and a maize and soybean meal concentrate;
and (ii) a sweetened TMR in which a
brown sugar food product constituted 1.5%
of the dietary dry matter. The treatments
were arranged as follows: (i) control TMR
fed on both sides of a divided feed bunk;
(ii) sweetened TMR fed on both sides of a
divided feed bunk; and (iii) both rations
fed on alternating (daily) sides of divided
feed bunks in tie stalls. The observation
periods were 2 weeks in duration. A choice
of control or sweetened ration did not
affect feed intake. However, the authors
noted that the outcome of their experiment
might have been affected by the composi-
tion of the control ration, its similarity to
the sweetened ration, availability of both
diets simultaneously when a choice was
offered and use of a TMR rather than
separate feeds or even simpler mixtures
of feed ingredients. Another experiment
in the same laboratory (Nombekela and
Murphy, 1995) indicated a transient
increase in consumption of a sucrose-
supplemented diet during the first 2 weeks
after parturition.
The acceptability of traditionally
unpalatable feeds, such as animal protein
by-products, has been improved by treat-
ment with sugars. For example, non-
enzymatically browning of meat and bone
meal with xylose solutions has significantly
increased feed intake in lactating Holstein
dairy cows (Allen et al., 1997). Twenty
cows housed in a tie stall barn were
allowed access to two individual feed con-
tainers of equal size and accessibility for
each cow. Naive cows were allowed access
for 30 min to 4.5 kg of two grain mixes,
each containing 250 g kg^1 treated or
untreated meat and bone meal, top-dressed
onto a basal ration. Cows consumed 16%
more of the grain mix containing the treated
meat and bone meal on day 1, but nearly
62% more by day 8. Feed intake of the
basal ration increased by 12.2% when the
treated product was top-dressed versus the
untreated product. The xylose-treated meat
and bone meal was substantially more
acceptable and resulted in greater feed
intake when contained in a top-dressed
supplement.
Olfaction and feed preferenceWhen flavours are used to manipulate the
senses of cattle, the intensity of the flavour
is a function not only of taste, but also of
olfaction. Olfaction and taste function
together to create a given perception of a
food (Arnold et al., 1980). These two
senses detect and then quantify chemo-
sensory stimuli in feed and provide the
information on which eating decisions are
based. The sense of smell determines the
presence of volatile substances, whereas
taste detects sweet, sour, salty or bitter
compounds in a feed ingredient. There is
evidence that dietary preference and total
feed intake are altered in bulbectomized
and anosmic cats and poultry (Snapir and
Robinzon, 1989). To date, little information
is available concerning olfaction and feed
preference in cattle due in large part to the
lack of a good technique that can separate
the effects of taste and olfaction.NeophobiaCattle associate sensory information about
harmful phytochemicals (such as poisonous
plants) with appropriate behaviour through
instinct, learning as an individual, learning
as part of a social group or combinations
of these behaviours (Albright, 1993).
Ruminants almost always sample only a
small amount of a new feed when it is first
offered. This cautious sampling, or even
complete rejection of new feeds, is termed
neophobia or ‘fear of the unknown or new’.
Neophobia, and not unpalatability, is
the primary factor influencing feeding
behaviour by naive or inexperienced herbi-
vores (Launchbaugh, 1995). Neophobia
typically is displayed as a period of low or
rapidly accelerating feed intake prior to a
stable maximum feed intake level. This
behaviour pattern is innate and typically is
exhibited when feedlot diets are first
offered to animals even though the feeds
are not inherently toxic (Launchbaugh,
1995). Neophobia tends to be more
pronounced in experienced adult animals,
individual animals not part of a socialFeeding Behaviour 379