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Ruminal digestion of leguminous forage, potatoes and fodder beets in batch culture - I. Fermentation pattern

Eriksson T, Murphy M


The effects on rumen fermentation of fodder beets and potatoes as substrates per se and as modifiers of the rumen microbiota were tested in two experiments using a 700 ml batch culture system. In the first experiment, seven diets were incubated for 5 h with rumen fluid from either dry cows fed at maintenance energy intake (MFL) or with rumen fluid from lactating cows adapted to fodder beets (BFL) or potatoes (PFL). Diets were: silage (S) or a mixture 60:40 on dry matter (DM) basis of silage and one of the following carbohydrate supplements: barley/oats 1: 1 (BO), raw potatoes (RP), steam boiled potatoes (BP), frozen potatoes (FP), fodder beets (FB) or barley/oats/raw potatoes 1:1:2 (BORP). The silages were alfalfa (ASIL), grass (GSIL) and a mixture 1:1 (DM basis) of the two (AGSIL). Diets were ranked with respect to the amounts of carbohydrates fermented during 5 h as: FB = BP > BO > BORP > RP = FP = S, while rumen fluids in that respect were ranked PFL > BFL > MFL. FB diet did not result in butyrate proportions that differed from the BO diet. The rumen fluid means for butyrate proportion (mmol/mol total VIA, volatile fatty acids) were 80,130 and 107 for MFL,BFL and PFL, respectively. The FB diet caused lactate concentrations of 72.3, 33.7 and 25.0 mmol/l for MFL, BFL and PFL, respectively. In the second experiment, a grass silage/barley diet (60:40 on DM basis) was incubated in the same in vitro system with rumen fluid from lactating cows adapted to 0, 1 or 2 kg DM potatoes. No linear trend for fermentation intensity versus potato inclusion was recorded, but rumen fluid from cows fed I kg DM potatoes had a shorter lag phase and slightly lower end-time pH (5.37 versus 5.48, P < 0.001) than the two other rumen fluids. It was concluded that the larger amounts of substrate fermented with fodder beets or boiled potatoes have a potential to supply more energy for microbial synthesis than a barley/oat grain mixture or raw potatoes. Replacement of barley/oat grain by fodder beets should not imply any risk for decreased supply with glucogenic substrates as such a diet was found to maintain the propionate proportion of total VFA and besides produce substantial amounts of lactate, which would be converted to mainly propionate in vivo. (C) 2003 Elsevier B.V. All rights reserved

Publicerad i

Animal Feed Science and Technology
2004, Volym: 111, nummer: 1-4, sidor: 73-88