The effect of pelleting on the voluntary intake and digestibility of leaf and stem fractions of three grasses

Abstract

I . Leaf is eaten in greater quantities than stem of similar digestibility. T o determine whether this difference is caused by physical or chemical factors, leaf and stem fractions from Digitaria decumbens, Chloris gayana and Setaria splendida were fed ad lib. to sheep in the chopped and pelleted forms. Pellets were made from leaf and stem which had been ground through a screen with 3 mm holes. All sheep received a protein and mineral supplement. 2.Voluntary intake of chopped leaf was 34 % higher than that of the chopped stem fraction (40.3 and 30.0 g/kg b o d y -~e i g h t~' '~ respectively, P < 0.01) although dry matter digestibility ratios were similar (0.478 and 0.450 respectively, P > 0.05). The higher intake of leaf was associated with a larger surface area (13400 and 5200 mma/g for chopped leaf and stem respectively), lower bulk density (60 and 180 kg/mS respectively) and lower neutral-detergent fibre (706 and 724 g/kg respectively), acid-detergent fibre (383 and 413 g/kg respectively) and lignin (42 and 59 g/kg respectively) contents. Chopped leaf was retained in the reticulo-rumen for a shorter time than the stem fraction (19.9 and 26.4 h respectively).3. Grinding and pelleting increased the voluntary intake of the leaf fraction by 88 yo and the stem fraction by 60 %. This increased voluntary intake caused by grinding and pelleting was not accompanied by any significant changes in the chemical composition of the diet. Grinding and pelleting reduced the time that the food was retained in the reticulo-rumen and this change appeared sufficient to account for the observed increases in voluntary intake.4. It was concluded that the higher intake of the leaf fraction of grasses is caused by differences in retention time of food in the reticulo-rumen. These differences in retention time are caused by differences in physical properties and not chemical composition.Studies with separated leaf and stem of five tropical grasses have shown the voluntary intake of leaf to be 46% higher than that of stem despite a slightly lower dry matter (DM) digestibility of the leaf fraction (Laredo & Minson, 1973). This higher intake of the leaf was associated with a larger surface area initially available to bacterial degradation and a shorter retention time of DM in the reticulo-rumen. When the leaf and stem were finely ground there was no difference in the rate of DM digestion in vitro (Laredo & Minson, 1973). The leaf fractions contained more nitrogen but less fibre and Iignin than the corresponding stem fractions.If the voluntary intake of leaf and stem fractions is limited by physical factors, then voluntary intake will be increased if the physical properties of the diet are changed by grinding and pelleting. However, if the low intake of the stem is caused by a nutrient deficiency then grinding and pelleting will not increase voluntary intake (Minson, 1967).The object of this study was to identify the cause of the lower voluntary intake of stem. Measurements were made of the digestibility of leaf and stem fractions of thre...

Opportunities to improve fiber degradation in the rumen: microbiology, ecology, and genomics

“…There are a number of well‐established technologies that can reliably be used to increase the digestibility of fiber in the rumen based on mechanical and chemical treatment of plant material before it is consumed. In this review we will not discuss this technology, which has been previously considered [7,245–247]. We will only concentrate on developments of some newer technologies.…”

Ammonium Hydroxide Treatment on Wheat Straw

“…Reduction of particle size may reduce the time which feed particles are exposed to rumen microbes and accelerate the flow of digesta through the alimentary tract, thereby lowering the efficiency of digestion (Greenhalgh and Wainman, 1972;Hashizume et al, 1975;Laredo and Minson, 1975). The increased fecal energy losses per unit of forage eaten as a result of the rapid rate of passage of ground material from the rumen, is partially compensated by increased voluntary feed intake (Greenhalgh and Reid, 1974;Heaney et al, 1963;, and by reduced energy losses as methane and heat increment (Blaxter and Graham, 1956;Paladines et al, 1964).…”

Biochanin A improves fibre fermentation by cellulolytic bacteria

“…Whereas the development of technologies for modifying fibrous substrates to enhance ruminal fibre digestibility has been successful (Burroughs et al . ; Wilkins and Minson ; Laredo and Minson ; Agosin and Odier ; Cherney et al . ; Hu et al .…”

“…Strategies for improving cellulose hydrolysis and consequent energy conversion have been extensively explored, including those targeting both substrate modification (e.g., mechanical and chemical pretreatments, genetic manipulation) and genetic and ecological manipulation of the rumen cellulolytic guild (e.g., inoculation; Krause et al 2003). Whereas the development of technologies for modifying fibrous substrates to enhance ruminal fibre digestibility has been successful (Burroughs et al 1960;Wilkins and Minson 1970;Laredo and Minson 1975;Agosin and Odier 1985;Cherney et al 1991;Hu et al 1991), attempts at manipulation of the cellulolytic guild itself have so far been unsuccessful (Hungate 1966;Varel et al 1995;Krause et al 1999Krause et al , 2001aKrause et al , 2001bDehority and Tirabasso 2000). Therefore, strategies for improving cellulolytic fermentative efficiency by ecological manipulation of the cellulolytic guild are of interest.…”