My first Publication CC April Edition-19-High Resolution | Page 42

Pet Nutrition
Composition
Brewer’s yeast (Saccharomyces cerevisiae)
is derived from drying the slurry that
remains aft er beer and ale fermentation.
Due to diff erent practices of breweries, the
composition varies, but can be put at 41%
protein, 3% fat, 0.5% crude fi ber, 6% ash, 5%
moisture and 44.5% nitrogen-free extract
(6). Dried, whole yeast contains about 10%
of both mannan-oligosaccharides (3) and
beta-(1,3)/(1,6)-glucans (4).
Palatability
In two-pan tests, individual animals have
simultaneous access to an excess quantity
of two foods for a limited period (18). Food
consumed from each pan is measured.
Preference can be quantifi ed as intake ratio
for test and reference food. By comparison,
in the home setting, pet’s liking and owner’s
acceptance of a single, unfamiliar product
are crucial for repeat purchase.
Bolstered by preference data in promotional
materials, yeast is oft en included in petfood
for fl avor enhancement. Brewer’s yeast in
petfood was preferred over corn wet milling
yeast from industrial ethanol production
(6, 19). Technically, the former could
be eff ectless while the latter depressed
palatability.
Digestibility
Dogs received an extruded reference diet
as such or with brewer’s yeast in 85:15
mixing ratio (7). Apparent total tract
digestibilities of crude protein for the
reference and yeast-containing diet were
84.7 and 86.2% of intake (n=7/diet). With
the diff erence method, the digestibility of
protein in brewer’s yeast was calculated to
be 88.8%. Two forms of sugarcane yeast had
protein digestibilities of 63.0 and 74.7% (7).
Protein digestibility for other types of yeast
extracts was 72.4% in dogs (8) and 78.6%
in cats (9).
Palatability research in dogs (7, 8, 14, 20)
showed that in fi ve out of 7 tests replacement
of diet ingredients by a yeast preparation
produced an intake ratio ≥ 2, which was the
case in one out of four cat tests (9, 15, 21,
22). Adding yeast to petfood does not always
appreciably enhance palatability.
Beagles, aged 5-9 months, were dosed daily
with a gelatin capsule holding spherules of
live S. cerevisiae CNCM I-4407, equaling
about 4.4% of the dry, high-fi ber food
off ered (10). Yeast versus placebo capsules
produced a 2.8-fold increase in fecal yeast
counts, while leaving apparent protein and
fat digestibilities unchanged.
Protein source
Mean apparent protein digestibility for the
fi ve yeast preparations (7-9) was 75.5%,
which is comparable to 78% as reported
for poultry by-product meal (11). For dogs
and cats, the limiting amino acid in brewer’s
and concentrated yeast is methionine plus
cystine (cf. 7, 12, 13).
In dogs, feeding dry food containing 30%
of a yeast preparation caused voluminous,
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Yeast and fl ea control
Dogs fed dry food were infested weekly
with cat fl eas (23). For fi ve weeks, they
daily received some canned food without or
with 14 g active or inactive brewer’s yeast,
matching 5.6% in dry food. Yeast did not
aff ect weekly fl ea counts.
watery stools (7, 8). Poor fecal consistency
was not reported for cats fed wet food
mixed with 30% (on a dry matter basis)
concentrated yeast (9). Dogs and cats fed
dry food containing 7.5 or 10% of a dried
yeast had good stool quality (7, 14, 15).
Yeast preparations contain 1 to 3% total
purines (16). Feeding dry food with 10%
yeast to Dalmatian dogs may induce a two-
fold rise in renal urate excretion (17), thereby
increasing the risk of urate urolithiasis.
Creature Companion | April 2019 • Vol. XII • Issue 4 • Noida
Anti-yeast food
A starch-restricted diet is thought to cut off
glucose supply of pathogenic yeasts, thereby
mitigating canine skin and ear infections
with yeast (24-28). Th e theory is fl awed and
eff ectiveness is unproven.
* Dr Anton C Beynen writes this exclusive
column on dog and cat nutrition every month.
He is affi liated with Vobra Special Petfoods.