Site of Digestion of Starch in the Gastrointestinal Tract of Dairy Cows and Its Effect on Milk Yield and Composition

The potential steroid hormone contribution of farm animals to freshwaters, the United Kingdom as a case study.

Ultrasonic morphology of corpora lutea and central luteal cavities during the estrous cycle and early pregnancy in heifers.

Publisher Summary This chapter discusses interrelations between progesterone and the ovary, pituitary, and central nervous system in the control of ovulation and the regulation of progesterone secretion. The relationships between progesterone and the central nervous system (CNS), the pituitary, and the ovary have been chosen as a framework upon which to build the discussion of these problems because progesterone affects the activity of these three essential elements of the reproductive system in ways that are directly or indirectly related to the growth of follicles and ovulation. Regardless of where, in the process of ovulation, the primary point of action of progesterone lies, a complete picture of its participation in the control of ovulation can be had only by considering its primary action in relation to all possible secondary ones. The fact that the administration of progesterone induces ovulation does not prove, of course, that spontaneous ovulation is the result of the action of progesterone.

Interrelations between progesterone and the ovary, pituitary, and central nervous system in the control of ovulation and the regulation of progesterone secretion.

Intravascular catheters were placed in the umbilical, uterine and maternal peripheral circulations of 16 Jersey cows between 240 and 260 days of gestation. Foetal plasma cortisol, blood gases and pH, and maternal plasma oestrogen, progesterone and cortisol were measured in ten animals during late pregnancy and throughout spontaneous parturition; all delivered live foetuses although parturition was earlier than normal and the placenta was generally retained. The gradual pre-partum rise in foetal plasma cortisol during the last week ofgestation (from 10\\p=n-\\20ng/ml 7 days before parturition to 51 \\m=+-\\5 ng/ml in the last 3 h before delivery) was much less marked than the abrupt increase immediately after birth when the cortisol concentration invariably doubled. Maternal plasma oestrogen rose from 0.35 \\m=+-\\0.04 ng/ml to 1\\m=.\\20\\m=+-\\0.11 ng/ml during the week before parturition. Progesterone concentrations remained stable until a sudden fall 1\\p=n-\\2days before delivery. The slight alterations in maternal plasma cortisol during this period were not statistically significant. The maternal plasma oestrogen levels were higher in the uterine vein than in the periphery, whereas uterine venous progesterone concentrations were significantly lower than in the peripheral circulation. The hormonal changes associated with the artificial induction of labour

W.R. Gomes

Papers

Progestin Levels in Corpora Lutea and Progesterone in Ovarian Venous and Jugular Vein Blood Plasma of the Pregnant Bovine

Progestin Levels in Jugular and Ovarian Venous Blood, Corpora Lutea, and Ovaries of the Nonpregnant Bovine

Effect of ovariectomy on concentration of progesterone in blood plasma and urinary estrogen excretion rate in the pregnant bovine.

Progestin Content of Ovaries and the Effect on Assessment of Luteal Activity in the Bovine