Farm Animal Metabolism and Nutrition

recovered from young broilers after the
enzyme had passed through the crop and
proventriculus. The activity recovery
percentage from the terminal ileum for
both broiler and 40 kg pigs was between 8
and 32% (Table 19.7). Therefore, a
considerable portion of the added activity
is lost in the protease-rich environment of
the gut and small intestine.

Measuring feed enzyme activity

Part of the problem with the interpretation of
feed enzyme experiments is that the enzyme
activity level is often not expressed or, if it is
noted, then the units or method of measur-
ing activity varies from one enzyme product
to the next. In addition to this, once the
enzyme is added at low concentration to the
feed, it is often even harder to measure the
enzyme activity level. Cowan (1993) tested
four methods of measuring enzyme activity
in feed both before and after pelleting. The
methods and results were as follows:

1.The standard assay for the enzyme in
question which proved insensitive with
only 400–800 fungal enzyme units added
per kg.
2.The ELISA analysis was sensitive, but
antisera for all the enzymes to be tested
were not available.
3.Measurement of reducing sugars after
enzyme action and extraction of the
enzyme from the feed was inaccurate due
to the high background of reducing sugars.
4.Measurement of reducing sugars after
extended incubation had similar problems
as 3.

Cowan (1993) found that the only

accurate method of measuring enzyme

activity was to extract the enzyme from the

feed and measure the activity using the

standard assay after an extended incubation

time. Cowan’s method, although it works

for a number of enzymes, is much more

complicated than the technique developed

by Walsh et al.(1995) for 
-glucanase.

Walsh et al. (1995) developed a simple

radial diffusion assay for 
-glucanase

activity which has a precision of ±4% and

is sensitive enough to measure activities as

low as 0.5 kg t^1 supplement equivalent.

The Walsh et al. (1995) assay requires no

specialized equipment and measures

diffusion of an enzyme containing feed

extract through agar containing 
1–4 and


1–3 linkages from the glucan lichenan.

There appears to be scope for further

research into the use of media suitable for

other commonly used fibre-degrading feed

enzymes.

Measuring anti-nutritive factors in feed

The accuracy of feed enzyme supplementa-

tion would be significantly improved if we

had cheap, rapid and accurate techniques

for measuring anti-nutritive factors in the

feed. Book values for NSP or phytate, by

their very nature, are averages, and can be

significantly different from what is found

in practice.

For example, both the season (winter

and spring) and the year in which a crop

was grown can influence the amount of 
-

glucan in barley (Jeroch et al., 1995). Jeroch

420 D.I. Officer

Table 19.7.Recovery of enzyme activities (U g^1 ) from diets and the terminal ileum of young pigs and
broilers given
-glucanase- and
-xylanase-supplemented diets (values in parentheses % of total added).

Sample
-Glucanase
-Xylanase

Total added enzyme 104 130

Recovered from pig feed 127 (122%) 88 (68%)
Recovered from pig ileum 33 (32%) 28 (22%)

Recovered from broiler feed 83 (80%) 83 (64%)
Recovered from broiler ileum 8 (8%) 25 (19%)

After Chesson (1993).