151 research outputs found
Heterogeneity of within-herd variances for conformation and its relationship to various herd parameters in the U.S. Holstein population
No full textTwo data sets of first-parity classification records were analyzed to examine heterogeneity of variances for conformation in the U. S. Holstein population. Data set I included records for final score and linear descriptive traits on cows scored from 1983 through 1986. Results indicated a strong negative correlation (r = -.59) between within-herd standard deviation for final score and herd-mean final score.
Regression analysis suggested a curvilinear decrease (concave up) in within-herd standard deviation for final score with increasing herd-mean final score. Within-herd standard deviations for linear descriptive traits demonstrated a linear decline with increases in herd-mean final score.
Daughter contemporary deviation for final score was regressed on her sire’s Predicted Difference type within 25 mean/standard deviation subclasses. Response to selection was greatest in high-mean/variance herds and least in low-mean/variance herds.
Restricted maximum likelihood estimates of sire and error variance were approximated within each of 5 herd-mean subclasses of the data. Regressions revealed environmental variance for final score decreased curvilinearly (concave up) with increasing herd-mean final score. Genetic variance declined linearly. Heritability demonstrated no significant trend. For most linear traits, environmental variance decreased linearly with increasing herd-mean final score. Linear decreases in genetic variance were noted for foot angle, udder depth and rump angle, Heritability had positive trends for body depth, angularity, rear udder height, udder support, and teat placement.
Data set II included first-parity final scores on cows classified from 1967 to 1986. Relationships estimated between herd mean and within-herd variance for final score on recent data were confirmed. Positive trends over time were noted for: within-herd standard deviation for final score, the antagonistic relationship between herd mean and within-herd variance, the antagonistic relationship between average Predicted Difference type and within-herd variance, and average herd-mean Predicted Difference type.
Results indicate selection for final score was occurring in the population. Differences in within-herd selection differentials accounted for 24% of the differences in within-herd variance for final score.Ph. D
Postoperative irradiation for squamous cell carcinoma of head and neck: Retrospective comparison of accelerated radiochemotherapy and standard radiotherapy
No full textBackground: Comparison of accelerated radiochemotherapy (aRCT) and standard radiotherapy (sRT) in postoperative treatment after macroscopically complete resection of squamous cell cancers of head and neck. Material and Methods: 229 patients treated within the same period had either (no randomization) postoperative radiotherapy with conventional fractionation (60-70 Gy, 2.0 Gy per day) or received 2 fractions of 2.1 Gy per day, 8 times\textbackslash{}week, up to a total dose of 56.7 Gy with a treatment split after 2 weeks and simultaneous low dose cisplatin or carboplatin on treatment clays (cumulative dose >66 mg/m(2) or 550 mg/m(2) in 83% of patients). Results: 65 patients completed their course of twice-daily irradiations within a maximum of 35 days and therefore had aRCT; their 3-year locoregional tumor control (Kaplan-Meier estimate) was 86%, whereas that of 42 patients with prolonged twice-daily radiochemotherapy was 65% (p=0.0509). After sRT, i.e. 1 fraction daily and treatment time up to 45 days, locoregional tumor control was 67%, this result being significantly inferior to that after aRCT (p=0.0282). In multivariate analysis, pN stage, tumor site oral cavity/floor of mouth, high/moderate differentiation of squamous cell carcinoma and conventional surgery (versus CO2-laser surgery) were significantly predictive of locoregional failure. Whereas nodal status, the strongest prognostic factor, was evenly distributed among aRCT and sRT patients, there was a misbalance of 3 risk factors favoring the aRCT collective. Superior tumor control after aRCT was confirmed unilaterally for nearly each subgroup (significant for recurrent tumors, close margins, pN1/2a-b). For pN2c/pN3 nodal stage, the results after aRCT were by tendency worse than after sRT, possibly due to a particularly long interval between surgery and start of radio(chemo)therapy for the patients with aRCT (mean 58.0 days vs. 43.8 days, p=0.037). Among the total of patients the 3-year hazard for late toxicity Ill-IV was 31% after twice-daily treatment and 17% after conventionally fractionated radiotherapy (p=0.083). Conclusions:This retrospective analysis provides some evidence that accelerated radiotherapy with simultaneous chemotherapy is more potent than standard radiotherapy. However, as multivariate analysis misses significance and the influence of misbalance of some prognostic factors among aRCT and sRT patients remains unclear, only a randomized trial with stratification according to risk factors as well as a defined interval between surgery and initiation of RT can provide more evidence
