Influence of the ratio between wheat straw and ground barley, ground corn or dried sugar beet pulp on in sacco dry matter degradation of ryegrass and wheat straw, rumen fermentation and apparent digestibility in sheep

Abstract

Castrated male sheep were fed with 5 different rations varying in the straw to concentrate ratio between 100: 0, 75: 25, 50: 50, 25: 75 and 0: 100. Ground barley, ground corn and dried sugar beet pulp were used as concentrate sources. Chopped winter wheat straw was fed as roughage source. All rations were supplemented with a protein-mineral-vitamin-premix. In sacco dry matter degradability of artificially dried ryegrass, untreated and ammonia treated wheat straw was measured within three rumen fistulated sheep. Nylon bags were incubated for 48 h in the rumen of sheep. Volatile fatty acids of rumen fluid were determined by gas chromatography. Samples were taken via rumen fistula 3 h after morning feeding. Apparent digestibility of organic matter and fibre fractions of total rations were determined within five sheep. Increased concentrate portion decreased in sacco dry matter degradability of incubated roughages. Decrease of dry matter degradability was much higher for ammonia treated (from 55.0 to 22.5%) and untreated straw (from 50.9 to 22.7%) than for ryegrass (from 75.6 to 69.2%), when concentrate increased from 0 to 100% of ration. The highest concentrate portions did not show any increase of degradability of ammonia treated straw. Specific concentrate effects were observed when 75 and 100% concentrate were fed (unphysiological level). Ground barley as concentrate source decreased rumen pH to a larger extent (down to 5.18) than corn and sugar beet pulp (down to 5.60 and 5.57). Sheep suffered from rumen acidosis in some cases. Higher concentrate levels increased concentration of total volatile fatty acids of rumen liquid and molar concentration of propionate and butyrate, but decreased acetate. Various concentrate sources showed different influences on parameters of rumen fermentation. Apparent digestibility of organic matter of total rations increased from 52.7 to 86.1% if concentrate portions enhanced from 0 to 100%. High portions of ground barley decreased cellulolytic activity and fibre digestion. On the other hand high levels of sugar beet pulp increased digestibility of crude fibre and neutral detergent fibre.

In vitro fermentation pattern and acidification potential of different sources of carbohydrates for ruminants given high concentrate diets

“…Maize is a model of cereal grain, with a high proportion of starch, although it is available in the gut at a relative moderate rate compared to other grains (Offner et al, 2003;Lanzas et al, 2007). As a byproduct of cereal processing, wheat bran includes a variable but important proportion of starch (100 to 240 g/kg), highly available since it is from wheat, and its cell wall contains a major proportion of fermentable hemicelluloses (Maes & Delcour, 2001;FEDNA, 2010). Sugarbeet pulp has high proportions of both neutral detergent fibre (Fondevila et al, 1994;FEDNA, 2010) and soluble fibre, mostly pectins, that can be fermented at a similar rate than soluble starch (Fondevila et al, 2002), whereas CT is a source of both soluble fibre and soluble sugars (Hall, 2002;Barrios-Urdaneta et al, 2003).…”

“…As a byproduct of cereal processing, wheat bran includes a variable but important proportion of starch (100 to 240 g/kg), highly available since it is from wheat, and its cell wall contains a major proportion of fermentable hemicelluloses (Maes & Delcour, 2001;FEDNA, 2010). Sugarbeet pulp has high proportions of both neutral detergent fibre (Fondevila et al, 1994;FEDNA, 2010) and soluble fibre, mostly pectins, that can be fermented at a similar rate than soluble starch (Fondevila et al, 2002), whereas CT is a source of both soluble fibre and soluble sugars (Hall, 2002;Barrios-Urdaneta et al, 2003). Finally, SU was chosen as a model for soluble sugars that are almost completely used by most rumen microbes in less than an hour (Hristov et al, 2005).…”

“…Besides, concentrate feeds with a rapid rate of fermentation contribute themselves to enhance rumen acidification, but their potential in this sense cannot be evaluated in a strongly buffered medium. Feeds potential of acidification is generally assumed, though to a variable extent, for cereal grains (Chai et al, 2004;Lanzas et al, 2007) and even more for sources of soluble sugars (Huhtanen & Khalili, 1992;Hoover et al, 2006), but it should also be considered for highly fermentable fibrous feeds, such as citrus pulp or sugarbeet pulp, rich in pectins and fermentable hemicelluloses (Flachowski et al, 1993;DePeeters et al, 1997;Barrios-Urdaneta et al, 2003). In addition some cereal byproducts, such as wheat bran, may include important proportions of rapidly available starch that is fermented at a high rate by rumen microbes (Maes & Delcour, 2001).…”

Effects of lucerne particle size and source of dietary carbohydrates on in situ degradation and ruminal variables in sheep

“…For this reason, an alternative to consider is the supplementation of forages with soluble fibre-rich diets or feeds high in digestible neutral detergent fibre (NDF) that usually have a less negative effect on the rumen environment and thus on cellulolysis than the supplementation with starch-or sugarrich feeds (Bampidis and Robinson, 2006). Studies have been conducted on effects of different nonfibrous carbohydrate sources on performance and ruminal metabolism in sheep (Bhattacharya and Sleiman, 1971;Ben-Ghedalia et al, 1989;Carey et al, 1993, Flachowsky et al, 1993Cooper et al, 1996). To our knowledge, however, those studies are missing that compare different sources of neutral detergent soluble carbohydrate in mixed diets at different forage particle size.…”

“…When sheep were fed high-concentrate diets, i.e. up to 750 to 1 000 g/kg of diet dry matter (DM), rumen pH on a barleybased diet decreased to a larger extent (down to 5.18) than on a sugar beet pulp-based diet (down to 5.57) (Flachowsky et al, 1993).…”