Perspectives for artificial insemination and genomics to improve global swine populations

Civilizations throughout the world continue to depend on pig meat as an important food source. Approximately 40% of the red meat consumed annually worldwide (94 million metric tons) is pig meat. Pig numbers (940 million) and consumption have increased consistent with the increasing world population (FAO 2002). In the past 50 years, research guided genetic selection and nutrition programs have had a major impact on improving carcass composition and efficiency of production in swine. The use of artificial insemination (AI) in Europe has also had a major impact on pig improvement in the past 35 years and more recently in the USA. Several scientific advances in gamete physiology and/or manipulation have been successfully utilized while others are just beginning to be applied at the production level. Semen extenders that permit the use of fresh semen for more than 5 days post-collection are largely responsible for the success of AI in pigs worldwide. Transfer of the best genetics has been enabled by use of AI with fresh semen, and to some extent, by use of AI with frozen semen over the past 25 years. Sexed semen, now a reality, has the potential for increasing the rate of genetic progress in AI programs when used in conjunction with newly developed low sperm number insemination technology. Embryo cryopreservation provides opportunities for international transport of maternal germplasm worldwide; non-surgical transfer of viable embryos in practice is nearing reality. While production of transgenic animals has been successful, the low level of efficiency in producing these animals and lack of information on multigene interactions limit the use of the technology in applied production systems. Technologies based on research in functional genomics, proteomics and cloning have significant potential, but considerable research effort will be required before they can be utilized for AI in pig production. In the past 15 years, there has been a coordinated worldwide scientific effort to develop the genetic linkage map of the pig with the goal of identifying pigs with genetic alleles that result in improved growth rate, carcass quality, and reproductive performance. Molecular genetic tests have been developed to select pigs with improved traits such as removal of the porcine stress (RYR1) syndrome, and selection for specific estrogen receptor (ESR) alleles. Less progress has been made in developing routine tests related to diseases. Major research in genomics is being pursued to improve the efficiency of selection for healthier pigs with disease resistance properties. The sequencing of the genome of the pig to identify new genes and unique regulatory elements holds great promise to provide new information that can be used in pig production. AI, in vitro embryo production and embryo transfer will be the preferred means of implementing these new technologies to enhance efficiency of pig production in the future

Effects of dietary conjugated linoleic acid on growth and body composition of control and IGF-I transgenic pigs

Both dietary conjugated linoleic acid (CLA) and presence of the IGF-I transgene are reported to alter the fat:lean content of pigs. The purpose of this study was to compare the growth and body composition of control and IGF-I transgenic pigs in response to dietary CLA. Transgenic (TG) pigs expressing the IGF-I gene and sibling control (C) progeny were produced by mating two half-sib G-1 transgenic boars to non-transgenic gilts. At 60 kg each pig was scanned by dual-energy X-ray absorptiometry (DXA) for body composition analysis, then placed on an 18% crude protein diet containing either 2% corn oil (CO diet) or 1.2% CO plus 0.8% CLA. Thus, the four genotype-diet combinations were: C-CO (n=25), C-CLA (n=25), TG-CO (n=24), and TG-CLA (n=23). Each pig was scanned again at 110 kg. All pigs were slaughtered at 120 kg and the right half-carcass was scanned by DXA. Results of the DXA scan at 60 kg revealed that the TG pigs were less fat (15.0%) than the C pigs (18.8%, P < 0.05). During growth from 60 to 110 kg, the tissue gain for the C-CO, C-CLA, TG-CO, and TG-CLA groups consisted of 16.6, 14.5, 13.2, and 13.0 kg of fat (P < 0.05, C-CO vs. C-CLA and C vs. TG); and 30.6, 32.6, 33.7, and 33.8 kg of lean (P < 0.05, C-CO vs. C-CLA and C vs. TG), respectively. There were only minor differences in bone growth. For the same groups, chemical analysis of the half-carcass revealed 29.2, 27.1, 23.8, and 22.8% fat (P < 0.05 for C-CO vs. C-CLA and C vs. TG), respectively. Overall, the effects of CLA were less than those of TG on body or carcass composition; however, during the treatment period from 60 to 110 kg, the effects were similar. TG pigs did not respond to CLA as much as did control pigs.Effets de l’acide linoléique conjugué sur la croissance et la composition corporelle de porcs normaux et transgéniques IGF-I. L’acide linoléique conjugué (CLA) et la présence du transgène IGF-I ont tous deux des effets sur la composition corporelle du porc. L’objectif de cette étude était de comparer la croissance et la composition corporelle de porcs normaux et transgéniques IGF-I recevant dans leur ration du CLA. Des porcs transgéniques exprimant le gène IGF-I (TG) et des porcs témoins (C) ont été produits en croisant 2 verrats transgéniques de la même famille avec des truies normales. A 60 kg, chaque porc a été scanné par absorptiométrie biphotonique à rayons X (dual-energy X-ray absorptiometry, DXA) et a reçu une ration avec 18 % de matières azotées, contenant soit 2,0 % d’huile de maïs (CO), soit 1,2 % d’huile de maïs et 0,8 % de CLA. Ainsi 4 combinaisons génotypes × rations ont été obtenues : C-CO (n=25), C-CLA (n=25), TG-CO (n=24) et TG-CLA (n=23). Chaque porc a été de nouveau scanné à 110 kg. Tous ont été abattus à 120 kg et leur demi-carcasse droite scannée et analysée chimiquement. Les résultats de la scanographie faite à 60 kg montrent que les porcs TG avaient une teneur moindre en gras (15,0 %) que les porcs C (18,8 %, P < 0,05). Durant la période de croissance de 60 à 110 kg, le gain tissulaire des groupes C-CO, C-CLA, TG-CO et TG-CLA se composait de 16,6, 14,5, 13,2 et 13,0 kg de gras (P < 0,05, C-CO vs. C-CLA et C vs. TG) et 30,6, 32,6, 33,7 et 33,8 kg de viande maigre (P < 0,05, C-CO vs. C-CLA et C vs. TG), respectivement. La croissance osseuse n’a montré que de faibles variations. Pour les mêmes groupes, la teneur en gras de la demi-carcasse, mesurée par analyse chimique, était de 29,2, 27,1, 23,8 et 22,8 % (P < 0,05, C-CO vs. C-CLA et C vs. TG) respectivement. D’une manière générale, les effets du CLA ont été moins prononcés sur la composition corporelle et sur la carcasse que ceux dus à la présence du transgène IGF-I, mais ils ont été semblables durant la période expérimentale de 60 à 110 kg. Les porcs TG ont été moins sensibles à l’apport de CLA que les porcs témoins

