Presenter Information

D H. Rearte, INTA
F J. Santini, INTA

Publication Date

1993

Description

Dairy production in Argentina is based on grazing of temperate pasture. Concentrate is used as a supplement at a level no higher than 30% of the diet. Milk yield is high but butterfat content of milk is lower on pasture than on indoor feeding diet based on processed forage and concentrate. Rumen fluid of cows on grazing was characterised by low pH (5.8-6.2), high volatile fatty acid concentration (90-120 mmoUI) and a low acetate:propionate ratio (<2.5). Hydrolysis of forage protein in rumen is high and the percentage of dietary amino acids reaching the duodenum is low (20- 30% ). This rumen environment occurs only with cows on grazing because when fresh forage is cut and fed to cows Indoors, pH and acetate:propionate ratio is higher and NH3 concentration is lower. Rumen fermentation was also modified when pasture forage was offered wilted instead of fresh. Concentrate supplementation at a level no higher than 30% of total diet did not affect the rumen environment, but it was modified by corn silage supplementation.

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Rumen Digestion of Temperate Pasture: Effects of Milk Yield and Composition

Dairy production in Argentina is based on grazing of temperate pasture. Concentrate is used as a supplement at a level no higher than 30% of the diet. Milk yield is high but butterfat content of milk is lower on pasture than on indoor feeding diet based on processed forage and concentrate. Rumen fluid of cows on grazing was characterised by low pH (5.8-6.2), high volatile fatty acid concentration (90-120 mmoUI) and a low acetate:propionate ratio (<2.5). Hydrolysis of forage protein in rumen is high and the percentage of dietary amino acids reaching the duodenum is low (20- 30% ). This rumen environment occurs only with cows on grazing because when fresh forage is cut and fed to cows Indoors, pH and acetate:propionate ratio is higher and NH3 concentration is lower. Rumen fermentation was also modified when pasture forage was offered wilted instead of fresh. Concentrate supplementation at a level no higher than 30% of total diet did not affect the rumen environment, but it was modified by corn silage supplementation.