Dry Lot Research Articles

61 Rapid changes in fecal pH in horses fed either a mixed diet or pasture

Horses need to maintain a stable microbial population to support proper digestion and nutrient absorption, and most changes in feeding are done over a 5–7-d period to minimize digestive upset. A healthy gastrointestinal system typically has a pH of 6.5–7.0, and fiber fermenting bacteria like Streptococcus spp and Lactobacillus spp create an optimal environment for digestion and useable energy production. The objective of this study was to compare spring pasture grazing to a mixed diet to see the influence of diet on fecal pH within a short period of time. Nine mature geldings were used to measure the changes in fecal pH between the 2 diets for a period of 4 d. Horses were assigned to a control group (n = 5) maintained on pasture only, and a restricted group (n = 4) on a dry lot with access to mixed grass hay and a textured concentrate. Approximately 200g of feces were collected from each horse to produce 30mL of fecal liquid. The change in fecal pH, which was defined as the difference in the pH levels between d 4 and d 0 (baseline), was calculated for each horse. The averagechange in pH for the mixed diet group was 0.312 (standard deviation (SD) = 0.295), while the average change in pH for the pasture group was −0.678 (Standard deviation (SD) = 0.227). Since the size of each treatment group was small, the assumption of normality required for the independent measures t-test could not be reliably assessed. Therefore, the non-parametric Mann-Whitney U test was used, which showed that the change in fecal pH was significantly larger in the mixed diet group (Median (Mdn) = +0.295) than in the pasture group (Mdn = - 0.700), U = 20, P = 0.016, using an exact sampling distribution for U. In conclusion, horses on a dry lot fed a mixed diet had an increase in fecal pH compared with a decrease in fecal pH for pastured horses, with both changes occurring within 4 d. No horses exhibited any digestive or behavioral problems, which suggests that bacterial population and activity changes may safely occur more quickly than previously thought.

96 Evaluation of prolonged hay net use on the rostral oral cavity and salvia production in adult horses

Previous hay net studies have focused on behavior, consumption, and feed wastage; yet none have evaluated effects in the oral cavity. To investigate the effects of prolonged hay net use on rostral soft tissue and saliva production, 8 stock-type horses were evaluated for dental health and floated by a dental technician to ensure consistency. Horses were blocked by body weight (BW; 558.6 ± 13.8kg), body condition (BC; 6.5 ± 0.2), sex (mares: n = 5; geldings: n = 3), and age (10.1 ± 1.1yr) and randomly assigned to one of 2 feeding treatments for 70d. Horses on control (CON; n = 4) were offered loose hay in a tub; horses in the experimental group (NET; n = 4) were offered hay encased in a slow-feeder hay net (Texas Hay Net, 3.81cm2 openings). Horses received coastal bermudagrass hay at 1.5% of BW daily along with a commercial concentrate (Equilene® Pellets) at ≤0.7% of BW as-fed to maintain BC. Horses were kept in individual dry pens with access to feed, water, and salt for 16 h/day, and then group-housed in dry lots with only ad-libitum water and salt for 8hr/day. Feed intake was recorded daily by the collection and weighing of orts. All horses were assessed weekly using digital and thermography (FLIR®) images to document changes in rostral oral tissue. Blind reviewers analyzed images for changes in rostral oral cavity scores (ROCS) ranging from no damage (ROCS = 7) to severe damage (ROCS = 21).Biweekly saliva measurements were taken immediately before hay offering and 1hr after consumption using 2 disposable oral swabs (Munkcare®, 18cm3 each) held at the exit of the sublingual gland. Statistics were formulated using 3-way repeated measures ANOVA using R Statistical Program®. Intake was not influenced by feeding method (P = 0.874), nor was saliva production (P = 0.570). NET horses had numerically higher pre-consumption saliva values (5.27 ± 0.41g) compared with CON horses (4.55 ± 0.49g). Saliva production increased post-1hr consumption (P ≤ 0.001) confirming production was a result of mastication. The surface temperature of the oral cavity was not affected by treatment (P = 0.471) and was within normal ranges. Average total ROCS did not differ between treatments (NET: 11.0 ± 0.2; CON: 12.2 ± 0.2; P = 0.251) but increased with time (P ≤ 0.01). Use of a hay net for 70d did not influence intake or negatively affect rostral tissue, indicating a level of safety long-term. Based on these findings, feeding from a hay net over a 1hr period did not influence saliva production; however, in future studies, saliva production should be evaluated over an entire consumption period.

82 Responses to a combined exercise and transport stressor following dietary supplementation of anti-endotoxin IgY in mature horses

