PSXVI-28 Late-Breaking: Effects of Preconditioning (Value Added Programs) on the Health, Performance, Mannheimia haemolytica, and Pasteurella multocida in Cattle Received on Winter Wheat Pasture

Bovine respiratory disease (BRD) is a persistent health problem impacting the beef industry. Research shows improved health and performance in preconditioned (PRECON) calves compared with nonpreconditioned (NONPRE) or commingled (COMM) calves received in the feedlot but little research has been focused on calves received on winter wheat pasture prior to feedlot entry. Our objective for this presentation is to investigate the effects of preconditioning on the health and performance of newly received beef calves on winter wheat pasture. Mixed breed steers (n = 145) were purchased from an auction barn in Dalhart, Texas, as PRECON (n = 70) or NONPRE (n = 75) and were transported to the Clayton Livestock Research Center in Clayton, New Mexico, for this 112-d study trial. Three treatments were used in this completely randomized design: PRECON (n = 50), NONPRE (n = 50) and COMM (n = 45). Upon arrival, steers were offloaded into separate pens. On d 0, steers were processed using a standard health protocol along with collection of nasopharyngeal (NP) swabs, randomly allocated to treatment, and released onto a 120-acre winter wheat pasture split into three paddocks with a common water source; weights were collected again on d 2, 90, and 112. There were no statistical differences in morbidity and mortality rates between treatments. Weight gain was analyzed using PROC GLM of SAS from d 0 to d 90. COMM steers had greater weight gains than PRECON (P = 0.04) and NONPRE (P = 0.02) steers. NP swabs were used to show the distribution of Mannheimia haemolytica (MH) serotype A1, A2, and A6 and Pasteurella multocida (PM) by day and by treatment. No statistical differences were observed in serotype distribution of MH A1, A2, or A6 or in PM. PRECON steers displayed no health or performance advantage over NONPRE or COMM steers.

PSVII-17 Use of a dimethyl carbonate extraction for rumen fluid volatile fatty acid quantification by gas chromatograph mass spectrometry

Analysis of rumen fluid volatile fatty acids (VFA) is typically conducted by injecting acidified aqueous rumen fluid into a gas chromatograph (GC) with a flame ignition detector (FID). Water in GC samples can lead to poor peak shape and to contamination of inlets, potentially causing sample carryover. Aqueous methods are not well suited for use in mass spectrometer (MS) detector systems. The objective of this project was to validate a dimethyl carbonate (DMC) extraction process and GCMS method for rumen VFA analysis. To perform the extraction, 100 µL of sample, KHSO4 (50 g/L), and 2-ethylbutyrate (internal standard; 0.86 mM) are added to a microcentrifuge tube (in order) followed by 1 mL of DMC. The mixture is thoroughly vortexed and centrifuged. The organic layer (top) is removed and placed in a GC vial. The DMC extract is injected (0.5 µL) into an Agilent 5977B GCMS (8:1 split injection) with a polar DB-FFAP column. The column was held at 105°C for 5 min, increased at 10°C/min to 150°C, then 65°C/min to 240°C, and held constant for 10 min. The assay is linear for acetate from approximately 2 mM to at least 130 mM and covers the expected values of rumen concentrations for the other VFA. Recovery of VFA from spiked rumen fluid was tested at three concentrations in rumen fluid from steers fed a finishing diet or grazing wheat pasture. Recovery was not affected by the diet of the animals (P > 0.19) or the amount of VFA spiked (P > 0.27) and averaged 99.9% for all VFA, with valerate being the lowest (95.9%). Including the 10 min hold at 240°C at the end of each run prevented carryover from sample to sample. This method appears to perform well in a GCMS system and accurately and precisely quantify rumen fluid VFA.

62 Effects of forage allowance and supplementation on performance of steers grazing wheat pasture

A 72-d trial was conducted to estimate the combined effect of forage allowance and a fiber-based energy supplement in stocker cattle grazing wheat. Eight pastures (2.7 to 5.1 ha) each contained seven test steers (initial BW = 210 ± 36 kg). Weekly, additional steers were stocked in each pasture in a put and take method to achieve forage allowance of either 2.5 or 5.5 kg forage DM / kg steer BW (4 pastures each). Two pastures in each forage allowance were fed daily with a supplement containing 50% wheat midds and 50% soybean hulls at the rate of 1.5 kg per steer. Forage mass was measured twice weekly using a calibrated rising plate meter. Cattle were weighed weekly on calibrated scales. Data were analyzed using linear regression with pasture as the experimental unit. Mean ADG was 1.36 kg/d. One pasture in the high forage allowance, non-supplemented treatment was removed because we were unable to maintain the designed forage allowance. The interaction of forage allowance and supplement was not significant (P = 0.37) for ADG, and supplementation did not affect ADG (P = 0.20), however increased forage allowance tended to improve ADG (P = 0.06, 0.21 kg ADG per kg forage allowance). To further investigate forage DMI, a 14-d trial began on day 36. Three of the seven test steers in each pasture were randomly chosen and administered 7 ± 0.1 g of TiO2 daily at 0700 as an external marker to estimate fecal output. Forage DMI (at an assumed 72% DM digestibility) averaged 2.1% of midpoint BW, below our expectation. Additional forage allowance tended to improve estimated forage DMI (P= 0.06), but supplement had minimal effect (P = 0.30).

