Browsing by Author "Holt, Tim, committee member"

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Open Access
Effects of direct-fed microbials on weight gain and gastrointestinal bacteria microbiome composition in weaned heifers
(Colorado State University. Libraries, 2019) Doubet, Curtis, author; Pond, Kevin, advisor; Engle, Terry, committee member; Holt, Tim, committee member
Weight gain and fecal analysis on 179 heifer from two breeds of cattle, Angus and Salers, were analyzed after being treated with a direct fed microbial (DFM) supplement. Heifers were split into one of three treatment groups with the control being drenched with water, a second group being drenched with 1/2oz of the DFM, and a third group being drenched with 1oz of the DFM. Heifers were monitored over a four week period and drenched on day 0 and day 28 to measure changes in weight gain and microbiome composition. Fecal samples were taken rectally from the fecal group (FG) weekly during the duration of the trial. Overall, the final model ANOVA resulted in a p-value of .9689, concluding no significant difference between the 3 treatment levels for weight gain. Time proved to be the predominant driver of gastro-intestinal microbial composition and probiotic supplementation did not lead to significant changes to the microbiome community structure. Chao1 and ACE models ran on fecal samples indicate significant impact of probiotic treatment on microbial richness and indicate that supplementation leads to greater diversity and, in turn, may mean a more robust microbiome.
Open Access
Effects of monensin sodium and plant extracts containing cinnamaldehyde, capsicum oleoresin, and eugenol on days to puberty, gain, pregnancy rate, and feed efficiency in developing beef heifers receiving a high roughage diet
(Colorado State University. Libraries, 2014) Bigler, Bo, author; Peel, Kraig, advisor; Ahola, Jason, advisor; Whittier, Jack, committee member; Holt, Tim, committee member
To view the abstract, please see the full text of the document.
Open Access
Evaluating the genetic relationship between high elevation pulmonary arterial pressure and moderate elevation feedlot performance and carcass traits
(Colorado State University. Libraries, 2020) Briggs, Emma, author; Speidel, Scott E., advisor; Enns, R. Mark, advisor; Thomas, Milt G., committee member; Holt, Tim, committee member
The objective of the study was to evaluate if a genetic relationship exists between post weaning pulmonary arterial pressure (PAP) measured at high elevation and traits associated with moderate elevation feedlot performance and carcass traits. For this study, PAP (collected 1992-2018; n = 6,898), feedlot performance (2014-2018; n = 558), and carcass data (2001-2018; n = 1627) were obtained from the Colorado State University Beef Improvement Center Angus herd. At an elevation of 2,115 m, post weaning, PAP measurements were collected; subsequently, a selected group of steers were relocated to a moderate elevation feedlot (1,500 m) where feedlot performance data was collected. Genetic relationships were evaluated with a series of 5-trait models using REML statistical approaches. Traits in this analysis were assigned contemporary groups, fixed effects and a direct genetic random effect. A maternal additive and permanent environmental effect was included to weaning weight in the analysis. The heritability estimate for PAP was 0.20 ± 0.03. Genetic correlations between PAP and feedlot traits were positive, with estimates of 0.32 ± 0.20 (average dry matter intake) and 0.03 ± 0.17 (average daily gain). The strongest genetic correlation between PAP and carcass performance traits were those of rib eye area (-0.30 ± 0.12) and calculated yield grade (0.29 ± 0.12). Genetic correlations between PAP and marbling score, back fat, or hot carcass weight were 0.00 ± 0.13, -0.07 ± 0.13, and 0.14 ± 0.10, respectfully. These results suggest a favorable genetic relationship exists between PAP and feedlot and carcass traits. As cattle with lower post-weaning PAP move to lower elevation feedlot, they could potently have heavier muscled carcasses compared to their high PAP contemporaries.