Immunoglobulin Y elicits positive effects in domestic livestock with gastrointestinal or inflammatory diseases; however, there are limited studies in horses. To test the hypothesis that dietary anti-endotoxin IgY (IgY) has a positive effect on gastrointestinal health and mitigates systemic inflammation in horses undergoing exercise, 30 stock-type horses (578 ± 59 kg BW; 14 ± 3 yr) were used in a completely randomized design. Horses were stratified by BW, age, and sex and then randomly assigned to treatments: 0 g/d IgY (CON; n = 10), 1 g/d IgY (TRT1; n = 10), or 2 g/d IgY (TRT2; n = 10). Horses were fed every 12 h, with dietary treatments (Camas Inc., Le Center, MN) top-dressed on the morning concentrate for 33 d. Horses were maintained in dry lots with ad libitum access to Coastal bermudagrass hay. Horses were exercised 5 d/wk for 1 h. On d 0 and 30, BW and BCS were recorded, and blood was collected for complete blood cell count (CBC) and serum blood chemistry. On d 32, horses were transported 270 km and underwent a 3.2 km exercise stressor on concrete at a walk with maximum 15 min of trot. Whole blood, serum, and fecal samples collected via rectal palpation were obtained pre-, post-, and 24 h post-trailering. Fecal pH was determined by a portable meter, and serum cytokine (TNFα, IL-4, IL-10, IL-1β, IL-17, IFN-α, IFN-γ) and chemokine (CCL2, 3, 5 and 11) concentrations weremeasured using a multiplex platform. Whole blood DNA was extracted using a commercial DNA extraction kit. For gut permeability analysis, 16s rDNA was analyzed via qPCR and calculated as fold change from d 0. Data were analyzed using PROC MIXED of SAS v9.4. Dietary IgY did not affect BW, BCS, blood chemistry, or CBC (P ≥ 0.17). Fecal pH decreased over time (P ≤ 0.01). There was no treatment × time interaction for 16S rDNA (P = 0.45). Dietary treatment affected circulating 16S rDNA (P < 0.01) where TRT2 (1.89-fold) was greater than CON (0.70-fold), and TRT1 (1.24-fold) was intermediate. A significant time effect (P = 0.001) was observed for 16S rDNA where fold change decreased after the stressor from 1.90-fold for pre-, to 1.02 for post-, and 0.92 for 24 h post- trailering. There tended to be a treatment × time interaction (P = 0.08) for CCL3, as CON was greater at 24 h and TRT2 declined post-trailering, returning to baseline by 24 h. Levels of CCL5 decreased (P < 0.01) and TNFα tended to decline (P = 0.06) through 24 h post trailering in all treatment groups. Other cytokines and chemokines were non-detectible. Despite greater circulating 16s rDNA with higher treatment dosages, there was no effect on systemic inflammatory markers.

52 Influence of Saccharomyces cerevisiae CNCM I-1077 on the intestinal environment, gut permeability, and markers of systemic inflammation in horses fed a high starch diet

Probiotics may balance the hindgut environment and relieve systemic inflammation in horses fed high starch concentrates to meet energy requirements. Therefore, 30 mature Quarter Horse geldings (545 ± 58 kg BW) were used in a randomized complete design for 32-d to test the hypothesis that supplemental live Saccharomyces cerevisiae CNCM I-1077 (SC; Levucell® SC Advantage) stabilizes the intestinal environment, reduces gut permeability, and decreases inflammation when horses are fed a high starch diet. Horses were stratified by BW, age, and body condition score (BCS) and randomly assigned treatments consisting of either a concentrate formulated with 2g starch • kg BW−1 • meal−1 (CON, n = 15) or the same concentrate top-dressed with 25 g/d SC(TRT, n = 15) containing 20 billion cfu. Horses were fed individually in stalls (3 × 3 m) every 12 h. Between meals, horses were housed in adjacent dry lots with ad libitum access to Coastal bermudagrass hay and water. On d 0 and 32, BW and BCS were recorded and blood samples were collected immediately before feeding (h 0) and at h 2, 8, 16, and 24 post meal. Samples were analyzed for serum D-lactate using a colorimetric assay, chemokine (CCL2) and cytokine (TNFα) concentrations were measured using a multiplex platform, and whole blood 16s rRNA sequencing was performedusing Illumina MiSeq. Fecal samples were obtained on d 0, 16, and 32 via rectal palpation before the morning meal and at h 8, 16, and 24 post meal. Fecal pH was determined using a portable pH meter and fecal starch was measured via concentration analysis. Data were analyzed using PROC MIXED of SAS v9.4. Non-normal data (CCL2) were log-transformed. From d 0 to 32 BW increased (P ≤ 0.01), independent of treatment, with no change in BCS (P = 0.97). Fecal starch was undetectable indicating nearly complete digestion of dietary starch regardless of treatment. On d 0, fecal pH declined to h 16 (P ≤ 0.01) in both groups and returned to baseline by h 24 post meal. At h 0, CON had lower fecal pH on d 32 than d 0 (P ≤ 0.01). D-lactate peaked at h 8 on d 0, and CON was greater (P ≤ 0.01) than TRT. On d 32, D-lactate tended to be higher in TRT (P = 0.10) at 16 h post meal compared with CON. LogCCL2 and TNFα declined (P ≤ 0.02) across treatments to d 32. Fold change of percent reads from d 0 in bacterial 16s rRNA was not different between treatment groups. A high starch diet initially reduced fecal pH and increased BW but after 32 d, there was no difference in intestinal inflammation or gut permeability, regardless of SC supplementation.

