Feeding behaviour in turkeys with a change-over from crumbs to pellets

Applied Animal Behaviour Science 125 (2010) 132–142

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Feeding behaviour in turkeys with a change-over from crumbs to pellets Stéphanie Lecuelle a,b,∗ , Isabelle Bouvarel a , Anne-Marie Chagneau b , Philippe Lescoat b , Florence Laviron b , Christine Leterrier c a b c

Institut Technique de l’Aviculture, 37380 Nouzilly, France INRA, UR83 Recherches Avicoles, 37380 Nouzilly, France UMR 85 Physiologie de la Reproduction et des Comportements, INRA, CNRS, Haras Nationaux, 37380 Nouzilly, France

a r t i c l e

i n f o

Article history: Accepted 21 April 2010 Available online 14 May 2010 Keywords: Feeding behaviour Feeding transition Hardness Colour Intake Films

a b s t r a c t Poultry receive different diets during their rearing but these changes can result in a major reduction in feed intake and subsequently in growth. This problem is widespread in turkeys, especially with feed changes from crumbs to pellets. This experiment aimed to analyse behaviour during this change-over and identify the respective cues involved. Moreover, because pellet colour and hardness have been shown to influence feeding behaviour, differences in these cues were used to investigate their impact on behaviour during the change-over. Ninety-six caged turkeys were fed with crumbs until 28 days of age. They were divided into five groups: a control group that received crumbs throughout the experiment and four experimental groups each receiving one of four pellet types contrasting in colour and hardness. Feeds were distributed at the beginning of the light period and feed intake was measured every 20 min for 2 h on three different days: before feed transition (D − 1), during change-over from crumbs to pellets (D0) and 24 h after transition (D + 1). Animals were filmed two minutes each day at the beginning of the light period. Feed intake significantly decreased within the first 20 min of change-over (D0) in experimental birds and was lower than for controls. This drop disappeared after 24 h. Feed ingestion behaviours (open-beak pecking and swallowing) were lower on D0 than on D − 1 and D + 1, whereas exploration of the feed was higher. The delay between accessing the feed for the first time and the first peck was two times higher on D0 than D − 1 indicating that visual cues induced neophobia in touching feed. Birds reduced swallowing behaviour and dropped feed more often on D0 than on D − 1 supporting the idea that touch appears to reduce ingestion behaviour. However, pellets with different hardness and colour induced similar behavioural changes. The birds that used a closed beak on their first contact with the pellets had a lower feed intake during the first 20 min and a longer delay before swallowing than those that pecked with their beak open. This study demonstrates significant short-term reactions during feed transition related to distal and proximal cues of the food particles. It also highlights different feeding behaviours according to birds, and demonstrates individual sensitivity to feed change. © 2010 Elsevier B.V. All rights reserved.

1. Introduction ∗ Corresponding author at: ITAVI, INRA, 37380 Nouzilly, France. Tel.: +33 247 427 285; fax: +33 247 427 778. E-mail address: [email protected] (S. Lecuelle). 0168-1591/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2010.04.009

In husbandry systems, poultry receive successive diets according to their nutritional needs and beak size. These changes in diet entail changes in raw materials and the

S. Lecuelle et al. / Applied Animal Behaviour Science 125 (2010) 132–142

manufacturing process as well as feed particle size and shape. Under rearing conditions these changes can cause a reduction or a halt in feed intake among chickens or turkeys (Picard et al., 1999). This reaction at change-over is also observed in wild birds (Sturnus vulgaris) which decrease their intake and increase exploratory behaviour when they change from mealworms to crumbs (Freidin et al., 2009). However, until now, few experiments have studied the feeding transition in poultry in detail. From observations under commercial conditions, one out of three turkey flocks changes its feeding behaviour significantly during the feed transition period (Visavi research program financed by ANR, Cidef and CIP, data not published). Feed transition is thus an issue for producers and farmers because performance can decrease and sanitary conditions deteriorate due to pecking being redirected toward litter or faeces (Vilarino et al., 1997). These transition problems demonstrate that poultry are able to detect a diet change and to compare familiar and unknown feed. Their feed intake involves three phases: firstly, identifying the food using sensorial detection, followed by prehending and then swallowing (Picard et al., 2000). Initially, when new feed is given, poultry use distal cues such as vision (Marples and Roper, 1996) and odour (Turro, 1994) cues to analyse it. This can lead to a food neophobia in the short-term. Birds need to touch new food to identify it completely (Yo et al., 1997). Proximal factors used by poultry are tactile (Gentle, 1985) and taste cues (Roper and Marples, 1997) which require a physical contact with the food. Touch and sight appear to be the two main senses used by poultry in food identification while chickens’ sense of smell seems to be used more in learning to feed (Turro, 1994). Taste seems poorly developed, possibly because it is related to the lack of chewing and to the bird’s horny tongue (Kuenzel, 1989). In fact poultry have very acute sight due to a highly developed visual system with four types of cone cells (Goldsmith, 2006) and many specific areas on the retina (Güntürkün, 2000), and a high sensitivity to colour (between 380 and 700 nm). The bird’s beak allows fine palpation using 15–20 specialized dermal papillae containing highly specialized microscopic mechanoreceptors (Merckel and Herbst corpuscles) situated at the tip of the lower beak (Gentle and Breward, 1986). Under commercial rearing conditions it is the transition from crumbs to pellets at 30–40 days of age which causes the most problems. Indeed, this feed transition involves a change in form with an increase in particle size and changes in raw materials to meet nutritional requirements. When the same raw materials are used to produce different pellets, it can be assumed that taste and smell are similar; however tactile and visual cues can be different due to different feed-manufacturing processes resulting in different hardness (Thomas and van der Poel, 1996) and colour. These can lead to modifications in some behaviours, such as the number of pecks at the food, and a decrease in feed intake during transition despite similar pellet shape and size (Chagneau et al., 2006). Previous experiments have demonstrated the effect of hardness and colour on animal preferences under other conditions than transition. During a free choice

