Oestrogen Function in Established Lactation in the Cow

Abstract

In a series of six experiments the effect on milk yield and composition of injecting oestradiol monobenzoate (OB) at five dose levels has been studied on seventy-six cows of the Ayrshire, Guernsey, Friesian and Shorthorn breeds.The doses ranged from 6\m=.\25to 100 mg, and all produced increases in the percentage of non\x=req-\ fatty solids. These changes were due mainly to increases in the protein, lactose and ash fractions and persisted for periods of several weeks. When more than 25 mg OB were injected, fat percentages also increased and milk yields declined. At the 12\m=.\5 mg level, significant increases occurred both in the yields of fat (lb.) and non-fatty solids (lb.). These results indicated that galactopoietic responses could be obtained only within a restricted dose-range, the limits of which were affected by stage of pregnancy and differences in breed.The considerable similarity which exists between these results and the changes occurring in the milk of pregnant cows during a normal lactation suggests that the latter are probably determined by a progressive rise in blood oestrogen levels as pregnancy advances. The results are discussed in relation to the effect of pasture oestrogens on milk composition and with regard to the possibility of improving the quality of milk by oestrogen administration.In contrast to the large number of investigations which have provided information on the role of oestrogens in mammary gland growth and development, relatively few experiments have been planned with the object of defining the functions of these hormones in established lactation. Folley [1936] and Waterman, Freud & Vos-de Jongh [1936] first showed that oestrogens could inhibit lactation in the cow and this was subsequently confirmed by Folley, Scott-Watson & Bottomley [1941] and Stanley & Owen [1941]. Since ovariectomized cows were not included in these or later studies, it was impossible to determine whether or not the presence of the ovary was required to produce this response. Recently, however, Folley [1956] has reviewed the results of similar experiments on other species and has suggested that the inhibi¬ tory action of oestrogen is probably due to a synergism between oestrogen and progesterone. Folley [1936] also provided the first evidence that oestrogens could produce changes in milk composition. These consisted of increases in the percentages of fat and non-fatty solids which in some cows persisted for several months. As a decline in milk yield at the time of injection was merely transient, Folley [1936] considered that this was an example of galactopoiesis and described it as an 'en¬ richment effect'. Similar results were obtained by Folley & Scott-Watson [1938] and Spielman, Ludwick & Petersen [1941] in experiments involving the use of synthetic rather than naturally occurring oestrogens. In an extension of this work, however, Folley et al. [1941] were less successful than previously in separating the apparent inhibitory and

Effect of Oestrogen Administered in Early or Late Lactation on the Yield and Composition of Milk in Sheep

“…The propor¬ tion of cells of Donné (vacuolated macrophages) had increased from 1 % to approxi¬ mately 30 % of total cells. discussion The finding that oestrogen administered in high doses to lactating ewes severely reduced milk yield is consistent with results of earlier studies in ruminants (Folley, 1936;Folley, Scott-Watson & Bottomley, 1941;Hutton, 1958). In the present studies injections of 5000 pg OB resulted in a significant decrease in lactose concentra¬ tion and increases in both leucocyte number and the proportion of vacuolated macro¬ phages in milk suggesting that involution had begun.…”

“…Previous workers have found that administration of oestrogen to lactating rumi¬ nants leads to an enrichment of the milk secreted in conditions of both decreasing and increasing milk yield (Hutton, 1958;Calista, 1965). If the dose of oestrogen injected is sufficient to inhibit milk secretion the percentage enrichment appears to be simply a result of the decline in milk yield and the results for ewes injected with 5000 pg OB are consistent with this suggestion.…”

“…High levels of exogenous oestrogen inhibit milk production (Hutton, 1958;Calista, 1965) but the effect of low doses on milk secretion is far from clear. Stimula¬ tion of milk secretion after administration of low doses of oestrogen has been reported in cows (Browning, Fountaine, Marion & Atkeson, 1957) and goats (Desclin & Derivaux, 1953).…”

Multilevel regulation of steroid synthesis and metabolism in the bovine placenta

“…The shift towards more free oestrogens (oestrone and oestradiol) in late gestation is probably necessary for the preparation of the maternal genital tract for parturition, possibly promoting the relaxation of the pelvic ligaments and inducing cervical softening (Hoffmann et al, 1997;Wood, 1999). Oestrogens are important for the development of the mammary glands in preparation for lactation, as their receptors were found in the developing bovine mammary gland (Schams et al, 2003), yet it was also found that high level of oestrogens inhibit lactation in the cow (Folley, 1936;Hutton, 1958).…”

Proceedings of the Physiological Society, 16–17 January 1970, Mill Hill Meeting: Communications

“…This increased uterine blood flow during hypercapnia suggests that the limiting factor in the rise in umbilical oxygen content might be the rate of mass delivery of oxygen to the placenta. Mixner, Meites & Turner (1944) and Hutton (1958), has shown that subcutaneous injection, implantation or oral administration of oestrogens depresses milk yield in cows and goats, except at very low levels when an 'enrichment' effect is sometimes noted. In an attempt to define more closely the effects of oestrogen on lactation, continuous intravenous infusions of oestradiol were given to two lactating, non-pregnant goats (Daphne, Gail) in each of two experiments.…”