Feedlot Heifers Research Articles

PSVI-16 An evaluation using a visual health scoring system with vaginal temperatures of newly received feedlot heifers on immune status

PSVI-16 An evaluation using a visual health scoring system with vaginal temperatures of newly received feedlot heifers on immune status

Effect of palm kernel cake inclusion on intake, digestibility, nitrogen balance, feeding behavior, and weight gain of feedlot heifers

Effect of palm kernel cake inclusion on intake, digestibility, nitrogen balance, feeding behavior, and weight gain of feedlot heifers

Cattle Feeding Benchmark Data: Fall & Winter 2022 Spring & Summer 2023

A summary of closeouts from the fall of 2022 through the summer of 2023 is provided on feedlot heifers, steers, mixed pens and preconditioning cattle.

Cattle Feeding Benchmark Data: Fall & Winter 2021 Spring & Summer 2022

A summary of closeouts from the fall of 2021 through the summer of 2022 is provided on feedlot heifers, steers, mixed pens and preconditioning cattle.

Effects of parenteral or intranasal modified-live virus respiratory vaccination and revaccination on day 14 in auction-derived feedlot heifers

Auction-derived beef heifers were received in 12 arrival blocks and randomized to 4 treatment groups: 1) parenteral MLV vacci­nation on d 0 (INJ), 2) intranasal MLV vaccination on d 0 (INT), 3) parenteral MLV vaccination on d 0 and revaccination with intranasal on d 14 (INJ-R), 4) intranasal MLV vaccination on d 0 and revaccination with intranasal on d 14 (INT-R). Pen was experimental unit, with 12 pens/treatment and 65 to 76 heif­ers/pen in a randomized complete block design. Performance, health, carcass traits and BRSV and H. somni frequency of car­riage in the nasopharynx of revaccinated groups on d 0 and 60 was determined. Morbidity (P = 0.95), mortal­ity (P = 0.80), and other health variables (P > 0.74) did not dif­fer. However, an improvement in gain-to-feed (G:F) (P = 0.04), increased ribeye area (REA) (P ≤ 0.01) and percentage of edible livers (P ≤ 0.01) was observed for INJ and INJ-R. The BRSV (P = 0.09) and H. somni (P < 0.01) frequency of carriage in the naso­pharynx increased with time but no treatment effect (P ≥ 0.23) nor treatment x day interaction (P ≥ 0.29) existed. Revaccina­tion with an intranasal MLV did not impact health or growth, and arrival intranasal vaccination (INT and INT-R) resulted in less G:F and REA concomitant with increased liver absces­sation, compared to parenteral (INJ and INJ-R). Detection of H. somni in the nasopharynx was frequent on d 60, suggesting important prevalence of this bacterial pathogen in the south­ern U.S. cattle population.

Impacts of economic factors influencing net returns of beef feedlot heifers administered two implant programs and fed for differing days-on-feed from pooled randomized controlled trials.

The objective of this research was to evaluate the effects of two implant programs and differing days-on-feed (DOF) on net returns of beef feedlot heifers using sensitivity analyses of key economic factors. Crossbred beef heifers [n = 10,583; initial weight 315kg (± 20.1 SD)] were enrolled across three trials (one Kansas, two Texas feedlot trials). Heifers were blocked by arrival and randomly allocated to one of six pens, resulting in a total of 144 pens and 24 blocks. Pen was randomly assigned to treatment as a 2 × 3 factorial. Implant programs were: IH + 200-Revalor-IH at initial processing, and a terminal implant after approximately 90 DOF (Revalor-200), or, XH-a single implant at initial processing (Revalor-XH). The DOF treatments were: heifers fed to a standard baseline endpoint (BASE) or heifers fed for an additional + 21 or + 42 d beyond BASE. Pen-level partial budgets were used for economic sensitivity analyses, which varied price points of single pricing components with all other components fixed. Variable components were live-fed cattle prices, base carcass prices (i.e., dressed), Choice-Select spread (CS-spread), and feed and yardage prices (FYP). For each, a Low, Mid-Low, Middle, Mid-High, and High price was chosen. Linear mixed models were fit for statistical analyses (α = 0.05). There were no significant two-way interactions (P-values ≥ 0.14). Regardless of the variable component evaluated, XH heifers had poorer net returns than IH + 200 at all prices (P ≤ 0.04). Selling live, the + 21 and (or) + 42 heifers had lower net returns than BASE at every fed cattle price point (P < 0.01). Selling dressed, the + 21 and (or) + 42 heifers had lower returns than BASE at Low, Mid-Low, and Middle fed cattle base prices (P < 0.01); there were no significant DOF differences at Mid-High, or High prices (P ≥ 0.24). Net returns were lower for + 42 than BASE at all CS-spreads (P ≤ 0.03), while BASE and + 21 did not differ significantly. Longer DOF had lower net returns than BASE when selling live at every FYP (P < 0.01) except at the Low price (P = 0.14). Selling dressed, there was no significant effect of DOF at Low or Mid-Low FYP (P ≥ 0.11); conversely, extended DOF had lower net returns than BASE at Middle, Mid-High, and High FYP (P < 0.01). Overall, there was minimal economic evidence to support extending feedlot heifer DOF beyond the BASE endpoint, and when feeding longer, larger reductions in return were observed when marketing live as opposed to dressed.

