Etude méthodologique sur la mesure des différences artério-veineuses mammaires chez la vache laitière

et al. 1982

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Summary. Effects of ruminal infusion of volatile fatty acids and duodenal infusion of caseinate on digestion and metabolism in the dairy cow. l. -Production and digestion.The effects on the metabolism of dairy cows of two energy levels (85 and 110 p. 100 of requirements) in factorial combination with two nitrogen levels (70 and 100 p. 100 of requirements) were studied in a 4 x 4 latin square by the responses of milk constituent secretion and mammary nutrient uptake.

Section: )unclassified

Effets sur la digestion et le métabolisme des vaches laitières d'infusions d'acides gras volatils dans le rumen et de caséinate dans le duodénum. I. — Production et digestion

Rulquin¹,

Fléchet²,

et al. 1982

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“…Outre les mesures portant sur l'ingestion, la production de lait et la digestion dans le rumen et dans l'intestin (Rulquin, 1982) (Rulquin, 1981 (Rulquin, 1981 (Linzell, 1967 (Mepham, 1982 Elliot, 1980 ;Rulquin, 1981) (Rulquin, 1982 Linzell, 1974). Elle pourrait correspondre à la diminution de l'activité de la lipoprotéine lipase mammaire qui est enregistrée avec ce type de régime (Emery, 1973 (Rulquin, 1982 Clark, 1975).…”

Section: Introductionunclassified

Effets sur la digestion et le métabolisme des vaches laitières d'infusions d'acides gras volatils dans le rumen et de caséinate dans le duodénum. Il. — Métabolisme général et mammaire

Rulquin¹,

Fléchet²,

et al. 1983

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Summary. Effects of !uminal infusion of volatile fatty acids and duodenal infusion of caseinate on digestion and metabolism in the dairy cow. II. -General and mammary metabolisms.In a previous study (Rulquin, 1982) (table 2).2) The infusion of caseinate mainly caused arterial levels and A-V differences of all essential amino acids to increase (an average of 60 and 55 %), and especially those of branched amino acids (104 and 57 %). According to their respective variations in the artery and duodenum, methionine, threonine, phenylalanine, histidine and lysine seemed to be, in this order, the most limiting ( fig. 3).3) The associative effect between energy and nitrogen that caused wide variations in milk secretion constituents produced no significant change in A-V differences ; it only affected arterial levels of urea, isoleucine, valine, phenylalanine and threonine. Of the limiting amino acids mentioned previously, histidine and lysine seemed to be limiting only with the low energy level (fig. 4).These effects have been discussed in relation with putative hormonal changes caused by infusions and possibly orienting the utilization of nutrients towards extra-mammary tissues or modifying the effectiveness of their utilization by the udder.Introduction.

“…En (Mepham, 1982 (Rulquin, 1981(Rulquin, , 1982(Rulquin, , 1983 (Christensen, 1977). Pour la méthionine, la thréonine et la valine, acides aminés ayant plusieurs systèmes de transport, ces relations ( fig.…”

unclassified

“…Pour la méthionine, la thréonine et la valine, acides aminés ayant plusieurs systèmes de transport, ces relations ( fig. 3) (Rulquin, 1981 ;Fleet et Mepham, 1985). Certaines hormones peuvent être à l'origine des modifications de la captation, c'est le cas des glucocorticoïdes (Kronfeld, 1982) Mepham (1985).…”

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Utilisation des produits terminaux de la digestion par la mamelle chez la vache laitière

Rulquin¹,

Fléchet²,

et al. 1986

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Summary. Use of the end-products of digestion by the udder of the dairy cow.Relations between mammary arterio-venous (AV) differences and arterial level were studied for glucose, acetate and beta-hydroxybutyrate on 172 samples and for blood essential amino acids on 20 samples, pooled by day and by cow. The data were obtained from 32 experiments on 5 cows eating various diets (Rulquin, 1981(Rulquin, , 1983. AV differences in acetate and beta-hydroxybutyrate were highly related to the arterial levels (R = 0.97 and 0.86) and averaged 74 and 41 % of these levels ( fig. 11. On the other hand, the AV difference in glucose was poorly (R = 0.5) related to the arterial levels.Among the essential amino acids, only AV differences in phenylalanine, leucine, arginine, isoleucine and histidine were linearly related to the arterial levels (R = 0. 78, 0.73, 0.68, 0.63, 0.60) (fig. 2). AV differences in lysine, methionine, valine and threonine were more related to the AV differences of other amino acids than to the arterial levels ( fig. 3).These results have been discussed in connection with different mammary metabolic transport systems and with the ability to modify mammary nutrient input by dietary manipulation.Introduction.