16 Comparison of the cecal and fecal microbiome in horses administered antibiotics over a 16 d period

Antibiotic administration to horses has been shown to potentially result in diarrhea or colitis due to the disruption of the gastrointestinal microbiome (i.e., dysbiosis). This study aimed to evaluate the effects of an antibiotic challenge on the cecal and fecal microbiome. It was hypothesized that an antibiotic challenge would reduce the microbial diversity and increase the abundance of opportunistic pathogens in the microbiome of healthy horses. Ten mature horses consisting of both Thoroughbred and Quarter Horse breeds (cecally cannulated, n = 5; non-cannulated, n = 5) were housed in partially covered dry lots and fed twice daily at 0700 and 1500 in individual stalls. Rations consisted of 4.54 kg of Purina® Strategy GX® (CP = 14.24%, Ca = 1.20%, P = 0.70%) and Standlee® Timothy hay (CP = 14.6%, Ca = 0.60%, P = 0.30%) fed at 2.0% BW. All horses were administered trimethoprim sulfa (SMZ) at 30 mg/kg BW twice daily during both feedings over a 16-d period. Cecal fluid (cannulated horses only) and fecal samples were collected and stored at −80°C on d 1 (before challenge), 7, 14, and 16. Bacterial DNA was extracted using the Quick-DNA Fecal/Soil Microbe Miniprep kit (Zymo Research, Irvine, CA) and the V3-V4 region of the 16S rRNA gene was sequenced using the Illumina 16S Protocol (San Diego, CA). Differences between sample type and day for β diversity using Principal component analysis onBray-Curtis distance and α diversity (Shannon's Index) were statistically analyzed using PERMANOVA and Kruskal-Wallis, respectively. A P-value ≤0.05 was considered significant. Beta diversity (community composition) differed significantly between sample types (R2 = 0.21, P = 0.001). Alpha diversity (richness and evenness) of the cecal microbiome decreased from 4.84 ± 0.26 (±SEM) on d 1 to 4.10 ± 0.12 on d 7 and then returned close to d 1 values by d 15 and d 16 (P < 0.05). The fecal microbiome followed a similar pattern by decreasing in diversity from 5.19 ± 0.13 on d 1 to 5.09 ± 0.20 on d 14 and then returning close to d 1 values by d 16 (P < 0.05). The relative abundances of 2 genera, containing opportunistic pathogens, Sarcina and Shigella numerically increased across time in both sample types. Results suggest that the fecal microbiome may not be fully representative of the cecal microbiome, agreeing with current literature. However, the patterns in the fecal microbiome observed in the present study reflected the changes in the cecum resulting from SMZ administration. These results indicate the potential utility of fecal samples as a non-invasive marker of significant microbial alterations in the hindgut.

Evaluation of an Oral Supplemental Cannabidiol Product for Acceptability and Performance in Mature Horses.

Thirty stock type geldings (15 ± 3 years; 556 ± 63 kg BW) were used in a randomized complete design over 28 days to determine the influence of cannabidiol (CBD) oil supplementation levels on body weight, body condition, and blood chemistry. Horses were randomly assigned to one of three dietary treatments (n = 10 per treatment) formulated with canola oil to provide 1.50 mg CBD/kg BW (TRTA), 0.75 mg CBD/kg BW (TRTB), or 0.00 mg CBD/kg BW (canola oil; CTRL). Treatments were top-dressed onto concentrate and individually administered twice daily. Horses were maintained in adjacent dry lots and received coastal bermudagrass hay ad libitum. Body weight and body condition scores (BCS) were obtained every 14 days. On day 0 and 28, blood was collected via jugular venipuncture and serum was harvested to perform a blood chemistry panel and drugs of abuse screening at the Texas Veterinary Medical Diagnostic Laboratory. Data were analyzed using PROC MIXED of SAS (v9.4), and the model included treatment, time, and the treatment × time interaction, and linear and quadratic orthogonal polynomial contrasts to partition sum of squares. Analysis of composited treatment samples revealed lower CBD concentrations than indicated from initial testing by the manufacturer (0.13 mg CBD/kg in TRTA; 0.12 mg CBD/kg in TRTB). At this level of supplementation, canola-based CBD oil was well-accepted by mature horses, banned substances were not detectable in blood, and blood chemistry parameters were not adversely affected as a result of supplementation. More research is warranted to describe the discrepancy between formulated levels compared to tested levels of CBD in the canola-based supplement.

Rumen Fluid Amine/Phenol-Metabolome of Beef Steers with Divergent Residual Feed Intake Phenotype

The amine/phenol-metabolome of rumen fluid was analyzed to identify amino acid metabolism-related biomarkers associated with phenotypic selection for low or high residual feed intake (RFI) in beef cattle. Fourteen beef steers (most feed-efficient (HFE; RFI = −1.89 kg/d, n = 7) and least feed-efficient (LFE; RFI = +2.05 kg/d, n = 7)) were selected from a total of 56 crossbred growing beef steers (average BW = 261 ± 18.5 kg) after a 49-d feeding period in a dry lot equipped with two GrowSafe intake nodes. Rumen fluid samples were collected 4 h after feeding on d 56, 63, and 70 from the HFE and LFE beef steers. Metabolome analysis of the rumen fluid was performed using chemical isotope labeling/liquid chromatography-mass spectrometry to identify all metabolites containing amine/phenol chemical groups, which are mostly amino acid metabolites. A total of 493 metabolites were detected and identified in the rumen fluid. The partial least squares discriminant scores plot showed a slight separation between the two groups of steers, and a total of eight metabolites were found to be differentially abundant (FDR ≤ 0.05). Out of the eight differentially abundant metabolites, four metabolites (isomer 1 of cadaverine, baeocystin, 6-methyladenine, and N(6)-methyllysine) qualified as candidate biomarkers of divergent RFI phenotype based on area under the curve ≥ 0.70. The results of this study revealed that divergent RFI phenotype is associated with alteration in rumen amine/phenol-metabolome of beef steers.

