The effect of supplementation with maize starch and level of intake of perennial ryegrass (Lolium perenne cv. Endura) hay on the removal of digesta from the rumen of sheep

Abstract

1. Eight wether sheep were offered a diet of perennial ryeigrass (Loliumperenne cv. Endura) hay once daily at two levels of intake (1 1 and 16.5 g dry matter (DM)/kg live weight (LW)) with or without maize starch (175 g DM/kg hay DM). The experiment consisted of four periods. each lasting 32 d. Rates of digestion of the hay were measured by incubation in dacron bags and rates of passagc using chromium-mordanted hay. Rumen pool sizes of DM, organic matter and fibre were measured by emptying the rumen.2. The inclusion of starch in the diet appeared to increase significantly (P < 0.01) the lag phase before the start of fibre digestion, as observed both in the dacron bag studies and in the slower initial disappearance of digestible neutral-detergent fibre (NDF) from the rumen recorded by emptying of rumen contents. However, there was no significant effect of starch on apparent digestibility of fibre in the whole tract.3. The main effect of increasing the level of feeding wax, to increase the rate of passage with a consequent decrease in overall digestibility. The fractional rate of passage increased from 0.0318 to 0.0400 as the level of feeding increased, while apparent digestibility of NDF decreased from 0.755 to 0,724.4. On all treatments the weight of indigestible fibre in the rumen remained more or less constant between 5, 10 and 15 h after feeding, but was significantly lower at 24 h. These results suggest that a high proportion of the outflow of material from the rumen not associated with feeding appears to occur during the second half of the feeding cycle.The quantity of digesta present in the rumen can be an important factor in influencing the voluntary intake of roughage diets by ruminants (Balch & Campling, 1969). Roughages contain a high level of fibre and since the rate of digestion of fibre is slower than that of other fractions (Van Soest, 1975), factors affecting this rate may thus be implicated in intake control. The effect of soluble carbohydrates in depressing cellulolysis is well documented (El-Shady et al. 1961; Terry et al. 1969;Mertens & Loften, 1980) and often leads to a depression in voluntary intake. However, the relation between this depression and rumen volume has not been studied in detail.The relation between rumen pool sizes and intake level has been studied by a number of workers, mainly with diets of oat straw (Pearce, 1967) , 1984;Ulyatt et al. 1984). The increase in rumen pool size has generally been less than the increase in intake, presumably due to the increase in rate of passage as intake level increased. The effect of concentrate: forage on the rate of passage is not clear, since Uden (1984) observed no effect of an increased ratio while Colucci et al. (1982) reported higher rates of passage with high-forage diets compared with low-forage diets.or forages (Moseley & JonesThe experiment reported here was designed to study the effects of supplementation of a forage diet with starch and to see how the responses obtained were influenced by level of feeding. The responses measured w...

Utilization of nutrients as influenced by different restriction levels of feed intake under sub-tropical conditions in crossbred calves

“…On the other hand, the intrinsic activity of microbes, which depends mainly on ruminal milieu, is not largely modified by intake (Doreau et al, 2003). This is shown by the low variation in situ OM and fibre degradation of some forage (Aitchison et al, 1986). Contrary, protein degradability seems to increase when intake decreases, as revealed by direct measurements of non-microbial protein duodenal flows in sheep (Merchen et al, 1986) or by in situ ruminal measurements in goats (Zhao et al, 1993).…”

“…Organic matter digestibility decreased with underfeeding (64.5 and 53.7%, respectively, at high and low intakes) without modification of mean ruminal or total tract retention times (Grimaud et al, 1999) and they also confirm that, at intakes below maintenance, digestibility can decrease when feed intake is restricted, contrary to the general view described in the literature. Conversely, with forage based diets in situ DM degradability either did not vary (Aitchison et al, 1986) or increase (Kabre et al, 1995) when intake decreased and digestibility increased. Kabre et al (1994) found that such an increase was due to a higher enzymatic activity of cellulolytic bacteria.…”

“…The intake of DM, OM, CP, EF, NDF, ADF and hemicellulose (g/d or g/kg w 0.75 ) was significantly (P b 0.05) different among 4 groups (Table 2) as envisaged by the experimental design. This decrease in feed intake might have resulted in a more efficient mastication, by longer time spent eating and ruminating per kg ingested feed as also observed by Ulyatt et al (1984) and Aitchison et al (1986). As a consequence ruminal particle size decreases and the surface attacked by micro-organisms increases and the structure of feed is more disrupted by chewing (Mudgal and Ray, 1965).…”

Factors Affecting the Mean Retention Time of Particles in the Forestomach of Ruminants and Camelids

“…Most investigators have found that MRT of particles and of fluid decreases when level of feed intake increases (Thornton and Minson 1972;Grovum and Williams 1977;Mudgal et al 1982;White et al 1984;Ledoux et al 1985;Aitchison et al 1986;Faichney and Gherardi 1986;Merchen et al 1986;Shaver et al 1986;Waghorn et al 1986;Funk et al 1987;Deswysen and Ellis 1988;Lindberg 1988;Uden, 1988). However, doubling the intake leads to only a 20-40% decrease of particle MRT in the forestomach; and some investigators have not found any significant effect of the intake level on MRT (Ulyatt et al 1984;Van Vuuren 1984).…”

Comparison of methods to describe the kinetics of digestion and passage of fibre in sheep

“…23 The rate constants for passage from the rumen were estimated for hay by fitting the model of Dhanoa et al 24 to the excretion patterns of chromium-mordanted hay, as described by Aitchison et a1.21. 22 These estimates were termed kh and kl, respectively.…”