EVALUATION OF ALTERNATIVE RISK SPECIFICATIONS IN FARM PROGRAMMING MODELS

The use of alternative probability density functions to specify risk in farm programming models is explored and compared to a traditional specification using historical data. A method is described that compares risk efficient crop mixes using stochastic dominance techniques to examine impacts of different risk specifications on farm plans. Results indicate that a traditional method using historical farm data is as efficient for risk averse producers as two other methods of incorporating risk in farm programming models when evaluated using second degree stochastic dominance. Stochastic dominance with respect to a function further discriminates among the distributions, indicating that a density function based on the historic forecasting accuracy of the futures market results in a more risk-efficient crop mix for highly risk averse producers. Results also illustrate the need to validate alternative risk specifications perceived as improvements to traditional methods.Risk and Uncertainty,

HEALTH INSURANCE COVERAGE FOR PENNSYLVANIA DAIRY FARM MANAGERS

A survey of more than 1200 Pennsylvania dairy farm managers showed that almost 20% of those managers do not have health insurance. Of those farm managers with health insurance, 67% had insurance acquired through the farm business. Farm characteristics and demographic information were used to determine indicators of health insurance coverage. Age, education, net farm income, off-farm income, milk marketing cooperative membership, and intensity of hired labor use all had significant effects on the likelihood of having health insurance and on whether such insurance was provided by the farm business.Agribusiness, Health Economics and Policy,

THE EFFECT OF MANAGERIAL ABILITY ON FARM FINANCIAL SUCCESS

The effects of managerial ability on farm financial success are analyzed for a 1990 sample of Pennsylvania commercial dairy farms using structural latent variable techniques. Latent factors related to dairy, crop, and financial management are used with herd size to explain farm financial success, measured by net farm income. Results indicate the relative importance of each management variable toward farm financial success.Farm Management,

Applications of artificial intelligence to mission planning

The scheduling problem facing NASA-Marshall mission planning is extremely difficult for several reasons. The most critical factor is the computational complexity involved in developing a schedule. The size of the search space is large along some dimensions and infinite along others. It is because of this and other difficulties that many of the conventional operation research techniques are not feasible or inadequate to solve the problems by themselves. Therefore, the purpose is to examine various artificial intelligence (AI) techniques to assist conventional techniques or to replace them. The specific tasks performed were as follows: (1) to identify mission planning applications for object oriented and rule based programming; (2) to investigate interfacing AI dedicated hardware (Lisp machines) to VAX hardware; (3) to demonstrate how Lisp may be called from within FORTRAN programs; (4) to investigate and report on programming techniques used in some commercial AI shells, such as Knowledge Engineering Environment (KEE); and (5) to study and report on algorithmic methods to reduce complexity as related to AI techniques

Conceptus Competition for Nutrients in the Porcine Uterus: Different Strategies Exhibited by the Meishan and Yorkshire Pig Breeds

Previous research from our laboratory demonstrated that Meishan conceptuses develop more slowly and synchronously to day 30 of gestation than conceptuses of U.S. pig breeds. Furthermore, the reduced size of the Meishan conceptus on day 30 allows more Meishan than Yorkshire conceptuses to occupy the same amount of limited uterine space. As a result, Meishan litter size is significantly larger than that of U.S. pig breeds (13−14 vs. 9-10 piglets/litter). An additional consistent, but unexpected, finding in the Meishan pig was the observation that there was significantly greater amounts of unoccupied uterine space in the Meishan than the Yorkshire female at term. We previously demonstrated that an additional strategy of the Meishan female to increase fecundity was to super-vascularize its placental membranes so that oxygen and nutrient transfer from the sow could be accomplished over a reduced surface area, negating the necessity of further placental growth. These data suggested that when a Meishan conceptus dies, the placenta of its neighbors need not grow into this newly vacated space, whereas the Yorkshire conceptus might increase the size of its less vascular placenta to use the opportunity. Therefore, it was our objective to confirm that Yorkshire conceptuses, but not Meishan conceptuses increase their placental size when adjacent conceptuses are experimentally destroyed on day 40 of gestation. To accomplish this objective, pregnant Meishan and Yorkshire females were laporatomized on day 40. One uterine horn was randomly chosen to be receive alternative fetal crushing (i.e., every other fetus in the horn was crushed by mechanical pressure), whereas the other uterine horn served as the control horn. At slaughter on day 111 of gestation (term = 114 days), we found no differences in fetal weight between the control and treated horns regardless of breed. Similarly, there was no difference in placental weight or surface area or implantation site length (the length of placental attachment in the uterine horn) between the control and treated horns in the Meishan. In contrast, however, there was a marked increase in placental weight and surface area, as well as implantation site length for conceptuses in the treated horn of the Yorkshire gilts versus the control horn. Furthermore, the unoccupied spaces between Meishan conceptuses in the treated horn were 2-fold greater than for conceptuses in the control horn, whereas there were no differences in the length of unoccupied spaces between conceptuses in the Yorkshire’s control or treated horns. These data suggest that in the Meishan treated horn, conceptuses do not use this extra space as effectively as conceptuses in the Yorkshire treated horn. The inability of Meishan placenta to grow into adjacent unoccupied spaces may not be detrimental to conceptus survival due to its greater ability to increase vascular density in response to increasing fetal demands. If U.S. pig breeds have the potential to increase placental vascularity, rather than increase in placental size to nourish the growing fetuses, the potential exists for increasing litter size due to a decrease in uterine competition throughout gestation