Nutritional and productive performance of purebred Nellore heifers and crossed with Brangus and Braford finished in a feedlot system.

This study evaluated the nutritional and productive performance of Nellore purebred heifers and crossbred Brangus x Nellore (BGNE) and Braford x Nellore (BFNE) in a feedlot system. Thirty heifers (10 of each genetic group) with an average age of 18 months and an initial body weight of 261 kg were used. The experiment was structured and conducted according to a completely randomized design, with three treatments. Heifers received two diets (60 days each) during the experimental period. The experiment lasted 120 days with four experimental periods. Nellore heifers had a lower intake than crossbred heifers (P <0.05). There were no differences between BGNE and BFNE heifers, which had higher final body weight, average daily gain, feed efficiency, hot carcass weight and carcass length than NE heifers. Crossed heifers presented better fat cover than NE heifers. However, NE heifers had higher carcass dressing Despite presenting lower carcass yields than Nellore heifers, crossed heifers are more efficient and have higher performance and better fat cover on the carcass than purebred Nellore heifers. Crossbreeding synthetic breeds, such as Brangus and Braford breeds, with the Nellore breed is an effective way to increase the productivity and efficiency of feedlot heifers in tropical regions.

Effects of intranasal or parenteral respiratory vaccination administered on-arrival or delayed in auction-derived feedlot heifers

The objective was to evaluate health, performance and serum antibody responses of auction-derived heifers to an intranasal or parenteral MLV administered on d 0 or 28. Three arrival blocks of heifers, initial BW = 459 lb ± 1.7 lb (208 kg ± 27kg; n = 600), were randomly assigned to treatments consisting of 15 pens/treatment with pen as the experimental unit and 10 heifers/pen. Treatments were: 1) Bovilis® Nasalgen® 3 and Bovilis® Vista® BVD on d 0 (NAS0); 2) Bovilis® Vista® 5 SQ on d 0 (VIS0); 3) Bovilis® Nasalgen® 3 and Bovilis® Vista® BVD on d 28 (NAS28); 4) Bovilis® Vista® 5 SQ on d 28 (VIS28). Body weight and blood samples were collected on d 0, 28 and 56. Activity (351.4 vs 354.3 min/d) and rumination time (282.6 vs 285.4 min/d) was less (P &lt; 0.01) for delayed vs arrival vaccinated heifers. A timing χ vaccine χ day interaction existed (P &lt; 0.01) for BRSV- and IBRV-specific antibody titers; VIS28 had the greatest (P &lt; 0.01) BRSV antibody titer on d 56. For IBRV antibody titer on d 28, VIS0 was greatest, NAS0 was intermediate, and VIS28 and NAS28 were least (P &lt; 0.01). Percentage of chronically ill heifers were reduced for arrival vs delayed (1.3 vs 4.7%; P = 0.02) and arrival vaccinated had a reduction in antimicrobial treatment cost ($4.63 vs $7.31; P = 0.02). Data indicate improvement in some health outcomes for the parenteral route and arrival timing of MLV, but performance was not affected.

