Browsing by Author "Speidel, Scott E., advisor"
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Item Open Access Evaluating the genetic architecture of the Japanese Wagyu breed within the United States(Colorado State University. Libraries, 2022) Heffernan, Kathryn, author; Speidel, Scott E., advisor; Thomas, Milt, committee member; Enns, Mark, committee member; Blackburn, Harvey, committee member; Holt, Timothy, committee memberThe objective of this thesis is to better understand the genetic architecture of Japanese Wagyu cattle in the United States to improve on current breeding strategies, as well as help to develop new strategies to increase the genetic diversity of the U.S. Wagyu population. For this study, pedigree data (n = 48) were collected on full-blood Japanese Wagyu sires and dams, and high-density genotype data (n = 414) were collected on Japanese Wagyu, Ayrshire, Brahman, Brangus, Devon, Holstein, Milking Devon, Milking Shorthorn, Shorthorn, Simmental, South Devon, Angus, Jersey Island, and Brown Swiss cattle. Inbreeding coefficients were calculated from the pedigree data and averaged 0.19, with a minimum coefficient of zero, max coefficient of 0.43, and a standard deviation of 0.08. Using the genotypes, a principal component analysis (PCA), an admixture graph, and a phylogenetic tree were computed to ascertain the population structure and breed composition of modern Japanese Wagyu cattle in relation to other breeds. The majority of the Japanese Wagyu had an elongated dispersal that overlapped with the origin of the PCA graph. Japanese Wagyu also averaged 85.5% indicine influence as indicated by the admixture graph, and the phylogenetic tree showed Japanese Wagyu as the closest branch to the root breed Brahman. These results suggest that Japanese Wagyu are an inbred population. While mostly Bos indicus, these results suggest that Japanese Wagyu are admixed with low percentages of Bos taurus breeds such as Simmental and Brown Swiss.Item 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 memberThe 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.Item Open Access Feedlot heart disease: understanding heart score and its relationships to economically relevant traits(Colorado State University. Libraries, 2022) Kukor, Isabella, author; Speidel, Scott E., advisor; Enns, R. Mark, advisor; Holt, Timothy N., committee member; Thomas, Milton G., committee memberThe increasing occurrence of feedlot heart disease caused by pulmonary hypertension has precipitated a growing concern from producers and geneticists alike. Utilization of genetic technology for selection and breeding decisions has made a substantial amount of progress in past decades within economically relevant traits, but the focus on high performing cattle may have had adverse consequences on cardiovascular fitness. Pulmonary hypertension has become a more frequent occurrence in low to moderate elevation feedlots, causing feedlot death and the potential to predispose cattle to co-morbidities. Previously, once considered only a high-altitude issue, pulmonary hypertension appears prevalent in high genetic merit cattle within moderate elevation, high plains feedlots. With no options for treatment, management, and prevention in feedlot cattle may be the only strategy for producers struggling with the balance of desirable, fattening cattle and pulmonary hypertension risk. The objective of this study was to establish the foundation for a new heart grading system known as heart score and discover its genetic and phenotypic relationships with economically relevant traits and differentiate phenotypic differences between healthy and unhealthy scored Angus-influenced cattle. The third chapter of this thesis included phenotypic differences between cattle with healthy and unhealthy heart scores (n = 1,422). Data were obtained from Cactus Feed Yard LLC in Canyon, Texas over a two-year period (2020-2022). Means were compared between heart score groups (1,2 & 3+) to test for significant differences between the two groups. Linear models and the ANOVA table displayed significant fixed effects to each model. Systolic, diastolic, PAP, and marbling scores differed among groups (P < 0.05), while hot carcass weight displayed a tendency (P < 0.10). Unhealthy heart scored cattle tended to be heavier carcasses associating heavier cattle with pulmonary hypertension. Healthy heart scored animals had overall lower (P < 0.05 ) PAP, systolic, and diastolic measurements. The fourth chapter of this thesis highlighted the differences between repeated PAP measurements at 9 and 14 months of age. The cohort of Angus influenced cattle were housed at a feedlot in Canyon, TX and was a moderate altitude (1,080 m). Repeated PAP measurements exhibited an increase in PAP measurements between 9 months and 14 months of age, which were later grouped by their heart scores. No differences were observed among heart scored cattle at 9 months (mean minimum: 39.61 ± 2.47; mean maximum: 40.36 ± 3.47) but distinct differences were observed among cattle grouped