Short communication

Effect of early dietary experiences on the development

of feeding preferences in semi-intensive sheep

farming systems—a brief note

Panagiotis E. Simitzis a, Joseph A. Bizelis a,Stelios G. Deligeorgis a,*, Kostas Feggeros b

a Department of Animal Breeding and Husbandry, Faculty of Animal Science,

Agricultural University of Athens, 75 Iera Odos, 118 55 Athens, Greeceb Department of Animal Nutrition, Faculty of Animal Science,

Agricultural University of Athens, 75 Iera Odos, 118 55 Athens, Greece

Accepted 20 June 2007

Available online 27 July 2007

Abstract

The crucial role of the periweaning period in the development of lamb feeding preferences was examined

in the present study. Twenty-four female lambs were fed with a commercial diet, supplemented with

oregano essential oil (1 ml/kg) between the 15th and 55th day of their life, in the absence of ewes. After the

55th day, animals consumed the same diet, without the oregano oil dietary supplementation. Lambs were

later individually subjected to feeding preference tests at the age of 3, 5, 7, 9 and 11 months old. Each test

lasted 25 min and it was a free choice situation between 4 different test feeds supplemented with eucalyptus

or mint or orange or oregano essential oil (1 ml/kg). As it was shown, previous exposure to oregano flavour

influenced future acceptance of oregano-supplemented feed, as it is described by feed intake (P < 0.001),

occurrences and duration of eating (P < 0.01), especially after the age of 9 months old.

# 2007 Elsevier B.V. All rights reserved.

Keywords: Weaning; Oregano; Lamb; Feeding behaviour; Learning; Preference

1. Introduction

The first days of life represent a period of enhanced learning and contribute drastically to the

formation of olfactory and other preferences. The ability to modify feeding behaviour as a result

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Applied Animal Behaviour Science 111 (2008) 391–395

* Corresponding author. Tel.: +30 2105294447; fax: +30 2105294442.

E-mail address: sdel@aua.gr (S.G. Deligeorgis).

0168-1591/$ – see front matter # 2007 Elsevier B.V. All rights reserved.

doi:10.1016/j.applanim.2007.06.010

of previous experience has been demonstrated for rats (Myers et al., 2005), rabbits (Bilko et al.,

1994), dogs (Ferrell, 1984), pigs (Langendijk et al., 2007), cattle (Hodgson, 1971) and sheep

(Lynch and Bell, 1987). Especially in ruminants, weaning is a very crucial period, since it

encompasses the array of behavioural, nutritional, morphological and physiological changes that

constitute the transition to an independent existence (Martin, 1984).

Diet selection is a complicated procedure and represents an interplay between animals’

genetic predispositions and its early dietary learning, through feeding experiences (Provenza and

Balph, 1987). Undoubtedly, learning preferences for certain flavours and aversions for others is

very crucial for normal development and survival, especially at the early stages of life (Amiri

et al., 1998). Neural mechanisms for flavour-nutrient associations are developed even before

weaning, allowing young animals to learn the associations between flavours and nutritive

consequences (Myers et al., 2005).

Early exposure to a particular feed has proven to be an effective method of ensuring that lambs

will readily accept that feed when offered again later in life. Lambs exposed to a flavoured feed

(Nolte and Provenza, 1992) or a specific type of forage (Nolte et al., 1990; Ramos and Tennessen,

1992) early in life, express a preference towards them, when these feeds are incorporated later in

animals’ diet. However, information is needed to elucidate the development of feeding

preferences and develop a system of management in which animals could be trained to readily

accept particular feeds.

The objective of the present study was, therefore, to highlight the influence of periweaning

flavour exposure on future feeding preferences in lambs and examine persistence of these

preferences by implementing feeding preference tests at different ages.

2. Materials and methods

Twenty-four Chios female lambs were used in the present study. They were housed in two identical pens

(12 lambs/pen) with the same direction and orientation, the same covered area (2 m2/lamb) and similar

troughs for feeding. Prior to weaning (45th day), lambs stayed with their mothers for about 2 h, twice daily,

and they had free access to alfalfa hay. Ewes’ diet consisted of concentrated feed and alfalfa hay, and the

offered quantity was adjusted according to their needs. After the 15th day of age, the same concentrated

feed, supplemented with oregano essential oil (1 ml/kg) was offered to lambs ad libitum, in the absence of

ewes. Ewes had neither direct nor indirect exposure to the oregano supplemented feed. After weaning and

till the 55th day, lambs received alfalfa hay and the concentrate supplemented with oregano essential oil.