311 Evaluation of Post-Transit Growth Performance and Carcass Characteristics of Feedlot Heifers Sourced and Finished in Different Regions of the U.S

Abstract The objective was to evaluate growth performance and carcass traits following transit of feedlot heifers sourced and finished in different geographical regions in the U.S. Yearling heifers [n = 190; initial body weight (BW) 483 and 425 kg for SD and TX sourced, respectively] were used in a 2×2 factorial arrangement of origin state (SD vs TX) and finishing state (SD vs TX). Heifers were allotted on d -1 into four treatments: sourced from SD and finished in SD (SD-SD), sourced from SD and finished in TX (SD-TX), sourced from TX and finished in SD (TX-SD), and sourced from TX and finished in TX (TX-TX). Heifers were weighed on d -1, 3, 15, 28, 56, 78 (TX-TX and SD-TX) and 90 (SD-SD and TX-SD). On d 0, SD-TX and TX-SD heifers were shipped to the finishing location and weighed the following morning (d 1) to determine transportation shrink. To monitor transportation effects, vaginal temperature probes were inserted into all SD-TX and TX-SD heifers and a portion of SD-SD and TX-TX heifers on d -1 and removed on d 3. Clinical attitude scores (CAS) were recorded on d -1, 0, 1, 2 and 3 for indications of bovine respiratory disease symptoms. The GLIMMIX procedure of SAS was used to analyze growth performance and carcass measures with fixed effects of origin and finishing state. The MIXED procedure was used for CAS and temperature data with the same fixed effects and time as a repeated measure. Transported heifers had reduced temperatures (P &amp;lt; 0.05) during transit and post-transit compared with non-transported heifers. Temperatures of transported heifers increased (P &amp;lt; 0.05) during loading and unloading. On d 0, 1 and 3 there was a shift in the distribution of heifers that had a CAS score greater than 0 for TX-TX, SD-TX and TX-SD. Cattle endured high ambient temperatures (temperature humidity index value &amp;gt; 75) 54% and 18% of the feeding period for TX and SD finished heifers, respectively. All cumulative growth performance measures and carcass trait interactions were statistically significant (P &amp;lt; 0.05) besides initial BW, percent shrink of transported heifers, average daily gain, dressing percent, ribeye area and liver abscess severity, which were similar (P &amp;gt; 0.30). There was a shift in the distribution (P &amp;lt; 0.05) towards a greater proportion of Yield Grade 1 and Select carcasses for heifers fed in TX compared with those fed in SD, likely due to fewer days on feed. Overall, heifers transported to higher ambient temperatures had reduced dry matter intake, quality grades (QG) and limited growth recovery (45 kg lighter) compared with non-transported heifers. Heifers transported to lower ambient temperatures recovered growth and had improved QG at the same level of rib fat compared with non-transported heifers.

PSXII-22 Analysis of the Upper Respiratory Tract Microbiome in Newly Received Feedlot Heifers According to Subsequent Incidence of Bovine Respiratory Disease

Abstract This study compared the relative abundance of bacteria in the upper respiratory tract (RT) of newly received feedlot heifers according to incidence of bovine respiratory disease (BRD). Angus-influenced heifers (n = 76) were transported for 1,100 km (11 h) to the feedlot (d -1). At feedlot arrival (d 0), heifers were weighed [initial shrunk body weight (BW) = 234 ± 15 kg] and a nasal swab collected for analysis of the upper RT microbiome. Heifers were ranked by arrival BW and allocated into 6 pens on d 1 where they remained until d 55. Heifers were evaluated daily for BRD signs (d 0 to 55), and a final shrunk BW was recorded on d 56 (16-h feed and water deprivation). Heifers were classified according to number of antimicrobial treatments for BRD received (0, 1, or ≥ 2), or according to time of first incidence of BRD signs [no incidence (NOBRD), early incidence (EARLY; 4.1 ± 0.1 d), or late incidence (LATE; 18.5 ± 9.6 d). All data were analyzed using heifer as the experimental unit, the PROC MIXED procedure of SAS and Satterthwaite approximation to determine the denominator degrees of freedom for tests of fixed effects. The first model statement included the number of BRD treatments received, the second model statement included the time of first incidence of BRD signs. Average daily gain decreased linearly (P = 0.04) according to number of BRD treatments and was less (P = 0.04) in LATE and tended (P = 0.08) to be less in EARLY compared with NOBRD heifers. The abundance of the phyla Tenericutes increased linearly (P &amp;lt; 0.01), while the abundance of Firmicutes, Bacteroidetes, Actinobacteria, Verrucomicrobia, Spirochaetes, Euryarchaeota, Chlorobi, and Chloroflexi decreased linearly (P ≤ 0.05) according to number of BRD treatments. Heifers classified as EARLY had greater (P = 0.01) abundance of Tenericutes and less (P = 0.03) abundance of Firmicutes compared with NOBRD, as well as less (P ≤ 0.03) abundance of Euryarchaeota and Chloroflexi compared with both NOBRD and LATE heifers. The abundance of the genera Mycoplasma increased linearly (P &amp;lt; 0.01) while the abundance of Corynebacterium, Blautia, Jeotgalicoccus, Clostridium, and Dietzia decreased linearly (P ≤ 0.03) according to number of BRD treatments. Heifers classified as NOBRD had less (P = 0.01) abundance of Mycoplasma compared with EARLY, and greater (P ≤ 0.05) abundance of Corynebacterium, Jeotgalicoccus, Dietzia, and Planomicrobium compared with EARLY and LATE heifers. Collectively, heifers that developed BRD had altered upper RT microbiome at the time of feedlot arrival compared with heifers that remained healthy, particularly increased prevalence of Tenericutes phylum and Mycoplasma genera. Such differences in upper RT microbiome were heightened in heifers that developed BRD shortly after arrival, or that required multiple antimicrobial treatments.