Developing Breeding Objectives for Targhee Sheep
No full textBreeding objectives were developed for Targhee sheep at different levels of prolificacy and triplet survival. Economic weights (EW) were derived for estimated breeding values (BV) from National Sheep Improvement Program genetic evaluations for 120 d weaning weight (WW), maternal milk (MM), yearling weight (YW), fleece weight (FW), fiber diameter (FD), staple length (SL), and prolificacy (PLC; lambs born/100 ewes lambing). A commercial flock was simulated, accounting for nonlinear relationships between performance and profit. Ewes were assumed mated to sires of specified BV and profit was derived from lifetime performance of lambs and replacement females from that lamb crop. Economic weights were determined as change in profit from use of sires with BV that were one additive standard deviation above the mean for each trait [1.98 kg for WW, 1.62 kg for MM, 2.90 kg for YW, 0..36 kg for FW, 0.99 microns for FD, 0.74 cm for SL, and 17.58 lambs/100 ewes for LC], while holding all other BV at breed average. Separate breeding objectives were derived for different ways of meeting increased nutrient needs (P = purchase hay, R = rent pasture, and L= limited flock size) and for different market lamb values (D = discounting lamb value for heavy weights, ND = no discount for heavy lambs). Based on replicated simulations, relative EW did not vary with prolificacy or triplet survival (P > 0.15) but were affected by feed costs and lamb market values (P 0.90 indicated that an index could be used across multiple scenarios with little loss of selection efficiency. Indexes derived within feed cost scenarios (P, R, and L) and lamb value scenarios (D, ND) were strongly intercorrelated (r > 0.97). Correlations among average indexes for feed cost scenarios (0.97 for R and P, 0.70 for R and L; 0.85 for P and L) indicated that two feed cost scenarios could be used depending on whether winter forage was limited (L) or not (NL). The correlation between average indexes for these two scenarios was 0.78. Indexes were presented for combinations of feed cost and lamb value scenarios. Two indexes were suggested, representing the scenarios that apply to a large portion of Targhee producers. These indexes were for discounting heavy lambs with limited winter forage (D-L: 1.0 WW + 0.14 MM __ 0.76 YW + 1.22 FW __ 0.36 FD - 0.09 SL + 0.25 LC) and discounting heavy lambs with additional available forage (D-NL: 1.0 WW + 0.24 MM __ 0.34 YW + 1.65 FW __ 0.41 FD - 0.14 SL + 0.33 LC). For a standardized selection differential of one for the index, the expected changes in mean index value were 1.92 per ewe per generation for D-L and D-NL, respectively.Master of Scienc
Breed group effects on pregnancy rate and ewe performance in different seasons of the year
No full textThirty-one Dorset (D), 24 Finnish Landrace (F), 35 Barbados Blackbelly x Dorset (BD), 10 Dorset x Finn (F), 24 Finn x Dorset (FD) and 35 grade Rambouillet (R) ewes were exposed to rams in various seasons. Ewes were born in 1979 or 1980; no R ewes were born in 1980. Ewes were bred in April, 1980 (APR80); November, 1980 (NOV80); August, 1981 (AUG81); May, 1982 (MAY82); and April, 1983 (APR83). Ewes born in 1980 entered the study in NOV80. The analytical model used to describe ewe performance included effects of ewe birth year (EBY), breed/EBY, season/EBY, breed x season/EBY and ewe (random).Master of Scienc
Female Dispersal and Inbreeding in the Red-cockaded Woodpecker
No full textDispersal is a critical life-history component; it determines gene flow and has profound effects on population structure, demography, social systems, and population viability. To add to our knowledge of dispersal and, in particular, our understanding of the relationship between dispersal and inbreeding, I studied three aspects of the biology of the red-cockaded woodpecker: dispersal of breeding females; the costs, benefits, and frequency of inbreeding; and the effect of inbreeding on natal dispersal.
