Influence of the Boar on Litter Size

Although the role of the boar in achieving a high conception rate among sows in a herd has long been recognized, the sow has gene rally been considered to be solely responsible for litter size. Litter size is determined by (l) the number of eggs ovulated, (2) the quality of eggs ovulated as evidenced by the ability of the eggs to be fertilized and develop into normal embryos, (3) the ability of the uterus to provide the proper environment for implantation and the development of normal embryos during pregnancy and (4) the number and quality of sperm received by the female at mating as evidenced by the ability of the sperm to fertilize the eggs and insure normal development of the embryo. The factors which determine litter size may be affected by nutrition, age of animals, temperature, light, hormone balance, disease and various other stresses on the animal. This study was made to determine if differences in fertility level exist among boars and to determine whether these differences, if they exist, can affect litter size

Estrus Synchronization and Artificial Insemination of Swine

For years scientists have been trying to find drugs or hormones that will control the reproductive cycle and bring gilts into estrus together to be bred at the same time. The only compound tested to date which has been successful in achieving this goal without also producing undesirable side effects is one called by the tradename Aimax. During a normal estrous cycle, gonadotropic hormones are released from the pituitary gland and are carried by the blood to the ovary where these hormones stimulate the production of estrogen by the ovary and cause ovulation. When Aimax is fed to female swine, it prevents the release of gonadotropic hormones from the pituitary gland. Without stimulation from gonadotropic hormones, ovulation does not occur and the ovary does not produce the estrogen needed to bring sows and gilts into estrus. Thus, Aimax fed to sows or gilts prevents them from ovulating or coming into estrus. Most females will then exhibit estrus accompanied by ovulation five to seven days following withdrawal of Aimax from the feed. With the increasing interest among South Dakota Swine Producers in estrus synchronization and artificial insemination, this study was made to compare these techniques with unsynchronization and natural service under practical farm conditions in South Dakota

Relationship of Some Semen Characteristics of the Boar to Fecundity of the Sow

As the price-cost squeeze be comes more critical to the pork producer, every fact or which affects net profit must be critically weighed. The profit making potential of a swine herd increases directly with an increase in the number of live offspring produced per sow. The production of large litters is dependent on high fertility in both the sow and the boar. The fertility of boars will vary from complete sterility to high fertility . An actual breeding test is the only highly reliable method of those used to measure fertility level in the boar, but boars of complete sterility can usually be detected by semen testing. Since an actual breeding test is a very expensive method of determining the fertility level of a boar, it would be highly desirable to develop a rapid inexpensive method for determining the fertility level o f boars so that boars of low to moderate fertility could be eliminated from the herd be fore use. The purpose of this study was to determine the relationship between certain measures of semen quality in the boar and fecundity in the sow and to measure the variation among boars with respect to these measures of semen quality

Transmission Losses in Left-handed Materials

We numerically analyze the origin of the transmission losses in left-handed structures. Our data confirms that left handed structures can have very good transmission properties, in spite of the expectable dispersion of their effective permeability and refraction index. The large permittivity of the metallic components improves the transmission. High losses, observed in recent experiments, could be explained by the absorption of the dielectric board

The Influence of Alfalfa Coumestrol on the Reproductive Performance of Gilts

In Australia during the early 1940\u27sa syndrome known as clover disease was observed in sheep grazing subterranean clover. This syndrome was characterized by a marked reduction in fertility which was later proved to be due to a high content of estrogenic substances in the clover. Alfalfa has since been shown to contain varying levels of these plant estrogens. The most important of the plant estrogens present in alfalfa is coumestrol because of its relatively greater biological potency than the other plant estrogens and because of its more frequent occurrence. Plant physiologists have shown that alfalfa infected with certain fungus diseases contains a level of coumestrol which increases with the amount of disease present in the alfalfa plants. Since alfalfa meal is such an important source of nutrients for farm animals and is often included in swine rations this study was conducted to determine if alfalfa plants with coumestrol levels in excess of 100 parts per million (ppm) would have any effect on the reproductive performance of gilts when included in their ration

Transmission Studies of Left-handed Materials

Left-handed materials are studied numerically using an improved version of the transfer-matrix method. The transmission, reflection, the phase of the reflection and the absorption are calculated and compared with experiments for both single split-ring resonators (SRR) with negative permeability and left-handed materials (LHMs) which have both the permittivity and permeability negative. Our results suggest ways of positively identifying materials that have both permittivity and permeability negative, from materials that have either permeability or permittivity negative

Refraction of Electromagnetic Energy for Wave Packets Incident on a Negative Index Medium is Always Negative

We analyze refraction of electromagnetic wave packets on passing from an isotropic positive to an isotropic negative refractive index medium. We definitively show that in all cases the energy is always refracted negatively. For localized wave packets, the group refraction is also always negative.Comment: 5 pages, 3 figure

Resonant and anti-resonant frequency dependence of the effective parameters of metamaterials

We present a numerical study of the electromagnetic response of the metamaterial elements that are usedto construct materials with negative refractive index. For an array of split ring resonators (SRR) we find that the resonant behavior of the effective magnetic permeability is accompanied by an anti-resonant behavior of the effective permittivity. In addition, the imaginary parts of the effective permittivity and permeability are opposite in sign. We also observe an identical resonant versus anti-resonant frequency dependence of the effective materials parameters for a periodic array of thin metallic wires with cuts placed periodically along the length of the wire, with roles of the permittivity and permeability reversed from the SRR case. We show in a simple manner that the finite unit cell size is responsible for the anti-resonant behavior

Theoretical investigation on the possibility of preparing left-handed materials in metallic magnetic granular composites

We investigate the possibility of preparing left-handed materials in metallic magnetic granular composites. Based on the effective medium approximation, we show that by incorporating metallic magnetic nanoparticles into an appropriate insulating matrix and controlling the directions of magnetization of metallic magnetic components and their volume fraction, it may be possible to prepare a composite medium of low eddy current loss which is left-handed for electromagnetic waves propagating in some special direction and polarization in a frequency region near the ferromagnetic resonance frequency. This composite may be easier to make on an industrial scale. In addition, its physical properties may be easily tuned by rotating the magnetization locally.Comment: 5 figure