Open Access
In vivo and in vitro attributes of copper, zinc, and manganese sources in beef cattle nutrition
(Colorado State University. Libraries, 2023) Guimaraes, Octavio, author; Engle, Terry T., advisor; Wagner, John, committee member; Geornaras, Gina, committee member; Nair, Mahesh, committee member; Holt, Tim, committee member
Trace minerals are not just vital components in the diets of domestic livestock species; they are also essential for ensuring optimal performance, health, reproduction, and a robust immune system. In today's volatile markets, producers and nutritionists face the challenge of meeting predefined goals and targets. They must employ strategies that can maximize production and efficiency. The intricate mechanisms governing the digestion, absorption, and storage of copper (Cu), zinc (Zn), and manganese (Mn) are influenced by various factors, including diet type, breed, life stage, among many others. Research has uncovered intriguing opportunities to enhance the utilization of trace minerals (TM) in ruminant nutrition. To further our comprehension of the digestion, absorption, and retention of modern trace mineral forms, this study conducted 3 experiments aimed at investigating the in vivo and in vitro characteristics of hydroxy trace minerals (HTM), organic chelated trace minerals (CTM), and sulfate trace minerals (STM) forms of Cu, Zn, and Mn. This dissertation is the continuation of a Master Thesis submitted by Guimaraes et al., 2021. In the current series of experiments the influence of TM source on digestibility and ruminal solubility was investigated. The objectives of experiment 1 were to determine the effects of TM source on 1) nutrient digestibility and ruminal fermentation, 2) concentrations of soluble Cu, Zn, and Mn in the rumen following a pulse dose of TM, and 3) Cu, Zn, and Mn binding strength on ruminal digesta using dialysis against a chelating agent in steers fed a diet formulated to meet the requirements of a high producing dairy cow. Twelve Angus steers fitted with ruminal cannulae were adapted to a diet balanced with nutrient concentrations similar to a diet for a high producing lactating dairy cow for 21 d. Steers were then randomly assigned to dietary treatments consisting of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either sulfate (STM), hydroxychloride (HTM) or complexed trace minerals (CTM). The experimental design did not include a negative control (no supplemental Cu, Mn, or Zn) because the basal diet did not meet the NRC (Nutrient Requirement for Beef Cattle) requirement for Cu and Zn. Copper, Mn, and Zn are also generally supplemented to lactating dairy cow diets at concentrations approximating those supplied in the present study. Following a 14-d adaptation period, total fecal output was collected for 5-d. Following the fecal collection period, rumen fluid was collected for VFA parameters. On the following day, the same diet was provided for 14 d, without supplemental Cu, Zn, and Mn. This period served as a wash-out period. A pulse dose of 100, 400, and 600 mg of Cu, Zn, Mn, respectively, from either STM, HTM, or CTM, was administered via ruminal cannulae to the steers on day 15. Over a 24-h period ruminal samples were obtained every 2-h. Following centrifugation, the supernatant was analyzed for Cu, Mn, and Zn. Ruminal solid digesta samples from times 0, 12, and 24 hours after bolus dosing were exposed to dialysis against Tris-EDTA. The digestibility of NDF and ADF were lesser in STM vs. HTM and vs. CTM supplemented steers. Steers receiving HTM and CTM had greater total VFA concentrations than STM, and molar proportions of individual VFA were not affected by treatment. Ruminal soluble Cu and Zn concentrations were greater post dosing in STM and CTM supplemented steers at 2, 4, and 6 h for Cu and 4, 6, 8, 10 and 12 h for Zn when compared to HTM supplemented steers. The release of Cu and Zn from ruminal solid digesta following dialysis against Tris-EDTA at 12 and 24 h post-dosing was greater for steers receiving HTM compared to those receiving STM or CTM. Results indicate trace mineral source impacts: 1) how tightly bound Cu and Zn are to ruminal solid digesta; 2) fiber digestion; 3) and ruminal total VFA concentrations. The objective of experiment 2 was to evaluate the effects of sources of STM and HTM fed at the same levels on 1) nutrient digestibility and fermentation characteristics, 2) ruminal solubility of Cu, Zn, and Mn following a pulse dose of trace mineral I, and 3) binding strength of Cu, Zn, and Mn on ruminal solid digesta upon dialysis against a chelating agent. Minor dietary changes can have a direct impact on ruminal pH, temperature, microbial population, and redox potential, which will influence fermentation, and ultimately affect nutrient digestibility. These changes can influence or be influenced by the solubility of certain TM in the rumen. Rumen soluble TMs can alter nutrient digestibility, fermentation, and increase chances of antagonistic interaction. Twelve ruminally cannulated Angus steers (BW 587.6 ± 23.1 kg) were adapted to a diet balanced to meet requirements of finishing steers for 21 d. Steers were then randomly assigned to dietary treatments consisting of Cu, Mn, and Zn supplemented at 18, 40, and 90 mg/kg DM, respectively, from STM or HTM sources (n = 6 steers/treatment; experimental unit = steer). Following the 14 days treatment adaptation period total fecal output was collected for 5 d. Digestibility of DM, CP, Starch, NDF, and ADF was not affected (P > 0.15) by TM source. On d 6, rumen fluid was collected at 0, 2, and 4 h post feeding for VFA analysis. There were no treatment x time interactions for any VFA measured. However, HTM steers had greater (P < 0.05) ruminal molar proportions of propionate and tended (P < 0.07) to have greater molar proportions of valerate compared to STM steers. Steers fed STM had greater (P < 0.05) molar proportions of butyrate compared to HTM steers. Steers were then fed the same