Dispersal of breeding female red-cockaded woodpeckers is strongly associated with inbreeding avoidance and mate choice, weakly associated with site choice, and not found to be associated with social constraints. Estimates of mortality for non-dispersing and dispersing breeding females were 24 and 59 percent per year, respectively-rare evidence of the cost of breeding dispersal.
Significant costs of close inbreeding were found. Closely related pairs (kinship coefficient greater than 0.1) had lower hatching success as well as lower survival and recruitment of fledglings than unrelated pairs. Moderately related pairs (kinship coefficient between 0 and 0.1) and moderately inbred individuals had increased hatching success, but did not produce more young.
Despite documented costs of close inbreeding and a predictable spatial distribution of closely related males near the natal territory, female fledglings disperse a median of only two territories and a modal distance of one territory. Natal dispersal of females is affected by closely related males on the natal site but unaffected by closely related males or moderately related males that are off the natal site.Master of Scienc
Budget Analysis of Spring, Fall with Winter Clean-up, and High-Fertility Fall Lambing Systems in a Simulated Fixed Forage Resource
No full textA successful business needs to generate enough cash to cover expenses, current debt, and family living expenses, pay interest on owned and borrowed capital, maintain productivity, and earn a reasonable return for the operator. Income from sheep production is generally only part of a total farm and nonfarm income. Thus options, opportunity costs, and decisions regarding the sheep production enterprise are not isolated; they affect other agricultural enterprises. Sheep production consistently returns profits to producers, which makes it an enticing agricultural enterprise. There are advantages in raising sheep in Virginia, such as abundant, high-quality forage, moderate climate, pasture improvement, and good access to markets with high demand for lamb. The disadvantages to sheep production are unavailable and inexperienced labor and operators, predators, and inconsistent market demand and supply. Sheep producers have the opportunity to choose which lambing system fits their existing operations and lifestyle. The use of economic analysis enables operator to make sound business management decisions.
To compare different lambing systems (spring, fall with winter clean-up, and high-fertility fall) in a systematic way, a simulation model was constructed with a fixed forage resource of 50 acres of pasture including typical Virginia mountain pasture plus various amounts of fescue for stockpiling. The simulation included a production calendar; nutritional requirements for ewes, lambs, and artificially reared triplets; growth rates for lambs; lambing distributions; forage growth; and enterprise budgets including income, costs, and returns. A economic analysis was performed for each lambing system with average prices or with plus or minus one standard deviation for prices of corn, SBOM, and market lambs, and price differentials for market lambs across lambing seasons.
Comparisons of each lambing systems produced various results. In spring lambing, only 78 ewes could be maintained on the fixed forage resource, while the fall with winter clean-up and high-fertility fall lambing system each had 115 ewes. This result occurred because of limited forage in July and August and higher nutrient requirements for spring lambing in those months. The overall nutrient requirements were higher in the fall with winter clean-up and high-fertility fall lambing than in spring lambing as a result of the increased ewe and lamb numbers. Concentrate consumption by lambs was also greater for fall with winter clean-up and high-fertility fall lambing than for spring lambing because of the increased numbers of lambs. Because of the low number of ewes and lambs, spring system produced the most hay. Labor costs were highest in fall with winter clean-up lambing because of the two lambing seasons.