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test, turkeys exhibited short-term preferences for lighter coloured feeds (Chagneau et al., 2003). When the particles were the same size, broilers ate hard faster than soft pellets (Picard et al., 1997). On the other hand, Nir et al. (1994) showed that hard pellets resulted in a decrease in feed intake, probably due to excessive hardness. However, it is difficult to separate the impact of each physical parameter because the animal perceives many food cues at the same time. Thus behavioural analysis is required to understand how birds react during feed transition and to determine whether they react to distal (sight) or proximal (touch) factors. The present experiment focused on feed transition from crumbs to pellets and hypothesised that turkeys use sight and touch to detect this change. The aim was firstly to investigate the turkey’s initial reaction to distal and proximal cues, particularly visual and tactile cues, and secondly to describe between-individual variability. The physical characteristics of hardness and colour of pellets were used in a factorial design to determine their impact during the feed transition. Turkeys were individually caged to measure the kinetics of individual feed intake and they were filmed to observe their feeding behaviour. 2. Materials and methods 2.1. Animals and housing The experiment was carried out at the Unité Expérimentale Avicole (Poultry Research Station) of INRA, Tours. One hundred and twenty one-day-old male turkeys (BUT9) were kept in groups in cages until D23. At D23, 96 turkeys with a bodyweight close to the group mean were chosen and placed in a 2-floor battery of individual cages (37 cm × 23 cm × 43 cm) specially equipped with transparent plastic feeders (20 cm × 10 cm × 15 cm) positioned behind a grid. The battery was housed in an environmentally controlled room. Birds were kept under an artificial lighting schedule similar to that used in husbandry systems: lighting was reduced from 24L to 20L/D on day 4, to 18L/D on day 8 and then gradually decreased to 15L/D from day 10 until the end of the experiment. Fifteen hours of lighting was divided into two periods: the first from 09:00 am to 14:00 (5 h) and the second from 17:00 to 03:00 (10 h). Turkeys received the same starter diet ad libitum until D28 (Table 1). The control group consisted of 24 birds and the remaining 72 animals were divided into four experimental groups. In the four experimental groups, the feed varied in colour and hardness according to a factorial design. At D29 and D30, control animals were given the same starter feed while each of the four experimental groups was given a different pelleted feed. At D30, each bird was weighed to measure growth. 2.2. Feed preparation Crumb starter was supplied by a manufacturer. Pellets were manufactured by the experimental feed mill at the Unité Expérimentale Avicole of INRA, Tours. Four different types of pellets varying in composition and pelleting pro-

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(L) = 65 mm) with steam at 70 ◦ C for hard pellets (H), (2) a single pelleting device (Ø = 4 mm, L = 45 mm) without steam at 60 ◦ C for soft pellets (S). Thus four pellet types were obtained: hard-dark (HD), soft-dark (SD), hard-light (HL), soft-light (SL). On each test day, feeders of all birds were removed during the dark phase 1 h before the first light phase. Then feeders containing new feed were introduced at the beginning of the first light phase. Each experimental group was fed one of the four pellet types on D29 and D30. On each test day, turkeys were fed ad libitum.

