Objective: Our objective was to evaluate how a particular zeolite-based flow agent affected ergot alkaloid digestion and physiological markers associated with fescue toxicosis. Materials and Methods: Twenty-four steers (226 +/- 27.6 kg) were used to test effects of enhanced zeolite-based flow agent (KALLSIL, Kemin Industries, Des Moines, IA) on ergot-like alkaloid digestion. Treatments were control (E+) or enhanced zeolite inclusion (E+Z; 2 g/kg, DM basis). Steers were limit-fed diets (1.8% of BW, DM basis) containing 465 mu g of ergovaline/kg of DM. Rectal temperature and respiration rate were recorded daily at 0700 and 1200 h from steers in a room kept at 18.5 degrees C +/- 0.33 degrees C, 32.6% +/- 2.19% relative humidity. Blood was collected on d 1, 7, 14, and 21 to measure prolactin. On d 21 prolactin stores were measured following infusion of thyrotropinreleasing hormone (TRH; 1 mu g/kg BW). Feces and urine were collected every 8 h from d 17 to 20, with 2-h advancement daily for digestibility, N balance, and recovery of ergot-like alkaloids. Results and Discussion: Digestion and N balance were not affected by treatment. Zeolite did not affect fecal recovery of ergovaline. Serum prolactin declined over time. Serum prolactin was greater in steers fed E+Z. Following TRH infusion, prolactin was numerically greater for E+Z. Rectal temperatures and respiration rates were not affected by E+Z. Implications and Applications: Under the conditions of this experiment, addition of this particular zeolite

Objective: Our objective was to evaluate the effects of an herbicide containing aminopyralid and metsulfuron (Chapparal; Corteva Agriscience, Indianapolis, IN) following spring -applied nitrogen fertilizer on stocker cattle performance, forage species composition, seedhead density, and ergovaline concentration. Materials and Methods: Each year (n = 3), 96 steers (266 + 19.3 kg) were randomly assigned to sixteen 1.8 -ha pastures. Pastures were randomly assigned 1 of 4 treatments: no herbicide or nitrogen (NEGCON) or herbicide (140 g/ha) with 0 kg/ha N (CHAP0N), 67 kg/ha N (CHAP67N), or 134 kg/ha N (CHAP134N). Ammonium nitrate was applied March 7 +3.6 d, and herbicide was applied April 14 +1.5 d. Steers began grazing 72 h after herbicide application. Steer weight, standing forage height, forage nutritive value, and alkaloid concentrations in tall fescue tillers were measured monthly. Tall fescue seedhead frequency and forage species frequency were collected June 14 +3.1 d. Results and Discussion: Tall fescue seedheads were reduced by 68% within pastures receiving herbicide. Herbicide application did not affect ergovaline concentration, but ergovaline concentration increased across months. Nitrogen fertilizer tended to quadratically increase forage mass. Steer ADG was greater in pastures treated with fertilizer and herbicide than in those not treated. Implications and Applications: Under the conditions of this experiment, application of herbicide containing aminopyralid and metsulfuron to tall fescue pastures decreased seedhead concentration but did not affect ergovaline. Nitrogen fertilizer increased forage mass on pastures treated with herbicide, and the combination improved steer gain under a short -duration continuously grazed system.