In the economic analysis system, each lambing was compared. With 10-year average prices for market lambs, corn, and SBOM, high-fertility fall lambing had the greatest income (14,695), and spring lambing (7,935), followed by fall with winter clean-up lambing (6,084). This was the result of increased ewe and lamb numbers in high-fertility fall and fall with winter clean-up lambing than spring lambing. High-fertility fall lambing had the greatest returns (4,025), and spring lambing ($2,028). On a fixed forage resource, increasing fertility in fall lambing clearly results in increased returns. In this model, forage availability controlled the number of ewes that a lambing system can have because of limited summer growth and had a major impact on profits. Conclusions of Tolman (1993) differed from those found within this thesis. On a per ewe basis, she found that spring lambing to yielded the highest returns whereas this thesis found that high-fertility fall lambing yielded the highest returns. A key difference between this study and that of Tolman (1993) was after weaning this thesis feed fall lambs stockpiled fescue and she feed fall lambs feed in dry lot.Master of Scienc
Reconstruction of metabolic pathways by the exploration of gene expression data with factor analysis
No full textMicroarray gene expression data for thousands of genes in many organisms is quickly becoming available. The information this data can provide the experimental biologist is powerful. This data may provide information clarifying the regulatory linkages between genes within a single metabolic pathway, or alternative pathway routes under different environmental conditions, or provide information leading to the identification of genes for selection in animal and plant genetic improvement programs or targets for drug therapy. Many analysis methods to unlock this information have been both proposed and utilized, but not evaluated under known conditions (e.g. simulations). Within this dissertation, an analysis method is proposed and evaluated for identifying independent and linked metabolic pathways and compared to a popular analysis method. Also, this same analysis method is investigated for its ability to identify regulatory linkages within a single metabolic pathway. Lastly, a variant of this same method is used to analyze time series microarray data.
In Chapter 2, Factor Analysis is shown to identify and group genes according to membership within independent metabolic pathways for steady state microarray gene expression data. There were cases, however, where the allocation of all genes to a pathway was not complete. A competing analysis method, Hierarchical Clustering, was shown to perform poorly when negatively correlated genes are assumed unrelated, but performance improved when the sign of the correlation coefficient was ignored.
In Chapter 3, Factor Analysis is shown to identify regulatory relationships between genes within a single metabolic pathway. These relationships can be explained using metabolic control analysis, along with external knowledge of the pathway structure and activation and inhibition of transcription regulation. In this chapter, it is also shown why factor analysis can group genes by metabolic pathway using metabolic control analysis.
In Chapter 4, a Bayesian exploratory factor analysis is developed and used to analyze microarray gene expression data. This Bayesian model differs from a previous implementation in that it is purely exploratory and can be used with vague or uninformative priors. Additionally, 95% highest posterior density regions can be calculated for each factor loading to aid in interpretation of factor loadings. A correlated Bayesian exploratory factor analysis model is also developed in this chapter for application to time series microarray gene expression data. While this method is appropriate for the analysis of correlated observation vectors, it fails to group genes by metabolic pathway for simulated time series data.Ph. D
Genetic evaluation of ewe productivity and its component traits in Katahdin and Polypay sheep
No full textThe objectives of this dissertation were to evaluate genetic influences on ewe productivity, its growth and reproductive components, and measures indicative of accelerated lambing performance. Genetic parameters were estimated for total weight of litter weaned per ewe lambing (TW) and its components, number of lambs born (NB), number of lambs weaned (NW) and average weight of lambs weaned (AW), measured as traits of the ewe, and lamb survival (LS) and weaning weight (WW), measured as traits of the lamb, in Katahdin sheep. Heritabilities of TW, NB, NW, and AW, were 0.12, 0.12, 0.09, and 0.13, respectively. Heritability of WW was 0.15 to 0.20. Genetic effects on LS were negligible. Genetic correlation of TW with NB, NW, and AW averaged 0.30, 0.90, and 0.74, respectively, those of NB with NW and AW averaged 0.72 and 0.01, respectively, and that between NW and AW averaged 0.50. Direct genetic effects on WW were independent of NB and NW, but correlation between maternal genetic effects on WW and animal genetic effects on NW averaged 0.35.