PSVI-12 Comparison of a Visual Health Scoring System with Vaginal Temperatures of Newly Received Feedlot Heifers

Abstract Newly received feedlot cattle frequently succumb to bovine respiratory disease (BRD), which can be visually diagnosed and medically treated by employing a 4-point scoring system based on depression, appetite, respiration, and temperature (DART). Using this system, cattle are treated with antimicrobial medications for BRD if they have a rectal temperature (RT) ≥ 40°C and a DART score of 2 (scale = 1 to 4), or if they have a DART score of 3 or 4 regardless of the 40°C RT threshold. However, cattle often exhibit several visible clinical symptoms of BRD but do not have an RT above the 40°C threshold to warrant medical treatment. The objective of this study was to evaluate if DART scoring could be used to identify cattle with elevated vaginal temperatures (VT) throughout a 28-day receiving period. Upon feedlot arrival, 198 crossbred heifers (primarily Angus influence; initial BW = 219 ± 63 kg) were initially processed, weighed, and allocated to one of 10 soil-surfaced pens (12 x 35 m; 20 heifers per pen). A blank Controlled Intravaginal Drug Release (CIDR) device attached with an indwelling temperature probe (iButton DS1925L) was inserted vaginally into each heifer to collect and store VT every 10 minutes for 28 days. All heifers were evaluated daily (0700 h) for signs of morbidity by three individuals (blinded from each other) implementing the DART scoring system. Individual DART evaluations were then pooled prior to determination of heifers needing further evaluation for medical treatment. Results confirmed that DART score increases as VT increases (P &amp;lt; 0.001). Similarly, mean time DART ≥ 2 (TDART≥2) increased as mean time VT ≥ 40°C (TVT≥40) increased (P &amp;lt; 0.001). Accuracy of DART ≥ 2 to VT ≥ 40°C analogous by day is denoted as (MATCH). Simple regression analysis of MATCH and TVT≥40 for determining accuracy of visually diagnosing clinical BRD, was MATCH = 0.89 – 0.71 × TVT≥40 (r2 = 0.70; P &amp;lt; 0.001). The accuracy to visually diagnose BRD decreases as the number of days spent with a VT ≥ 40°C increases. Average daily gain decreased (P &amp;lt; 0.001) as TDART≥2 and TVT≥40 increased. The BRD symptoms indicating high VT and DART score (P ≤ 0.01) were nasal discharge, anorexia, abnormal respiration, and teeth grinding. Additionally, weakness, cough, lowered head, and ocular discharge indicate greater DART score (P ≤ 0.01). Basophils and hemoglobin decreased with elevated VT and DART score (P ≤ 0.02). Monocytes increased with increased DART score (P ≤ 0.04). In conclusion, data from this evaluation employing VT sensors and the DART scoring method provided an overview of how effective clinical BRD can be visually diagnosed, therefore contributing to the improvement and development of more effective strategies for identifying respiratory diseases in feedlot cattle.

