(352.03 ± 19.61 kg) were fed according to the treatments: STEP for 6-d or 9-d and REST for 6-d or 9-d. In each study, 48 animals (two per pen) were randomly chosen for blood collection, which was performed at end of the adaptation period and on Day 21 of the studies. Blood samples were collected from the jugular vein, and blood LBP concentration, expressed as ng·mL-1, was determined by using a commercial ELISA kit. For the irst study, a signiicant (P = 0.01) period main effect was observed, in which animals on Day 21 presented greater concentrations of LBP than those at end of the adaptation period (128.1 vs. 56.7). A signiicant (P = 0.01) interaction was observed between protocols and duration of adaptation, where animals in REST protocol of 14-d had greater blood LBP concentration (157.2) than cattle in STEP protocol of 9-d (91.0), which had greater blood LBP concentrations than animals in REST protocol of 9-d (67.3) and STEP protocol of 14-d (54.2). In the second study, no signiicant (P > 0.10) protocols and duration of adaptation main effects were observed. However, a signiicant (P = 0.01) period main effect was observed, in which animals on Day 21 of the study present greater concentrations of blood LBP when compared to those at the end of the adaptation period (615.3 vs. 136.6). As the normal cattle blood LBP range varies from 50 to 500 ng·mL-1, adapting feedlot Nellore cattle in 14-d, regardless of the protocol, seems to be the most feasible option. Key Words: acidosis, endotoxin, Nellore 1859 (W318) The effects of OmniGen-AF on serum metabolites, calcium concentrations and hormones of the adrenal axis during heat stress in lactating Holstein cows. L. W. Hall*1, F. A. Villar1, J. D. Allen2, J. D. Chapman3, N. M. Long4 and R. J. Collier1, 1The University of Arizona, Tucson, 2Northwest Missouri State, Maryville, 3Prince Agri Products, Inc., Quincy, IL, 4Clemson University, Clemson, SC The objective was to evaluate physiological, behavioral and hormonal changes in lactating cows supplemented with OmniGen-AF (Prince Agri Products, Inc.) subjected to heat stress. Thirty lactating Holstein cows from an Arizona were assigned to a control diet (CON, n = 15h) or control diet plus OmniGen-AF (OG, n = 15h). Cows within diet were balanced by DIM, milk production and parity (91 ± 5.9 DIM, 36.2 ± 2.5 kg/d, and 3.1 ± 1.4). The cows were fed OG at 56 g/h/d for 52 d on the dairy, added to the TMR. On d 52, six cows were randomly selected from each of the diet groups, transported to the Agricultural Research Center (ARC), University of Arizona and housed in environmentally controlled modules (EM). Original diet assignments were continued. The OG was top-dressed 2x/d (28 g/feeding) with molasses as the carrier and the CON cows received the molasses carrier 2x/d. Both were mixed into the top one-third of the TMR. In the EM, all cows were subjected to 7 d of thermal neutral (TN), 10 d of heat stress (HS), and 4 d of TN. Feed intake, milk production, J. Anim. Sci Vol. 92, E-Suppl. 2/J. Dairy Sci. Vol. 97, E-Suppl. 1 and milk composition were measured daily. Rectal temperatures and respiration rates were recorded 3x/d (0600, 1400, and 1800 h). Blood samples were taken on Days 7 (TN), 8 (HS), 10 (HS), 17 (HS) and 18 (TN) during the ARC phase and analyzed for selected blood metabolites, hormones and immune biomarkers. Serum cortisol levels were highest on d 8 for both the CON and OG fed cows however OG cows had signiicantly lower cortisol (P < 0.05) on Day 8 (CON = 0.8372 ug/dL; OG = 0.4838 ug/dL). No differences were detected at the other time points. Serum insulin and plasma glucose levels were not different between CON and OG cows. The OG cows maintained lower SCC compared to CON (P < 0.01). Serum calcium were not different, however, serum NEFA (P = 0.10) tended to be greater in OG cows throughout the 21 d ARC phase. Although serum cortisol were lower in OG