Table 1 Composition and characteristics of feeds. Diets Ingredient (%) Soybean meal Corn Wheat Corn starch Wheat bran Sunflower meal Rapeseed meal Pea Vegetal oil Dicalcium phosphate Calcium carbonate Salt Dicarbonate dl-Methionine l-Lysine HCl Threonine Premix Calculated content ME (kcal/kg) CP (%) Lysine (%) TSAA (%) Threonine (%) Tryptophan (%) Calcium (%) Available phosphorus (%)

Crumbs starter

Light pellets

40.40 20.00 19.90

42.7 10.00 32.20 5.00

3.00 5.00 3.00

Dark pellets 35.95 28.74 12.48

3.00 3.00 0.81 0.13 0.29 0.30 0.53 0.14 0.50

4.30 2.04 0.63 0.30

4.00 4.00 6.00 5.00 2.15 0.54 0.30

0.18 0.10

0.16 0.13

0.50

0.50

2800.00 26.00 1.70 1.08 1.05 0.30 0.10 0.65

2850.00 24.70 1.40 0.95 0.93 0.31 0.10 0.49

2850.00 24.40 1.40 0.95 0.93 0.29 0.10 0.49

2.00

2.3. Physical characteristics of feeds (Table 2) Individual pellet length was measured using a calliper on a sample of 5 g (200 repetitions/feed) and this was very similar between diets. It varied from 3.7 to 4.4 mm according to treatments. Hardness was measured on 100 particles (>2 mm) of each diet using an INSTRON 5543 (INSTRON, Guyancourt Cedex, France). Hardness (H) was expressed as the maximum load necessary to break the pellet over the upper outer surface area: H=

Supplied per kilogram of diet: vitamin A (retinol), 13,500 IU; vitamin D3, 3870 IU; vitamin E (tocopherol), 90 mg; vitamin K3, 4.5 mg; thiamin, 4.5 mg; riboflavin, 7.2 mg; vitamin B5, 2.25 mg, pyridoxine, 6.3 mg; vitamin B12, 0.018 mg; niacin, 90 mg; folic acid, 2.7 mg; biotin, 0.27 mg; cholin 495 mg; manganese, 73 mg; zinc 81 mg; iron, 52 mg; copper, 18 mg; iodine, 1.8 mg; selenium, 0.18 mg; cobalt, 0.54 mg, sulphur, 0.005 mg, magnesium, 0.001 mg; antioxidant, 4.5 mg. A coccidiostat was added at 0.05% of the diet (Cygro). Calculated using the table published by Sauvant et al. (2002).

cess but with very similar nutritional contents were used during the transition period (Table 1). Two formulae were used to obtain contrasting colours: “light” (L) and “dark” (D) (Table 1). For each formula, two pelleting processes were used to obtain hard (H) and soft (S) pellets. Mash feed was pelleted using: (1) a double pelleting device (diameter of the die-hole (Ø) = 4 mm, length

ML ×l×R

where H: hardness, MPa; ML: maximum load, N; l: length of pellet, mm; R: radius of pellet, mm. The distribution of particles and the percentage of fine particles of crumb and pellets were measured on a 100-g sample treated for 3 min using different mesh screens from 0.6 mm to 3 mm. The percentage of fine particles (particles <0.6 mm) ranged from 0.3% (HD and HL) to 4.6% (crumb). Resistance of pellets to abrasion was measured using a SABE (SABE Distribution, Chauche, France) durabilimeter with 500-g samples for 20 s using a 2 mm screen. Resistance to abrasion was expressed as the percentage of pelleted particles that resisted abrasion, calculated by weighing the fine particles that passed through the screen (±0.01 g). Resistance to abrasion for the experimental pellets ranged from 10 (SD) to 65 (HD)%. Colour was measured using a Commission Internationale d’Eclairage L*a*b* Hunterlab spectrocolorimeter

Table 2 Physical characteristics of four turkey feeds: soft and light pellets (SL), hard and light pellets (HL), soft and dark pellets (SD) and hard and dark pellets (HD). Crumbs

Pellets

Diet

Starter

SL

HL

SD

HD

Compression ratea

21.7

11.25

16.25

11.25

16.25

Pellet preparation

Steam

Cold

Steam

Cold

Steam

0.88

0.51 13.19 1.27 4.06

1.11 61.85 0.29 3.72

0.41 10.27 2.44 4.14

1.11 65.47 0.34 4.38

52.32 5.71 19.84

52.57 5.14 19.98

47.48 4.20 18.92

46.01 3.82 18.57

Hardness (MPa) Resistance to abrasion (%) %Fine particles (<0.6 mm) Length (mm) Colourb L* a* b* a b

4.57

55.35 4.85 22.19

Compression rate = the ratio of the length to the diameter of the die-hole. Colour was measured using a Commission Internationale d’Eclairage L*a*b* Hunterlab spectocolorimeter.