Ewe fertility, NB, LS, and WW were modeled using stochastic simulation and used to derive NW, AW, and TW to test alternative predictors of genetic merit for TW. A random 8% of WW observations were set to missing values and AW and TW were recalculated to evaluate the effects of data reporting inconsistencies on efficacy of different prediction strategies. Four alternative predictors of estimated breeding values (EBV) for TW involved direct univariate prediction (TW1), an index of EBV for NW and AW (TW2), indirect prediction using data for NW and AW and genetic correlations among NW, AW and TW (TW3), and indirect prediction augmenting TW3 with data and genetic correlations involving NB (TW4). To validate efficacy of predictors, daughter data sets were generated from the original ewes and their realized TW were regressed on alternative predictors. Regression coefficients from TW1, TW3, and TW4 were close to the expected value of 0.50 whereas those from TW2 were less than 0.50. Model Rsquare statistics were similar among predictors when there were no missing WW data but regressions involving TW1 had lowest model R-square when some WW data was missing.
Ewe lamb fertility (ELF), ages at first, second, and third lambings (AGE1 to AGE3), first and second lambing intervals (INT1 and INT2), and number of lambings by 38 mo of age (LAMB3) were evaluated for an accelerated lambing Polypay flock. Relationships among these traits and NB and WW were estimated. Heritability of ELF, AGE1, AGE2, AGE3, INT1, INT2, and LAMB3 were 0.14, 0.39, 0.28, 0.36, 0.00, 0.09, and 0.27, respectively. Heritability of AGE2 and AGE3 were negligible after accounting for variation in AGE1. Genetic correlations of ELF with AGE1 and AGE2 were -0.89, -0.91, respectively, and that with LAMB3 was 0.89. Genetic correlations of LAMB3 with AGE1 and AGE2 were -0.49 and -1.00, respectively. Genetic correlations of ELF and LAMB3 with direct genetic effects on WW were close to -0.70, but correlations with maternal genetic effects on WW were 0.88 and 0.58, respectively. Prolificacy was independent of ELF and LAMB3.Ph. D
Effects of breed and ram exposure on Spring estrous behavior and Summer fertility in domestic ewes
No full textThe present studies were conducted to check the effects of acute ram introduction into a flock of anestrus ewes in Virginia. Ewes were bled via jugular venipuncture twice weekly and serum samples were radioimmunoassayed for progesterone (P4) content as an indicator of estrous activity. All rams were fitted with crayon equipped marking harnesses for use as an indicator of mating behavior in ewes. The first study tested the effects of introduction of vasectomized rams into a flock: of' 50 Dorset (D) and 50 Hampshire (H) purebred ewes in either May or June. More D ewes ovulated (96% vs 72% for H ewes) and mated (80% vs 20% for H ewes) in May. Of ewes which mated in May 65% D but no H ewes continued to cycle in June after removal of rams. Of ewes exposed to rams in June no difference among breeds was observed in percentage of ewes ovulating but more D ewes (72%) mated than H ewes (44%). Twenty-four percent of D but no H ewes cycled continuously throughout the 68 d or the study. Lambing date significantly affected mating behavior in H but not D ewes.
The second study tested the effects of ram breed on incidence of mating and subsequent lambing in Rambouillet x Q Suffolk ewes In June and July of 1984 and 1985. Ewes were Q pre-exposed to either confined Suffolk (S) or Dorset (D) Q yearling rams or no (N) ram for 2 wk prior to breeding by Q either S or D rams. Lambing date was significantly affected by breeding treatment in 1984 and by pre-exposure treatment in 1985. Sixty-three percent of the ewes lambed in 1984 while 65% lambed in 1985.Master of Scienc
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