The differential plasma and ruminal metabolic pathways and ruminal bacterial taxa associated with divergent residual body weight gain phenotype in crossbred beef steers

Abstract We applied ruminal and plasma metabolomics and ruminal 16S rRNA gene sequencing to determine the metabolic pathways and ruminal bacterial taxa associated with divergent residual body weight gain phenotype in crossbred beef steers. A group of 108 crossbred growing beef steers (average BW = 282.87 ± 30 kg) were fed a forage-based diet for a period of 56 d in a confinement dry lot equipped with GrowSafe intake nodes to determine their residual body weight gain (RADG) phenotype. After RADG identification, blood and rumen fluid samples were collected from beef steers with the highest RADG (most efficient; n = 16; 0.76 kg/d) and lowest RADG (least efficient; n = 16; −0.65 kg/d). Quantitative untargeted metabolome analysis of the plasma and rumen fluid samples were conducted using chemical isotope labelling/liquid chromatography–mass spectrometry. Differentially abundant metabolites in each of the plasma and rumen fluid samples between the two groups of beef steers were determined using a false discovery rate (FDR)-adjusted P-values ≤ 0.05 and area under the curve (AUC) &amp;gt; 0.80. Rumen and plasma metabolic pathways that were differentially enriched or depleted (P ≤ 0.05) in beef steers with positive RADG compared to those with negative RADG were determined by the quantitative pathway enrichment analysis. A total of 1,629 metabolites were detected and identified in the plasma of the beef steers; eight metabolites including alanyl-phenylalanine, 8-hydroxyguanosine, and slaframine were differentially abundant (FDR ≤ 0.05; AUC &amp;gt; 0.80) in beef steers with divergent RADG; five metabolic pathways including steroid hormone biosynthesis, thiamine metabolism, propanoate metabolism, pentose phosphate pathway, and butanoate metabolism were enriched (P ≤ 0.05) in beef steers with positive RADG, relative to negative RADG steers. A total of 1,908 metabolites were detected and identified in the rumen of the beef steers; results of the pathway enrichment analysis of all the metabolites revealed no metabolic pathways in the rumen were altered (P &amp;gt; 0.05). The rumen fluid samples were also analyzed using 16S rRNA gene sequencing to assess the bacterial community composition. We compared the rumen bacterial community composition at the genus level using a linear discriminant analysis effect size (LEfSe) to identify the differentially abundant taxa between the two groups of beef steers. The LEfSe results showed greater relative abundance of Bacteroidetes_vadinHA17 and Anaerovibrio in steers with positive RADG compared to the negative RADG group, while steers in the negative RADG group had greater relative abundance of Candidatus_Amoebophilus, Clostridium_sensu_stricto_1, Pseudomonas, Empedobacter, Enterobacter, and Klebsiella compared to the positive RADG group. Our results demonstrate that beef steers with positive or negative RADG exhibit differences in plasma metabolic profiles and some ruminal bacterial taxa which probably explain their divergent feed efficiency phenotypes.

PSI-6 The Influence of a Single Administration of Prostaglandin on Estrus Synchronization in Range Sheep Production

Abstract Administration of a single injection of prostaglandin after ram introduction has previously been reported as an effective method to synchronize estrus in ewes housed in a dry lot setting. The objective of this study was to investigate the effectiveness of a single injection of prostaglandin administered at the beginning of the breeding season after ram introduction, on estrus synchronization in range ewes. Western Whiteface cross ewes, of which thirty-six were ½ blood South African Meat Merino (SAMM) and seventeen ¼ blood SAMM (total n=53) were assigned to one of two treatments: control (CON; n=26) or one injection of prostaglandin (PG; n=27). Ewes were utilized in a complete randomized block design and were stratified by SAMM percentage, body condition score (BCS) and age. Ewes assigned to PG treatment were administered 3 mL of prostaglandin IM (Lutalyse, Zoetis Animal Health) approximately 60 h after rams were introduced with ewes. Rams (n=4) were applied with marking paint and placed with ewes on (d 0: December 21) and remained for the duration of the 56 d breeding season for natural service. Ewes were observed for estrus twice daily at 0730 h and 1700 h for d 0-10 and d 16-21 of the breeding season, by an experienced evaluator. At lambing, birth weight, sex, and type of birth was recorded. The MIXED and GLIMMIX procedures of SAS were used to analyze estrus response, ewes bred in the first 5 d of the breeding season, days to lambing, lambing date, number of lambs born, and lamb weight. South African Meat Merino percentage was included as an independent variable but was found to be nonsignificant and was removed from the statistical model. The proportion of ewes bred during the first 5 d of the breeding season was not different among the two treatments (P ≥ 0.60). There was no difference between the PG ewes and the CON ewes for the date of estrus (P ≥ 0.82). There was no difference between the PG ewes and the CON ewes for the lambing date (P = 0.60). Treatment did not influence days to lambing (P ≥ 0.25). The number of lambs born per ewe tended to be influenced by treatment (P &amp;lt; 0.08), with PG ewes tending to have more lambs than CON ewes. Lamb weights were not different among treatments (P ≥ 0.50). In conclusion, the administration of a single PG injection after ram exposure did not influence estrus expression, days to lambing, or lambing date, however, PG ewes did tend to have more lambs.

