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Effect of the supplementation of a high-concentrate diet with sunflower and fish oils on ruminal fermentation in sheep
7 pages, 4 tables.-- Available online 21 Jan 2009.This study was conducted to test the hypothesis that the supplementation of a highconcentrate
diet with lipids, reportedly a good strategy for improving the nutritional
value of ruminant-derived products, may not necessarily be associated with detrimental
effects on ruminal fermentation in sheep. Four ruminally cannulated adult ewes were
fed a high-concentrate diet, with no oil (Control diet), for a 14-day adaptation period.
Afterwards, they were fed the same basal diet but supplemented with sunflower oil [20
g/kg fresh matter (FM)] and fish oil (10 g/kg FM) (SOFO diet) for a further 11 days, to
investigate the impact of the addition of oils on the ruminal fermentation of the diet. On
days 0 (Control), 3 and 10 of the experimental period rumen fluid was sampled at 0, 1.5,
3, 6 and 9 h after the morning feeding, for analysis of pH, and ammonia, lactate and
total volatile fatty acid (VFA) concentrations. Alfalfa hay was incubated in situ, using
the nylon bag technique, for 12 and 24 h to examine the effect of oil supplementation on
ruminal disappearance of dry matter (DM), crude protein (CP) and neutral detergent
fibre (NDF). On days 0 and 11, rumen fluid was collected just before the morning
feeding and used to incubate alfalfa hay and the Control and SOFO diets by means of
the in vitro gas production technique. The mean concentrations of acetate (87.8 vs 73.7
mmol/L) and butyrate (21.2 vs 17.7 mmol/L) were reduced by oil supplementation (P<
0.05) and the total VFA showed a tendency (P= 0.098) to be lower with the SOFO diet
(139.0 vs 122.1 mmol/L). However, none of the other in vivo ruminal fermentation
parameters were affected by the treatment (P> 0.10). The oil supplementation affected
neither in situ rumen disappearance of DM, CP and NDF of alfalfa hay, nor rates of gas
production (P> 0.10). On the other hand, a little, but significant reduction in cumulative
gas production was observed when the experimental diets were incubated with rumen
fluid derived from animals fed the oil-rich diet (P< 0.05).
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Overall, the results suggest that the supplementation of high-concentrate diets with
sunflower oil (20 g/kg FM) plus fish oil (10 g/kg FM) had little effect on ruminal
fermentation and therefore its use to improve the nutritional value of ruminant-derived
products cannot be precluded.This work was supported by the Spanish Ministry of Science
and Innovation (Project AGL2008-04805-C02-02) and the Council of Castile and León (Project CSI01B08).Peer reviewe