Reproductive Fertility in Herd Bulls

Herd bulls have a large influence on many aspects of beef operations, especially an operation’s profitability. For example, percent calf crop weaned is the single most important factor influencing profitability, and the number of cows bred during the breeding season plays the largest role in percent calf crop weaned. Therefore, an operation’s profitability is directly tied to the herd bull’s breeding ca¬pability. In addition, herd bulls supply half of the genetics to all the calves he sires; therefore, bull selection can be the most powerful method of genetic improvement in the herd. Herd bulls also influence overall herd fertility more than any other single animal; the loss of fertility by a bull can mean the potential loss of an entire calf crop. For the above reasons, and because greater than 90% of the beef cows in the United States are bred by natural service, it is important that bulls be managed to optimize breeding performance. There are several factors that influence bull fertil¬ity. First, the bull must have developed properly and have reached puberty to be fertile. Second, the bull’s physical characteristics, such as scrotal circumference, mating abil¬ity, and semen quality, play a role in his fertility. Third, the bull’s libido and social dominance influence his fertility

Increasing Your Calf Crop by Management, Pregnancy Testing, and Breeding Soundness Examination of Bulls

Percent calf crop weaned is influenced more by man¬agement decisions than by any other single factor in a cow herd, and therefore can be a very important factor in annual returns for a cow-calf operation. Percent calf crop weaned is calculated by dividing the number of calves weaned by the total number of females exposed during the breeding season. As shown in Table 1, as percent calf crop weaned increases, pounds of calf weaned per cow exposed increas¬es and production cost per hundred pounds of calf produced decreases. Increasing weaning weights approximately 50 pounds is equal to an increase of 10% in calf crop weaned

Bull Management and Nutrition

Proper management and nutrition of bulls is essential to ensure cow/calf producers maximize reproductive efficiency and genetic improvement of the calf crop. In addition, the herd bull influences overall herd fertility more than any other single animal, and loss of fertility by a bull can cause substantial loss to a potential calf crop. Each cow produces one calf per year; however, bulls should contribute to the calf crop by 25 to 60 times via siring 25 to 60 calves. Additionally, bulls influence their daughters’ production in the cow herd. Therefore, bull selection can be the most powerful method of genetic improvement in the herd, but bulls with low fertility, structural problems and low libido reduce the percent calf crop weaned

Bull Management and Nutrition

Proper management and nutrition of bulls is essential to ensure cow/calf producers maximize reproductive efficiency and genetic improvement of the calf crop. In addition, the herd bull influences overall herd fertility more than any other single animal, and loss of fertility by a bull can cause substantial loss to a potential calf crop. Each cow produces one calf per year; however, bulls should contribute to the calf crop by 25 to 60 times via siring 25 to 60 calves. Additionally, bulls influence their daughters’ production in the cow herd. Therefore, bull selection can be the most powerful method of genetic improvement in the herd, but bulls with low fertility, structural problems and low libido reduce the percent calf crop weaned

A study of the development of the subterranean system of the Johnson grass plant

Call number: LD2668 .T4 1952 R8Master of Scienc

Fabrication and Testing of Low Cost 2D Carbon-Carbon Nozzle Extensions at NASA/MSFC

Subscale liquid engine tests were conducted at NASA/MSFC using a 1.2 Klbf engine with liquid oxygen (LOX) and gaseous hydrogen. Testing was performed for main-stage durations ranging from 10 to 160 seconds at a chamber pressure of 550 psia and a mixture ratio of 5.7. Operating the engine in this manner demonstrated a new and affordable test capability for evaluating subscale nozzles by exposing them to long duration tests. A series of 2D C-C nozzle extensions were manufactured, oxidation protection applied and then tested on a liquid engine test facility at NASA/MSFC. The C-C nozzle extensions had oxidation protection applied using three very distinct methods with a wide range of costs and process times: SiC via Polymer Impregnation & Pyrolysis (PIP), Air Plasma Spray (APS) and Melt Infiltration. The tested extensions were about 6" long with an exit plane ID of about 6.6". The test results, material properties and performance of the 2D C-C extensions and attachment features will be discussed