S. Lecuelle et al. / Applied Animal Behaviour Science 125 (2010) 132–142 Table 3 Description of seven observed behaviours and measures. Behaviours

Description

First contact Pecking, beak closed Pecking, beak open

Bird pecks feed with beak closed Bird pecks feed with beak open

Intake Swallowing Stretching neck

Bird swallows food Bird stretches neck

Exploration Dropping feed Scratching feeder Scattering food

Measures Occurrence Latency

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Occurrence and latency of each behaviour were calculated (Table 3). Latency of neck stretching had to be replaced by the number of animals carrying out this behaviour for each day because neck-stretching behaviour was rare and latency could not be tested. 2.5. Statistical analysis

Bird drops food Bird scratches feeder with feet Bird moves feed with a lateral movement of the beak and flips the feed out of the feeder. This is a natural foraging behaviour and allows birds to search for preferred food Number of times the behaviour is observed Length of time before the behaviour is observed for the first time

(SOCEMI, Metz, France). L* represents the lightness, a*, red–green and b*, blue–yellow. 2.4. Consumption and behaviour during the transition period Measures on feeding behaviour were carried out at D28: the day before transition (D − 1), D29: during the pellet transition (D0) and D30: 24 h after transition (D + 1). On each of these 3 days the feed consumption of each bird was measured every 20 min for 2 h and at 24 h after feed distribution. Birds were filmed using video equipment installed in front of the cage. Behaviour was recorded for the first two minutes after receiving feed only in experimental groups to observe the short-term reaction during feed change-over. Indeed, the first reaction (first 2 min) corresponds to the first contact with new feed. The films were then slowed down 5 times and viewed annotating observations using The Observer® 4.0 software. When analysing the video recordings 2 out of the 72 turkeys had to be eliminated for D − 1 and D0, and 8 in total for D + 1 because of the poor quality of the recordings. A behavioural index, comprising seven behaviours (Table 3.), was created and the feeding behaviour of each bird was observed. Two types of pecking were observed, “Pecking with closed beak” and “Pecking with open beak”. Some of the “Pecking with open beak” behaviours were followed either by “Swallowing” or “Dropping food” (Picard et al., 1997). Swallowing could be followed by a stretching of the neck. We calculated the total number of pecks (by adding number of pecks with beak closed and with beak open) and the number of exploration pecks (by subtracting pecking followed by swallowing from the total number of pecks). The position of each bird was recorded in relation to the feeder: “At the Feeder” indicating when the bird passed its head through the grid to the feeder, or “Away from the Feeder”.

All data were analyzed using STATVIEW program version 5. Factors tested were considered as significantly different if P < 0.05. Data were analysed using nonparametric tests because the data were not normally distributed. 2.5.1. Hardness and colour effect A Kruskal–Wallis test was used to test the difference between the quantities of the four types of pellet eaten (HD, SD, HL, and SL) at 20 min and at 24 h after transition on D0. Results show that turkeys ate similar quantities of each pellet type on D0 (P = 0.4). A Mann–Whitney test was used to test the difference between quantities of light and dark (L and D) pellets and between soft and hard (S and H) pellets eaten at 20 min and 24 h after transition on D0. The effect of colour and hardness on behaviour was tested with a Mann–Whitney test on D0. Results show that turkeys ate similar quantities of each pellet type on D0 and behaviours were not significantly different between the four types on D0. Therefore the analyses that followed were performed on all the experimental groups together. 2.5.2. Transition effect The effect of feed change on feed intake was tested by comparing the difference in the quantity of feed eaten between the control and experimental groups (for all pellets) on D0 every 20 min for the first 2 h with a Mann–Whitney test (Fig. 1). The differences in intake of experimental groups between D − 1, D0 and D + 1 were analysed using a Friedman test (Fig. 1). A Friedman test was used to compare the occurrence and latency of each behaviour and the total time spent at the feeder between the 3 days of observation (D − 1, D0 and D + 1) (Table 4). Some turkeys first pecked with an open beak and others with it closed. When the first behaviour was “Pecking with open beak”, it could be followed either by “Swallowing” or “Dropping food”. The first two behaviours of each turkey were then observed on D − 1, D0 and D + 1 (Fig. 2) and the number of turkeys demonstrating these behaviours was calculated. In this way, the number of turkeys having the same first two behaviours was compared between D − 1, D0 and D + 1 with a McNemar test. 2.5.3. Individual variability effect Birds were divided into three groups according to their first pecking behaviour and their second swallow behaviour on D0 (“sensitivity” to the new feed): nonsensitive (NS) – the bird swallowed immediately after the first peck with open beak; medium sensitive (MS) – the

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Table 4 Occurrence (number per sequence of film), latency of observed behaviours, and time accessing the feeder for the three observation periods D − 1 (crumbs), D0 (pellets) and D + 1 (pellets). n = 70.

