[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Clarification regarding in vitro digestion of whole crops



Dear foragers!
Based on some replies that I received, I guess I should have been more clear 
stating the problem of using the Tilley and Terry method for digesting 
herbage of whole crops.

We have problems repeating results when digesting fresh whole-maize and fresh 
whole-wheat. The lack of repeatability occurs within samples, within growing 
season and among growing seasons. In ring tests between three laboratories in 
Denmark, there has been more variation in digestibility of fresh whole crops 
compared with whole-crop silage and herbage and silage of conventional 
forages (mainly ryegrass or ryegrass-white clover mixtures). The standard 
deviation between duplicate samples was as high as 6% for whole-maize herbage 
compared with 2 to 3% for conventional forage.

The in vitro method is standardized and cows receive one third concentrate 
and two thirds hay. The feeding of hay,  whole-wheat silage, or whole-maize 
silage also has been compared when digesting fresh whole-crop samples 
according to Tilley and Terry. We did not find any consistent improvement in 
in vitro results by using whole-crops in the standard diet. It would have 
been nice to use fresh whole-crops in the standard ration, but obviously this 
is not manageable. In vitro results are calibrated with samples from in vivo 
trials in which sheep are used. By using sheep, we reduce costs and we can 
study more samples each year.      

We do not necessarily think that the Tilley and Terry method is wrong to use, 
because the variation in in vitro results for herbage of whole crops has not 
worsened over the years. It is just that farmers demand better methods for 
predicting energy concentration of forages before and after ensilage.


Sincerely,

Christer Ohlsson


************************************************
Christer Ohlsson, Senior scientist
Department of Forage Crops and Potatoes
Research Centre Foulum
P.O. Box 21
DK-8830 Tjele, Denmark

Phone: +45-89991833
Fax:   +45-89991839
Present E-mail: CO%AFGK%Plante1@Foulum.min.dk
New E-mail (from 25 April, 1996): CMO@AFGK.SP.DK
************************************************

*************************************************************
* This message  was sent through forage-mg@oes.orst.edu
* To unsubscribe from  this list, send the  following in
* the body (not the subject line) of an email message to
* forage-mg-admin@oes.orst.edu:  unsubscribe forage-mg