Soybeans can provide ruminally degradable protein, lipid, and metabolizable amino acid (AA) to lactating dairy cows; however, soy-based trypsin inhibitors can limit protein digestion in nonruminants. Eight ruminally cannulated lactating Holstein cows were used to evaluate the impacts of soy-based trypsin inhibitors on nutrient disappearance, lactation, and plasma AA bioavailability. Treatments were abomasal infusion of 0 or 400 g/d casein or a crystalline AA analog of casein with unroasted or roasted soybeans fed at 10% dry matter (DM). Data were analyzed using the MIXED procedure of SAS. Measures of digestion were determined from fecal output determined with acid detergent insoluble ash and urine output determined from measures of urine creatinine. Neither soybean processing (P >= 0.20) nor the source of abomasal infusion (P >= 0.60) impacted nutrient digestibility. Ruminal ammonia, isobutyrate, and isovalerate were increased (P <= 0.01) among cattle consuming unroasted soybeans. Source of infusion did not affect (P >= 0.38) ruminal volatile fatty acids or nitrogen metabolism. Ruminal N metabolism was largely unaffected by soybean processing although microbial N efficiency was greater (P < 0.01) among cows fed unroasted soybeans. DM intake and energy-corrected milk were greater (P < 0.01) in cows fed roasted compared to unroasted soybeans. The proportion of fat, protein, lactose, and solids not fat (SNF) in milk did not differ between soybean processing or postruminal AA source, but fat, protein, lactose, and SNF yield was greater (P <= 0.01) when cows were fed roasted soybeans because milk yields were greater when cows were fed roasted vs. unroasted soybeans. As expected, infusion of casein or its crystalline AA analog increased plasma essential AA and milk urea nitrogen concentration. The rate of increase in essential AA concentration in plasma was 2.9x greater for casein than for crystalline AA. These data seem to indicate that soy-based trypsin inhibitors have no impacts on postruminal AA bioavailability when fed to cows and that metabolizable protein from casein is greater than from crystalline AA.

Abstract The objective of the study was to determine effects of increasing amounts of conventional (CONV) or high-oleic (HO) soybean in diets fed to mid-lactation dairy cows on dry matter intake (DMI) and performance. Rumen and duodenally cannulated cows (n = 8) were split into two groups and placed in a split-plot design. The whole plot factor was type of soybean (CONV vs. HO) and was provided to cows in a crossover arrangement so that each cow was provided both types of soybeans throughout the experiment. The subplot factor was amount of soybeans (0, 4, 8, 12%). Each group of cows receiving the same type of soybean were placed in a 4 x 4 Latin square with treatment sequences balanced for carryover effects. Diets were formulated to contain 18.5% crude protein and to slightly exceed requirements for ruminally degradable protein. Additions of soybeans replaced soybean meal and soybean hulls so that diets provided similar amounts of soy-based protein and fiber. During the last 4 d of each 14-d period, spot samples of feed, orts, and milk were collected together with measures of milk production and feed intake. Data were analyzed using the MIXED procedure of SAS. There were no interactions of soybean type and amount on lactation or DMI except for measures of milkfat, milk energy concentration and milkfat yield. Increasing amounts of HO resulted in a quadratic response in milkfat and energy concentration together with measures of milkfat yield. Specifically, these measures were greater (P ≤ 0.02) when cows were fed diets containing 4 and 8% HO compared with diets containing 0 or 12% HO; increasing amounts of CONV had no impact (P ≥ 0.32) on milkfat and energy concentration or milkfat yield. Measures of milk yield were not affected by type or amount of soybean (P ≥ 0.54), but measures of energy corrected milk yield (ECM) tended to respond differently to increasing amounts of soybean from either CONV or HO (P = 0.07). Interestingly, ECM responded quadratically (P = 0.02) to increasing amounts of HO but not to increasing amounts of CONV (P ≥ 0.58). Overall, however, ECM tended (P = 0.06) to be slightly greater with HO compared with CONV (42.5 vs. 41.1 kg/d). Yet, DMI was also greater (P ≤ 0.01) with HO compared with CONV (26.6 vs. 24.4 kg/d). Differences in DMI, therefore, resulted in a tendency (P = 0.07) for greater efficiency of ECM production when cows were fed CONV vs. HO. Overall, treatments had no effect on measures of milk protein, urea-nitrogen, solids-not-fat or lactose concentrations or yields. These data seem to indicate that performance responses among lactating cows to increasing amounts of HO are dynamic but that responses to CONV are not.

