Farm Animal Metabolism and Nutrition

Chapter 11

In Sacco Methods

P. Nozière and B. Michalet-Doreau^1

Département Elevage et Nutrition des Animaux,

Unité de Recherches sur les Herbivores, INRA Theix, France

Introduction

As predictive models for estimating the
nutritive value of feeds for ruminant live-
stock have become increasingly complex in
their approach, they have highlighted the
need for an accurate characterization of the
degradation kinetics of different feed frac-
tions. A direct method of measuring the
rumen degradation of feeds consists of
placing a small amount of foodstuff in an
undegradable porous bag, suspending the
bag in the rumen and measuring the dis-
appearance of feed components after
incubation. This technique is very old, and
was used for the first time by Quin et al.
(1939). They used silk bags which were
introduced in the rumen via a cannula.
This technique was used again later to
investigate the ruminal degradation of
cellulose and the dry matter (DM)
digestibility of a range of feeds. However,
in all the studies, no attempt to describe
the degradation curves by regression was
made. It was not until the 1980s that this
technique was used to obtain an evaluation
of the rate and extent of degradation in the
rumen. New ruminant rationing models
(protein system) require determination of

the dynamic aspects of feed nitrogen (N)

degradation in the rumen and have adopted

the in saccotechnique to characterize it.

One of the limitations of the in sacco

technique is its low repeatability and its

lack of reproducibility, as is confirmed by

the results of the ring-tests carried by

Oldham in the UK, Vérité in France and by

Madsen and Hvelplund in the EC, as

reported by Michalet-Doreau and Ould-Bah

(1992). To be able to take data from

different laboratories in feed tables and use

them to interpret the results from produc-

tion experiments in different countries, a

standardized in sacco method was

proposed following on the EEC-EAAP

meeting in 1986 where the present situa-

tion regarding protein evaluation systems

for ruminants was presented. The first part

of this chapter will examine methodo-

logical aspects.

Many in saccodata are provided by

the numerous kinetic studies of N dis-

appearance which were used to elaborate

the modern systems for evaluation of feed

and protein requirements for ruminants.

Increasingly this technique is also used to

describe the kinetics of degradation of

other feed components such as starch and

(^1) Corresponding author.
© CAB International2000. Farm Animal Metabolism and Nutrition
(ed. J.P.F. D’Mello) 233