Bioscientifica Proceedings

Summary. Identical twin pairs of dairy cows (one twin being placed with 4 calves for multiple suckling while the other was machine milked) were used to study the hormonal changes associated with anoestrus. Experiments were conducted to examine the effect of multiple suckling on the interval to first oestrus post partum, concentrations of LH and progesterone post partum, and the LH response to LH-RH or oestradiol-17β. The effects of hormo...

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 mammals, growing oocytes have characteristically high levels of RNA synthesis. After the initiation of meiosis, that is germinal vesicle breakdown, this RNA synthesis ceases. Although there is limited evidence for RNA synthesis by the zygote, significant amounts of RNA synthesis do not occur until a species-specific cell stage. In pigs, significant amounts of mRNA synthesis cannot be detected before the four-cell stage. There appear to be three qualitatively different ...

Summary. Changes in uterine blood flow throughout pregnancy appear to be due to steroid-induced alterations in uterine arterial tone and contractility. Arterial contractility is a transient reduction in luminal diameter in response to nerve stimulation or to an alpha-1 adrenergic agonist, leading to short-term reduction in uterine blood flow. Tone is the pressure exerted by an arterial segment against an intraluminal flow (distensibility) and is considere...

On the basis of established surgical procedures for embryo recovery and transfer, the early pig embryo can be subjected to various manipulations aimed at a longterm preservation of genetic material, the generation of identical multiplets, the early determination of sex or the alteration of the genetic make-up. Most of these procedures are still at an experimental stage and despite recent considerable progress are far from practical application. Normal piglets have been ob...