in their 14-month PAP (mean minimum: 45.27 ± 5.69; mean maximum: 79.20 ± 21.09). High heart scores were associated with higher PAP measurements. There was a correlation of 0.20 between the measurements showcasing a positive trend between measurements, but also the inability of PAP measurements taken at 9 months may not be predictive of cattle's scores at 14-month-old. Furthermore, there were no differences between phenotypic traits of the cattle who had greater PAP differences between their measurements. The third study estimated the heritability of heart score and the phenotypic relationships with economically relevant traits (n = 1,507) in progeny of 88 sires. Phenotypes included heart scores, PAP (14 months), hot carcass weight, marbling, ribeye area, and backfat. Heart score was found to have a moderate heritability estimate 0.28 ± 0.10. Heart score had a very strong genetic correlation with PAP, and strong correlation with hot carcass weight. Positive genetic correlations were found between heart scores and carcass traits with genetic correlations between 0.07 to 0.63. Overall, these results suggest heart scores to be useful in genetic selection for a healthier cardiopulmonary system. while not drastically influencing carcass traits.Item Open Access Genetic parameters for fertility and production traits in Red Angus cattle(Colorado State University. Libraries, 2017) Boldt, Ryan John, author; Enns, R. Mark, advisor; Speidel, Scott E., advisor; Koontz, Stephen, committee memberTo view the abstract, please see the full text of the document.Item Open Access Genetic relationship between ewe longevity and structural foot and leg traits in sheep(Colorado State University. Libraries, 2022) Yazar Gunes, Hilal, author; Enns, R. Mark, advisor; Speidel, Scott E., advisor; Thomas, Milton G., committee member; Holt, Timothy, committee memberTo view the abstract, please see the full text of the document.Item Open Access Heritability and repeatability estimates of first service conception and first cycle calving in Angus cattle(Colorado State University. Libraries, 2019) Foxworthy, Heather, author; Enns, R. Mark, advisor; Speidel, Scott E., advisor; Thomas, Milton G., committee member; Callan, Robert, committee memberDescribed as the ability of an individual to conceive and remain pregnant, fertility remains one of the largest economic impacts on cattle producers. Infertility and(or) sub-fertility in the cow herd can result in financial losses due to a reduction in calf crop, lower quality calves, and increased breeding and replacement costs. Improving reproductive efficiency via altered management and selection could prove useful for cattle managers to minimize these costs while increasing genetic gain and income. However, historically the investigation of fertility traits has been minimal due to the binary nature of many of the traits making analysis difficult. In addition, given the nature of the phenotypes, heritability estimates of fertility traits are generally low, suggesting minimal genetic influence and therefore slow rates of genetic gain. First service conception (FSC) is a binary trait that describes the outcome of the first service of artificial insemination (AI) with success or failure phenotypes. Furthermore, a trait termed first cycle calving (FCC) describes the ability of a female to calve within a 21-day period of the due date based on the initial opportunity for conception in the first 21 days of the breeding season. The objectives of this thesis included the further investigation of the influential factors, genetic and environmental, on the success of first service conception and first cycle calving with the end result estimates of heritability and repeatability for these traits in Angus cattle. Data used for this analysis was sourced from the Colorado State University Beef Improvement Center (1985 to 2018; CSU-BIC; N = 8,206) near Saratoga, Wyoming where an Angus cow herd is managed for research purposes. The data used included breeding and ultrasound records, as well as data on the resulting and previous calves. Model selection resulted in fixed effects of birth year (P < 0.001), mating type (insemination based on estrus or during mass mating; P < 0.001), contemporary group consisting of synchronization protocol, semen type, and mating year (P < 0.001), previous calving ease (P < 0.001), and covariates of mating age in days (P < 0.01), and post-partum interval (P < 0.001) for both FSC and FCC. Variance components for the two traits were estimated using a REML procedure and then combined into estimates of heritability and repeatability. Analysis resulted in estimates of 0.03 ± 0.02 and 0.15 ± 0.03 for FSC and FCC, respectively for both heritability and repeatability when considering the entire female reproductive lifespan. When observations were segregated into immature and mature categories of beef females one to four years of age at mating and five years or greater, differences in parameter estimates became apparent. Estimates of heritability for FSC in immature and mature