cows, serum ACTH levels at each sampling point were higher (P < 0.0001). Results suggest that feeding OG to lactating cows reduced many of the effects associated with HS by reducing cortisol. However, ACTH increased in OG cows suggesting that OG may alter adrenal response to ACTH. Additional research is needed to determine the cause of reduced serum cortisol and elevated serum ACTH in cows fed OG. Key Words: heat stress, lactating cows, OmniGen-AF 1860 (W319) Assessment of the effect of plant tannins on rumen fermentation and gut microbial diversity in goats using 16S rDNA amplicon pyrosequencing. B. R. Min*1, C. Wright1, P. Ho2, J. S. Eun3, N. Gurung1 and R. Shang1, 1Tuskegee University, Tuskegee, AL, 2 Montgomery Blair High School, Silver Spring, MD, 3 Utah State University, Logan Two grazing experiments were performed to 1) investigate the effects of supplementing condensed tannins (CT)-containing pine bark (PB) powder on ADG, ruminal fermentation, and gut microbial diversity dynamics, and 2) to quantify the inluence of different sources of tannins supplementations on ruminal fermentation and gut microbial diversity changes of goats grazing winter pea and ryegrass dominant forages. In Exp. 1, 20 Kiko cross male goats (Capra hircus; initial BW = 39.7 ± 2.55 kg) were randomly assigned to 2 experimental diets (alfalfa pellet vs. PB powder). Alfalfa pellet (no CT as a control) or PB (11% CT) was supplemented at 0.8% BW for targeted total DMI of 1.2% BW. The remainder DMI of each diet was obtained from grazing for 60 d. In Exp. 2, 12 Kiko cross goats were used to measure ADG, ruminal fermentation, and gut microbial population in the rumen of goats grazing bermudagrass. The animals were randomly assigned to 3 experimental diets: 1) no tannins (control), 2) chestnut extract at 100 g/d (CTE), and 3) quebracho CT extract at 100 g/d (QCTE). In Exp. 1, ADG was greater (P < 0.05) in PB (209 g/d) than the control (188 g/d). However, goats grazing winter pea and ryegrass forages with PB supplementation decreased (P < 0.05) concentrations of acetate (14.4 vs. 15.1 mM), propionate (3.34 vs. 3.83 mM), 905 butyrate (1.82 vs. 2.00 mM), and total VFA (22.5 vs. 23.7 mM) compared to those in the control, respectively. Bacterial population in PB-supplemented group was greater for Bacteroides (20.5 vs. 33.2%), Firmicutes (67.2 vs. 57.3%), and Proteobacteria (1.15 vs. 1.44%) phylum compared with control group, respectively. In Exp. 2, ADG was greatest for CTE (275 g/d) than QCTE (148 g/d) and the control (79.4 g/d). Goats grazing bermudagrass pasture with CTE had greater (P < 0.05) concentrations of acetate, propionate, butyrate, and total VFA compared to those in QCTE and control. Bacterial population in CTE-supplemented group was greatest for Bacteroides (51.5, 52.9, and 35.3%), Firmicutes (40.2, 36.7, and 55.9%), and Proteobacteria (2.28, 2.18, and 1.49%) phylum compared with QCTE and control group, respectively. Rumen archaeal population, however, was greatest in control group (0.70%) compared with CTE (0.23%) and QCTE (0.22%) group. Supplementing tannins in goat diets such as CTE, QCTE, or PB powder has the potential to improve ADG and modify rumen bacterial and archael population. Key Words: goats, gut microbial diversity, tannins 1861 (W320) Effect of supplemental chelated Cu, Zn, and Mn on antioxidant status and hoof health of lactating cows. X. J. Zhao1, J. H. Wang2, Y. M. Wang*3 and L. Wang1, 1College of Animal Science and Veterinary Medicine, Shandong Agriculture University, Taian, China, 2College of Animal Science, Zhejiang University, Hangzhou, China, 3Novus International Trading (Shanghai) Co., Ltd, Shanghai, China The objective of the study was to evaluate effect of supplemental Cu, Zn, and Mn as chelated trace mineral (CTM) on antioxidant status and hoof health of dairy cows. Forty eight Holstein cows in early lactation (DIM = 65) were randomly assigned into 