At the feeder

D0 ± se pellets

D + 1 ± se pellets

P: Friedman

91.91 ± 1.58b 3.60 ± 0.34a 1.55 ± 0.42b 4.99 ± 0.85

85.71 ± 1.99a 8.40 ± 0.66b 0.90 ± 0.35a 7.15 ± 1.60

89.70 ± 2.14b 3.40 ± 0.36a 1.74 ± 0.81ab 8.34 ± 2.12

***

Distal behaviour First peck

Occurrence Occurrence Latency (s) Occurrence Latency (s) Ratio (%) Occurrence

140.14 ± 7.46 138.00 ± 7.50b 5.41 ± 0.95 2.10 ± 0.54a 41.07 ± 7.69b 2.87 ± 1.30a 14.87 ± 1.76a

83.83 ± 5.65a 69.00 ± 5.67a 8.68 ± 1.84 14.8 ± 1.61c 18.00 ± 2.30a 23.35 ± 2.64c 47.64 ± 2.61b

158.41 ± 7.88c 152.30 ± 8.19b 8.76 ± 2.15 6.1 ± 1.21b 36.70 ± 5.24b 5.64 ± 10.70b 42.86 ± 3.16b

***

Total number of pecks Pecking, beak open Pecking

Pecking, beak closed Pecking, beak closed/ total no. of pecks Exploratory pecking (total number of pecks-swallowing)

Proximal behaviour

Swallowing

Latency (s) Occurrence Latency (s) Occurrence Latency (s)

15.30 ± 2.68 125.30 ± 6.69a 6.66 ± 1.17a 0.40 ± 0.10a 38.42 ± 7.73

8.03 ± 1.68 36.20 ± 4.45b 18.92 ± 3.01b 10.00 ± 1.01c 16.29 ± 2.31

10.43 ± 2.13 115.50 ± 7.06a 10.63 ± 2.23a 4.00 ± 0.71b 31.13 ± 4.63

Other

Dropping feed

Stretching neck

Occurrence Number of birds Occurrence Latency (s) Occurrence Latency (s)

9.60 ± 1.15c 56c 1.10 ± 0.52a 34.60 ± 7.94 2.20 ± 0.73a 29.67 ± 6.10

0.20 ± 0.07a 12a 13.30 ± 2.25c 28.11 ± 2.81 11.60 ± 1.56b 28.23 ± 3.69

0.80 ± 0.23b 21b 4.90 ± 1.13b 40.03 ± 5.70 2.30 ± 0.55a 40.45 ± 6.6

Other behaviours and exploration

Scattering food Scratching feeder

a,b,c

Indicate values are significantly different. * P < 0.05. ** P < 0.01. *** P < 0.001.

b

*** **

NS

***

NS *** * *** ***

NS *** *** ***

NS *** *** ***

NS ***

NS

S. Lecuelle et al. / Applied Animal Behaviour Science 125 (2010) 132–142

D − 1 ± se crumbs Duration (s) Occurrence Latency (s) Latency (s)

Behaviours

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Fig. 1. (a) Comparison of feed intake between control group (C – crumbs) and experimental groups (P – all pellet types) at 0–20 min, 20–40 min, 40 min to 1 h, 1 h to 1 h20, 1 h20 to 1 h40 and 1 h40 to 2 h after lights switch on, on D0. Mann–Whitney probabilities indicate group effect: *P < 0.05; **P < 0.01; ***P < 0.001. (b) Comparison of feed intake of experimental birds (P – all pellet types) between days (D − 1 with crumbs, D0 with pellets, D + 1 with pellets) at 0–20 min, 20–40 min, 40 min to 1 h, 1 h to 1 h20, 1 h20 to 1 h40 and 1 h40 to 2 h. Friedman probabilities indicate day effect: *P < 0.05; **P < 0.01; ***P < 0.001.

bird drops the feed immediately after the first peck with open beak; sensitive (S) – the birds first peck was with a closed beak (Fig. 2). Differences of latency and/or occurrence between the three groups for the five variables: feed intake at 20 min, number of pecks, “Swallowing”, first peck and % pecking with closed beak were analysed with the Kruskal–Wallis test followed by a Mann–Whitney U-test. The effect of physical characteristics of pellets (colour and hardness) on the sensitivity of the birds was analysed with a Chi-square test on the D0 values (Table 5).

though birds ate a similar quantity of hard and soft pellets after the first 20 min, they tended to eat more hard than soft pellets (P = 0.08) over the 24 h after receiving their feed. There were only slight differences between dark and light pellet types and between hard and soft pellet types for all behaviours. Hard pellets generated a higher number of “Scratching feeder” behaviour per sequence than soft pellets (7.5 vs 1.98 for soft, P < 0.005). Animals tended to exhibit more “Dropping food” behaviour for light than dark pellets (7.89 vs 5.58 for dark, P < 0.07).