Role of Vascular Endothelial Growth Factor in Placental Vascularization

The ratio of a fetus’s weight to that of its placenta has been used in our laboratory as an estimate of placental efficiency, which defines the number of grams of placenta required to support a gram of fetus. Because the pig placenta is noninvasive, nutrients from the mother must diffuse from uterine blood vessels to placental blood vessels at the placental-endometrial interface. A pig placenta can respond to increasing fetal nutrient demands by either increasing in size, and thus surface area in contact with the endometrium, or by increasing the number of blood vessels per unit area at the fetal-maternal interface. Previous studies from our laboratory have shown Meishan and Yorkshire conceptuses gestated in a Meishan uterus had markedly smaller placentae than Meishan or Yorkshire conceptuses gestated in a Yorkshire uterus whereas fetal weights across the two uterine environments were much more similar. These data suggested that conceptuses in a Meishan uterine environment have a greater vascular density at the placentalendometrial interface. Greater densities of blood vessels can be achieved by either vasodilation (increasing the diameter of existing blood vessels) or angiogenesis (growth of new vessels from preexisting ones). Hypoxia, or inadequate oxygen transport, has been shown to increase angiogenic factors, such as vascular endothelial growth factor (VEGF), which stimulate blood vessel development. It is possible that VEGF may be important in stimulating increased blood vessel density in the pig placenta, as it has been to shown to do in the ovine placenta. Our objective was to determine if VEGF mRNA expression was associated with placental and/or endometrial vascular density, placental efficiency, and litter size during late gestation. We observed a positive association of both placental vascular density (r=0.37, p\u3c0.05) and VEGF mRNA levels (r=0.35; P\u3c.05) with placental efficiency . There was also a positive correlation between VEGF mRNA levels and the number of conceptuses in a litter (r=0.42; P\u3c.05) on day 70, 90, and 110 of gestation. Although Yorkshire uteri exhibited greater endometrial vascular density than Meishan uteri on day 70 of gestation, placentae of conceptuses gestated in a Meishan uterus had greater amounts of VEGF mRNA than placentae of conceptuses gestated in a Yorkshire uterus. The greater amounts of placental VEGF mRNA of conceptuses gestated in a Meishan uterus on day 70 may have resulted in the increased placental vascular density observed on day 90. We conclude that the increased litter size of the Meishan female may stem from her having smaller, more vascular placentae than placentae of conceptuses gestated in the uterus of a Yorkshire female, to allow for efficient nutrient delivery to the fetus. The increased placental vascular density of a conceptus gestated in the uterus of a Meishan female may result from increased placental VEGF mRNA production induced from an endometrial induced hypoxia on day 70 of gestation

Use of Asynchronous Embryo Transfer to Investigate the Role of Uterine-embryo Timing on Placental Size

The ability of the uterus to accommodate a finite amount of placental tissue appears to be a major limitation to litter size. Meishan preimplantation conceptuses contain fewer cells, produce less estradiol-17β, elongate to a shorter length, and exhibit a reduced placental size throughout gestation than Yorkshire conceptuses. Uterine luminal embryonic estradiol-17β and growth factor content are positively associated at elongation. Based on these data, we have argued that growth factor quantity regulates the length an embryo attains at elongation, and ultimately limits placental size. Recently, we injected Meishan gilts every 6 hours with estradiol-17β on day 12 and 13 of gestation, resulting in a 40% increase in placental size at term compared with vehicle-injected Meishan gilts. This study was conducted to determine if transfer of embryos into the oviducts of asynchronous females (more or less advanced uterine environments) would alter fetal and/or placental size at term. Embryos (1 to 4 cells) were flushed from the oviducts of each donor gilt on day 2.5 of gestation and transferred in equal numbers to the oviducts of a recipient gilt on day 1.5, 2.5, or 3.5 of their estrous cycle. Gilts were slaughtered on day 112 of gestation and fetal and placental weight, placental surface area, and implantation site lengths were determined. Although litter sizes were similar (8.4 ± 1.1), conceptuses transferred to day 3.5 recipients had heavier fetuses (1.57 ± .09 vs. 1.23 ± .04 kg, P\u3c.001), larger placental surface area (1812 ± 106 vs. 1458 ± 43 cm 2 , P\u3c.01) and occupied longer implantation site length (34 ± 3 vs. 25 ± 1 cm, P\u3c.001) than those transferred to recipients on day 1.5 or 2.5. These data demonstrate that oviductal transfer of embryos to a reproductive tract as little as 24 hours more advanced can result in dramatic alterations in placental growth and function during gestation

Ovarian responses to undernutrition in pregnant ewes, USA

In most mammals oogonia proliferate by mitosis and begin meiotic development during fetal life. Previous studies indicated that there is a delay in the progression to the first stage of meiotic arrest in germ cells of female fetuses of undernourished ewes. We report that underfeeding (50% NRC requirement beginning on Day 28 of pregnancy) provokes an increase in oxidative base lesions within DNA of mid-gestational (Day 78) fetal oogonia; this condition was associated with up-regulation of the tumor suppressor/cell-cycle arrest modulator p53, antiapoptotic factor Bcl-2, and base-excision repair polymerase β. Fetal ovarian weights and germ cell concentrations were not altered by nutrient deprivation. Ovaries of ewes on control diets (100% NRC) contained more tertiary follicles than their restricted counterparts; however, peripheral venous estradiol-17β was not different between groups. There was no effect of treatment on p53 accumulation in maternal oocytes. Luteal structure-function was not perturbed by undernutrition. No fetal losses were attributed to the dietary restriction. It is proposed that DNA of interphase fetal oogonia is vulnerable to oxidative insults perpetrated by a nutritional stress to the dam, and that multiple/integrated adaptive molecular response mechanisms of cell-cycle inhibition (providing the time required for base repairs) and survival hence sustain the genomic integrity and population stability of the germline