Bioscientifica Proceedings

The ancestral wild pig is a short day length seasonal breeder. The domestic pig appears to have retained some of this seasonality as evidenced by a reduction in fertility during the summer—autumn period. The most important aspect of this seasonality is a reduction in the number of mated sows that farrow. Many of these sows conceive and embryos develop normally for 20 - 25 days before pregnancy is terminated and the sow returns to oestrus (25 - 35 days after mating). In ot...

Efficient production of high quality semen is of major importance to artificial insemination (Al) organizations. The semen produced should be free of contagious organisms, be of high quality, have good storage properties, fertilizing capacity and be of high genetic value. The best approach to prevent the spreading of microorganisms via semen in the process of Al is to collect semen from boars free from specific diseases, for example pseudorabies virus or leptospirosis. An...

Research in France and in the UK confirms the prolificacy of the Chinese Meishan breed to be about three to four piglets greater than that of control Large White females. Crossbreeding studies clearly indicate that this breed difference is due to genes acting in the dam and not in the litter itself. There is high heterosis for litter size in F1 Meishan x Large White crossbred females, such that their litter size is similar to or greater than that of purebred Me...

The immune system discriminates 'self' from 'non-self', and eliminates that which it determines to be non-self. Mammalian pregnancy appears to represent a failure of self-non-self discrimination, yet it is a highly successful reproductive strategy. We present evidence that the immune system of the female pig responds to the challenges of both mating and the presence of conceptuses. Mating induces an influx of inflammatory leukocytes into the endometrial stroma and uterine...

Implantation/placentation in domestic pigs is preceded by synthesis ot oestrogen by the conceptus to maintain functional corpora lutea throughout pregnancy and a rapid morphological transformation of conceptuses from spherical to long filamentous thread-like structures. Initial conceptus expansion, reaching a metre in length, not only delineates the surface area for placental attachment, but also provides the mechanism for delivery of oestrogen to signal events necessary ...

Despite the importance of fertilization for animal production, species preservation and controlling reproduction, the molecular basis underlying fertilization is not well understood. More progress has been made in mice than in other mammals, but targeted deletion of specific genes in the mouse has often yielded unexpected results. The pig is also a useful animal to study, as large numbers of pig gametes can be acquired easily. However, it appears that the pig zona pelluc...

Summary. Follicular development during early lactation in the sow is characterized by a large population of small-sized follicles and a small population of medium-sized follicles. As lactation progresses there is a gradual shift in number of follicles into medium- or large-sized categories and the percentage of follicles classified as atretic declines. Weaning at birth often leads to aberrant follicular development, apparently because the positive feedbac...

The resumption of ovarian follicular development during lactation and after weaning in sows is a complex process that ultimately determines rebreeding efficiency of sows. Ovarian follicular development before weaning is heterogeneous because multiple patterns of development are observed when individual sows are compared. Sows can have relatively inactive ovaries before weaning with follicles of < 2 mm in diameter. Other sows have nonovulatory follicular waves in which...

In pigs, as in other species, fetal growth retardation is associated with reduced birth weight and increased risk of fetal and neonatal death. As there are few opportunities after birth to remedy the detrimental effects of low birth weight, it is important to understand both the intrinsic and extrinsic factors associated with inadequate fetal growth and to determine when growth retarded fetuses deviate from the growth trajectory of their normal sized littermates. Inadequately ...

Since 35 years ago boar semen has been frozen and used for artificial insemination (Al). However, fertility of cryopreserved porcine sperm has consistently been low as boar sperm are more sensitive to cellular stress imposed by changing osmotic balance, oxidative stress, low-temperature exposure, cryo-protectant intoxication etc. and are less able to compensate for these deficiencies at commercially applicable dosages. Additionally, differences in sperm freezability amon...