Dietary fenugreek seed extract improves dry matter intake, apparent total tract nutrient digestibility, and alters whole blood transcriptome of Holstein dairy heifers.

This study was conducted to evaluate the effects of dietary supplementation of a fenugreek seed extract (SAP) as a source of saponins on dry matter intake, blood metabolites, apparent total tract nutrient digestibility, and whole blood transcriptome of Holstein dairy heifers. Eight heifers (BW = 477 ± 23.8 kg) were stratified by BW and then randomly assigned to one of two treatments in a cross-over design with two 35-d experimental periods and a 14-d wash-out between the two periods. The heifers were housed individually in eight dry lot pens. Each pen was equipped with one GrowSafe intake node. Treatments were 1) corn silage-based diet with no additive (CON) and 2) corn silage-based diet plus 2 g per hd per d of SAP. Dairy heifers fed supplemental SAP had higher (P ≤ 0.05) DMI and apparent total tract digestibility of dry matter, crude protein, and neutral detergent fiber compared to CON. Dairy heifers fed supplemental SAP had lower (P = 0.03) blood urea nitrogen and higher (P = 0.01) blood glucose concentration compared to CON. Pathway analysis via gene set enrichment analysis revealed increased (FDR ≤ 0.05) transcript levels for gene sets belonging to ISG15 antiviral mechanism, metabolism of proteins, citric acid cycle and respiratory electron transport, ATP synthesis by chemiosmotic coupling, and complex I biogenesis in dairy heifers fed supplemental SAP compared to CON. Decreased (FDR ≤ 0.05) transcript levels for gene sets associated with erythrocytes take up/release carbon dioxide, release/take up oxygen, and O2/CO2 exchange in erythrocytes were also observed with SAP supplemental group. Taken together, our results revealed that fenugreek seed extract can be used as an effective dietary supplement for dairy heifers to improve intake and digestibility, and alter the host transcriptome toward improved energy and amino acid metabolism, improved antiviral immune status, and reduced oxidative stress damage.

PSIV-B-17 Effects of Weaning Method on Performance of Crossbred Beef Calves

Abstract English cross beef calves (n=115; BW = 245 + 40 kg) were used in the first of a three-year project to examine the effects of three weaning systems on post weaning performance. Cattle were stratified by age of dam and assigned to: 1) Drylot (DRY), 2) Pasture (PAST) or 3) Fenceline (FEN) weaning system. Calves in DRY were physically separated from their dams and fed a mixed ration across 4 pens. Calves in PAST were physically separated from their dams and assigned to 2 pastures consisting of Bermudagrass and fed a supplement. Calves in FEN were separated from their dams in adjacent pastures (n = 2) but maintained nose contact with their dams and fed a supplement. Pasture analysis from PAST and FEN were used to calculate the amount of supplement, so that total NE would be similar to that fed to DRY. Cattle were weighed weekly, until d 28, then weighed on d 56. Pen/pasture were the experimental unit, animal within pen was the random effect, data were analyzed using PROC Mixed. No differences (P &amp;gt; 0.10) were noted with BW at d 0, 7 or 28; however, both FEN and PAST had greater BW at d 15 (P = 0.05) and tended to have greater BW at d 21 (P = 0.06); nevertheless, by d 56, DRY had greater BW compared with FEN and PAST (P=0.03). Similarly, ADG tended to be greater in FEN and PAST from d 0-14 (P= 0.06) and from d 0-21 (P = 0.07). Overall ADG from d 0-56 was greater for DRY compared with PAST and FEN (P = 0.03). By design, cattle in DRY had more measurable DMI compared with PAST and FEN at all points (P &amp;lt; 0.0004). Cost of gain was greater (P= 0.02) with more economical gain associated with FEN and PAST compared with DRY (P = 0.02).

364 Comparison of Semi-Confined and Pasture-Based Fall Calving Beef cow Systems

Abstract Conversion of perennial grasslands to crop land in U.S. Northern Plains has resulted in a need to evaluate alternative management strategies for cow-calf production. A 3-yr study was conducted to compare beef cow/calf performance in two different August-calving cow systems. Multiparous beef cows (n = 318) were allocated to 8 replicates, and replicate was randomly assigned to drylot (DL) or pasture (PAST) treatments. From mid-gestation (March/April) until breeding (October), DL cows were limit-fed to meet requirements and PAST cow grazed perennial pasture. Feed resource during the 47-d breeding period (November/December) varied by year and treatment. However, pregnancy rates did not differ (P=0.72) between treatments within year. Both treatments went to corn residue at the time of weaning (late January) and grazed for 37 d. A treatment × year × time interaction (P&amp;lt;0.01) was observed for cow BW, BCS, and calf BW. In Year 1, cow BCS at pre-calving, breeding, and weaning was less (P&amp;lt;0.01) for DL (5.3) than PAST (6.2; 1 to 9 scale). Weaning weights in Year 1 were less (P&amp;lt;0.05) for DL (178 kg) than PAST (183 kg) calves. In Year 2, cow BCS was less (P&amp;lt;0.01) in DL (6.1) than PAST (6.7) at pre-calving and breeding, but did not differ (P=0.12) at weaning. At weaning in Year 2, calf BW of DL (212 kg) was greater (P&amp;lt;0.01) than PAST (201 kg). Like Year 2, DL cows in Year 3 had decreased (P&amp;lt;0.01) BCS at pre-calving compared with PAST (7.3 vs. 7.7). However, breeding BCS (6.8) did not differ (P=0.98). In Year 3, cow BCS at weaning was greater (P&amp;lt;0.01) for DL (7.1) than PAST (5.9) but calf BW at weaning did not differ (P=0.17). Cow and calf performance are not sacrificed in semi-confined cow-calf systems and are a reasonable alternative to traditional pasture systems.

