Publish Date: April 9, 2010
By definition, anestrus is a condition in swine during which females do not exhibit estrous cycles. During anestrus, the ovaries are relatively inactive and neither large follicles (ovarian structures that contain an ovum or egg, and that secrete large quantities of estrogen; Figure 1) or functional corpora lutea (ovarian structures that secrete progesterone; Figure 2) are present. Anestrus usually results from insufficient secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamic area of the brain. In cycling gilts and sows, GnRH travels by blood to the anterior pituitary gland, a pea-sized organ located near the base of the brain, where it causes secretion of the gonadotropins, luteinizing hormone (LH) and folliclestimulating hormone (FSH). The LH and FSH in turn, stimulate growth of ovarian follicles, ovulation and in the case of LH, normal function of corpora lutea.
Publish Date: March 25, 2010
Boars have a profound influence on the swine breeding program. Not only do they provide a source of genetic improvement, but they also affect farrowing rate and litter size. Although nutrition of the boar is often given the least amount of attention compared to pigs in other phases of production, it serves as an important factor in determining reproductive performance of the breeding herd and overall animal well-being. Nutrient status influences libido (sex drive), structural soundness and longevity, sperm production, and semen quality. Factors affecting nutrient requirements include age and stage of maturity, body condition, environmental conditions, and ejaculation frequency. Many farms feed boars the sow gestation diet(s), but this feeding program may neglect some of the unique nutrient requirements that must be accounted for to optimize breeding herd performance in working boars. Scientific research regarding the nutrition of boars is lacking. Therefore, feeding strategies used in the pork industry and those presented in this paper are based on a minimal amount of research.