Effect of Roughage Particle Size on Ruminal, Digestive and Metabolic Characteristics of Early-Weaned Lambs Fed Pelleted Corncob-Concentrate Diets

Abstract

Two experiments were conducted to determine effects of feeding corncobs of various mean particle size (MPS) on ruminal, digestive and metabolic characteristics of early-weaned lambs fed pelleted 74.9% concentrate:25.1% corncob diets. The MPS of corncobs in diets was 6.5, 5.4, 1.4 and .8 mm, respectively. As particle size decreased, percentage starch decreased and percentage neutral detergent fiber (NDF), acid detergent fiber (ADF) and cellulose increased. In Exp. 1, 28 crossbred rams (seven/treatment, avg initial wt, 15.3 kg) were used in a randomized complete-block design. In Exp. 2, lambs from Exp. 1 were re-weighed (avg initial wt, 16.8 kg) and fed the same diets as in Exp. 1. In Exp. 1 and 2, lambs ingested dry matter (DM) equal to 2.68 and 3.74% of body weight, respectively. In Exp. 1, apparent DM digestibility was unaffected by corncob MPS; however, in Exp. 2, DM digestibility was highest (68.8%) for lambs fed the 6.5-mm diet and lowest (63.8%) for those fed the .8-mm diet. Apparent starch digestibility was high (greater than 98.8%) in both experiments. Neutral detergent fiber and ADF digestibilities were highest for lambs fed the 1.4-mm diet (50.5 and 43.6%, Exp. 1; 39.6 and 28.9%, Exp. 2). A dramatic increase (6.8 to 39.1%) in acid detergent lignin (ADL) digestibility was observed in Exp. 1 as corncob MPS decreased. In Exp. 2, ADL digestibilities were similar for lambs fed the 6.5-, 5.4- or 1.4-mm diets (avg value, 5.9%) and highest for those fed the .8-mm diet (29.7%). Nitrogen metabolism was unaffected by corncob MPS. In Exp. 1, digestible energy intake, corrected for urinary losses, did not differ among treatments but in Exp. 2, lambs consuming the 6.5-mm diet had higher corrected digestibility energy intakes (1,926.6 kcal/d) than did those fed other diets (avg, 1,832.4 kcal/d). Ruminal pH sampled 4 h post-feeding was highest for lambs consuming the 6.5-mm diet (6.25) in Exp. 1 and the 1.4-mm diet (5.89) in Exp. 2. Lowest ruminal pH (5.30 and 5.36, respectively) was for lambs consuming the .8-mm diet in Exp. 1 and the 5.4-mm diet in Exp. 2. Ruminal lactate concentrations were variable within and among treatments. Total ruminal volatile fatty acid (VFA) concentrations were similar across treatments but in Exp. 2, there was a shift in molar proportions from acetate to propionate as corncob MPS decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

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

“…In many studies where animals were fed with long, chopped or ground roughage, only a slight or even no decrease of particle MRT was found for the ground diets (Jaster and Murphy 1983; Weston and Kennedy 1984;Bergner and Klenke 1985;Kerley et al 1985a,b ;Kinser et al 1985;Faichney and Gherardi 1986;Firkins et al 1986;Martz and Belyea 1986;Welch 1986;Hunt et al 1987;Cherney et al 1988;Shaver et al 1988;Stokes et al 1988). In many studies where animals were fed with long, chopped or ground roughage, only a slight or even no decrease of particle MRT was found for the ground diets (Jaster and Murphy 1983; Weston and Kennedy 1984;Bergner and Klenke 1985;Kerley et al 1985a,b ;Kinser et al 1985;Faichney and Gherardi 1986;Firkins et al 1986;Martz and Belyea 1986;Welch 1986;Hunt et al 1987;Cherney et al 1988;Shaver et al 1988;Stokes et al 1988).…”

Digestion by sheep of ground and unground dried molassed sugarbeet pulp diets and the effect of partially replacing the beet pulp with barley

“…It is difficult to account fully for the differences observed. Grinding of the MSBP appears to have resulted in an increased content of NDF and reduced content of N. Kinser et al (1985) and Kerley et al (1985) observed similar changes in the chemical composition of maize after grinding and suggested that the higher content of NDF was due to a reaction between starch and fibre as particle size was reduced by grinding. If such a reaction occurred in MSPB with grinding, sugar rather than starch must have been one of the reactants.…”