Abstract

A database was developed from 16 scientific publications to explore mechanisms controlling rumen turnover. The database included 70 treatment means (43 cattle and 27 sheep) from experiments in which rumen contents were measured by complete manual evacuation or by slaughter. Rumen turnover was estimated as the ratio between rumen contents (kg of DM) and feed intake (kg of DM/h). Predictors were intake, body weight (BW), metabolic BW (BW0.75), and the dietary components crude protein (CP), neutral detergent fiber (NDF), neutral detergent solubles (NDS), acid detergent lignin and ash. The best linear models obtained to predict rumen turnover (T) for NDF, NDS, dry matter (DM) and acid detergent lignin (LIGN), respectively, were:

TNDF = 23.84 - 10.26 ln(D-NDFI);	r2 : 0.28, P < 0,001
TNDS = 17.08 - 13.39 ln(D-NDSI);	r2 : 0.76, P < 0,001
TDM = 20.16 - 10.14 ln(D-NDSI);	r2 : 0.65, P < 0,001
TLIGN = 37.69 - 30.77 ln(D-NDFI);	r2 : 0.70, P < 0,001

These curvilinear relationships were likely due, at least for NDF and lignin, to the increase in rumen NDF content (% of BW) that occurred when intake of dietary, or forage, NDF (% of BW) increased. In the database, turnover of NDF and NDS showed additive behavior. No differences were found between cattle and sheep in rumen NDF, NDS and DM turnovers. When fed at the same level of intake of forage NDF (% of BW), sheep had significantly lower rumen NDF contents (% of BW) than cattle. The rumen evacuation technique is a valuable tool to explore interspecies relationships. The use of this large dataset derived from the scientific literature improved the understanding of the relationships existing among feed intake, body size and the components of rumen turnover, and allowed their quantification.

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