high concentrate diet without supplemental Cu, Zn, or Mn for 14 d. On d 15 steers received a pulse dose (via rumen cannulae) from either STM or HTM. Ruminal samples were obtained at 2 h intervals starting at -4 and ending at 24 h relative to dosing. There was a treatment x time interaction (P < 0.05) for ruminal soluble Cu concentrations. Ruminal soluble mineral concentrations were greater (P < 0.05) for Cu at 4, 6, 8, and 16 h post dosing in STM compared to HTM supplemented steers. There was no treatment x time interaction for ruminal soluble Zn or Mn concentrations. The release of Cu, Zn, and Mn from ruminal solid digesta following dialysis against Tris-EDTA at 12 and 24 h post-dosing was greater (P < 0.01) for steers receiving HTM compared to those receiving STM. Results of this experiment indicate that trace mineral source affects how tightly bound Cu, Zn, and Mn are to ruminal solid digesta, and that ruminal solubility of Cu differs between STM and HTM sources and may impact rumen fermentation characteristics. Experiment 3: This study analyzed samples from experiments investigating TM source effects on nutrient digestibility, short-chain fatty acid production, Cu, Zn, and Mn ruminal solubility, and binding strength in rumen insoluble digesta. Twelve Angus steers (5+ years old) participated in three studies: Study 1 (Guimaraes et al., 2020, 2021; medium quality forage diet), Study 2 (Guimaraes et al., 2022; dairy type diet), and Study 3 (unpublished, Chapter 3 of this dissertation; high concentrate diet). Due to impacts on digestibility, fermentation, mineral solubility, and binding in all studies, microbiome analysis was conducted to assess potential bacterial and protozoa population shifts from all studies. In Study 1 (medium quality forage diet), Papillibacter was the predominant species in the rumen. Rumen samples showed a significant time point impact on Shannon's PD (P < 0.05). Beta diversity analysis using unweighted UniFrac revealed notable differences in community diversity between rumen and fecal samples (q < 0.001). Rumen microbiota clustered at multiple time points. No beta diversity differences between STM and HTM were observed at baseline (Time A, q = 0.23), but differences emerged after adaptation (Time C, q < 0.03) and during total collection (Time F, q < 0.01). ANCOM analysis revealed higher abundance of Papillibacter, Ruminoccoccaceae, and Prevotellaceae in rumen samples, regardless of TM source. No significant differences were found in fecal samples. ANCOM analysis did not detect measurable differential abundance between trace mineral sources in fecal or rumen samples following Alpha and Beta diversity results. In Study 2 (dairy diet), Moraxellaceae was the most prevalent species within the rumen. Rumen samples showed a significant time point effect on Shannon's PD (P < 0.001), with noteworthy differences between several time points. However, TM source had no impact on Shannon's PD (P = 0.15). Fecal samples showed no differences in time points or TM sources. Beta diversity analysis using unweighted UniFrac revealed a significant distinction between microbial community diversity in rumen and fecal samples (q < 0.001). Rumen microbiota clustered differently at various time points. Trace mineral source did not affect Beta diversity, but there was a tendency toward greater diversity with HTM supplementation (q = 0.07). ANCOM analysis found higher abundance of ASVs Moraxellaceae, Planococcaceae, Ruminoccoccaceae, and Prevotellaceae in the rumen environment, regardless of TM source. No significant differential abundance was detected between TM sources in rumen samples, consistent with Shannon's PD diversity analysis. In Study 3 (high concentrate diet), Moraxellaceae and Planococcaceae were the most abundant in rumen samples. Rumen samples showed a significant impact of collection time point on Shannon’s PD (P < 0.001), with significant differences between several time points. However, TM source had no effect on Shannon’s Diversity (P = 0.19). Interestingly, Shannon’s Diversity in feces showed significant differences between TM sources (P < 0.03), with STM having lesser diversity than HTM. There was no effect of time point in fecal samples (P = 0.38). Beta diversity analysis using unweighted UniFrac revealed clear differences between microbial diversity in rumen and fecal samples (q < 0.001). ANCOM analysis found higher abundance of ASVs Moraxellaceae, Prevotellaceae, Planococcaceae, and Ruminoccoccaceae in the rumen environment, regardless of TM source. In conclusion, this study provides valuable insights into the complex interplay between TM sources, the rumen microbiome, and various aspects of rumen health and function. While TM sources did not significantly alter the rumen microbiome composition, time points demonstrated substantial effects on microbial communities. These findings contribute to our understanding of how dietary factors can influence rumen ecology and function, with potential implications for livestock nutrition and management strategies. In conclusion, while experiment 1 showed that HTM and CTM sources positively impacted fiber digestibility and ruminal VFA concentrations compared to STM, experiment 2 indicated that the diet type could influence these effects. However, ruminal soluble mineral concentrations remained greater in STM-supplemented steers. Experiment 3 further highlighted the differences in rumen and fecal microbiota diversity between TM sources. These findings underscore the importance of selecting the appropriate TM source based on specific dietary and production requirements. The interactions between TMs, diet type, and the rumen microbiome are complex and require further investigation to optimize ruminant nutrition and overall well-being. This research builds upon previous studies and contributes valuable insights into the utilization of TMs in ruminant nutrition, paving the way for more informed decision-making in livestock production practices.