Abstract Plant secondary metabolites (PSM) such as condensed tannins, hydrolysable tannins, saponins and essential oils purportedly impact rumen fermentation at low inclusion rates in beef cattle diets. Twelve steers (347 ± 23 kg BW) of British and continental influence were allocated to 1 of 4 replicated 3 x 3 Latin squares. Latin squares each had 14 d periods (10 d adaptation and 4 d for sample collection). All cattle were fed ground warm-season hay (89.5% DM, 92.8% OM, 65.9% NDF, 43.6% ADF, 6.70% CP) at 1.5% of BW (DM-basis) and supplemented with soybean meal at 0.18% of BW (DM-basis) once daily. Treatments consisted of a blend of tannins, saponins and essential oils provided at 0% (Control), 0.1% (Low) and 0.3% (High) of hay offering. Treatments were mixed with daily soybean meal allotment and provided before feeding of hay. Urine and feces were completely collected from d 11 through 14 at 0730 h and daily amounts of urine and feces produced were measured gravimetrically. Measures of gaseous exchange were determined via indirect calorimetry on d 13 and 14. Open-circuit respiration calorimeters (91.4 × 91.4 × 191.2 cm) were used to collect respired gas and ruminal methane production. Total oxygen consumption and production of carbon dioxide and methane were calculated from the difference in concentration of oxygen, carbon dioxide, and methane from air exhausted from each calorimeter and concentration of oxygen, carbon dioxide, and methane in ambient air and multiplied by amounts of air flowing from each calorimeter standardized for temperature, pressure, and humidity. Data were analyzed for a Latin square using the MIXED procedure of SAS with fixed effect of treatment, period and square and random effect of steer. Linear and quadratic contrast coefficients were assigned using PROC IML for uneven spacing of treatments. Significance was declared when P ≤ 0.05. Per experimental design, forage N and OM intake did not differ (P ≥ 0.77). Apparent total tract digestion of OM, NDF and ADF did not differ (P ≥ 0.66) among treatments. Fecal nitrogen excretion, and the percentage of N excreted in feces increased linearly (P = 0.01). N balance tended (P = 0.08) to decrease linearly with increasing PSM supplemented. Methane (L/kg DMI) was not affected (P = 0.28) by treatments. Methane, GE, DE, and ME (mcal/kg DMI) was unaffected (P = 0.19) by treatment. Under the conditions of this experiment, a blend of PSM had little effect on rumen fermentation or energy metabolism in beef steers.

Probiotics are purported to improve gastrointestinal tract health across a variety of species. Thus, we evaluated the effects of supplementing a blend of Bacillus spp. on performance and immune function in immature beef cattle. Crossbred heifers (n = 192) were stratified by initial body weight (196 ± 15.4 kg) and randomly assigned to 1 of 24 pastures (1.8 ha each) of Kentucky 31 tall fescue. Heifers were offered 2.84 kg daily of a commodity feed blend and the supplement contained either no probiotic (CON) or of Bacillus spp. (BAC). Bacillus spp. was offered at 3 grams per head per day. Heifers were weighed on consecutive days on d 0 and 1, along with d 84 and 85 to establish initial and final body weight. Interim weights were taken every 28 d. A humoral response to chicken egg albumin (OVA) was established following a subcutaneous injection with OVA. To assess heifers’ immune responses, plasma was taken from two heifers per pasture on d 1, 15, 29, 43, and 57. Plasma samples were measured for the presence of anti-OVA IgG, proinflammatory cytokines, anti-inflammatory cytokines, and chemokines. There were no trt*day interactions (P ≥ 0.30) for plasma response variables. Concentrations of pro-inflammatory cytokines IL-1α and IFN-γ decreased (P ≤ 0.01) in heifers supplemented with BAC. The anti-inflammatory cytokine IL-1 F5 decreased (P = 0.02) with BAC supplementation. Chemokines MIG and MIP-1β also decreased (P ≤ 0.03) with BAC supplementation. Heifers fed BAC tended to display (P = 0.09) greater titers of anti-OVA IgG than the control. Body weight and average daily gain did not differ (P ≥ 0.53) throughout the experiment. Under the conditions of this experiment, heifers supplemented with Bacillus spp. demonstrated modulated immune responses.