265 Manger Space Restriction Does not Negatively Impact Growth Efficiency of Feedlot Heifers Program fed a Concentrate-Based Diet to Gain 1.36 kg Daily

Abstract The objective of this research was to determine the influence manger space restriction had on program fed feedlot heifers during the growing phase. Charolais × Angus heifers [initial body weight (BW) = 329 ± 22.1 kg] were used in a 109-d backgrounding phase study. Heifers were received from a ranch in western South Dakota approximately 60 days before study initiation. Initial processing (53 days before study initiation) included individual BW measurement, application of a unique identification tag, vaccination against viral respiratory pathogens (Bovi-Shield Gold 5, Zoetis, Parsippany, NJ) and clostridial species (Ultrabac/Somubac 7, Zoetis), and administration of doramectin pour-on (Dectomax, Zoetis) for control of internal and external parasites. All heifers were administered 36 mg of zeranol (Ralgro, Merck Animal Health, Madison, NJ) at study initiation. Upon study initiation, heifers were assigned to 1 of 10 pens (n = 5 pens/treatment with 10 heifers/pen) in a randomized complete block design (blocked by location). Each pen was randomly assigned to 1 of 2 treatments: 20.3 cm (8IN) or 40.6 cm (16IN) of linear bunk space/heifer. Heifers were individually weighed on days 1, 14, 35, 63, 84 and 109. Heifers were programmed to gain 1.36 kg daily based on predictive equations for a medium frame steer calf set forth by the California Net Energy System. To calculate predictive values, a final BW of 575 kg was assumed to be the mature BW of the heifers and tabular net energy values of 2.05 NEm and 1.36 NEg from d 1 to 22, 2.00 NEm and 1.35 NEg from d 23 to 82, and 1.97 NEm and 1.32 NEg from d 83 to 109 were used, because of ingredient inventory changes. Data were analyzed using the GLIMMIX procedure of SAS 9.4 with manger space allocation as the fixed effect and block as the random effect. No differences (P &amp;gt; 0.35) were observed between 8IN or 16IN heifers for initial BW, final BW, average daily gain, dry matter intake, feed efficiency, variation in daily BW gain (within pen standard deviation) or applied energetic measures. No differences (P &amp;gt; 0.50) were observed between treatments for morbidity. Although not statistically analyzed, 8IN heifers appeared to have looser stools during the first two weeks compared with the 16IN heifers. These data suggest restricting manger space allocation from 40.6 cm to 20.3 cm did not negatively influence gain efficiency or the efficiency of dietary net energy utilization in heifers programmed fed a concentrate-based diet to gain 1.36 kg daily. The use of tabular net energy values and required net energy of maintenance and retained energy equations are an effective means to program cattle to a desired daily rate of gain during the growing phase.

Comparative effectiveness of intranasal and parenteral vaccines for prevention of bovine respiratory disease in feedlot heifers

Comparative effectiveness of intranasal and parenteral vaccines for prevention of bovine respiratory disease in feedlot heifers

Revealing the diversity of internal body temperature and panting response for feedlot cattle under environmental thermal stress

Core body temperature (CBT) regulation is crucial for mammalian wellbeing and survival. Cattle pant to dissipate excess heat to regulate CBT when ambient conditions exceed thermoneutral zones. However, to date, neither the variability in cattle heat response, the lagged response of CBT to thermal indices, nor the diurnal patterns of thermal indices, CBT and panting have been reported in the literature. We decomposed thermal indices, CBT and panting time-series data for 99 feedlot heifers across three discrete heat events into diurnal, trend and residual components. Both raw and decomposed data were analysed to explore the lagged CBT and panting responses and the association between series. We show ambient thermal conditions impact CBT with a 1-h lag despite a lag of between 1.5 to 3 h from raw data. Average individual panting scores were used to identify heat-susceptible and heat-tolerant cattle. Heat-susceptible cattle showed greater CBT (P < 0.01) between 8:00 and 23:00 and greater panting duration (P < 0.05) between 10:00 and 18:00 than heat-tolerant cattle under the same thermal conditions and these variations followed a similar pattern despite differences in cattle breed. This new information enables targeted amelioration and selection of individuals against heat susceptibility.

Calves severely affected by bovine respiratory disease have reduced protection against histone toxicity and exhibit lower complement activity.