After the 55th day of their life, lambs were fed with the same diet, consisted of alfalfa hay and concentrate,

without oregano essential oil supplementation. The amount of the offered feed was adjusted to animals’ needs

at the different stages of their development. At the age of 3, 5, 7, 9 and 11 months old, lambs were individually

subjected to feeding preference tests. These tests were implemented in four identical experimental pens

equipped with four similar troughs. Immediately following 5 min of adaptation in the rest area, lambs were

exposed simultaneously to four test feeds in the test area of the experimental pen for 25 min. Test feeds

consisted of the concentrated feed that lambs ate daily, supplemented with eucalyptus or mint or orange or

oregano essential oil (1 ml/kg). Prior to feeding preference tests, lambs were allowed 3 days to become

accustomed to the testing procedure in the experimental pens, by being exposed to non supplemented feed in

the testing facilities, following the procedure that was implemented during feeding preference tests.

During each testing period, the position of test feeds in the four troughs of each pen did not change.

However, the positions of test feeds in the four troughs were not the same among the four experimental pens.

The test order of lambs was counterbalanced over the five feeding preference tests (at different ages) to

control for time of day (7:00 or 7:40 or 8:20 or 9:00 or 9:40 or 10:20 a.m.), experimental pen effect and

position of test feed in the troughs.

P.E. Simitzis et al. / Applied Animal Behaviour Science 111 (2008) 391–395392

Feeding behaviour of lambs in the test area of experimental pens were recorded using two Panasonic

PV120 video cameras fitted with a 3.6 mm lens and mounted 3 m above the pen floor. Each camera was

placed in a fixed position in order to record feeding behaviour patterns of lambs tested in two adjacent

experimental pens (1 camera/2 pens). Quantities of consumed test feeds were weighted and components of

feeding behaviour (occurrences and duration of eating for each test feed) were video recorded. Video

recordings were later played in a Panasonic 6040 TimeLap video recorder-TV set and the behavioural

components described above were measured.

Variables of behavioural patterns (feed intake, occurrences and duration of eating) clearly deviated from

normal distribution. Non-parametric analyses were thus employed and results are presented in medians with

interquartile ranges (in brackets). Friedman two-way analysis of variance (ANOVA) on ranks was used to

verify whether the preference of lambs was different towards the four test feeds. When differences between

test feeds were detected, ANOVA was then followed by Student–Newman–Keuls multiple range tests to

evaluate which test feed was responsible. Statistical analysis was carried out using SAS (2005).

3. Results and discussion

As it was observed during the periweaning period, lambs initially consumed small quantities

of the examined diet supplemented with the oregano essential oil, but they gradually increased

their feed intake, especially after weaning, from 100 to 300 g feed per lamb and day,

approximately. In general, sheep make associations between feed cues and postingestive

feedback, by sampling novel feeds and adjusting intake based on their effect. Meal size and diet

composition are controlled by anticipation of postingestive effects to avoid nutritional excesses

or deficiencies (Provenza and Balph, 1988).

Rates of feeding behavioural elements for oregano supplemented test feed, during feeding

preference tests, were higher compared to the other offered supplemented feed, especially after

the age of 9 months old (Table 1). During feeding preference tests at the age of 3, 5 and 7 months

P.E. Simitzis et al. / Applied Animal Behaviour Science 111 (2008) 391–395 393

Table 1

Effect of lamb age on feeding behaviour elements during feeding preference tests, presented as medians (interquartile

range)

Essential oil Age (months)

3 5 7 9 11

Occurrences of eating

Eucalyptus 0.5 (5)a 0 (2)a 0.5 (4)ab 0 (0)a 0 (0)a

Mint 1 (2)a 0 (1)ab 0 (1)a 0 (1)a 0 (1)a

Orange 2 (5)a 1 (4)ab 0 (1)a 1 (2)a 0 (1)a

Oregano 3 (5)a 2 (4)a 1.5 (4)b 2 (2)b 2 (3)b

Duration of eating (min)

Eucalyptus 0.13 (4.75)a 0 (1.75)a 0.25 (5)a 0 (0)a 0 (0)a

Mint 0.25 (1.75)a 0 (0.5)a 0 (1.5)a 0 (0.75)a 0 (0.5)a

Orange 1.38 (5.5)a 0.25 (2)a 0 (0.5)a 0.5 (5)ab 0 (0.5)a

Oregano 1.75 (3)a 1.38 (5)a 1 (4.25)a 1.5 (3.75)b 5.5 (5.5)b

Feed intake (g)

Eucalyptus 10 (150)a 0 (100)a 15 (250)a 0 (0)a 0 (0)a

Mint 0 (100)a 0 (20)a 0 (100)a 0 (25)a 0 (25)a

Orange 75 (200)a 10 (100)a 0 (20)a 25 (200)a 0 (25)a

Oregano 75 (150)a 75 (200)a 50 (150)a 100 (200)b 400 (400)b

a,bRates among the supplemented test feeds (eucalyptus, mint, orange and oregano) in a column with different letters are

significantly different (Friedman–Anova analysis followed by Student–Newman–Keuls test, P < 0.01).

old, lambs sampled all the offered test feeds, although rates of behavioural components for the

oregano-supplemented feed tended to be higher than the other test feeds. After the age of 9

months old, occurrences of eating (P < 0.01), duration of eating (P < 0.01) and feed intake

(P < 0.001) were significantly higher in the case of oregano than the eucalyptus, mint or orange

supplemented diets (Table 1).

