The effects of calcium and sodium loading on organic matter digestibility and mineral absorption in sheep. 1. Digestion in the forestomachs and small intestine

Abstract

Experiments were conducted on sheep cannulated to the rumen, duodenum and ileum to study the effects of Ca and Na loading (5 and 10 times the ARC requirements) on digestion in the rumen and intestines. The introduction of calcium lactate (19.6%) or sodium chloride (9.6%) into extruded feed mixtures had no significant effect on degradation in the rumen (apparent digestibility of organic matter in the forestomachs averaged 40%, ileal digestibility 61%) or on the pH of ruminal (5.73), duodenal (3.37) or ileal (7.63) digesta. Excess sodium in the diet reduced (P < 0.05) microbial protein synthesis in the rumen (7.69g N-MP/d) in comparison with control sheep and those loaded with Ca (10.46 and 10.74 g N-MP/g) as well as the apparent digestibility of total nitrogen in the small intestine.

The effects of calcium and sodium loading on organic matter digestibility and mineral absorption in sheep. 2. Absorption of minerals

“…The relationship between loading sheep with Na (or Ca) and the dynamics of digestive processes and between pH values and the dynamics of some elements in the rumen were discussed in earlier studies (Leontowicz et al, 1995). When animals are loaded with Na, the sodium level of the saliva rises while that of potassium decreases; a similar relationship between the Na and K concentrations in the rumen was found by Chii and Phillips (1993).…”

“…The intake of extruded concentrates, hay and water is described in a previous paper (Leontowicz et al, 1995). Table 2 gives the apparent digestibility coefficients of ash, Mg, Ca and P in the forestomachs and small intestine.…”

“…These results indicate that there was a large amount of Na supplied with saliva and intestinal juices to the duodenum of sheep in groups I and II, which according to NRC (1980) is about 80%. Sodium ions play an important role in absorption of sugars and amino acids in the small intestine (Grim, 1980), but an excess of Na in the ration did not affect total nitrogen absorption in the small intestine in the same animals (Leontowicz et al, 1995). In these studies, significant differences were found between groups in Na digestibility in the studied segments of the digestive tract; the highest absorption of Na in the small intestine was in control sheep (98%), the lowest in the sheep loaded with Na (60%; P<0.05).…”

“…A detailed description is given in the first part of this study (Leontowicz et al, 1995). Dry matter (DM), ash, chromium (Schiirch et al, 1950) were assayed in freeze-dried samples of intestinal digesta, while mineral elements were determined after mineralization the samples in concentrated NH0 3 in hermetic Teflon vessels in a microwave oven.…”