Feed-back control of milk secretion in the goat by a chemical in milk.
In order to investigate the nature of the inhibition of milk secretion during a long milking interval, goats were treated in three possible ways: (i) milked twice daily at 08.00 h and 16.00 h or (ii) milked thrice daily at 00.00 h, 08.00 h and 16.00 h, or (iii) milked thrice daily at 00.00 h, 08.00 h and 16.00 h, but at 00.00 h the milk removed was replaced with an equal volume of isosmotic sucrose solution. The latter treatment was carried out in order to subject the gland to a degree of physical distension equivalent to that on treatment (i). On either thrice-daily milking or thrice-daily milking with sucrose replacement, milk secretion rate over the 16.00-08.00 h period was significantly higher (by about 10% in both cases) than on twice-daily milking. Secretion rates of lactose, milk protein, citrate and calcium during the 00.00-08.00 h period were similar on either thrice-daily milking or thrice-daily milking with sucrose replacement; the secretion rate of fat was significantly higher on thrice-daily milking with sucrose replacement. Secretion rates of Na+, K+ and Cl- were significantly higher on thrice-daily milking with sucrose replacement. In the case of Na+, the increased Na+ secretion rate was sufficient to create a normal Na+ concentration in the milk/sucrose mixture removed at the next milking. In the cases of K+ and Cl-, their secretion rates were not sufficient to restore their concentrations to normal by the next milking.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002951:Citrates / Q000378:metabolism; D005246:Feedback; D005260:Female; D006041:Goats / Q000502:physiology*; D007774:Lactation; D007785:Lactose / Q000378:metabolism; D008892:Milk / Q000378:metabolism*; D008894:Milk Proteins / Q000378:metabolism; D011247:Pregnancy; D012636:Secretory Rate; D012964:Sodium / Q000378:metabolism; D013395:Sucrose / Q000494:pharmacology
D002951:Citrates; D008894:Milk Proteins; D013395:Sucrose; D012964:Sodium; D007785:Lactose; D002118:Calcium