females were 0.04 ± 0.04 and 0.02 ± 0.05, respectively while repeatability was estimated for the two categories at 0.04 ± 0.04 and 0.08 ± 0.04. These estimates for mature females suggested a detectable influence of the permanent environment; however, all estimates are considered low for their respective parameter. When estimating the parameters for FCC, heritability was estimated at 0.04 ± 0.07 and 0.21 ± 0.04 for immature and mature female categories, respectively; while repeatability values were 0.11 ± 0.07 and 0.21 ± 0.04, respectively. These estimates suggest a permanent environmental effect; however, estimates of both parameters for immature females were low, while those for mature females can be classified as moderate. The findings suggested that altering temporary environmental management should remain the most critical factor when improving female reproduction. The largest genetic contribution was for FCC in mature females resulting in more potential for selection and culling based on the phenotype for that trait.Item Open Access Heterosis and breed percentage effects on reproductive performance and preweaning traits in a multibreed beef cattle herd in Panama(Colorado State University. Libraries, 2023) Gonzalez Murray, Roderick Alexander, author; Speidel, Scott E., advisor; Enns, R. Mark, advisor; Thomas, Milton G., committee member; Coleman, Stephen J., committee member; Holt, Timothy, committee memberPanama is located in Central America and is characterized by a tropical climate. Given the tropical climate conditions, Zebu cattle (Bos indicus) are the most predominant breeds in cow–calf systems due to greater resistance to internal and external parasites, and greater tolerance to elevated ambient temperatures and humidity when compared to Bos taurus beef breeds. Zebu is a breed that is reproductively inefficient due to Age at First Calving (AFC) being over 36 months and having longer calving intervals (CI), ranging between 12.2 to 26.6 months. The Panamanian cow-calf system reports an average annual birth rate of 55%, with a range of 35% to 60%, depending on the province. This reduced efficiency reported in the cattle production system is also reflected in low kilograms of weaned calves per cow exposed to AI or Bull (80kg) to 120 WW/cow exposed), high age at first calving (over 36 months), long calving interval (more than 450 days), and perhaps low-income returns ranging between 8 to 15% per dollar invested. The reproductive efficiency of a herd is one of the main components of a cow-calf system economically. Other important traits that affect the system efficiency and profitability are the preweaning traits: birth weight (BW) and weaning weight (WW). The lack of system efficiency and profitability is why different breeds have been introduced to the country to be used in crossbreeding systems to obtain the benefits of heterosis in growth and reproductive traits. The beneficial effects of crossbreeding on animal performance have been well established, benefiting low heritability traits such as those related to reproduction. For that reason, in tropical environments, matching the optimum cow numbers with the correct genetic potential in the appropriate production environment can maximize economic benefits. In the tropics, reduced pre- and post-weaning growth and reproductive efficiency are the main limiting factors in the cow-calf system. Preweaning traits are a combination of the direct genetic, maternal genetic, maternal permanent environment, and temporary environmental effects. The challenge for farmers in Latin American countries is to identify those animals that achieve maximum productive performance in a given agro-ecological environment, and to maintain a balance between longevity and generation intervals, in order to obtain the greatest genetic gain per unit of time. Knowledge of the genetic effects of breeds and their crosses in various climatic and forage conditions can be used to identify optimal breed combinations and crossbreeding systems for existing markets. Based on the heterogeneity of herds in tropical regions due to the introduction of multiple breeds and the different crossbreeding systems utilized, it is necessary to carry out a multibreed evaluation that includes all crossbred and purebred individuals into a single analysis and accounting for the direct and maternal breed and heterosis effect evaluation. As we mentioned above, different breeds have been introduced in Panamá, but no genetic evaluation program has been developed in the country, to improve the efficiency of cow-calf production. However, it is important to evaluate the breed groups and heterosis effect through productivity indicators to know the relative performance of the breeds and crosses of Zebu and Bos taurus cattle in the cow–calf system. Therefore, the objectives of this study were to determine heterosis and breed percentage effects on reproductive performance and preweaning traits in a multibreed beef cattle herd in Panama. For this, traits like age at first calving (AFC), calving