164 The effects of energy and lasalocid supplementation on forage intake and energetics of cattle grazing wheat pasture

Cattle grazing wheat have the potential to gain BW exceptionally well, but excessive nitrogen intake results in increased excretion and increased greenhouse gas (GHG) emissions. Supplemental grain with the addition of an ionophore given to ruminants grazing wheat is a potential practice for producers to increase nitrogen efficiency while decreasing GHG emissions. Therefore, the objective of this experiment was to quantify the effects of energy and lasalocid supplementation on nutrient intake, respiratory gas fluxes, and performance of grazing cattle. Heifers (n = 18) were used in a 49-d experiment that consisted of two 21-d blocks with 7 d between them (initial BW=311±17.3 kg and 339±16.7 kg, Block 1 and 2, respectively). Heifers were assigned randomly to 1 of 3 treatments; no supplement (Control, n = 6), 2.95 kg control feed/d (Energy, n = 6), or 2.95 kg feed with lasalocid/d (Lasalocid, n = 6). Cattle grazed an 8.1-ha paddock of winter wheat and had access to a GreenFeed system used to quantify the respiratory gas fluxes (CH4, CO2, and O2). Cattle were weighed on d 0 and 21 of each block, on d 15 to 21 cattle were gathered every 12 h and fecal samples were collected. Data were analyzed using the PROC MIXED in SAS. Methane emissions were not affected (P = 0.58) by treatment, but supplemented cattle had greater (P = 0.04) CO2 emissions and O2 consumption (P = 0.03). Hence, ADG tended to be greater for supplemented cattle (P= 0.09) compared to Control (1.22 and 1.00 kg, respectively); but no effect (P = 0.88) was observed for the Lasalocid. Fecal output was greater for supplemented cattle (P < 0.01), but forage intake was lower (P < 0.01) and nutrient intake was higher (P < 0.01) for supplemented cattle compared to Control. Supplemented cattle had lower forage intake with greater CO2 emissions and O2 consumption, but the Lasalocid did not affect any parameter.

40 Effect of calving season in an artificial insemination program on finishing performance and carcass traits

Spring (SPRING) and fall (FALL) born steers (n = 211) were used in a mixed effects model to evaluate calving season and conception method [artificial insemination (AI) or natural service (NS)] on finishing performance and carcass traits. SPRING were weaned in October, grazed dormant range for 90 days and grazed wheat pasture for 90 days before shipping to finish. FALL were weaned in May, and grazed tallgrass prairie for 120 days before shipping to finish. Initial and final BW, days on feed, ADG, DMI, and gain to feed efficiency were evaluated as performance measures. Dry matter intake and gain:feed were analyzed on pen basis. Hot carcass weight, yield grade, fat thickness, ribeye area, and marbling score were collected at harvest. Bodyweight of SPRING and AI steers were heavier (P ≤ 0.05) entering and leaving the feedlot than FALL and NS steers, respectively. Compared to FALL steers, ADG (P < 0.01) and DMI (P = 0.03) were greater for SPRING and required less days on feed (P ≤ 0.05). Calving season and conception method (P ≥ 0.2) did not affect gain:feed. Conception method (P = 0.5) did not affect ADG, DMI, and days on feed. SPRING had higher yield grades (P < 0.01) and increased in fat thickness (P = 0.01) compared to FALL steers. There were no differences (P = 0.2) in hot carcass weight, ribeye area, and marbling score due to season of birth. Steers born from AI mating had greater hot carcass weight (P = 0.01) and marbling score (P = 0.02), but conception method did not affect yield grade, fat thickness, and ribeye area (P > 0.2). These results demonstrate SPRING steers are heavier entering and leaving the feedlot, have higher ADG and DMI, and require less days on feed; however, gain:feed, hot carcass weight, ribeye area, and marbling score did not differ from FALL steers. An economic analysis is needed to validate an AI program based on calving season in north-central Oklahoma.