146 Effect of Short-Term Nutritional Increase 30 Days Prior to Artificial Insemination on ADG and Reproductive Efficiency in Beef Heifer Development Systems

Abstract The objective of this study was to determine if increasing nutrition 30d before AI would optimize overall heifer pregnancy rates. Angus crossbred heifers were used in a 3-yr study (n=100/yr) at the West Central Research and Extension Center, North Platte, NE. Heifers were blocked by BW and randomly assigned to 1 of 3 groups for the winter period (average 131±3.5d/yr): upland range (RANGE), dry lot low (DLLO), or dry lot high (DLHI). The same diet was offered to DLLO and DLHI until 30d prior to AI, where DLHI received increased nutrients. Heifers developed on RANGE grazed winter range with 0.45kg/d 30%CP cake until the treatment period where they received DLLO diet. Heifer ADG in DLLO (0.64±0.06kg) and DLHI (0.64±0.06kg) was greater (P=0.02) than RANGE (0.25±0.06kg) during the development period, but no differences were seen in ADG during the 30d treatment period between DLHI (1.12±0.13kg), DLLO (0.75±0.13kg), and RANGE (0.67±0.13kg). Heifers were synchronized with melengestrol acetate at 0.5 mg per head per d for 14d, and PGF2a given 19d later. Heifers were either bred on detected estrus or placed with bulls after 5d. All heifers were placed with bulls 10d following AI. Pre-breeding BWs were greater (P=0.0004) for DLHI (375.44±3.39kg) and DLLO (363.5±3.39kg) compared to RANGE (311.8±3.35kg.), but breeding ADG, between pre-breeding and first pregnancy diagnosis, was greater (P=0.0002) for RANGE (0.68±0.01kg) compared to DLHI (0.35±0.02kg) and DLLO (0.37±0.02kg). While pregnancy rates to AI were not different (P=0.43), final pregnancy rates tended to be greater (P=0.09) for DLHI (96%) and DLLO (95%) compared to RANGE (84%). No differences were observed in calving rate or heifers calving in the first 21d. While greater nutrition for DLHI and DLLO heifers led to higher BW, and tended to increase final pregnancy rates, overall short-term nutritional change had no detectable impact on AI conception.

PSIX-1 Predicting Beef Cattle dry Matter Intake

Abstract As increasing climate variability continues to strain agricultural production, priorities must be aligned with methods to maintain or improve current production processes, including advanced, technology-based methods of measuring individual feed and water intakes and increasing water use efficiency in cattle. A total of 745 animals were evaluated in eight test groups from 11/25/19 to 9/2/21 in a dry lot equipped with In-Pen Weighing Positions and Feed and Water-Intake Nodes. Relationships among average daily gain (ADG), dry matter intake (DMI), residual feed intake (RFI), water intake (WI), residual water intake (RWI), animal performance variables, and environmental variables at the individual animal level were investigated on a first test group of Angus bulls (n = 125) and crossbred steers (n = 53). Root mean square error (RMSE) was used as a measure of error between model-predicted and observed DMI. Random Forest (RF) analysis predicted the daily DMI, with RMSE 0.92 kg for bulls and 0.85 kg for steers. When performance measures were averaged across the entire test period, the RMSE using RF were 0.39 and 0.34 kg DMI for bulls and steers, respectively. Repeated measures Analysis of Variance (RM ANOVA) was used with the same set of predictive variables as in RF. DMI was strongly related to body weight, WI, short wave radiation (MJ), and relative humidity (%; all p&amp;lt; 0.0001). RM ANOVA predicted the daily DMI with (RMSE) 1.5 kg for bulls and 1.41 kg for steers and 0.75 and 0.61 kg DMI for bulls and steers across the entire testing period. Study results identify relationships between DMI, WI and other growth metrics in a dry lot, which must be explored in pasture to identify biomarkers of feed and water efficiency in cattle to improve sustainability of beef production in grazing systems.

