Quantitative digestion of fresh herbage by sheep: III. The movement of Mg, Ca, P, K and Na in the digestive tract

Abstract

Sheep prepared either with a rumen cannula, or with a rumen cannula plus re-entrant cannulae in the duodenum and ileum were fed fresh 'Ruanui' perennial ryegrass (R), 'Manawa' short-rotation ryegrass (M) and white clover (C) at dry-matter intakes ranging from 450 to 1000 g/24 h. Paper impregnated with chromic oxide was given once daily via the rumen fistula as a marker.Amounts of Mg, Ca, P, K and Na entering and leaving the small intestine and excreted in the faeces were regressed against the intake of each element for each sheep and these equations (all, other than the faecal excretion of Na, significant (P < 0-05)) were used to calculate the extent of apparent absorption or secretion in the stomach, the small intestine and the large intestine at two levels of OM intake (500 and 800 g daily).Quantities of Mg (at high intake), Ca and K (except sheep fed M) leaving the stomach were significantly lower (P < 0-05), while the amounts of P and Na were significantly higher (P < 0-01) than the amounts consumed. Quantities of Mg (at high intakes) and Ca leaving the small intestine were significantly higher (P < 0-05) while amounts of P, K and Na (at high intakes) were significantly lower (P < 0-05) than the corresponding quantities entering the small intestine. At both intakes in the case of Na and at the higher intakes in the case of the other mineral elements, quantities of Mg, Ca (except sheep fed C), P, K and Na excreted in the faeces were significantly less (P < 0-05) than the amounts entering the large intestine.Thus at the higher intakes there were net absorptions of Mg, Ca and K (except sheep fed M) from, and net secretions of P and Na into, the stomach. The small intestine was the major site of net absorption for P and K and a minor site for Na, while a net secretion of Mg and Ca occurred into this region. Net absorption of Mg, Ca, P, K and Na occurred from the large intestine at the higher intakes.The retention of Mg, Ca and P is discussed in relation to the animals' minimal daily requirements of these elements.

Intestinal absorption and secretion of total and lipid phosphorus in adult sheep fed chopped meadow hay

“…This agrees with the results of Pfeffer et al (1970), Grace et al (1974), Ben-Ghedalia et al (1975), Th6wis et al (1978), Poppi and Ternouth (1979) and Ben-Ghedalia, Tagari and Geva (1982). The Firsov, 1974) was not determined in this experiment.…”

“…The net absorption of P T in the small intestine reported in our experiment has also been mentioned by several other authors (Pfeffer et al, 1970 ;Ben-Ghedalia et al, 1975Poppi and Ternouth, 1979 ;Grace et al, 1974 ;Th6wis et al, 1978). Table 2 shows that P PL is largely absorbed in the small intestine.…”

“…Others have measured the flow of P along the digestive tract of sheep fitted with intestinal cannulas (Bruce et al, 1966 ;Pfeffer, Thompson and Armstrong, 1970 ;Grace, Ulyatt and MacRae, 1974 ;Leibholz, 1974 ;Ben-Ghedalia et al, 1975).…”

Transport of cations and anions across forestomach epithelia: conclusions from in vitro studies

“…Balance studies show that preintestinal Ca 21 absorption gains significance at higher Ca 21 intake. When Ca 21 intake rises to 8 g/day in sheep or to 120 g/day in cattle, absorption of Ca 21 is shifted to preintestinal regions (Grace et al, 1974;Khorasani et al, 1997;Schrö der and Breves, 2006 (Hö ller et al, 1988a and1988b;Schrö der et al, 1997;Wadhwa and Care, 2000). Active ruminal Ca 21 absorption can be increased by concentrate feeding (Uppal et al, 2003), in the presence of SCFAs (Schrö der et al, 1997 andWadhwa and Care, 2000;Uppal et al, 2003, LeonhardMarek et al, 2007a or by increasing the amounts of luminal chloride (Leonhard-Marek et al, 2007a), whereas sulfate ions seem to have stimulatory and depressing effects with no net change of Ca flux rates in vitro (Leonhard-Marek et al, 2007b).…”

II. Quantitative aspects of phosphorus absorptionin ruminants

“…The main intestinal absorption sites are in the duodenum [20] and jejunum [21][22][23]. The absorption of phosphorus from the large intestine is controversial: it is either inexistent [22] or very low [21,23,24] or substantial [25]. In adult sheep fed balanced phosphorus diets, phosphorus is mainly absorbed in the proximal jejunum.…”