3. Results

3.2. Feed intake during transition period

3.1. Hardness and colour effect

The feed intake of turkeys receiving pellets on D0 (for all groups) decreased significantly more than control birds for the first 20 min (Fig. 1a). On D0, after the first 20 min and throughout the first 2 h, turkeys receiving pel-

Feed intake of the light and dark pellet types was similar at 20 min and 24 h after transition on D0. However, even

Table 5 Comparison of number of birds according to their first pecking behaviour and their second swallow behaviour on D0: non-sensitive birds – pecked feed with beak open and swallowed immediately; medium-sensitive birds – pecked feed with beak open but then dropped it; sensitive birds – first pecked with beak closed. First peck

Pecking beak open Pecking beak closed

First swallowing

Non-sensitive Medium sensitive Sensitive

Hardness

Colour

H

S

12 14 8

11 17 8

P

L

D

P

NS

9 15 11

14 16 5

NS

NS: no-significant relationship between sensitivity and hardness or colour tested using a Chi-square test.

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Fig. 2. Series of first behaviours with number of birds carrying out the behaviour for the 3 days of observation: D − 1, D0 and D + 1.

lets ate more than those receiving crumbs (Fig. 1a). Birds receiving pellets at transition decreased their intake significantly on D0 compared to D − 1 and D + 1 at 20 min (D0 vs D − 1, P < 0.0001 and D0 vs D + 1, P < 0.0001; Fig. 1b). Between 20 min and 2 h, their intake of pellets was similar or higher on D0 and D + 1 than the intake of crumbs on D − 1.

3.3. Feeding behaviours during transition period The initial behaviour patterns changed between D0 and D − 1 with a recovery on D + 1. However, the proportion of the two kinds of first pecks was similar for D − 1, D0 and D + 1 (P = 0.09) (Fig. 2). Most of the first “Peck with open beak” behaviour was followed by swallowing when birds

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ate crumbs (D − 1) and 24 h after pellet transition (D + 1), which was not the case for the day of transition with pellets (D0) (P < 0.0001) (Fig. 2). On D0, birds spent significantly less time at the feeder than the other days, although they accessed the feeder more (Table 4). The delay to come to the feeder decreased on the change-over day compared to D − 1 and was intermediate at D + 1. First pecking latencies were similar on the 3 days (Table 4). During food change-over, the total number of pecks decreased significantly (P < 0.0001) and was higher on D + 1 than on D − 1. Birds reduced “Pecking with open beak” (P < 0.0001) on D0, whereas they increased the number of “Pecking with closed beak” significantly compared to D − 1 and D + 1. The percentage of “Pecking with closed beak” was higher on D0. Turkeys carried out more exploratory pecking on D0 and D + 1 than D − 1. “Pecking with open beak” latencies were the same on D0, D − 1 and D + 1 while “Pecking with closed beak” latencies decreased

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on the transition day compared to the other days. Turkeys swallowed significantly less when they received pellets (D0) than crumbs (D − 1) or than pellet D + 1 (P < 0.0001). Turkeys swallowed for the first time significantly later on the transition day than the days before and after transition. On D0, birds dropped more feed than on D − 1 with an intermediate value on D + 1. Latencies before dropping feed were the same for each day. Birds expressed more neck-stretching behaviour when they received crumbs than pellets and its occurrence was intermediate on D + 1 (Table 4). For other behaviours, “Scattering feed” increased from D − 1 to D0 and partly returned to its initial level on D + 1, “Scratching feeder” increased from D − 1 to D0 and returned to its original level on D + 1 (P < 0.0001) (Table 4). “Scattering food” and “Scratching feeder” latencies did not differ between the 3 days. The three groups of sensitivity to the new feed according to their first pecks and swallowing (NS, MS and S)

Fig. 3. Comparison of latency and occurrence between the three groups of birds according to their sensitivity to the new feed: white: non-sensitive birds (NS), hatched grey: medium-sensitive birds (MS), dark: sensitive birds (S) between the 3 days of observation: D − 1, D0, D + 1 for five behaviours “Feed intake” at 20 min, “number of pecks”, “Swallowing” (latency and occurrence), “first peck” and “% pecking – beak closed”. (a)–(c) Indicate values are significantly different between groups each day (Kruskal–Wallis test). Friedman probabilities indicate day effect within each group.