325 Candidate Plasma Biomarkers Associated with Residual Feed Intake in Beef Steers

Abstract We applied chemical group-based metabolomics to identify blood metabolic signatures associated with residual feed intake in beef cattle. A group of 56 crossbred growing beef steers (average BW = 261 ± 18.5 kg) were adapted to a high-forage total mixed ration in a confinement dry lot equipped with GrowSafe intake nodes for period of 49 d to determine their residual feed intake (RFI) classification. After RFI determination, weekly blood samples were collected three times from beef steers with the least RFI [most efficient (HFE); n = 8; RFI = - 1.93 kg/d] and greatest RFI [least efficient (LFE); n = 8; 2.01 kg/d]. Plasma was prepared by centrifugation and composited for each steer. Metabolome analysis was conducted using a chemical isotope labeling (CIL)/liquid chromatography–mass spectrometry. Analyzed metabolites included those containing amine/phenol-, carboxylic acid-, and carbonyl-chemical groups, which are metabolites associated with metabolism of amino acids, fatty acids, and carbohydrates, respectively. A total number of 495 amine/phenol-containing metabolites were detected and identified; pathway analysis of all these metabolites showed that arginine biosynthesis and histidine metabolism were enriched (P &amp;lt; 0.10) in HFE, relative to LFE steers. Biomarker analysis of the amine/phenol-metabolome identified methionine, 5-aminopentanoic acid, 2-aminohexanedioic acid, and 4-chlorolysine as candidate biomarkers of RFI [false discovery rate ≤ 0.05; Area Under the Curve (AUC) &amp;gt; 0.90]. A total of 118 and 330 metabolites containing carbonyl- and carboxylic acid-chemical groups, respectively, were detected and identified; no metabolic pathways associated with these metabolites were altered and only one candidate biomarker (methionine sulfoxide) was identified. These results identified five candidate metabolite biomarkers of RFI in beef cattle which are mostly associated with amino acid metabolism. Further validation using a larger cohort of beef cattle of different genetic pedigree is required to confirm these findings.

PSIV-B-19 Determining the Effect of Zinc Status on eye Health and its Relationship with Infectious Bovine Keratoconjunctivitis in Beef Calves

Abstract Crossbred beef calves (n = 30) were stratified by gender and BW and placed into 1 of 16 dry lot pens. Pens were allocated to either: 1) the control treatment (CON) with calves fed a basal ration containing 31 mg of zinc/kg DM; or 2) Zn supplemented treatment (SUP) with calves fed the basal ration supplemented with 30 mg of zinc/kg DM (provided as zinc amino acid complex). Growth performance was recorded every 28-d during the 143-d study. On d 115, cattle were given a commercial vaccine containing M. bovis and M. bovoculi bacterins. Blood samples were collected and analyzed for serum zinc, alkaline phosphatase activity (ALP, 28-d intervals), and vitamin A (d 0 and 143). Samples for serum and tear IgG concentrations specific for M. bovis and M. bovoculi were taken on d 115, 129, and 143. Data were analyzed as repeated measures, where appropriate, using the MIXED procedure of SAS. Dietary zinc status did not impact liver or zinc concentrations (P ≥ 0.36), BW (P ≥ 0.66) or ADG (P ≥ 0.14). There was no effect of treatment (P ≥ 0.16) or treatment by time interaction (P &amp;gt; 0.39) on tear IgG specific for either M. bovis or M. bovoculi. However, serum IgG concentrations specific for M. bovis were greater (P = 0.02) in CON calves compared with SUP calves, and serum IgG concentrations specific for M. bovoculi tended (treatment by time, P = 0.08) to increase more in CON calves. Both serum and tear IgG concentrations specific for either bacterin increased (day effect, P &amp;lt; 0.001) from d 115 to 143. Results did not support a relationship between dietary Zn and eye health in cattle. However, this could be explained by the similarity in liver and serum zinc concentrations.

Long-term evaluation of bale grazing as a winter-feeding system for beef cattle in central North Dakota

A 4-yr study was conducted to evaluate bale grazing as a winter-feeding system under central North Dakota winter conditions. Two winter-feeding systems, bale grazing (BG) paddocks or dry lot (DL) pen feeding, were compared over 4 winters using nonlactating pregnant Angus cows (2016/2017, n = 32, average BW = 590 ± 69 kg; 2017/2018, n = 40, 609 ± 61 kg; 2018/2019, n = 40, 635 ± 49 kg; 2019/2020, n = 40, 620 ± 31 kg). Cows in each winter-feeding system were offered the same hay. Cow performance was assessed from BW and BCS taken at the start and end of the study. Environmental conditions varied widely during the 4-yr study period. Dry matter intake averaged 11.9 kg/d and was not affected ( P = 0.66) by winter-feeding system. Cows in both winter-feeding systems lost weight but ADG was greater ( P = 0.02) in BG cows (−0.11 kg/d) relative to DL cows (−0.23 kg/d). Similarly, BCS loss was greater ( P = 0.01) in DL cows (−0.21) relative to BG cows (−0.08). System costs were lower ($1.75/cow per day) following BG relative to DL pen feeding ($2.12/cow per day). Results of this study suggest that bale grazing is a viable system for winter-feeding beef cattle in North Dakota. Greater animal performance during bale grazing coupled with the lower cost of bale grazing could improve profitability of a beef cow-calf production operation.

Identification of Key Pathways Associated With Residual Feed Intake of Beef Cattle Based on Whole Blood Transcriptome Data Analyzed Using Gene Set Enrichment Analysis.