Bovine respiratory disease (BRD) remains the greatest challenge facing the beef industry. Calves affected by BRD can manifest illness ranging from subclinical infection to acute death. In pathologies similar to BRD, extracellular histones have been implicated as major contributors to lung tissue damage. Histones are basic proteins responsible for DNA organization in cell nuclei, however when released extracellularly during cell injury or via neutrophil activation they become cytotoxic. Cattle suffering severe cases of BRD demonstrate reduced capacity to protect against the cytotoxic effects of histones, however, the protective mechanism(s) of serum remain(s) unknown. Therefore, the objective was to identify components within serum that contribute to protection against histone toxicity. Serum proteins from animals considered protective (P; N = 4) and nonprotective (NP; N = 4) against the toxic effects of histones were precipitated by the addition and incubation of exogenous histones. Proteins that interact with histones from both groups were isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified via label free "shotgun" proteomics. Sixteen candidate proteins increased by ≥2-fold change in P vs. NP animals were identified, with several associated with the complement system. A subsequent study was conducted to evaluate complement system activity and serum protective capacity against exogenous histones in feedlot heifers. Serum samples were collected from 118 heifer calves (BW at arrival = 229 ± 2.4 kg) at feedlot arrival. Animals were retrospectively assigned to groups consisting of: calves not requiring treatment with antibiotics for BRD (CONT; N = 80), calves treated once (1TRT; N = 21), calves treated twice (2TRT; N = 5), calves treated thrice (3TRT; N = 3), or calves that died from BRD within 1 wk of entering the feedlot (DA; N = 9). Serum from DA animals was less protective than CONT (P = 0.0005) animals against histone toxicity. Complement activity of DA animals was reduced compared to CONT (P = 0.0044) animals. Additionally, the use of both assays as a ratio resulted in increased ability to detect DA animals. Results suggest that cattle predisposed to severe cases of respiratory disease may have impaired complement activity presumably contributing to reduced protective capacity against histone toxicity.

Short communication: Analysis of the nasal microbiota in newly received feedlot heifers according to subsequent incidence of bovine respiratory disease.

This study compared the relative abundance of bacteria in the nasal cavity of high-risk beef heifers at feedlot arrival according to subsequent incidence of bovine respiratory disease (BRD). Angus-influenced heifers (n = 76) were transported for 1,100 km (11h) to the feedlot (d -1). At feedlot arrival (d 0), heifers were weighed [shrunk body weight (BW) = 234 ± 15 kg] and a nasal cavity swab collected for microbiota analysis. Heifers were ranked by arrival BW and allocated into 6 pens on d 1 where they remained until d 55. Heifers were evaluated daily for BRD signs (d 0 to 55), and a final shrunk BW was recorded on d 56 (16-h feed and water deprivation). Heifers were classified according to number of antimicrobial treatments for BRD received (0, 1, or ≥2), or according to time of first incidence of BRD signs [no incidence (NOBRD), early incidence (EARLY; 4.1 ± 0.1 d, ranging from 3 to 6 d), or late incidence (LATE; 18.5 ± 9.6 d, ranging from 10 to 28 d). Average daily gain decreased linearly (P = 0.04) according to number of BRD treatments, and was less (P = 0.04) in LATE and tended (P = 0.08) to be less in EARLY compared with NOBRD. The abundance of the Tenericutes phylum increased linearly (P < 0.01), while the abundance of other phyla (e.g., Firmicutes and Bacteroidetes) decreased linearly (P ≤ 0.05) and phyla diversity tended to decrease linearly (P = 0.10) according to number of BRD treatments. Heifers classified as EARLY had greater (P = 0.01) abundance of Tenericutes compared with NOBRD, whereas Tenericutes abundance in LATE heifers was intermediate and did not differ (P = 0.22) compared with EARLY and NOBRD. The abundance of Mycoplasma genus increased linearly (P < 0.01) while the abundance of other genera (e.g., Corynebacterium and Blautia) and genera diversity decreased linearly (P ≤ 0.03) according to number of BRD treatments. Heifers classified as EARLY had greater (P = 0.01) abundance of Mycoplasma and reduced (P = 0.01) genera diversity compared with NOBRD, and values noted in LATE heifers for these variables were intermediate and not different (P ≥ 0.27) compared with EARLY and NOBRD. Hence, heifers that developed BRD during the experiment had altered nasal microbiota at arrival compared with heifers that remained healthy, particularly increased prevalence of Tenericutes and Mycoplasma. Such differences in nasal microbiota were heightened in heifers that developed BRD shortly after arrival, or that required multiple antimicrobial treatments.

