Highlights
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- Can state-dependent learning be used to assess the welfare of feed-restricted broiler breeders?
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- Birds were taught to associate food rewards with ad libitum feeding and restricted feeding regimes.
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- Birds were then tested to see which food reward they preferred in a two-way choice test.
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- Birds showed some preference for the food reward associated with feed restriction.
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- This preference was sensitive to training and testing conditions and was not robust.
Abstract
This
paper reports three experiments that aimed to validate the use of
state-dependent learning (SDL) as a novel welfare assessment tool to
evaluate the hunger state of feed-restricted broiler breeders.
In
each experiment, birds alternated every 2 days between two food
rations: quantitative feed restriction (QFR) and ad libitum access to
the same feed (AL). Each food ration was paired with a different, end of
day, coloured food reward. It was predicted that the reward associated
with hunger (QFR FR) would be preferred to the food reward associated
with AL (AL FR) in a subsequent choice test. The SDL preference testing
took place after 4 and 8 days of training. Each bird was tested twice
(once per food ration fed on the test day).
In experiment 1 (pilot, n = 4),
birds preferred the QFR-associated reward during both tests (mean
(±S.E.M.) preference: QFR FR: 35.0 (±3.5) g; AL FR: 2 (±1.3) g, but
differential food reward intake between hunger states during training
confounded the results.
In experiment two (n = 12)
a smaller food reward was used during training to try and equalise
intake. The birds preferred the QFR FR in test 1 only (least significant
difference (L.S.D.) = 15.08, P < 0.05). The mean (±S.E.M.)
consumption in test 1 was: QFR FR: 31.6 (±4.3) g; AL FR: 9.41 (±2.3) g.
However, differential reward intake continued to confound the findings.
In experiment three (n = 8),
the food reward was made more palatable by feeding moist and food
reward intake during training was equalised between hunger states.
During testing, birds continued to show a significant preference in test
1 only (L.S.D. = 13.73, P < 0.05).
It
was concluded that SDL-derived preferences observed do exist but are not
a robust phenomenon. Therefore, further research is needed to quantify
factors influencing SDL development and maintenance before using SDL as a
tool to assess hunger in feed-restricted broiler breeders.
Keywords
- Broiler breeder;
- Feed restriction;
- State-dependent learning;
- Animal welfare;
- Choice test;
- Preference test
Copyright © 2015 Elsevier B.V. All rights reserved.