The objective of this experiment was to evaluate effects of postruminal flows of casein or glutamic acid on small intestinal starch digestion and to quantify changes in energy and nutrient balance. Twenty-four steers (body weight = 179 ± 4 kg) were duodenally infused with raw cornstarch (1.46 ± 0.04 kg/d) and either 413 ± 7.0 g casein/d, 121 ± 3.6 g glutamic acid/d or water (control). Measures of small intestinal starch digestion and nutrient excretion were collected across 4 d after 42 d of infusion and measures of respiration via indirect calorimetry were collected across 2 d after 48 d of infusion. Ileal starch flow was least among calves provided casein, but ileal starch flow was not different between glutamic acid or control. Small intestinal starch digestion tended to be greatest among calves provided casein, least for glutamic acid and intermediate for control. Casein increased ileal flow of ethanol soluble oligosaccharides compared to glutamic acid and control. Large intestinal starch digestion was not different among treatments. By design, N intake was greatest among cattle provided casein, intermediate among calves provided glutamic acid and least for control. Nitrogen retention was greater in response to casein compared to control and glutamic acid. Intake of gross energy from feed was similar across treatments, and gross energy from infusate was greatest for casein, intermediate for glutamic acid and least for control. Variation in gross energy intake from feed resulted in no difference in overall gross energy intake across treatments. Similar to measures of small intestinal starch digestion and N retention, casein increased calories of digestible energy and metabolizable energy, compared to glutamic acid and control, which did not differ. Postruminal infusions did not influence methane production, but heat production was greatest in steers infused with casein, intermediate for steers provided glutamic acid, and least for control. Overall, amounts of energy retained by casein tended to be nearly 34% greater than control, but glutamic acid had no impact on energy balance. Improvement in small intestinal starch digestion in response to casein increased energy and N retained; however, glutamic acid did not influence small intestinal starch digestion and energy or N balance in cattle, which seems to suggest that responses in small intestinal starch digestion to greater postruminal flows of glutamic acid become refractory across greater durations of time.

Crossbred steers (n = 60; beginning BW 454 ± 24 kg) were used in a split-plot design with a 2 x 3 factorial arrangement of treatments to determine effects of source of metabolizable AA and implant status on animal performance and feeding behavior. Calves were blocked by initial BW and assigned to 1 of 5 BW blocks. Pen (n = 2 pens, 6 steer/pen) within each BW block were fed diets formulated to meet the RDP requirement of cattle and provide 150% and 152% the metabolizable Lys and Met requirement (RP-AA), or a diet designed to meet RDP and closely match the predicted metabolizable Lys and Met requirement (RDP-ONLY; metabolizable Lys = 99.3% of required; metabolizable Met = 119% of required, NASEM, 2016). Subsequently, within pen two calves were randomly assigned to 1 of 3 implant strategies: no implant, moderate (100 mg trenbolone acetate and 14 mg estradiol; Synovex Choice) or potent (200 mg trenbolone acetate and 28 mg estradiol; Synovex Plus). Cattle were fed for 125 days and feed intake and feeding behavior was determined using a semi-autonomous feed monitoring system (GrowSafe System Ltd). Data were analyzed using the MIXED procedure of SAS. There was a tendency for an interaction of source of metabolizable AA and implant status on dry matter intake; calves with a moderate implant consumed less feed when fed RP-AA while calves with a potent implant consumed greater amounts. Dry matter intake was not affected by metabolizable AA supply (P = 0.87) or implant status (P = 0.43). There was an interaction of source of metabolizable AA and implant status on ADG; implanted calves gained similar amount regardless of source of metabolizable AA, but non-implanted calves fed RP-AA gained 25% less compared with RDP-ONLY diet. Moderate and potent implants had greater ADG (P < 0.01) than non-implanted cattle. Overall, ADG was not affected by source of metabolizable AA (P=0.95). Feeding behavior was largely unaffected by source of metabolizable AA or implant status. Feed intake per meal, number of meals per day, meal duration and visit duration were not influenced by source of metabolizable AA or implant status (P ≥ 0.16). Number of visits per meal tended (P = 0.07) to be greater for RP-AA while feeding rate tended (P = 0.09) to be less. There was a significant interaction of source of metabolizable AA and implant status on feeding rate (P < 0.01) as non-implanted and potently implanted calves ate feed at a lesser rate when fed RP-AA but moderately implanted calves fed RP-AA ate feed at a greater rate compared with RDP-ONLY. These data demonstrate that metabolizable AA requirements of growing cattle are dynamically related to implant status in cattle, but that implant status does not largely influence feeding behavior.

