(two experiments); Roth Maier and
Kirchgessner, 1995). The lack of response
to enzyme supplementation with layers
may be due to the age of the bird (starting
age 21–31 weeks), compared with the
digestively immature broiler chick. Stevens
et al. (1988) have also noted the effects of
enzymes on production declines with age.
Although Aimonen and Nasi (1991)
showed no effect of enzymes on laying
performance, the multienzyme supplement
used increased the apparent metabolizable
energy content of oats (from 11.8 to 12.1 MJ
kg^1 ) and improved FCR by 3%. The multi-
enzyme supplement only had an effect
when oats provided >8% crude fibre.
Nasi (1988) showed that a -glucanase
preparation had no effect on layer perform-
ance on barley-, wheat- or hulled oat-based
diets. Yet when Nasi (1988) included a cel-
lulase, -glucanase and protease formula-
tion, layer egg production and feed
conversion were improved. Graham (1991)
also measured a small improvement in egg
production with the addition of another
multienzyme product to a barley-based
diet. Other experiments which have mea-
sured improved egg production include
those of Iotsius et al.(1986), Adams (1989),
Jeroch (1991) (experiment 3) and Zang et
al.(1995). Addition of multienzyme sup-
plements has proven to be generally more
effective in improving egg production than
supplements which contained only one
enzyme.
In addition to some experiments
showing improved performance, there is a
hygiene benefit from the addition of
enzymes to rye, wheat and barley diets for
layers. Enzyme supplementation reduces
sticky droppings as a result of reduced
water intake (Jeroch et al., 1995) and
digesta viscosity (Bedford, 1993). Less
sticky droppings means fewer dirty eggs
(Francesh et al., 1995).
Enzyme supplementation tends to be
most efficacious in layers when -glucanase
products are added to diets with significant
amounts of barley. For enzyme addition to
wheat-based diets to be reliably beneficial
in terms of egg production, more work is
required to improve our knowledge of the
relationship between bird metabolism and
wheat carbohydrate chemistry. A quick,
cheap and reliable means of measuring the
NSP in wheat is warranted to improve the
reliability of adding enzymes to poultry
diets containing wheat.
Even though improvements in
digestibility with carbohydrase enzyme
supplementation of layer diets is generally
smaller than for broilers, significant
improvements in P digestibility and reten-
tion can be made. Schoner et al. (1993b)
showed that P excretion in layers was
reduced by 45–50% with 400–500 U kg^1
of phytase compared with a monocalcium
phosphate-supplemented control.
Recent findings are summarized below:
● Broilers are sensitive to many anti-
nutritional factors and therefore respond
favourably to appropriate enzyme
supplementation (i.e. -glucanases for
barley; pentosanases for rye and wheat;
phytase for phytate). Multienzyme
supplements tend to be more effective
than single activity supplements.
● The amount of enzyme required varies
with bird age and diet composition
(NSP, Ca, Zn and total and phytate P).
● Layers are less responsive to enzyme
supplementation than broilers. Benefits
such as less sticky droppings, increased
egg production and FCR have been
measured, especially when the enzyme
supplement has multiple activities.Enzyme Supplementation of Pig Diets
Unlike the broiler industry, the pig indus-
try has been more cautious in accepting
feed enzymes because the pig’s response to
them is less consistent. Compared with
poultry, the efficacy of feed enzymes in pig
diets has been less consistent. Young pigs
rely on enzymatic digestion for the release
of most of their nutrients, which means
that they are more susceptible to anti-
nutritional factors in their diet. By the time
a pig reaches 50 kg, around 30% of its
energy requirements come from fermenta-
tion in the hindgut (Rerat et al., 1987).412 D.I. Officer