latin square with treatments arranged as 3 factorial. Energy included control, 600 g glucose dosed once daily, 480 VFA infused over 8 h daily. Casein (120 or 240 g) was Steers had ad libitum access to prairie hay (5.8% CP). Jugular infusion 15N15N-urea measurement...

Condensed tannins (CT) may decrease greenhouse gas emissions and alter the site of N excreted by ruminants. We evaluated effect top-dressing a steam-flaked corn-based finishing diet (14.4% CP NEg 1.47 Mcal/kg) for beef cattle with commercially available CT extract at 3 levels (0, 0.5, 1.0% diet, DM basis). Angus-crossbred steers ( = 27; 350 ± 32 kg initial BW) were individually fed via Calan gates 126 d. Diet digestibility balance estimated after 34 95 d on feed (Phase 1 Phase 2,...

Six duodenally and ileally cannulated steers were used in 3 sequential studies to measure 1) basal nutrient flows from a soybean hull-based diet, 2) small intestinal digestibility of raw cornstarch continuously infused into the duodenum, 3) responses starch digestion duodenal infusion 200 or 400 g/d casein. Our objective was evaluate cattle over time increasing amounts MP. On average, consumed 3.7 kg/d DM, 68 dietary N, 70 starch. Starch flow duodenum (38 g/d), N 91 g/d. Small 57%, extensive...

Abstract The objective of this experiment was to evaluate effects postruminal flows casein or glutamic acid on small intestinal starch digestion and quantify changes in energy nutrient balance. Twenty-four steers (body weight = 179 ± 4 kg) were duodenally infused with raw cornstarch (1.46 0.04 kg/d) either 413 7.0 g casein/d, 121 3.6 acid/d water (control). Measures excretion collected across d after 42 infusion measures respiration via indirect calorimetry 2 48 infusion. Ileal flow least...

Effects of supplemental glucose and degradable intake protein on nutrient digestion urea kinetics in steers (Bos taurus) given ad libitum access to prairie hay (4.7% CP) were quantified. Six ruminally duodenally cannulated (initial BW 391 kg) used a 4 × Latin square with 2 extra steers. Treatments arranged as factorial included 0 or 1.2 kg 240 480 g casein dosed once daily. Each period 9 d for adaptation, total fecal urine collections, 1 ruminal duodenal sampling. Jugular infusion...

Abstract Two experiments were conducted to measure rates of ruminal disappearance, and energy nutrient availability N balance among cows fed corn husks, leaves, or stalks. Ruminal disappearance was estimated after incubation polyester bags containing leaves stalks in 2 separate ruminally cannulated a completely randomized design. Organic matter (OM) that initially disappeared greatest for least husks (P < 0.01), but amounts NDF intermediate stalks, 0.01). Amounts DM OM slowly However,...

Angus × Hereford beef heifers and steers (n = 460; initial BW 225 ± 35 kg) were randomly allocated to 1 of 3 ranch-of-origin weaning methods 28 d in duration: drylot + dam separation (D), pasture fence-line contact with dams (PF), supplemental feed delivered a bunk (PF+S). Calves assigned D fed diet formulated promote an ADG kg at DMI 2.5% (17.7% CP 0.93 Mcal NEg/kg). The PF calves had access native forage, PF+S forage received the rate 1% 3× weekly. After 28-d period, transported 4 h...

Grazing annual cool-season forages after oat grain harvest in South Dakota may allow an opportunity to increase efficient use of tillable land. However, data are limited regarding effects stocking density on diet selection, nutrient digestion, performance, and N retention by cattle grazing forage. Heifers were blocked initial BW (261 ± 11.7 kg) randomly assigned 1 12 paddocks (1.1 ha) graze a mixture grass brassica for 48 d. Each paddock contained 3, 4, or 5 heifers achieve 4 replicates each...

Six ruminally cannulated cows (570 ± 73 kg) fed corn residues were placed in a 6 × Latin square to evaluate predictions of diet composition from collected samples. After complete ruminal evacuation, 1-kg meals (dry matter [DM]-basis) containing different combinations cornstalk and leaf husk (LH) ratios 0:100, 20:80, 40:60, 60:40, 80:20, 100:0. Diet samples each meal by removal contents after 1-h either unrinsed, hand-rinsed or machine-rinsed effects endogenous compounds on composition....

Spring-born Angus×Hereford calves (n=433; average initial weight=229±37 kg) were assigned randomly to treatments that corresponded a length of time (d) between separation from their dam and transport feedlot: 60, 45, 30, 15, or 0 d. Weaning date varied by treatment; occurred on common at age (220±22 d) for all treatments. Calves vaccinated against diseases 14 d before maternal again the day separation. transported <20 km ranch-of-origin weaning facility following dams penned according...

A fungal endophyte, Epichloë coenophiala (Morgan‐Jones &amp; W. Gams) C.W. Bacon Schardl, naturally infects tall fescue [ Lolium arundinaceum (Schreb.) Darbysh.]. The common, toxic endophyte produces ergot alkaloids that cause the livestock disorder known as toxicosis. Strains of E. produce little or no are referred to “novel” associations and offer a solution objective this study was determine differences in animal preference ground cover among commercially available novel...

Providing supplements that enhance the efficiency of feed utilization can reduce methane (CH4) emissions from ruminants. Protein supplementation is widely used to increase intake and digestion low-quality forages, yet little known about its impact on CH4 emissions. British-cross steers (n = 23; initial body weight [BW] 344 ± 33.9 kg) were in a three-period crossover design evaluate effect protein beef cattle consuming forage ruminal CH4, metabolic carbon dioxide (CO2) emissions, intake,...

Cattle grazing wheat pasture in the southern Great Plains are sometimes fed an energy supplement; however, benefits of supplementation on nutrient balance, metabolism, and greenhouse gas emissions have not been elucidated. Therefore, we used 10 British crossbred steers (206 ± 10.7 kg initial BW) a respiration calorimetry study to evaluate effects losses, N digestibility green-chopped forage. The design was incomplete replicated 4 × Latin square with treatments 2 factorial arrangement. Steers...

Angus × Hereford calves (n = 430; initial BW 230 ± 32 kg) were stratified by sex, age, and assigned randomly to receive 0, 1, 2, or 3 doses of modified-live respiratory disease (BRD) vaccine before feedlot placement (0X, 1X, 2X, 3X, respectively). Calves from 2 sources weaned 29 d placed in a weaning facility at each ranch origin. Initial BRD vaccination occurred weaning, revaccinated according treatment assignments 14-d intervals. There no differences (P 0.49) the incidence morbidity during...

Angus×Hereford calves (n=409; initial BW=163±31 kg) were weaned early (~130 d of age) and assigned randomly to treatments that corresponded a length time (d) between separation from their dam transport feedlot: 0 (i.e., nonweaned), 15, 30, 45, or 60 d. Weaning date varied by treatment; occurred on common at age (160±19 d) for all treatments. Calves vaccinated against diseases 14 before maternal again the day separation. transported <20 km ranch-of-origin weaning facility following dams...

Journal Article 1665 WS Effect of corn-based supplementation on gas emissions, performance, and energetic losses steers grazing wheat pasture Get access P. Ebert, Ebert 1Department Agricultural Sciences, West Texas A&M University, Canyon, TX Search for other works by this author on: Oxford Academic PubMed Google Scholar E. A. Bailey, Bailey L. Shreck, Shreck 2USDA-ARS Conservation Production Research Laboratory, Bushland, N. Cole, Cole J. S. Jennings 3Texas A & M AgriLife Extension Center,...