Injection of bromocriptine mesylate has been used to mimic the symptoms of tall fescue toxicosis in beef cattle. Twelve steers (351 ± 11.82 kg) were used to investigate the effect of bromocriptine mesylate and heat stress on serum prolactin, rectal temperature, respiration rate, and innate/adaptive immune function. Steers were randomly assigned to receive an injection of saline (CON) or bromocriptine mesylate (BROMO; 0.1mg/kg BW) every three days. Animals were housed for 22 d in the Brody Climatology Laboratory at thermoneutrality (TN; 19.5±0.26°C; 10-d) before transitioning (2-d) to heat stress (HS; 27.2±0.26°C nighttime, 34.5±0.26°C daytime; 10-d). Cattle were fed 1.8% of BW (DM-basis) daily across two feedings. Rectal temperatures and respiration rates were measured daily at 0600, 0900, 1500, and 1800 h. Serum and plasma were harvested from blood collected on d 1, 9, and 21 (9th d of thermoneutrality and heat stress, respectively) and analyzed for prolactin and cytokines. Dry-matter intake was not affected by treatment (P=0.52) or temperature (P=0.78). Prolactin concentrations decreased (P=0.02) throughout the trial and decreased (P< 0.01) with BROMO. Rectal temperature and respiration rate were greater (P< 0.01) for BROMO during TN and HS. Rectal temperature and respiration rate were increased (P< 0.01) during HS. Pro-inflammatory cytokine (TNF-α, IFN-α, IFN-γ, IL-1α, IL-1β, IL-17, and IL-18) concentrations were greater (P< 0.01) for BROMO steers than CON. Heat stress increased (P< 0.01) pro-inflammatory cytokines with the exception of IL-18 (P=0.98) regardless of treatment. Anti-inflammatory cytokines (IL-13, IL-1-F5, IL-21, IFN-β, LIF) were decreased (P< 0.07) for BROMO steers with the exception of IL-10 (P=0.58). Regardless of treatment IL-13, IL-21, IL-10, and LIF concentrations were greater (P< 0.05) during HS. These results demonstrate that bromocriptine mesylate successfully mimicked the symptoms of fescue toxicosis. Innate and adaptive immune responses were influenced by treatment and temperature, potentially affecting beef cattle immune competency.

Forty Holstein bull calves were fed 1 of 3 starch-based milk replacers for either 10 or 35 days to determine responses in organ mass and small intestinal length. Calves (87.2 ± 7.7 kg) were bottle-fed a cornstarch-based milk replacer (727 g of cornstarch daily) alone, milk replacer with added casein (154.7 g/d) or milk replacer with added glutamate (45.5 g/d) for 10 or 35 d. Prior to receiving treatments calves were fed a commercial milk replacer for either 12 or 15 weeks so that measures of organ mass and small intestinal length were collected at the same day of age. Measures of organ mass were achieved after calves were euthanized and digesta was removed. Duodenum was defined as the first 1-m caudal to the pyloric sphincter. Jejunum and ileum were defined as the cranial and caudal halves of the remaining small intestines. Data were analyzed using the MIXED procedure of SAS. Average daily gain was 68% greater (P = 0.02) for calves fed casein compared to control, but glutamate did not differ from casein or control. Mass of the omasum, abomasum, jejunum, ileum, heart, or kidney and length of the jejunum or ileum were not affected by treatment (P ≥ 0.18); however, additions of casein increased (P ≤ 0.05) mass of the rumen, duodenum, large intestine, liver, and spleen. Greater duration of treatment increased rumen, abomasum, duodenum, jejunum, large intestine, heart, liver, and spleen mass (P ≤ 0.05), but there was treatment by duration interaction (P ≥ 0.18). Interestingly, there was an interaction (P < 0.01) for jejunal and ileal length in response to treatment and duration. Length of each segment increased with duration of treatment for calves fed casein or glutamate but lengths decreased in calves fed control for greater amounts of time.