1 of 2 treatments: 1) basal diet contains 17.2 mg Cu, 70.1 mg Zn, and 63.7 mg Mn/kg dry matter (CON); 2) basal diet supplemented with 150 mg Cu, 320 mg Zn and 130 mg Mn/head/d as CTM (Minitrex). Cows were gait scored using a 5-point Numerical Rating System where 1 and 2 are considered healthy, and ³ 3 lame. Cows in each treatment were blocked as lame cows (n = 12) or healthy cows (n = 12) when data was analyzed. Over the 180 d experiment, DMI, milk yield and milk composition was tested every 10 d. Blood samples and hoof samples were taken at Day 0, 90, and 180 to test the blood antioxidant variables and hoof hardness, respectively. There was no difference in DMI, milk yield and milk composition between healthy and lame cows (P > 0.05). Cows receiving CTM had less milk fat concentrations (P < 0.05) than CON, but no difference was observed on milk fat yield or other milk components (P > 0.05). No differences were detected in blood superoxide dismutase (SOD), reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde 906 (MDA) between healthy and lame cows (P > 0.05). Compared with CON, blood SOD, GSH, and GSH-Px in CTM cows were signiicantly increased while MDA and GSSG were signiicantly decreased (P < 0.05), and blood CAT was not affected by treatments (P > 0.05). Cows receiving CTM did not have hoof hardness that differed from the CON at Day 0 and 90, but had signiicant greater values than CON at Day 180 (P < 0.05). There was no interaction between CTM and cows health status. It was concluded that supplemental chelated Cu, Zn, and Mn could improve antioxidant status and hoof hardness regardless of lameness status. Key Words: chelated trace mineral; antioxidant status; hoof health 1862 (W321) Effects of supplemental bupleurum extract on serum hormone and immune globulin levels in heat-stressed dairy cows. X. Sun1,2,3, J. Cheng1,2,3, D. P. Bu3, L. Pan3, N. Zheng1,3,4 and J. Wang*1,3,4, 1 Ministry of Agriculture- Laboratory of Quality & Safety Risk Assessment for Dairy Products (Beijing), Beijing, China, 2College of Animal Science and Technology, Anhui Agricultural University, Hefei, China, 3State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China, 4Ministry of Agriculture- Milk and Dairy Product Inspection Center (Beijing), Beijing, China This experiment was conducted to evaluate the effects of bupleurum extract (BE) on serum hormone and immune globulin levels in dairy cows under heat stress. Forty lactating Holstein cows (75 ± 15 DIM, 37.5 ± 1.8 kg of milk/d, and 1.7 ± 0.4 parity) were randomly assigned to one of four treatments. Treatments consisted of 0 (control), 0.25, 0.5, or 1.0 g BE/kg DM. The experiment lasted 10 wk. Average temperature–humidity index (THI) was more than 72 throughout the experimental period. Blood samples were collected from all of animals via tail vein before the morning feeding on Days 0, 21, 42, and 63. Data were analyzed by MIXED model procedure of SAS 9.2. Compared with controls, cows fed 1.0 g/kg BE had higher thyroxine (T3) (1.43 vs. 1.16 ng/mL; P < 0.05) and prolactin (PRL) (230.50 vs. 188.19 uIU/mL; P < 0.05) levels, and 0.5 g/kg BE had the tendence to increase the T3 (1.27 vs. 1.16 ng/ mL; P < 0.10) level, but 0.25 and 0.5 g/kg BE had no effect (P > 0.05) on PRL level. Serum growth hormone (GH) level was increased (2.17 vs. 1.21 ng/mL; P < 0.05) in cows fed 0.25 g/ kg BE compared with control cows, and tended to be higher (1.76, 1.69 vs. 1.21 ng/mL; P < 0.10) in cows fed 0.5 and 1.0 g/kg BE. Supplementation of BE had decreased the cortisol (COR) levels (48.35, 49.43, 49.86 vs. 64.49 ng/mL; P < 0.05), but had no effect (P > 0.05) on the levels of thyroxine, Insulin, glucagon, neuropeptide Y, leptin, insulin-like growth factor, and heat shock protein 70. Cows fed 0.5 g/kg BE increased the immunoglobulin (Ig) A content (279.25 vs. 179.78 ìg/mL; J. Anim. Sci Vol. 92, E-Suppl. 2/J. Dairy Sci. Vol. 97, E-Suppl. 1