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Prairie Swine Centre is an affiliate of the University of Saskatchewan
Prairie Swine Centre is grateful for the assistance of the George Morris Centre in developing the economics portion of Pork Insight.
Financial support for the Enterprise Model Project and Pork Insight has been provided by:
Genetic determination of mothering ability and piglet growth in indigenous Mukota sows of Zimbabwe
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The objectives of this study were to estimate the direct and maternal genetic effects for weight of pigs at 21 days and at weaning (35 days) and growth rate from birth to weaning, and determine the genetic parameters for cumulative litter traits and mothering ability in Mukota sows. It was found that common environmental litter effects for these traits were low. Incorporating maternal genetic influence increased the precision of the heritability estimates. Maternal genetic influence tended to increase as the pigs grew. Since MA was not genetically correlated to either LTHRWT or LWWT, no antagonisms should be expected when selecting for mothering ability and increasing litter weights in Mukota pigs.
Roadmap for a Competitive Pork Industry in USA
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U.S. pork production increased by 11% at a time when higher feed costs should have caused a 6%
reduction in output. The industry has not yet felt the full economic costs
associated with this output expansion due to a perfect storm of other events
that worked to mitigate the impact of these economic forces. Key among these
events was a weakening of the U.S. dollar and a dramatic expansion of U.S.
exports to China. When and if the dollar strengthens, this will cause hardship
for U.S. pork producers even as it reduces feed costs. China imported more
pork because it made political and economic sense to do so. Now that the
Olympics are over, much of the political reason for these imports has been
eliminated. This means that exports will be maintained only if the Chinese
government allows market forces to operate. As labor shortages emerge in
China, fewer farm families will be willing to produce backyard pigs, a sector
that currently produces about half of all the pork produced in China. If China
responds to this problem by allowing a continuation of imports, then U.S. pork
producers might dodge the bullet and export their way out of the problem of
increased production. However, if China decides to restrict pork imports
despite these economic forces, then the U.S. pork industry will need to cut its
sow numbers by about 3%. This is less than one might otherwise have
expected in part because other countries have already adjusted and because
the price of almost all other foods has also increased.
A Review of Molecular Contrasts Between Arresting and Viable Porcine Attachment Sites
Posted in: Pork Insight Articles, Production by admin on August 14, 2007 | No Comments
Significant spontaneous fetal loss of unknown cause occurs in North American commercial swine. About 30% of conceptuses, thought to be genetically normal, are lost during the peri-attachment period. An additional 20% are lost at mid-pregnancy. Littermate endometrial and trophoblast biopsies were studied by quantitative real-time PCR for gene expression, and immunohistochemistry for protein expression at gestation day (gd)15–23 and 50. RNA analyses were also conducted on endometrial lymphocytes and arterial endothelial cells removed from biopsies by laser capture microdissection. Genes were selected for study from human literature and cloned as required. As in humans, angiogenic, cytokine, chemokine and chemokine decoy receptor gene expression occurs at the porcine maternal–fetal interface. In each tissue studied, distinct patterns of expression are found between early and mid-pregnancy, as well as between viable and arresting conceptus attachment sites. These changes involve both endometrial lymphocytes and dendritic cells. Restriction in endometrial angiogenesis, reduction in expression of the chemokine decoy receptor D6, and reduction in dendritic
cell numbers contribute to fetal arrest. In peri-attachment loss, interferon- c is more abundantly transcribed than tumor necrosis factor-a, but this ratio is reversed during midgestation failure. Further characterization of spontaneous fetal loss in pigs will identify targets for modification by hog producers and may provide a model for identification of antecedents to fetal loss in humans.
Our studies also characterize spontaneous fetal loss in pigs as an excellent animal model to assist in understanding the maternal–fetal interactions leading to pregnancy failure in humans. We have found porcine and human endometria, as well as trophoblasts, express similar cytokines, chemokines, and chemokine decoy receptors. The large amount of material available for study from porcine attachment sites, the reliability of spontaneous fetal arrest and its consistency of timing, the accessibility to timed pregnant reproductive tracts, and the ability to conduct paired sampling of littermates with different survival potential are all strong features that should complement studies in patients where these features are limiting.