Open Access
Pulmonary arterial pressure: repeated measures and dynamics due to changes in altitude and age
(Colorado State University. Libraries, 2022) Zimprich, Taylor R., author; Thomas, Milt, advisor; Speidel, Scott, committee member; Holt, Tim, committee member
High Altitude Disease (HAD) in cattle is a consequence of pulmonary hypertension (PH) induced by hypoxia at elevations > 1,500 m. Pulmonary arterial pressure (PAP) is a phenotypic indicator of animal susceptibility to PH and HAD and is moderately heritable (h2 = 0.26 to 0.34). The goal of this thesis was to evaluate repeated measures of PAP and dynamics. This goal was achieved with two studies and three objectives: 1) to explore and estimate correlations between different ages and elevations, 2) to determine usefulness of yearling moderate altitude PAP in beef bulls that are transported to high elevation for short- and longer-term management, and 3) to determine usefulness of feedlot entry PAP to additional PAP measures as the cattle approach finishing and harvest. The objective of Study I (Chapter 3) was to determine significant variables and estimate correlation between PAP measurements at moderate altitude and high altitude at differing ages. This scenario often occurs in the Western U.S. beef industry. Data consisted of breed, sire, mean PAP (mPAP) measures at each collection date, elevation, and bull age, from 2017-2019 (n = 89) spring-born bulls at the Colorado State University (CSU) Agriculture Research, Development, and Education Center (ARDEC; 1,524 m). A potential 5 PAP measurements were collected from each bull: 1) Weaning PAP at ARDEC (1,525 m); 2) Yearling PAP at ARDEC; 3) PAP after acclimating for 28 days at Fort Lewis College (FLC; 2,470 m), Hesperus, CO; 4) before returning to ARDEC from FLC after 110 days at FLC; and 5) after re-acclimating for 57 days to the moderate elevation at ARDEC when the bulls were 557 ± 2.92 d (18 mo) of age. In model development, yearling PAP measurement, elevation, and age were determined to be important (P < 0.05) sources of variation. Also, PAP increased (P < 0.05) from moderate altitude to high altitude. In Study II (Chapter 4), yearling PAP in the model accounted for more variation in the prediction of the initial high-altitude PAP than it did in the prediction of the subsequent high altitude PAP measurements. Results of this study suggested that the yearling PAP measurement collected at 1,525 m was only a moderate predictor of a PAP measurement collected after 21 days at 2,470 m and these types of predictions weaken after ~ 90 days at high elevation. Overall, Study II (Chapter 4) suggested that as time increased (p < 0.05) between the mPAP measures the amount of variation accounted by the initial mPAP measure declined (p < 0.05). However, PAP has been considered to be the most accurate indicator of an individual's susceptibility to HAD if is measured at high altitude and near 18 months of age (Holt and Callen, 2007). This thesis suggested that yearling PAP measured at moderate elevations was a moderate and short-term indicator of future PAP performance in beef bulls when moving to high altitudes. Yearling PAP measurements are likely less indicative of PAP, the longer bulls reside at high elevation. It should be noted that high-altitude PAP observations will likely have higher correlations and be a stronger indicator to future high-altitude PAP measures. The altitude of the ARDEC facility (1,525 m) of CSU is moderate; therefore, questionable if it yields enough hypoxic stress to determine if a bull has PAP that will be acceptable or unacceptable for lifetime residence in a mountainous beef production system. Breed was not a significant variable in this thesis. This is likely due to limited numbers being evaluated in each breed. To further study breed influence, greater numbers of bulls being analyzed is necessitated. Therefore, this challenge warrants additional research when considering the diversity of beef operations in the Western US.