We applied whole blood transcriptome analysis and gene set enrichment analysis to identify pathways associated with divergent selection for low or high RFI in beef cattle. A group of 56 crossbred beef steers (average BW = 261 ± 18.5 kg) were adapted to a high-forage total mixed ration in a confinement dry lot equipped with GrowSafe intake nodes for period of 49 d to determine their residual feed intake (RFI). After RFI determination, whole blood samples were collected from beef steers with the lowest RFI (most efficient; low-RFI; n = 8) and highest RFI (least efficient; high-RFI; n = 8). Prior to RNA extraction, whole blood samples collected were composited for each steer. Sequencing was performed on an Illumina NextSeq2000 equipped with a P3 flow. Gene set enrichment analysis (GSEA) was used to analyze differentially expressed gene sets and pathways between the two groups of steers. Results of GSEA revealed pathways associated with metabolism of proteins, cellular responses to external stimuli, stress, and heat stress were differentially inhibited (false discovery rate (FDR) < 0.05) in high-RFI compared to low-RFI beef cattle, while pathways associated with binding and uptake of ligands by scavenger receptors, scavenging of heme from plasma, and erythrocytes release/take up oxygen were differentially enriched (FDR < 0.05) in high-RFI, relative to low-RFI beef cattle. Taken together, our results revealed that beef steers divergently selected for low or high RFI revealed differential expressions of genes related to protein metabolism and stress responsiveness.

Microbiome network traits in the rumen predict average daily gain in beef cattle under different backgrounding systems

BackgroundBackgrounding (BKG), the stage between weaning and finishing, significantly impacts feedlot performance in beef cattle; however, the contributions of the rumen microbiome to this growth stage remain unexplored. A longitudinal study was designed to assess how BKG affects rumen bacterial communities and average daily gain (ADG) in beef cattle. At weaning, 38 calves were randomly assigned to three BKG systems for 55 days (d): a high roughage diet within a dry lot (DL, n = 13); annual cover crop within a strip plot (CC, n = 13); and perennial pasture vegetation within rotational paddocks (PP, n = 12), as before weaning. After BKG, all calves were placed in a feedlot for 142 d and finished with a high energy ration. Calves were weighed periodically from weaning to finishing to determine ADG. Rumen bacterial communities were profiled by collecting fluid samples via oral probe and sequencing the V4 region of the 16S rRNA bacterial gene, at weaning, during BKG and finishing.ResultsRumen bacterial communities diverged drastically among calves once they were placed in each BKG system, including sharp decreases in alpha diversity for CC and DL calves only (P < 0.001). During BKG, DL calves showed a substantial increase of Proteobacteria (Succinivibrionaceae family) (P < 0.001), which also corresponded with greater ADG (P < 0.05). At the finishing stage, Proteobacteria bloomed for all calves, with no previous alpha or beta diversity differences being retained between groups. However, at finishing, PP calves showed a compensatory ADG, particularly greater than that in calves coming from DL BKG (P = 0.02). Microbiome network traits such as lower average shortest path length, and increased neighbor connectivity, degree, number and strength of bacterial interactions between rumen bacteria better predicted ADG during BKG and finishing than variation in specific taxonomic profiles.ConclusionsBacterial co-abundance interactions, as measured by network theory approaches, better predicted growth performance in beef cattle during BKG and finishing, than the abundance of specific taxa. These findings underscore the importance of early post weaning stages as potential targets for feeding interventions that can enhance metabolic interactions between rumen bacteria, to increase productive performance in beef cattle.

9 Evaluating the Utility of Individual Cattle Brush Use Behavior as a Novel Behavioral Phenotype Regarding Productivity, Temperament, and Feeding Behavior of Bos Indicus Steers and Heifers Housed in Dry Lots

Abstract Little is understood about the relationships among environmental enrichment, temperament, productivity, and feeding behavior in cattle. The objective of this study was to examine the effect of divergent behavioral phenotypes for brush usage on temperament, productivity, and feeding behavior patterns in beef cattle. Four pens of Brahman cattle (n = 2 pens with 15 heifers/pen, and n = 2 pens with 19 steers/pen) were housed in dry lots each equipped with four electronic feedbunks (GrowSafe Systems). Animals were video recorded throughout an 85d commercial gain test. Video recordings were decoded on d 1, 2, 4, 8, 16, 32, and 64 using continuous observations for 15 minutes every 30 minutes from 08:00 to 20:00 to determine the total daily brush usage for focal animals that were selected based on d -19 exit velocities. Exit velocity and body weight were measured on d -19, 0, 1, 25, 50, and 70 and feeding behavior was monitored daily using the GrowSafe 4000E system. Animals were classified within gender into one of three phenotypes (high, medium, and low brush usage) based on ±0.5SD from the brush usage mean. A General Linear Mixed Model (PROC GLIMMIX) with brush use phenotype, sex and the interaction of these as fixed effects and pen as random effect was used for data analysis. For high and medium brush use phenotypes, steers had greater final BW than heifers (P = 0.0005), while heifer and steer final body weight did not differ when brush usage was low. High brush use steers had greater ADG (P = 0.0002) than high and medium brush use heifers, and low brush use steers and heifers. This same pattern was observed for DMI (P = 0.0003). Heifers were more temperamental than steers (P = 0.0008), and high and medium brush use heifers had faster exit velocities than low brush use steers. These results suggest that monitoring animal’s pleasurable behavior (brush use), rather than fear response alone, may be a useful behavioral indicator of cattle productivity.