interval (CI), gestation length (GL), birth weight (BW), and weaning weight (WW) that constitute important elements of the breeding objective of beef cattle producers were selected as the traits to evaluate in this study. All the reproductive and preweaning data utilized in this investigation was produced by a multibreed cattle population of the Livestock Experimental Station of Panama Agricultural Innovation Institute (IDIAP) in Gualaca, province of Chiriqui, Republic of Panama. The herd was comprised of the following genetic groups and breed percentage combinations: tropical adapted Brahman (BR), Nellore (Ne), Undefine Bos indicus (BI), Guaymi Creole (CR), Senepol (SP) Romosinuano (RS); Bos taurus (BT), Simmental (SM), Angus (AN), Red Angus (AR), Limousin (LM), Charolais (CH), Wagyu (WA), and Others (OTH); crossbreeds (CX), Beefmaster (BF), Three CX (F1 x different BT), R1(Backcross BR), R2 (Backcross BT), Composite (combination of at least 4 different breeds with less than 25% of Zebu), Upgraded Brahman (87.5% BR 12.5% BT), B1 (62.5% Zebu + 37.5% BT), B2 (62.5% BT + 37.5% Zebu). In general, this dissertation was divided into three different studies according to the physiological status of the individual producing the phenotypic record (e.g., calf, heifer, and multiparous cows). The first study estimated the influence of heterosis and breed percentage on age at first calving (AFC). An animal model was utilized to estimate variance components using data from 619 cows and 1,142 individuals in the pedigree from the multibreed herd with data collected between 2000 to 2019. The average AFC was 42.7 ± 10.5 months, with an estimated regression coefficient for AFC on heterosis of -0.046 ± 0.009 month/percent of outcross. Lower AFC was observed for the F1, R2, and B2, with 39.8 months, 39.9 months, and 39.5 months, respectively. A reduction in AFC was also observed for the Beefmaster (-0.13 ± 0.05 months) and the OTHER category (-0.14 ± 0.04 months). A heritability of 0.17 0.10 was estimated for AFC. These results suggest that heterosis had a beneficial influence on AFC measurements in a multibreed beef cattle herd in Panama. The second study focused on estimating the influence of heterosis and breed percentage on calving interval (CI) and gestation length (GL), and the correlation between age at first calving (AFC) and CI. Calving performance data included 1,291 repeated observations of CI and GL from 502 cows with a 3-generation pedigree consisting of 2,840 individuals in the pedigree with data collected between 2000 to 2021. A repeated records animal model was utilized to estimate variance components for both CI and GL. Additionally, a bivariate animal model was used to estimate the genetic correlation between CI and AFC. The average CI was 572.6 ± 140 days, and for GL was 284.2 ± 6.3 days, for this population. The regression of CI and GL on heterosis was not significant. A lower CI was observed for the F1, and Three CX, translating to 558.7 days and 567.2 days, which represents 2.3% and 1.3% reduction in CI, respectively when compared to the Zebu group. Calving interval was estimated to be lowly heritable (0.037 ± 0.026), however, a positive genetic trend over the duration of the study. The analysis between CI and AFC revealed a moderate genetic correlation (0.49 ± 0.36) which allows the establishment of a selection program to improve AFC and CI, due to the pleiotropic effect, which would improve the fertility of this multibreed herd in Panama. Finally, the third study aimed to estimate the influence of heterosis and breed percentage on birth weight (BW) and weaning weight (WW). Data from 900 calves with 2,843 individuals in the pedigree was utilized in a bivariate animal model for BW and WW was utilized to estimate variance components. The estimated regression coefficient for BW on heterosis was not significant, however, for WW was 0.072 ± 0.027 kg/percent of outcross. Lower BW and WW were observed for the Japanese, and B1, while R2 and Upgrade had the highest average WW. Heritability for BW was found to be low 0.14 ± 0.06 and moderate for WW 0.26 ± 0.09. The proportion of variation of WW accounted by the maternal permanent environment for WW was 0.2 ± 0.09. The estimated genetic correlation between additive genetic BW and WW was 0.63 ± 0.30, while a negative, additive genetic correlation was observed for WW and WW maternal -0.43 ± 0.37. These results suggested that heterosis had a beneficial influence on WW but a limited effect on BW. Additionally, increasing the percentage of WA and BR negatively influenced WW measurements in this multibreed population.Item Open Access Random regression models and their impact in the genetic evaluation of binary fertility traits in beef cattle(Colorado State University. Libraries, 2021) Sánchez Castro, Miguel Angel, author; Speidel, Scott E., advisor; Thomas, Milton G., advisor; Enns, R. Mark, committee member; Coleman, Stephen J., committee member; Frasier, W. Marshall, committee memberTo view the abstract, please see the full text of the document.