Farm Animal Metabolism and Nutrition

to improve digestive efficiency and/or

growth rate or milk production by

ruminant animals.

Effect of Feed Enzymes on Diet

Formulation and Feed Preparation

Feed enzymes are known to produce
variable responses even when given to the
same-aged animal and in similar diets.
Therefore, either variability in feed enzyme
formulations between batches of the same
product or variable composition of indivi-
dual ingredients is altering the effective-
ness of the same enzyme formulation.

Shelf life

Enzyme formulations have a shelf life that
is dependent upon storage conditions. A
product which has not been stored accord-
ing to the manufacturer’s recommendations
cannot be guaranteed to maintain its
enzyme activity.

Heat stability

Most feed manufactured for monogastric
animals is sold in a form which has been
heat processed. Therefore, any feed
enzyme product must be able to withstand
typical feed processing conditions. Fungal
enzymes tend to be less heat stable than
those derived from bacteria (Cowan, 1993).
Without any form of protection, fungal
enzymes rapidly lose activity above 60°C.

Fungal enzymes which have been

stabilized and granulated can withstand up

to 75°C and even 80°C if the granules are

coated. Some bacterial enzymes are

capable of tolerating between 85 and 90°C

for short periods.

Loss of some enzyme activity due to

heat may not always reduce animal

performance. For example, the retention of


-glucanase activity was measured by

Inborr and Bedford (1994) after broiler feed

was conditioned at 75, 85 or 95°C for 30 s

or 15 min before pelleting (Table 19.6).

Enzyme activity was reduced at all

temperatures and activity loss increased

with the longer conditioning time. Yet,

chicken performance was reduced only

when pelleting temperature exceeded

85°C. This research shows it is important

to know what effect feed processing condi-

tions are having on animal performance. If

processing conditions are adverse for

enzyme activity and these cannot be

altered, then application of liquid enzymes

post-pelleting is an alternative to develop-

ing heat-stable enzymes and enzyme

formulations. This technique ensures even

dosing of enzymes onto the feed and near

total recovery of enzyme activity (Cowan,

1993).

Once enzymes have survived feed

processing they must then retain their

activity inside the animal after consump-

tion. Chesson (1993) notes that fungal

polysaccharidases are not destroyed in

vitroby porcine proteases used singly or in

combination. Using solid phase markers,

Chesson (1993) found that around three-

quarters of ingested enzyme activity was

Feed Enzymes 419

Table 19.6.Effect of feed processing conditions on retention of
-glucanase activity (% of non-heat-treated
mash control; coefficient of variation = 13.8%, n= 14) and broiler gain and feed conversion ratio (FCR).

-Glucanase activity

Conditioning period Broiler performance

Temperature °C 30 s 15 min Gain (g) FCR

75 66 49 547 1.54

85 56 31 556 1.53

95 16 11 517 1.64

After Inborr and Bedford (1994).