Ž .
complexes Jones and Mangan, 1977 . PEG has been used to neutralize the negative Ž
. effects of condensed tannins on feed intake Silanikove et al., 1994 and digestibility
Ž .
Silanikove et al., 1996; Salawu et al., 1997 and attempts have been made to boost the Ž
ingestion of tannin-rich foliage by supplementing ranging cattle with PEG Smith et al., .
1995 . Goats fed tannin-rich foliage exhibit a cyclic pattern of meals, which is different from
goats fed a high-fiber tannin free diet. The characteristics of feeding activity recorded during 8 h were affected by PEG supplementation in goats fed a diet rich in condensed
Ž .
tannins Silanikove et al., 1997b . The effect of condensed tannins on the eating activity of cattle, and interactions with
PEG supplementation, have not been reported. In particular, although cattle seem to be deprived of adaptative features to tannins, they will ingest substantial amounts of tannin
rich vegetation. The way they adapt to such diets has not been investigated. Ž .
The aim of the present study was: i to quantify the effect of Q on feed intake and Ž .
ingestive behaviour in cattle; ii to clarify if changes in ingestive behaviour and feed Ž .
intake induced by Q in cattle can be reversed by feeding PEG; iii to clarify if the Ž
decrease in feed intake associated with feeding Q is due to short-term oral or
. post-ingestive effects or to digestive effects.
2. Materials and methods
Experiment 1 was aimed at establishing the dose of Q needed to negatively affect feed intake in Holstein heifers, and the dose of PEG needed to restore feed intake. The
purpose of experiment 2 was to assess the effects of Q and to clarify how they interact with PEG on feed intake and feeding behaviour.
2.1. Sites, housing and animals Experiment 1 was carried out at the Metabolic Cow Unit of the Agricultural Research
Organization at Bet Dagan. Experiment 2 was carried out at the Agricultural Youth Village of Eshel Hanassi in the Northern Negev of Israel. In both locations, heifers were
housed in individual pens in which daily food intake could be measured. In Eshel Hanassi, continuous weighing of the ration for each heifer was carried out, using an
electronic balance that weighed in the range of 0 to 50 kg with an accuracy of 10 g Ž
. Merav 2002, Shekel Balances, Bet Keshet, Israel . Water was available at all times and
water intake was measured using a ruler in calibrated plastic troughs. Four heifers were used in each of experiments 1 and 2. Initial body weights were 316.2 7.3 and
Ž .
358.0 13.0 kg average s.e. in Bet Dagan and Eshel Hanassi, respectively. Overall body gain was 145 30 grday.
2.2. Diets Ž
. Ž
Complete mixed diets CMDs , formulated to fulfill standard requirements NRC, .
Ž .
1989 were used in both experiments. CMD consisted DM basis of 14.3 oat hay,
9.9 pea hay, 10 wheat straw, 30.5 wheat silage and 35.3 commercial pelleted Ž
. concentrate Matmor, Ashdod, Israel . Chemical composition was 56.3 DM and, on
DM basis, 13.4 crude protein, 9.83 MJrkg metabolizable energy, 45.6 neutral detergent fiber. In both experiments, the ration was distributed once daily between 10:00
and 12:00. The diet was formulated to limit residues to 5 of offer. Food residues were gathered and weighed for each heifer individually before the daily ration was distributed.
Ž .
The quebracho meal used in both experiments Trask Chemical, GA contained 47 Ž
. condensed tannins, as assayed according to Hagerman and Butler 1978 .
2.2.1. Experiment 1: effects of quebracho meal and PEG on food intake During the first phase of this experiment, aimed at reaching approximate evaluation
of the amount of Q that decreases feed intake in heifers, all four heifers were fed the same diet. From day 0 to day 26, amounts of Q were gradually included in the diet from
0 to 500 g in increments of 50 or 100 g. On day 27, the Q allowance was reversed to 500 g and increased again to 1000 g on days 38–39. The second phase of the experiment
was implemented as a Latin square in which treatments were switched weekly. Heifers
Ž .
were allotted to one of the following treatments: CMD, without Q control, termed C , Ž .
supplemented with 1 kg of Q without PEG Q or supplemented with 1 kg of Q with Ž
. Ž
. Ž
. PEG MW 4000 given at two levels: 40 grday Q-PEG40 or 80 grday Q-PEG 80 .
2.2.2. Experiment 2: effects of quebracho meal and PEG on food intake and feeding behaÕiour
The experiment was designed as a Latin square with Q and PEG given at two levels: 0 and 625 grday for Q, and 0 or 250 g for PEG. Diets were given sequentially to each
heifer in four feeding cycles of 9, 6, 7 and 8 days. Heifers were allocated to cycles at random.
Ž .
During the control cycle termed C , heifers were fed a CMD with no Q and no PEG. During the PEG cycle, heifers were fed the control diet, supplemented with 250 g of
PEG, but no Q. During the Q cycle, heifers were fed the control diet, supplemented with 625 g of Q, but no PEG. During the Q-PEG cycle, heifers were fed with the control diet
supplemented with 625 g of Q and 250 g of PEG.
2.3. ObserÕations on behaÕiour experiment 2 The behaviour of heifers was continuously observed for 180 min on each of 18 days,
subsequent to distribution of the diet. This included the first day of each cycle, on which diets were novel to heifers, and the last day of each cycle, when heifers were presumed
to have adapted to their diets. One observer was in charge of recording one or two heifers. An eating bout was defined as the period of time during which the only
Ž .
behaviour was keeping the head in the food trough foraging on CMD , including head raising interruptions - 20 s in duration. Other behaviours were drinking, ruminating,
standing idle, and lying. The time at which eating was discontinued or resumed was recorded, together with the weight of the food trough. The time at which drinking was
discontinued or resumed was recorded, together with the level of water in the trough. The number and duration of eating and drinking bouts and the amount of food and water
ingested during each bout were calculated. On total, the behaviour analyses were based on 2756 observations.
2.4. Data analysis Behaviour data, as expressed in percentages of time devoted to a single behaviour,
were homogenized for variance, using arcsine transformation, before analyses of vari- ance were carried out. The effects of level of Q and PEG supplementation, of heifer and
Ž .
of feeding cycle, on feed intake experiments 1 and 2 , and on feeding behaviour Ž
. Ž
. experiment 2 were evaluated by bifactorial Latin square analyses SAS, 1985 . In
addition, paired T-tests were used to verify if PEG supplementation neutralised the effects of Q on feed intake and behavioural characteristics.
3. Results