63 Effects of forage allowance and supplementation on performance of steers grazing wheat pasture

A 72-d trial was conducted to estimate the combined effect of forage allowance and a fiber-based energy supplement in stocker cattle grazing wheat. Eight pastures (2.7 to 5.1 ha) each contained seven test steers (initial BW = 210 ± 36 kg). Weekly, additional steers were stocked in each pasture in a put and take method to achieve forage allowance of either 2.5 or 5.5 kg forage DM / kg steer BW (4 pastures each). Two pastures in each forage allowance were fed daily with a supplement containing 50% wheat midds and 50% soybean hulls at the rate of 1.5 kg per steer. Forage mass was measured twice weekly using a calibrated rising plate meter. Cattle were weighed weekly on calibrated scales. Data were analyzed using linear regression with pasture as the experimental unit. Mean ADG was 1.36 kg/d. One pasture in the high forage allowance, non-supplemented treatment was removed because we were unable to maintain the designed forage allowance. The interaction of forage allowance and supplement was not significant (P = 0.37) for ADG, and supplementation did not affect ADG (P = 0.20), however increased forage allowance tended to improve ADG (P = 0.06, 0.21 kg ADG per kg forage allowance). To further investigate forage DMI, a 14-d trial began on day 36. Three of the seven test steers in each pasture were randomly chosen and administered 7 ± 0.1 g of TiO2 daily at 0700 as an external marker to estimate fecal output. Forage DMI (at an assumed 72% DM digestibility) averaged 2.1% of midpoint BW, below our expectation. Additional forage allowance tended to improve estimated forage DMI (P= 0.06), but supplement had minimal effect (P = 0.30).

163 The effects of energy and lasalocid supplementation on forage intake and energetics of cattle grazing wheat pasture

Cattle grazing wheat have the potential to gain BW exceptionally well, but excessive nitrogen intake results in increased excretion and increased greenhouse gas (GHG) emissions. Supplemental grain with the addition of an ionophore given to ruminants grazing wheat is a potential practice for producers to increase nitrogen efficiency while decreasing GHG emissions. Therefore, the objective of this experiment was to quantify the effects of energy and lasalocid supplementation on nutrient intake, respiratory gas fluxes, and performance of grazing cattle. Heifers (n = 18) were used in a 49-d experiment that consisted of two 21-d blocks with 7 d between them (initial BW=311±17.3 kg and 339±16.7 kg, Block 1 and 2, respectively). Heifers were assigned randomly to 1 of 3 treatments; no supplement (Control, n = 6), 2.95 kg control feed/d (Energy, n = 6), or 2.95 kg feed with lasalocid/d (Lasalocid, n = 6). Cattle grazed an 8.1-ha paddock of winter wheat and had access to a GreenFeed system used to quantify the respiratory gas fluxes (CH4, CO2, and O2). Cattle were weighed on d 0 and 21 of each block, on d 15 to 21 cattle were gathered every 12 h and fecal samples were collected. Data were analyzed using the PROC MIXED in SAS. Methane emissions were not affected (P = 0.58) by treatment, but supplemented cattle had greater (P = 0.04) CO2 emissions and O2 consumption (P = 0.03). Hence, ADG tended to be greater for supplemented cattle (P = 0.09) compared with Control (1.22 and 1.00 kg, respectively), but no effect (P = 0.88) was observed for the Lasalocid. Fecal output was greater for supplemented cattle (P < 0.01), but forage intake was lower (P < 0.01) and nutrient intake was higher (P < 0.01) for supplemented cattle compared to Control. Supplemented cattle had lower forage intake with greater CO2 emissions and O2 consumption, but the Lasalocid did not affect any parameter.

Grain Yield and Beef Cow–Calf Growth Performance in Dual-Purpose and Conventional Grain Wheat Production Systems and Stockpiled Tall Fescue Pasturing

Dualpurpose wheat (Triticum aestivum L) can be used for cattle grazing while producing grain from the same crop. In a two-year study, wheat forage production, grain yield, and growth performance of beef cow–calf pairs grazed on wheat pasture for 2–3 weeks in spring was compared with the conventional wheat grain production system and stockpiled tall fescue (Festuca arundinacea (L.) Schreb) pasturing. Grazing wheat resulted in grain yield (4.1 vs. 4.6 t ha−1) and test weight (65.9 vs. 66.7 kg hL−1) similar to the conventional grain production system. Wheat accumulated significantly lower forage dry matter yield (0.9 vs. 1.9 t ha−1) in spring with higher crude protein (190.2–290.2 vs. 122.0–151.0 g kg−1) and low fiber contents compared to the stockpiled tall fescue pasture. Wheat pasture presented risk for the development of grass tetany with regard to N, K, Na, and Mg contents. Calves grazed on wheat gained 1143–1370 gd−1 body weight compared to the 826–879 gd−1 in the stockpiled tall fescue pasturing. Cows had inconsistent and mixed body weight change response. With warmer temperatures and adequate precipitation controlled grazing of wheat in spring by beef cow–calves offered weight gain benefits exceeding the stockpiled tall fescue pasturing and grain production similar to the conventional wheat grain system.