In a previous study (Simitzis et al., 2005), sheep without a flavour exposure precedent were

individually subjected to feeding preference tests. These tests were implemented in experimental

pens, where sheep were simultaneously exposed to four test feeds, consisted of the concentrated

feed that sheep ate daily, supplemented with eucalyptus or mint or orange or oregano essential

oil. As it was illustrated, sheep consumed higher amount of orange supplemented test feed

compared to the other offered feeds. Rates of feeding behaviour elements (feed intake,

occurrences and duration of eating) for the oregano supplemented feed appeared to be smaller

than the orange or eucalyptus supplemented test feed and higher than the mint supplemented test

feed. As a result, it can be concluded that palatability among the above test feeds has the

following order: orange, eucalyptus, oregano and mint. The above results indicate that the

preference for oregano-supplemented diet in the present experiment was more related to previous

exposure during periweaning period than to palatability. Moreover, this preference seemed not to

be a result of repeated exposure to oregano feed during tests, since it was not exhibited towards all

the offered test feeds or the orange supplemented feed, the test feed with the highest palatability.

Domestic livestock in semi-intensive sheep farming systems are often provided with

supplemental feeds, according to feedingstuffs’ availability. Intake of novel supplements at such

times is often quite variable, which lowers the productivity of the herd. Studies clearly indicate

that exposing livestock to the desired feeds early in life greatly enhances the probability that

young animals will consume large amounts of these later in life (Nolte and Provenza, 1992;

Ramos and Tennessen, 1992).

Learning plays a fundamental role in the acquisition of lambs’ dietary habits, especially early

in life, when it is most efficient. As it is demonstrated in the present study, although feeding

preferences of lambs started developing at the age of 3 months old, they became obvious after the

age of 9 months old. It is therefore clear that the manipulation of early feeding experiences during

the periweaning period, could influence dietary preferences and enhance future performance of

lambs.

Acknowledgement

P.E. Simitzis would like to thank the Greek State Scholarships Foundation for its support.

References

Amiri, L., Dark, T., Noce, K.M., Kirstein, C.L., 1998. Odour preferences in neonatal and weanling rats. Dev. Psychobiol.

33, 157–162.

Bilko, A., Altbaecker, V., Hudson, R., 1994. Transmission of food preference in the rabbit: The means of information

transfer. Physiol. Behav. 56, 907–912.

Ferrell, F., 1984. Effects of restricted dietary flavor experience before weaning on postweaning food preferences in

puppies. Neurosci. Biobehav. Rev. 8, 191–198.

Hodgson, J., 1971. The development of solid food intake in calves 1. The effect of previous experience of solid food, and

the physical form of the diet, on the development of food intake after weaning. Anim. Prod. 13, 15–24.

Langendijk, P., Bolhuis, J.E., Laurenssen, B.F.A., 2007. Effect of pre- and postnatal exposure to garlic and aniseed flavour

on pre- and postweaning feed intake in pigs. Livestock Sci. 108, 284–287.

P.E. Simitzis et al. / Applied Animal Behaviour Science 111 (2008) 391–395394

Lynch, J.J., Bell, A.K., 1987. The transmission from generation to generation in sheep of the learned behaviour for eating

grain supplements. Aust. Vet. J. 64, 291–292.

Martin, P., 1984. The meaning of weaning. Anim. Behav. 32, 1024–1026.

Myers, K.P., Ferris, J., Schlafani, A., 2005. Flavour preferences conditioned by postingestive effects of nutrients in

preweanling rats. Physiol. Behav. 84, 407–419.

Nolte, D.L., Provenza, F.D., 1992. Food preferences in lambs after exposure to flavours in solid foods. Appl. Anim. Behav.

Sci. 32, 337–347.

Nolte, D.L., Provenza, F.D., Balph, D.F., 1990. The establishment and persistence of food preferences in lambs exposed to

selected foods. J. Anim. Sci. 68, 998–1002.

Provenza, F.D., Balph, D.F., 1987. Diet learning by domestic ruminants: Theory, Evidence and Practical Implications.

Appl. Anim. Behav. Sci. 18, 211–232.

Provenza, F.D., Balph, D.F., 1988. Development of dietary choice in livestock on rangelands and its implications for

management. J. Anim. Sci. 66, 2356–2368.

Ramos, A., Tennessen, T., 1992. Effect of previous grazing experience on the grazing behaviour of lambs. Appl. Anim.

Behav. Sci. 33, 43–52.

SAS, 2005. Statistical Analysis Systems User’s Guide, Version 9.1.3. SAS Institute Inc, Cary, NC.

Simitzis, P.E., Feggeros, K., Bizelis, J.A., Deligeorgis, S.G., 2005. Behavioural reaction to essential oils dietary

supplementation in sheep. Biotechnol. Anim. Husb. 21, 97–103.

P.E. Simitzis et al. / Applied Animal Behaviour Science 111 (2008) 391–395 395