A Contribution to the Physiology of Lactation

Gaines, W.L.

doi:10.1152/ajplegacy.1915.38.2.285

Cited by 77 publications

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“…(8) Variations in intramammary pressure, prior to milking, do not affect the average fat content of cow's milk over a period. (9) There is no significant change in the fat globule size distribution pattern of either cow or sow milk as milking proceeds.…”

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confidence: 97%

“…(2) By milking a goat on its back after massaging tbe udder, Games (9) showed that the fat trend is still maintained, while Crowther(i) showed that the tendency for the fat percentage to increase is lost for a considerable portion of the milking if the quarter concerned is milked some time after the milking process is started in another quarter.…”

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“…According to this theory (6,9,10) the large globules are filtered out from the milk by the ductules, so that the first drawn milk contains only small globules. The strippings, according to this theory, contain a high percentage of large globules.…”

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507. Variations in the fat content of milk throughout the milking process

Whittlestone¹

1953

Journal of Dairy Research

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It is well known that the fat content of cow's milk increases as the cow is being milked. CrowtherO) showed that this effect is reduced as the period between what is now known to be let-down, and actual milking is increased. Johansson (2) has described the effect in detail and has measured the influence of a number of factors on this change in composition. He has shown that the rise in fat percentage is greatest in cows giving a large yield of milk, or milked after comparatively long intervals. Incomplete milking, or 'super milking' with the aid of Pitocin, were shown to have little effect on the average fat percentage measured over a period of several days. These experiments suggest that abnormally high or abnormally low intramammary pressures do not preferentially decrease fat secretion, any pressure effect apparently acting on both fat and serum in the same way. The writer has found (3) that the distribution of fat globule sizes does not usually change greatly throughout the milking of the cow.In contrast with the cow, the sow shows no trend in the fat content of her milk throughout milking, nor is there any definite change in the fat globule distribution (4). Microscopic examination shows that the globules in sow's milk are somewhat smaller than those of cow's milk, and do not appear to cluster. Sow's colostrum is different in this respect, in that the globules cluster and, unlike sow's normal milk, the colostrum creams readily.Because of the differences between sow's and cow's milk, the writer has undertaken an examination of current theories explaining the trends in composition of cow's milk, and has modified one of the theories in an attempt to explain all of the facts. The following section is a brief review of theories at present in circulation.The creaming theory. This theory (5,6) suggests that the richness of cow's strippings is due to the cream being drawn last. If creaming in the udder could occur, it would certainly explain the effects observed, just as the non-creaming properties of sow's milk would explain the lack of a trend in the fat content of the latter. Two basic facts, however, make the theory untenable:(1) Most of the cow's milk is held in the alveoli prior to let-down. The diameter of the filled alveoli is of the order of 40-80 units (7, 8) so that any creaming which occurs, does so within a small volume. When the alveoli contract at let-down, the contents of the many alveoli will be mixed so that creaming effects will be largely eliminated, except perhaps for the small number of alveoli which empty via a ductule leaving the bottom of the lumen.(2) By milking a goat on its back after massaging tbe udder, Games (9) showed that the fat trend is still maintained, while Crowther(i) showed that the tendency for the fat

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507. Variations in the fat content of milk throughout the milking process

Whittlestone¹

1953

Journal of Dairy Research

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“…As early as 1915 it was demonstrated that the pituitary had effect on milk secretion [69]. This finding was confirmed in 1928 by French investigators [70] who for some reason did not pursue their findings.…”

Section: Prolactinmentioning

confidence: 94%

Pituitary-gonadal axis: historical notes

Lindholm

2008

Pituitary

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Though it was appreciated at a very early time that removal of gonads had evident consequences, the anatomy and function of the gonads were essentially unknown in the Antiquity. It was not until around 1600 that men like Vesalius, de Graaf and Leeuwenhoek initiated rational studies on the structure and function of the gonads. The close relationship between gonads and hypothalamus/pituitary was recognized less than 100 years ago. The last pituitary hormone with gonadotroph effect was discovered a generation ago. This paper briefly describes some major points in the development of our knowledge of the pituitary-gonadal function. Considering the huge number of studies involved, this review reflects but a tiny fraction of the work laid down over millennia within this field.

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“…The nature of intramammary pressure during milking and in the interval between milkings has been studied by Gaines (1915), Tgetgel (1926), Whittlestone (1950Whittlestone ( , 1955, and Kitts, Merriman, and Berry (1963).…”

Section: Introductionmentioning

confidence: 99%