Effects of level of intake and of available volatile fatty acids on the absorptive capacity of sheep rumen

Abstract

The objective of this experiment was to determine the respective effects of level of intake and of the amount of volatile fatty acids (VFAs) present in the rumen on VFA ruminal absorption. In a factorial design, six ewes received a hay diet either at 126 or at 73% of energy maintenance requirements. Their capacity of absorption of VFAs was evaluated by the method of temporarily isolated rumens, in which the rumen was filled with solutions containing high or low amounts of VFAs. Rate of absorption (amount of VFAs absorbed per hour) was significantly higher, by 32% on average, in sheep fed the high intake than in sheep fed at low intake. The proportion of initial VFAs absorbed did not depend on the concentration of VFAs introduced in the rumen, so that the amount of VFAs absorbed varied as the concentration of VFAs introduced in the rumen. The decrease in intake resulted in a decrease by 32% in the rate of absorption of total VFAs. No interaction between concentration of VFAs and previous intake was observed. This suggests that the capacity of the rumen to absorb VFAs is reduced at low intake even if low amounts of VFAs are available.

Modulation of Na+ transport across isolated rumen epithelium by short‐chain fatty acids in hay‐ and concentrate‐fed sheep

“…The absorption of SCFA from the rumen of cows fed a diet containing 80% concentrate is 2–4 times higher than that in hay‐fed animals ( Dirksen et al., 1984). These observations have been confirmed in studies with sheep ( Gäbel et al., 1987; Doreau et al., 1997).…”

Effect of short‐term underfeeding on weight of splanchnic organs in ewes

“…In contrast with the present results, no effect of intake on the proportion of ruminai mucosa has been reported either between long-term underfed and maintenance fed ewes receiving a hay diet (Nozière et al, 1999) or between maintenance and ad libitum fed steers receiving a 90% concentrate diet (Johnson et al, 1987). The decrease in the proportion of ruminai mucosa in the ventral sac observed in the present experiment may be related to the drop in the absorptive capacity of the rumen previously reported in short-term underfed sheep (Doreau et al, 1997), since absorption of volatile fatty acids may occur mainly in the ventral sac, where bacterial enzyme activity is highest (Martin et al, 1999). However, no change in the proportion of ruminai volatile fatty acids appearing in the portal blood has been observed in short-term underfed ewes .…”

Effects of diet and osmotic pressure on Na+ transport and tissue conductance of sheep isolated rumen epithelium

“…Diet has long been known to influence physiological and biochemical functions (Nocek et al 1980; Dirksen et al 1984; Shen et al 2004) and the morphology of the rumen epithelium (Liebich et al 1987). Ruminal transport mechanisms are significantly enhanced by concentrate feeding (Dirksen et al 1984; Gäbel et al 1987 a ; Doreau et al 1997; Uppal et al 2003 b ). We have hypothesized that the diet‐dependent adaptation of the rumen epithelium also includes the protection of transport mechanisms and barrier function caused by hyperROP in the ruminal epithelium of HF sheep.…”