Influence d'une subcarence en phosphore et d'un excès de calcium alimentaire sur la phosphatémie et les teneurs en phosphore et calcium des contenus de rumen du mouton

Abstract

Summary. Effect of diets low in phosphorus and high in calcium on plasma inorganic and ruminal phosphorus and calcium concentrations.Four semi-purified diets with different calcium (Ca) and phosphorus (P) contents were given to adult sheep at a level of 1 kg daily plus 100 g of straw. The phosphorus was supplied as dicalcium phosphate, almost insoluble in rumen fluid. In the preliminary period, all the animals (16) were fed the test diet (NCa-NP) containing 8.4 g of Ca and 3.3. g of P.In the experimental period (table 3) two trials were carried out. In trial 1, two groups of 5 sheep each were given for 5 weeks a diet low in P (1 g/kg) and either low (2 g/kg) (diet BCa-BP) or high (10 g/kg) (diet HtCa-BP) in calcium. In trial 2, which lasted for 19 weeks, the HtCa-BP diet was compared to a high Ca (10 g/kg) normal P (3.3 g/kg) diet (diet HtCa-NP) ; two groups of 2 sheep each were fed both these diets every 3 hours, and one group (HtCa-BP) was fed twice daily.The concentration of ultrafilterable inorganic Ca (CaiU) in the rumen contents was related to the Ca level of the diet (tables 4, 5). However, individual variations were high and CaiU concentrations were negatively correlated to rumen pH ( fig. 7).When diets adequate in P were fed, ruminal concentrations of ultrafilterable P (PiU) were rather high (400-490 mg/1), showing the importance of endogenous P supply in the rumen. With an adequate P supply, a high Ca intake had no effect on either plasma or ruminal PiU.When low P diets were fed, there was a steady decrease in plasma Pi from 6 to 3.5 mg P/100 ml and in ruminal PiU from 500 mg/l to values lower than 300 mg/l up to 5-6 experimental weeks. These decreases were greatest with high Ca intake (HtCa-BP diet) ( figs. 2, 3 Introduction.

Effects of Drastic Changes in P Intake on P Concentrations in Blood and Rumen Fluid of Lactating Ruminants

“…Reducing P intake to levels just meeting net requirements, caused significant reductions in plasma Pi concentrations in cows and goats (CALL et al, 1987;DEITERT and PFEFFER:, 1993). Severe P deficiency caused even more pronounced reductions in plasma Pi in goats and sheep (DURAND et al, 1982;MANAS-ALMENDROS et al, 1982;PERGE et al, 1982;SCHNEIDER et al, 1985;BREVES et al, 1987;MUSCHEN et al, 1988).…”

Effect of reduction in phosphorus intake on salivary phosphorus secretion and on duodenal digesta and dry-matter flow in sheep

“…Feeding diets that are low in phosphorus has been shown to lead to a fall in the amount of phosphorus secreted into the gut via the saliva. This in turn leads to a reduction in the concentration of phosphorus within the rumen liquor and if this falls too far then rumen microbial activity is impaired (Durand et al 1982) with consequent harmful effects on digestion and appetite (Field, Suttle & Nisbet, 1975;Sevilla & Ternouth, 1980).…”

“…Since the publication of the Agricultural Research Council's (1980) revised estimates of requirement there have been a number of studies in which a marked reduction in plasma phosphate concentration and adverse effects on rumen microbial activity and appetite were seen in sheep fed diets containing phosphorus levels which, based on the Agricultural Research Council's (1980) estimates of requirement, would be considered adequate (Breves, 1983;Breves & Holler, 1983;Boxebeld et al 1983;Breves, Ross & Holler, 1985). Most of these diets in addition to being relatively low in phosphorus were, however, also rich in calcium, a factor which is known to influence the solubility of phosphorus within the rumen liquor and as such can adversely affect rumen microbial activity (Durand et al 1982). How far dietary phosphorus intake can be reduced at calcium intakes nearer to normal requirements before rumen microbial activity is affected is not clear and the object of this study was to provide information on this.…”

Physiologie de l'absorption intestinale du phosphore chez l'animal

“…Néan-moins, la stimulation par GH de la captation de P par une lignée entérocytaire (CaCo-2) in vitro est indépendante des concentrations en calcitriol du milieu, mais proportionnelle à celles d'IGF-1 (Fleet et al, 1994 (Guéguen, 1963(Guéguen, , 1965Young et al, 1966a et b ;Compère et al, 1967 ;Boxebeld et al, 1983 ;Braithwaite, 1984a ;Challa et al, 1989) Yano et al, 1991 ;Care, 1994 (Tomas et al, 1967 ;Scott et Beastall, 1978). Les phosphates salivaires assurent dans le rumen un apport de P sous une forme disponible pour couvrir les besoins des microorganismes, et ils contribuent à maintenir les conditions physicochimiques du milieu dans une zone favorable à la digestion microbienne (Durand et Kawashima, 1980 ;Durand et al, 1982).…”