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 of low-quality forages, yet little is known about its impact on CH4 emissions. British-cross steers (n = 23; initial body weight [BW] = 344 +/- 33.9 kg) were used in a three-period crossover design to evaluate the effect of protein supplementation to beef cattle consuming low-quality forage on ruminal CH4, metabolic carbon dioxide (CO2) emissions, forage intake, and ruminal fermentation. Steers individually had ad libitum access to low-quality bluestem hay (4.6% crude protein [CP]) and were provided supplemental protein based on (dry matter basis): cottonseed meal (CSM; 0.29% of BW daily; 391 g/d CP), dried distillers grains with solubles (DDGS; 0.41% of BW daily 563 g/d CP), or none (CON). Urea was added to DDGS to match rumen degradable protein provided by CSM. Ruminal CH4 and metabolic CO2 fluxes were obtained 2.4 +/- 0.4 times per steer daily using an automated open-circuit gas quantification system (GreenFeed emission monitoring system; C-Lock Inc., Rapid City, SD). Forage intake increased (P < 0.01) with protein supplementation; however, no difference in forage intake (P = 0.14) was observed between CSM and DDGS treatments. Flux of CO2 (g/d) was greater (P < 0.01) for steers fed CSM and DDGS than for steers fed CON. Steers supplemented with CSM had greater (P < 0.01) CH4 emissions (211 g/d) than DDGS (197 g/d) both of which were greater (P < 0.01) than CON (175 g/d). Methane emissions as a proportion of gross energy intake (GEI) were lowest (P < 0.01) for DDGS (7.66%), intermediate for CSM (8.46%) steers, and greatest for CON (10.53%). Steers fed DDGS also had the lowest (P < 0.01) ruminal acetate:propionate ratio (3.60), whereas CSM (4.89) was intermediate, and CON (5.64) steers were greatest. This study suggests that the common practice of supplementing protein to cattle consuming low-quality forage decreases greenhouse gas emissions per unit of GEI.

This study used 18 calves (295 ± 29 kg) and 18 yearlings (521 ± 29 kg) fed whole, cracked, or steam-flaked corn (SFC) to evaluate nutrient digestion and energy balance across different types of processed corn and sizes of cattle. Cattle were fed a diet comprised of 75% corn (dry matter [DM]-basis) from whole, cracked, or SFC to 2.5-times maintenance energy requirements. Subsequently, cattle were placed in individual stanchions, and urine and feces were collected together with measures of gas production via indirect calorimetry. Data were analyzed using the MIXED procedure of SAS. There was no interaction between corn processing and cattle size (P ≥ 0.40). Time spent ruminating (min/d) and rumination rate (min/kg DM intake [DMI]) were not affected by corn processing or cattle size. The eating rate (min/kg DMI) was faster (P < 0.01) for yearlings compared with calves. Total tract starch digestion was greatest (P = 0.01) for cattle fed SFC (97.5%), intermediate in cattle fed cracked (92.4%), and least in cattle fed whole corn (89.5%). Dietary digestible energy and metabolizable energy (Mcal/kg DMI) were greater (P ≤ 0.05) for cattle fed SFC compared with cracked or whole. A greater proportion of digestible energy was lost to heat production (P = 0.01) in cattle fed whole corn compared with cracked and tended to be greater (P = 0.08) in cattle fed SFC than cracked. Conversion of digestible energy to metabolizable energy in this study was more closely related to a dynamic model used to estimate metabolizable energy of feeds to dairy cows than to a linear model used to predict metabolizable energy of feeds to beef cattle. If library estimates of net energy for maintenance are correct, then retained energy (Mcal/d) should have been similar between each type of processed corn; however, retained energy was greater (P < 0.01) for cattle fed cracked compared with whole corn and tended to be greater (P = 0.06) compared with SFC. Yet, observed amounts of net energy based on measures of retained energy were not different (P ≥ 0.60) between cracked and SFC. Nitrogen balance was not affected (P ≥ 0.30) by corn processing or cattle size, although cattle fed cracked had numerically greater (P ≤ 035) N retention. These data indicate that physical processing of corn provides greater net energy to cattle in comparison to whole corn.