COLONY ISOLATION AND SECONDARY CULTURE OF FETAL PORCINE HEPATOCYTES ON STO FEEDER CELLS

The secondary culture of non-transformed parenchymal hepatocytes has not been possible. STO feeder cell-dependent secondary cultures of fetal pig hepatocytes were established by colony isolation from primary cultures of 26-d fetal livers. The liver cells had the typical polygonal morphology of parenchymal hepatocytes. They also spontaneously differentiated to form small biliary canaliculi between individual cells or progressed further to large multicellular duct-like structures or cells undergoing gross lipid accumulation and secretion. The secondary hepatocyte cultures expressed alpha-fetoprotein (AFP), albumin, and β-fibrinogen mRNA, and conditioned medium from the cells contained elevated levels of transferrin and albumin. STO feeder cell co-culture may be useful for the sustainable culture of hepatocytes from other species

A CONTINUOUS CULTURE OF PLURIPOTENT FETAL HEPATOCYTES DERIVED FROM THE 8-DAY EPIBLAST OF THE PIG

Continuous cultures of pluripotent prenchymal hepatocytes were derived from the epiblasts of 8-day-old pig blastocytes. The cells were polygonal and had phase-contrast dark, granular cytoplasm with prominent nuclei and nucleoli. These feeder-dependent cell cultures differentiated into large, multicellular, secretory, duct-like structures or formed small canaliculi between individual cells. Alternatively, the cells accumulated droplets that stained intensely with Oil Red O, a lipid-specific stain. Alpha-fetoprotein (AFP), albumin, and β-fibrinogen mRNAs were expressed as the cells differentiated in culture. Serum-free medium that was conditioned by the cells contained transferrin, AFP, and albumin. The growth and viability of the cells were inhibited by transforming growth factor β1 (TGFβ1) at concentrations ≥ 1ng/ml. The cell cultures grew slowly with doubling times of 2 to 3 d. One of the cultures, pig inner cell mass-19 (PICM-19), was passaged continuously for over 2 yr [\u3e100 population doublings (PD)] and appears to be an infinitely self-renewing cell population. The stem cell characteristics of the epiblast-derived fetal hepatocytes indicate that the cells may be unique for investigations of liver differentiation and organogenesis

Genetically enhanced cows resist intramammary Staphylococcus aureus infection

Mastitis, the most consequential disease in dairy cattle, costs the US dairy industry billions of dollars annually. To test the feasibility of protecting animals through genetic engineering, transgenic cows secreting lysostaphin at concentrations ranging from 0.9 to 14 mg/ml in their milk were produced. In vitro assays demonstrated the milk's ability to kill Staphylococcus aureus. Intramammary infusions of S. aureus were administered to three transgenic and ten nontransgenic cows. Increases in milk somatic cells, elevated body temperatures and induced acute phase proteins, each indicative of infection, were observed in all of the nontransgenic cows but in none of the transgenic animals. Protection against S. aureus mastitis appears to be achievable with as little as 3 mg/ml of lysostaphin in milk. Our results indicate that genetic engineering can provide a viable tool for enhancing resistance to disease and improve the well-being of livestock