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decreased their feed intake and their number of pecks on D0 (Fig. 3). These two behaviours were different for sensitive birds than for the others on D0 and D + 1. “Swallowing” behaviour decreased for all groups on D0 and on D + 1, although sensitive birds always swallowed less than the others (Fig. 3). “Swallowing” latency increased except for the non-sensitive animals on D0. Latency of the first pecks was longer for sensitive turkeys than the others on D − 1 and D0 (Fig. 3). The percentage of pecking with beak closed was higher for sensitive birds than the others on the 3 days. The body weight of birds was the same between the three groups. There was no effect of hardness and colour, on the groups (NS, MS and S) (Table 5). 4. Discussion 4.1. Feed transition from crumbs to pellets In this experiment, turkeys reacted to the change-over from crumbs to pellets by decreasing feed intake and increasing exploratory behaviours as soon as the new pellets were distributed. The same reaction was observed in wild birds (S. vulgaris) which decreased their intake and increased exploration behaviour when they received a new diet (crumbs) which they liked less than a preferred diet (mealworm) (Freidin et al., 2009). Poultry appear to react immediately to changes in physical characteristics of the diet (Nir et al., 1990). Broilers have been seen to adjust their feed intake within 10 min of a switch in feed particle size of the same diet (Quentin et al., 2004). In our experiment, on the transition day birds came to the feeder more quickly than the previous day which suggests a possible neophilia at this time, but this is not confirmed by the latency of the first peck at the feed and the delay between the first “at the feeder” and the “first peck” which was almost twice as high on D0 and D + 1 as on D − 1. Similarly, laying hens increase the latency of the first peck at transition to a feed of a different colour and size (Murphy, 1977). On change-over to pellets birds spent less time at the feeder, but put their heads into the feeder twice as many times as with crumbs, which could be linked to uncertainty and would explain the decrease in the total number of pecks. This suggests that there is a balance between an attraction towards an unknown feed (moving rapidly to the feeder on D0) and neophobia to touch the feed. There was also a switch towards more pecks with beak closed on the transition day. Many pecks are not followed by ingestion (Yo et al., 1997) and are called exploratory pecks since sensory cues can be gathered by pecking with a closed beak and can be associated with touching and exploring the feed. Stamp Dawkins and Woodington (1997) demonstrated that pecking was part of the process of object recognition in poultry and a way of learning about the environment. The increase in exploratory pecking may be driven by the need to gather information about the hardness or the roughness of pellets (Picard et al., 1997). Our results demonstrate that some birds used closed beak pecking immediately on receiving new feed, which suggest that these birds may have been alerted by visual cues. This would be in line with the idea that birds determine how they will peck before

pecking their food using visual cues as observed in chickens (Picard et al., 1997). The latency to the first peck with an open beak did not increase significantly on D0, but the turkeys took longer to swallow the first pellet. This suggests in this case that the use of tactile or taste cues could slow down swallowing. The raw materials of crumbs and pellets were slightly different particularly in their cereal content (corn and wheat). It would therefore appear that tactile and visual cues are more likely to be involved in this behavioural change than taste, which is less developed in birds. In the change-over from crumbs to pellets, particle shape, size and hardness were modified suggesting that at least one of these factors governs pecking efficiency and probably swallowing (Picard et al., 2002). In the present experiment, turkeys swallowed less when they received pellets on D0 after crumbs on D − 1 and this was similar to what was observed in chicks which carried out proportionally less “intake pecks” when fed pellets than when fed mash (Martaresche et al., 2000). Indeed, fewer pecks are necessary to consume the same quantity of pelleted feed than for mash. However, this fact cannot explain the decrease in swallowing since this activity was restored on D + 1 when birds were still fed pellets. On the other hand, this ease in eating pellets compared to crumbs could account for the reduced neck-stretching behaviour on D0 and D + 1, suggesting, that pellets are easier to swallow than crumbs once animals adapt to eating this food. The reluctance to swallow pellets on D0 is probably the result of birds being disturbed and anxious as demonstrated by different behaviours such as dropping pellets, scattering food or scratching the feeder (Picard et al., 1999). These behaviours could be used to search for familiar feel or size of particles, resulting in the new feed being perceived more negatively. Haskell et al. (2001) showed broilers decreased their intake and their frequency of pecking the feeder with a low than with a high energy diet, and they increased their frequency of scratching which could possibly be explained as a sign of frustration. After the first 20 min of pellet distribution, the intake was similar to that of crumbs in the controls, which is in line with observations from previous experiments (Chagneau et al., 2006; Vilarino et al., 1997). On D + 1, feed intake and most behaviours returned to basal levels however, some were still higher than on D0 (pecking with beak closed, dropping pellets, scattering food) indicating long-term effects of feed change. This reaction particularly suggests that tactile cues due to contact with pellets still lead to neophobic responses at this time. Provenza et al. (1995) showed this long-term effect on lambs which only ate more of a new feed 12 days after change-over to this feed. The bird gradually learns about its feed from sensorial cues and metabolic effects impacting on its choice and feeding behaviour (Meunier-Salaün and Picard, 1996). This feed recognition is initially distal without any contact with the food, as demonstrated in turkeys with the increased delay between initial observation and the first peck, and then proximal with a longer time before swallowing. Latency seems to be a good measure to differentiate between reactions to distal and proximal cues. In Marples and Roper’s (1996) study approach latencies of chickens were the same