Two experiments were conducted to evaluate the bioavailability of AA between polymerized and less polymerized or unpolymerized sources of AA. In the first experiment, 6 bull calves (53.8 ± 0.6 kg of body weight) were bottle-fed milk replacer that contained 0, 60, or 120 additional grams of AA from casein or acid hydrolyzed casein every 12 h. Plasma essential AA increased linearly with increasing intake of casein from either source. Branched-chain amino acids accounted for 74% of increases in essential AA, regardless of source of AA. Concentrations of nonessential AA increased linearly with increased intake of AA from acid hydrolyzed casein but only tended to increase in response to casein. Also, the rate of increase in total plasma AA concentration in response to acid hydrolyzed casein (4.3 µM increase per g of supplemental AA) tended to be 145% greater than casein (3.0 µM per g of supplemental AA). In a separate experiment, 6 additional bull calves (52.1 ± 0.9 kg of body weight) were bottle-fed milk replacer that contained 0, 4.8, or 9.6 additional grams of Lys from ε-polylysine or Lys-HCl each 12 h to measure Lys bioavailability between a polymerized and unpolymerized source of Lys. Plasma Lys concentrations increased linearly in response to greater Lys intake from Lys-HCl (slope = 13.51 µM/g Lys,), but plasma Lys concentrations did not change in response to increased intake of Lys from ε-polylysine. Plasma concentrations of Thr, Met, Glu, and Gln decreased linearly with increasing ε-polylysine intake, whereas concentrations of His, Val, Leu, and Ile increased linearly with increasing ε-polylysine intake. Data from these experiments suggest that the form of AA provided to calves should be considered when formulating diets to meet AA requirements.

Abstract Chemical seed-head suppression of endophyte infected tall fescue (Lolium arundinaceum) improves stocker cattle performance but may decrease forage yield. Spring nitrogen application increases tall fescue growth with a concomitant increase in ergot alkaloids, produced by the symbiotic endophyte Epichloë coenophiala. We hypothesized that greater amounts of nitrogen applied to tall fescue would increase forage yield and offset losses in forage production from chemical suppression of seed-heads with metsulfuron without effect on alkaloid concentration. Ninety-six steers (270 ± 20 kg) were randomly assigned to one of sixteen paddocks (1.8 ha) on April 18 and continuously grazed for 57 d. Paddocks were blocked by previous use (n = 4) and randomly assigned to one of four treatments; no metsulfuron, no nitrogen (NEGCON), metsulfuron with 0 (MET0), 67 (MET67), or 134 (MET134) kg/ha of ammonium nitrate, applied March 11. Steers grazing MET0 paddocks were removed 17 d early due to insufficient forage availability. Steer weight, forage yield, forage nutritive value and ergot alkaloids in forage samples were measured monthly. Seed-head frequency and species composition were determined in June. Metsulfuron application reduced (P < 0.01) tall fescue seed-heads by 80%. Metsulfuron decreased (P = 0.03) ergovaline but ergovaline increased (P < 0.01) at each monthly sampling across treatments. Nitrogen had no impact on ergovaline concentration (P = 0.50). Forage yield tended to be least (P = 0.07) for MET0, intermediate for NEGCON and MET67, and tended to be greatest for MET134 (P = 0.08). Steer ADG was not affected by treatment (P < 0.80). Metsulfuron decreased NDF (P=0.02) regardless of fertilization rate. Forage CP increased with fertilization (P < 0.01) and no differences were detected between NEGCON and MET0 (P = 0.45). Species composition was not impacted (P >0.07) by treatment. Metsulfuron decreased seed-head growth and ergovaline concentration in tall fescue. Additional nitrogen fertilizer ameliorated forage yield lost to metsulfuron application but did not impact steer gain.