Serum PCB levels and congener profiles among US construction workers

Abstract Background The presence of PCB in caulking (sealant) material found in masonry buildings has been well-documented in several countries. A recent investigation of 24 buildings in the greater Boston area found that 8 buildings had high PCB levels in caulking materials used around window frames and in joints between masonry blocks. Workers removing caulking material have been shown to have elevated serum PCB levels. Methods This project compared serum PCB levels among male workers who installed and/or removed PCB-containing caulking material from buildings in the greater Boston area with reference serum PCB levels from 358 men from the same area. Serum PCB levels were measured in the same laboratory by liquid-liquid extraction, column chromatography clean-up and dual capillary column GC/microECD analysis. Results When the congener profiles were compared between the reference population and the construction workers, the serum levels of the more volatile, lighter PCBs (di-, tri-and tetrachloro, sum of IUPAC# 6–74) were substantially higher among the construction workers. One of the youngest workers had the lowest total serum PCB levels (sum of 57 congeners) of all 6 workers, but the contribution of more volatile (less chlorinated) PCB congeners (#16, 26,28,33,74,66, and 60) was markedly higher than in other 5 workers and reference men. Only this worker was working on a job that involved removing PCB caulking at the time of the blood sampling. Conclusion While the results of this pilot study are based upon small numbers (6 construction workers who handled PCB caulking), the serum PCB levels among the construction workers exceed the referents. Comparison of the congener profiles suggests that there are substantial differences between the construction workers and the general population samples. These differences, and the similarities of profiles among the construction workers strongly suggest that occupational contact with caulking material can be a major source of PCB exposure for construction workers.http://deepblue.lib.umich.edu/bitstream/2027.42/117256/1/12940_2007_Article_124.pd

Native American Exposure to Iodine-131 from Nuclear Weapons Testing in Nevada

A great deal of work has been done reconstructing doses from Nevada Test Site fallout, yet the unique exposures of Native American communities continue to be neglected. It is possible to estimate the exposures of these communities through a process of collaborative information gathering and analysis. This paper builds on a previous exercise that demonstrated the substantial doses received through the consumption of contaminated game. The updated model includes new information on the deposition of iodine-131, an assessment of the neonatal thyroid doses received through breast milk, an exploration of the effect of population mobility on dose estimates, and estimates of thyroid cancer risk. All thyroid dose estimates from the rabbit exposure pathway are comparable in magnitude to National Cancer Institute comprehensive dose estimates that assume exposure to contaminated milk from backyard cows and goats. Dose estimates from the rabbit exposure pathway are larger than estimated doses from store-bought milk by an average factor of 6. Taking historical population mobility patterns into account may result in slightly lower estimates of dose. The quantification of this exposure pathway is considered be an advance toward a more appropriate dose reconstruction for communities with diets high in wild game. This research was completed money allocated during Round 5 of the Citizens’ Monitoring and Technical Assessment Fund (MTA Fund). Clark University was named conservator of these works. If you have any questions or concerns please contact us at [email protected]://commons.clarku.edu/clark_mtafund/1003/thumbnail.jp

Asteroid lightcurves from the Palomar Transient Factory survey: Rotation periods and phase functions from sparse photometry

We fit 54,296 sparsely-sampled asteroid lightcurves in the Palomar Transient Factory to a combined rotation plus phase-function model. Each lightcurve consists of 20+ observations acquired in a single opposition. Using 805 asteroids in our sample that have reference periods in the literature, we find the reliability of our fitted periods is a complicated function of the period, amplitude, apparent magnitude and other attributes. Using the 805-asteroid ground-truth sample, we train an automated classifier to estimate (along with manual inspection) the validity of the remaining 53,000 fitted periods. By this method we find 9,033 of our lightcurves (of 8,300 unique asteroids) have reliable periods. Subsequent consideration of asteroids with multiple lightcurve fits indicate 4% contamination in these reliable periods. For 3,902 lightcurves with sufficient phase-angle coverage and either a reliably-fit period or low amplitude, we examine the distribution of several phase-function parameters, none of which are bimodal though all correlate with the bond albedo and with visible-band colors. Comparing the theoretical maximal spin rate of a fluid body with our amplitude versus spin-rate distribution suggests that, if held together only by self-gravity, most asteroids are in general less dense than 2 g/cm$^3$, while C types have a lower limit of between 1 and 2 g/cm$^3$, in agreement with previous density estimates. For 5-20km diameters, S types rotate faster and have lower amplitudes than C types. If both populations share the same angular momentum, this may indicate the two types' differing ability to deform under rotational stress. Lastly, we compare our absolute magnitudes and apparent-magnitude residuals to those of the Minor Planet Center's nominal $G=0.15$, rotation-neglecting model; our phase-function plus Fourier-series fitting reduces asteroid photometric RMS scatter by a factor of 3.Comment: 35 pages, 29 figures. Accepted 15-Apr-2015 to The Astronomical Journal (AJ). Supplementary material including ASCII data tables will be available through the publishing journal's websit