Hematological and Performance Parameters Trend in Steers and Heifers in Feed Lot and Supplemented with Palm Oil (Elaeis guineensis Jack)

This study compares the daily weight gain (ADG) and the hematological profile of cattle in feed lot and supplemented with palm oil (POil). Overall, 20 male and 24 female Holstein-Cebu (5/8-3/8) cattle with an average weight of 249±43 kg were used. Three groups of eight animals each were formed with females, which were housed and received 0, 2, and 4% POil in the diet (FSWO, FS2O, FS4O). With males, only two groups were formed, one group that kept grazing and received 2% POil (MG2O, n=8) and one group stabled and received 4% POil (MS4O, n=12). Peripheral blood was obtained to determine the hematocrit (HCT), plasma protein concentration (TPP, g/dL), and eosinophil count (EOS), and a complete blood sample was processed in an automatic analyzer to determine the erythron and platelet formula. Analysis of repeated measures over time was performed. Stabled steers showed the highest ADG (1.5kg/d), whereas females received 2 or 4% oil had similar ADG levels (1.3 to 1.4kg/d) than grazing steers. At the first sampling, EOS counts were 1.5 x 103 cells/µL of blood, but they were reduced to 0.23 x 103 cells/µL of blood at the end of the study. The lowest HCT was obtained in grazing steers (32.8%). It is concluded that in stabled steers, the red formula is improved, and the EOS count reduced. Palm oil supplementation generated the highest daily weight gain in stabled steers.

Manger space restriction does not negatively impact growth efficiency of feedlot heifers program fed a concentrate-based diet to gain 1.36 kg daily.

The objective of this research was to determine the influence manger space restriction had on program-fed feedlot heifers during the growing phase. Charolais × Angus heifers [initial body weight (BW) = 329 ± 22.1 kg] were used in a 109-d backgrounding study. Heifers were received approximately 60 d prior to study initiation. Initial processing (53 d before study initiation) included individual BW, application of an identification tag, vaccination against viral respiratory pathogens and clostridial species, and administration of doramectin pour-on for control of internal and external parasites. All heifers were administered 36 mg of zeranol at study initiation and were assigned to 1 of 10 pens (n = 5 pens/treatment with 10 heifers/pen) in a randomized complete block design (blocked by location). Each pen was randomly assigned to 1 of 2 treatments: 20.3 cm (8IN) or 40.6 cm (16IN) of linear bunk space/heifer. Heifers were individually weighed on days 1, 14, 35, 63, 84, and 109. Heifers were programmed to gain 1.36 kg daily based on predictive equations set forth by the California Net Energy System. To calculate predictive values, a final BW of 575 kg was assumed to be the mature BW of the heifers and tabular net energy values of 2.05 NEm and 1.36 NEg from days 1 to 22, 2.00 NEm and 1.35 NEg from days 23 to 82, and 1.97 NEm and 1.32 NEg from days 83 to 109 were used. Data were analyzed using the GLIMMIX procedure of SAS 9.4 with manger space allocation as the fixed effect and block as the random effect. No differences (P > 0.35) were observed between 8IN or 16IN heifers for initial BW, final BW, average daily gain, dry matter intake, feed efficiency, variation in daily weight gain within each pen or applied energetic measures. No differences (P > 0.50) were observed between treatments for morbidity. Although not statistically analyzed, 8IN heifers appeared to have looser stools during the first 2 weeks compared to the 16IN heifers. These data suggest restricting manger space allocation from 40.6 to 20.3 cm did not negatively influence gain efficiency or the efficiency of dietary net energy utilization in heifers programmed fed a concentrate-based diet to gain 1.36 kg daily. The use of tabular net energy values and required net energy of maintenance and retained energy equations are effective means to program cattle to a desired rate of daily gain during the growing phase.