Objectives: The objective was to determine the effects of degree of steam flaking of corn (SFC) on performance of finishing cattle fed diets containing wet distillers grains with solubles (WDGS). Materials and Methods: Crossbred steers (n = 214: initial BW = 357 +/- 26.0 kg) and heifers (n = 121: initial BW = 323 +/- 30.9 kg) were randomly assigned to 54 pens and 6 diets containing 0, 15, or 30% WDGS and corn steam flaked to either 321 or 270 g/L bulk density (25 or 21 lb/bu, respectively) in a 2 x 3 factorial arrangement. Results and Discussion: There were no interactions between WDGS concentration and SFC bulk density for growth performance (P > 0.48), and growth performance was not influenced by the degree of steam flaking of corn (P > 0.29). Dry matter intake (P < 0.15) and ADG (P < 0.06) tended to respond quadratically to dietary WDGS. Gain efficiency tended (P = 0.15) to decrease linearly as dietary WDGS concentration increased. Carcass characteristics were not affected by SFC density but hot carcass weight (P < 0.12), DP (P < 0.01), and YG (P < 0.14) were affected by WDGS concentration. Decreasing bulk density of SFC tended (P < 0.11) to increase the frequency of liver abscesses. Implications and Applications: Results suggest optimal performance is achieved in SFC-based finishing diets when WDGS is fed at 15% of DM and that increasing the degree of steam flaking of corn to less than 321 g/L does not improve cattle performance in diets containing WDGS.

Prescribed fire may be a non-chemical alternative for seedhead suppression in endophyte-infected tall fescue forage systems. A study was conducted to observe the effects of a single prescribed burn on seed head production, ergot alkaloid concentration, forage production, forage quality, and stand composition in K31 tall fescue plots (endophyte infection=96%). Treatments of an undisturbed control (CON), March mow (MOW), March burn (EARLY), and April burn (LATE) were randomly applied to 56 square meter plots with ten replicates per treatment. Plots were sampled for forage quality and ergot alkaloid concentrations monthly from May to October. Forage production and species composition was recorded in June and October. Fescue seedhead count was conducted in May. After June sampling, plots were clipped to a height of 10 cm and litter was removed to simulate spring grazing. CON had greater (P < 0.01) total forage production in June than other treatments. MOW had greater (P < 0.01) forage production (≤107 kg/ha) than EARLY and LATE in June. There was no effect (P = 0.30) of treatments on forage production in October. LATE burn reduced (month × trt; P = 0.02) ergovaline concentration in June but all treatments were above the established threshold (150 ppb) for fescue toxicosis. Fescue seed head frequency was decreased (P < 0.01) by 50% in LATE plots. There was no treatment effect (P ≥ 0.22) on forb and non-fescue grass frequency in May, but warm season grass frequency was greater (P < 0.01) in LATE plots in October. Crude protein in LATE was greater than other treatments in May and both LATE and CON were greater than other treatments in June (P < 0.01). Neutral detergent fiber for LATE was less than other treatments in May and June (P < 0.01). Under conditions of this experiment, prescribed fire decreased seed head count and ergot alkaloid concentration, with a modest reduction in forage production.

A fungal endophyte, Epichloe coenophiala (Morgan-Jones & 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 tall fescue toxicosis. Strains of E. coenophiala that produce little or no toxic ergot alkaloids are referred to as "novel" endophyte associations and offer a solution to tall fescue toxicosis. The objective of this study was to determine differences in animal preference and ground cover among commercially available novel endophyte-infected tall fescue cultivars. Six cultivars of novel tall fescue and controls of common, toxic endophyte-infected and endophyte-free tall fescue were evaluated for animal preference, forage mass, forage removal, forage quality, and ground cover during a 2-yr grazing trial at Linneus, MO. Plots were grazed over nine grazing events by beef cattle (Bos spp.) during the 2-yr study, and some animals were fitted with GPS collars to determine which cultivar was grazed first and most often. 'BarOptima', a soft-leaf cultivar, was grazed first and most frequently. Forage mass, forage removal, and forage quality measurements of crude protein, acid detergent fiber, and neutral detergent fiber were similar among cultivars. Ground cover increased each year of the study, even though seed production was inhibited. In addition, rust (Puccinia spp.) susceptibility differed among cultivars. Under this management system, which used up to 24-h grazing periods and at least 8-cm stubble height, animal preference was not based on endophyte status.