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for new and familiar feed when there was no colour change. Thus under commercial conditions, blending the new with the old feed could reduce fear and the change-over effect. 4.2. Hardness and colour effects The reduction in ingestion behaviour during the changeover from crumbs to pellets was only very slightly affected by the colour and the hardness of the different pellets. In the present study, there was only a tendency for hard pellets to be eaten more than soft pellets. This is similar to Picard et al. (2000) who showed that turkeys ate hard pellets faster than soft pellets. No difference in feed intake was observed between light and dark pellets during transition, although poultry are able to detect different colours with a preference for certain colours under free choice conditions. Weeks et al. (1997) showed that when different coloured feed was given to poultry, most of them chose the yellow feed and Cooper (1971) showed turkey poults preferred green feed to other colours. The low effect of hardness and colour in our study could be explained by the fact that the differences in size and shape of crumbs and pellets was too great and masked the other tactile and visual cues; colour and hardness were secondary cues compared to size and shape in the present transition. Nevertheless, Stamp Dawkins and Woodington (1997) showed hens discriminated colour more than shape when they had to choose between two objects. Another explanation for this absence of effect on feeding behaviour at change-over could be linked to the large individual variability observed in behavioural changes and the insufficient number of animals in this study to obtain a significant effect of hardness and colour.

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vation is that already on D − 1 sensitive birds had different behaviours suggesting a greater sensitivity of these birds towards their feed. These birds carried out more pecks with the beak closed and had a higher swallowing latency than the others on D − 1. The higher activity of sensitive animals could explain their more marked reaction at transition. The swallowing latency and the number of exploratory pecks with beak closed could thus be useful factors to identify birds’ sensitivity to feed change. The sensitive birds identified in this way could thus be used to investigate the cues that induce reduced intake further, particularly the effect of distal cues because their behaviour was modified before touching the pellets (D − 1). By using sensitive birds in future studies to investigate the effect of a specific stimulus, the effects would be greater and thus easier to detect due to the birds lower reaction threshold. 5. Conclusion The behavioural changes observed during the changeover from crumbs to pellets appear to be affected by distal cues with an increased delay between the first sight and first touch, although the proximal cues appear more important because changes mainly occurred after the first peck. Neither the colour nor the hardness of the pellets induced variations in behavioural or intake, and the changes in shape and size of feed particles appear to have the greatest impact on feed change-over, particularly due to the tactile information they provide. In future experiments, the use of sensitive birds characterised by a high level of pecks with a closed beak and a high swallowing latency could provide a better understanding of reactions during feed transition. Acknowledgements

4.3. Individual variability In the present experiment, the change-over resulted in various behavioural responses that helped to distinguish birds whose behaviour was different on the change-over day but also the day before and after it. Not all the birds demonstrated the same behaviour before touching the feed. Some first pecked the feed with their beak closed and others with it open. Pecking the feed provided information about its tactile characteristics. “Pecking with beak open” can be followed by two other behaviours “Swallowing” or “Dropping feed” corresponding to the bird’s reactions to touching the feed. In the present experiment, birds which first pecked with an open beak swallowed faster than those which first pecked with a closed beak. The turkeys with an open-beak first peck appeared to be more prone to take and swallow the pellet directly and so were less sensitive to visual factors. Birds pecking first with a closed beak were more sensitive to feed transition demonstrated by a lower feed intake and less pecking and swallowing than the others. Around 38% of the pecks were carried out with the beak closed in sensitive birds with a longer latency to swallow, whereas this was only 18% in non-sensitive birds. This susceptibility to the new feed was maintained on D + 1 demonstrated by the number of pecks and swallowing events and resulted in a lower feed intake than for the moderately sensitive birds. An interesting obser-

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