A Review of Gene Expression in Porcine Endometrial Lymphocytes, Endothelium and Trophoblasts During Pregnancy Success and Failure
Posted in: Pork Insight Articles, Production by admin on June 13, 2007 | No Comments
In sows, the majority of fetal loss occurs in the implantation stage (G11-12), or later in mid-gestation. Angiogenesis must occur to provide nutrients to the growing fetuses, and can be done by increasing the surface area of the endometrial tissue or by increasing the density of blood vessels. VEGF binds to one of its two receptors on the maternal-fetal interface, and is responsible for endothelium cell proliferation, migration, and capillary permeability. Studying receptors for VEGF is complicated by the existence of a human, soluble VEGF-RI, and by PIGF which also binds VEGF-RI. Porcine endometrial cells have 2-3 times as many uterine natural killer cells (uNK), and studies on the purpose of this have mostly been performed for species other than porcine. Endometrial lymphocytes also contribute to angiogenesis, as indicated by VEGF and PIGF. In arresting conceptuses the levels of VEGF were lower, or not present, in lymphocytes; whereas, PIGF became elevated when failure was occurring. Increased PIGF could increase bioavailable VEGF, or help maturation of uNK cells. The level of transcription of either VEGF receptor was unchanged in conceptuse, but levels of VEGF-RI were higher in healthy sites to begin with. Endometrial endothelial cells attach to capillaries and make the blood-tissue interface, as well, they contribute to angiogenesis, provide paracrine signals for stem cell and organ development, and activate proliferation. Endothelial cells migrate by releasing degrading enzymes into the surrounding matrix, and moving into the opened area. Endothelial cells have increased PIGF and VEGF when pregnancy is occuring, and in fetal arrest VEGF transcription declines, but PIGF remains constant. Both receptors are transcribed, although VEGF-RII is done so at a higher level indicating endothelial cells and lymphocytes have different responses to VEGF. Porcine trophoblast research is limited, but in other species contributes to blood vessel development through angiogenesis, anti-angiogenesis, and vasoactive factors. Trophoblasts release the cytokines IFN-γ and IFN-δ, which are likely targeted to endometrial cells and could help activate and recruit lymphocytes. Trophoblasts transcribe higher VEGF than PIGF, but still at a lower level than lymphocytes. VEGF-RII is transcribed more than VEGF-RI, and VEGF-RI varies depending on gestation date, but does not vary during conceptuse failure. VEGF, PIGF, and VEGF-RII all decreased during conceptuse failure. Trophoblasts likely release stress signals to lymphocytes, which then withdraw angiogenesis and result in conceptuse failure. Lymphocytes, endothelial cells, and trophoblasts contribute to angiogenesis through transcription of VEGF, PIGF, VEGF-RI, and VEGF-RII. Angiogenesis is responsible for providing nutrients to conceptuses, and changes in transcription can indicate or contribute to pregnancy failure.
On-Farm Feed Inspections
Posted in: Pork Insight Articles, Production by admin on April 3, 2007 | No Comments
The Canadian Food Inspection Agency (CFIA) analyzes feed to ensure the ingredients, medication, contaminants, and ruminant feed material are all allowed and at acceptable levels. New medication regulations are in the process of being created, and acceptable medication levels are given in the Medicating Ingredient Brochure. Feed manufacturers are required to keep records on type and amount of medication used, and clean out procedures.
Management Practices that Optimize Productivity in the Nursery – Case Studies on What Works!
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The nursery is a critical point for pigs, and having a consistently healthy group can improve overall barn performance. Producing good weaned pigs depends on the sow operation. Good herd health and biosecurity, and strong herd productivity are important considerations. Nursery pigs should be uniform in size and immunity, and be at a known age. Good preparation will reduce the stress on pigs entering the nursery. The room should be properly cleaned, dried, and temperature, drinkers, and feeders adjusted. Sorting is generally inefficient, but the smallest pigs and sick pigs can be separated. The first 4 days are the most crucial, and attention and intervention should be applied early on to those that are not eating. Nursery feed is expensive, so budgeting and feeding age appropriate diets should be done to receive the most benefit while maintaining costs.
Managing Reproduction – Critical Control Points in Exceeding 30 Pigs Per Sow Per Year
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Reaching 30 pigs weaned/sow/year (PSY) remains a goal of many producers, and is used as a comparison number between pig producing countries. It can be achieved through many strategies, but the basics are to have healthy, fertile sows, proper insemination, reduced non-productive days, and high weaning rates. Of all the variables involved in PSY, the length of weaning to conception to first oestrus usually has potential for reduction. By maintaining sow weight throughout lactation sows can be bred sooner, and have more success in their next pregnancy. Although little change has been made to the general sow reproductive cycle, the knowledge of the timing has improved which can aid technicians in knowing when to breed. Ensuring successful insemination relies on proper technician training, and proper storage of viable semen. Non-productive days can be minimized by keeping sows healthy and in good body condition, detecting heat, and aggressive culling strategies. The number weaned can be increased by increasing litter size through genetics, or by reducing pre-weaning mortality. Reducing pre-weaning mortality can be helped by providing proper nutrition and temperature control, and by intervening when necessary. Herd health through maintain strict biosecurity is important because a disease outbreak can greatly reduce PSY, and can take a significant amount of time to recover from. Climate change can have an impact on PSY as hotter conditions tend to reduce productivity. This is especially true for sows housed outdoors. Through proper management the 30 PSY goal is achievable for individual producers, and is expected to be reached by a country average in the future.
New Tools to Make Genetic Progress
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Phenotypic selection and EBV have mainly been used to select breeding stock, but genetic knowledge could allow for selection of traits with low heritability and traits that are difficult to measure. Molecular genetics may be the technology that is able to provide selection for traits in a more convenient and accurate way, and earlier in the animal’s life. Molecular genetics have allowed many genes to be mapped, and genetic markers identified. These genetic markers can be used for marker-assisted selection, and can help identify genes that are related to economic improvements through breed-cross genome scans and candidate gene associated studies. Although some genes have been identified, many more remain unknown. Pig genome sequencing has begun, but the full sequencing would allow for further advancements and understanding. Sequencing analyzes the genome of one individual, so for genetic selection SNPs identify a large number of markers used for selection, and technology advancements have reduced the cost and time of doing so. Until the genome is sequenced, genetic selection can be done by using a combination of markers and EBV. Genetic selection is further complicated by the fact that research mainly uses purebred pigs, whereas commercial barns often use crossbreeds. To overcome this, selection on effects of markers can be used. Genetic selection could provide increased accuracy for selection, and with molecular technology and sequencing becoming more advanced and available it is soon to be a reality.