7 Evaluation of Finishing Performance and Carcass Characteristics of Beef Heifers with Variable Degrees of Heart Failure Risk and Differing Reproductive Tract Type

Abstract Tremendous economic loss is attributed to high altitude disease mortality of calves in the Mountain West and Great Plains region. Additional economic losses may be associated with changes in feed efficiency and carcass quality in animals at higher risk of heart failure during the finishing phase. Thus, the objective of the current study is to evaluate economically relevant traits throughout the finishing period to determine inefficiencies associated with variable levels of heart failure risk and reproductive tract type of beef heifers. Both intact reproductive tract (n = 19) and ovariectomized (n = 18) heifers were stratified by risk category, where initial pulmonary arterial pressure (PAP) levels at or below 42 mmHg were designated as low risk and those above 42 mmHg as moderate/high risk. Heifers were fed a grain-based diet for 125 d before transportation to the harvest facility on d 126. All heifers were weighed in 2 wk intervals. Heifers were PAP tested by a qualified veterinarian in approximately 3 mo intervals during the feeding period. Feed intake data was collected for the last 55 d prior to harvest using the Vytelle SENSETM bunk system. Time of harvest was determined based on live weight and final ultrasound 12th rib fat thickness. Data were analyzed using the ANOVA function of R with tract type and risk as fixed effects. Comparisons were tested using a significance level of α = 0.05 and 0.05 (P ≤ 0.10) were considered tendencies. There were no interactions of risk category and tract type on performance or carcass characteristics (P ≥ 0.14). There was a tendency for higher total intake (P = 0.07) and relative growth rate (P = 0.04) among moderate/high risk heifers compared to the low-risk category. Hot carcass weight, marbling score, ribeye area, and USDA yield grade were not impacted (P ≥ 0.16) by risk category. Intact heifers had greater (P = 0.02) total gain than their ovariectomized contemporaries. However, marbling scores were higher (P = 0.04) among ovariectomized heifers compared to those from intact heifers. These data suggest that risk category and tract type minimally influence performance and carcass characteristics in a population that selects sires with low PAP scores. It remains unclear if more initial divergence in PAP scores would elicit greater impacts on performance and carcass characteristics in feedlot heifers.

20 Young Scholar Talk PHD: Implications of Histone Toxicity and Complement System Activity in Sheep and Cattle During Immunomodulatory States Including Respiratory Disease and Pregnancy

Abstract The immunostimulatory and toxic effects of extracellular histones have been demonstrated in humans and rodents suffering from acute respiratory distress syndrome and acute lung injury. Accumulating evidence suggests intricate interactions between extracellular histones and immune complement system proteins occur as a regulatory mechanism. However, limited information is available on the interactions of complement system activity and histone toxicity during immunomodulatory events in livestock. Therefore, our current research is aimed at investigating the contributions of histone toxicity and complement system activity in relation to respiratory disease and pregnancy in wild and domestic sheep and cattle. In an initial study, feedlot heifers were evaluated for protective capacity against extracellular histones and complement activity related to subsequent disease outcomes. At feedlot arrival, serum samples were collected from 118 heifer calves (BW 229 ± 2.4 kg) and subjected to a histone toxicity assay and a 50% hemolytic complement activity assay. Heifers were retrospectively assigned as either never receiving treatment with antibiotics for bovine respiratory disease (NT; n = 80) or calves that died from bovine respiratory disease within 1 wk of entering the feedlot (DA; n = 9). Serum from DA animals was less (P &amp;lt; 0.001) protective against histone toxicity compared to NT heifers. Likewise, complement activity of DA animals was reduced (P &amp;lt; 0.05) compared to NT animals. These results suggest cattle predisposed to severe cases of respiratory disease have impaired complement system activity presumably leading to reduced protection against histone toxicity. In a second study, wild Alaskan Dall sheep (Ovis dalli dalli) and domestic sheep (Ovis aries) were evaluated for susceptibility to histone toxicity. Serum was collected from Debouillet sheep (n = 150) with no clinical signs of illness and serum of wild Alaskan Dall sheep (n = 135) was collected from live capture and release animals. Dall sheep serum was less (P &amp;lt; 0.05) protective against histone toxicity compared to Debouillet sheep. Low protection against histone toxicity may be related to higher reported disease states for wild sheep. Furthermore, recognizing that disease modulates immune function, it is also recognized pregnancy relies on immune system activation. Therefore, pregnant sheep serum was evaluated to determine the effect of histone toxicity and complement system activity. Serum was collected from Debouillet ewes (n = 8) and analyzed for histone toxicity protectiveness and complement activity. Serum was collected from ewes prior to breeding (d -0) and at d 1 and 17 of the estrous cycle. Serum protective capacity against histones and complement activity was not significantly different on d -0 compared to d 1 and d 17. Collectively, these data implicate the toxic effect of extracellular histones and complement system activity during respiratory disease states with less obvious observations during pregnancy.