Longitudinal effects of environmental enrichment on behaviour and physiology of pigs reared on an intensive-stock farm

Figures & data

Figure 1 Experimental setting. The two experimental pens and the onemeter elevated footboard for animal observation. Balls and Hoses lay free on the floor; Chains and Ropes were hung from the wall and ceiling, respectively. F, feeder; W, water.

Table 1 Description of the six behaviours recorded (Jensen, 1980; Fraser and Broom, 1990).

Behaviour	Description
Body-biting	Taking any part of the body of a pen-mate, except tail or ears, into the mouth
Tail-biting	Taking the tail of a pen-mate into the mouth
Ear-biting	Taking an ear of a pen-mate into the mouth
Belly nosing	Repeatedly nudging with snout into the belly of a lying pen-mate
Running	Running or scampering in the pen
Interaction with objects	Taking into the mouth, pushing, pulling, biting, chewing, licking an enrichment

Table 2 Number of scans (%) with Standard (S) and Enriched (E) pigs engaged in the different behaviours over eleven weeks.

Behaviour			Standard/Enriched status								Significance
Time 1	Time 2	Time 3	Time 4	Standard/Enriched status	Sex	Time	Time x Standard/Enriched status	RSD
	S	E	S	E	S	E	S	E
ABC	26.98	5.55^a	17.06	4.76^a	8.72	5.95	22.22	9.52^a	^***	^***	^**	^***	1.94
BB	6.35	0.79^a	7.93	1.18^a	5.16	3.57	13.49	4.76^a	^***	ns	^***	^**	1.23
TB	0.39^b	5.16	0^b	0.79	0.39	0.79	1.18	^***	ns	^**	^***	0.56
EB	16.66	4.36	3.96	3.57	2.77	1.98	7.93	3.57	^***	ns	^***	^**	1.12
Belly nosing	5.16	2.38	9.44	3.17^a	8.72	6.72	0	0.79	^**	ns	^***	ns	0.95

ABC, body-biting + tail-biting + ear-biting; BB, body-biting; TB, tail-biting; EB, ear-biting; S, Standard status; E, Enriched status;

*** P≤0.01;

** P≤0.05; ns, not significant (P>0.05);

RSD, residual standard deviation;

a S vs E P<0.05 within Standard/Enriched status x Time;

b S vs E P<0.01 within Standard/Enriched status x Time.

Figure 2 Frequency of interaction with the four enrichment items (mean percentage of scans ± SE) (N=14). Interaction with hemp ropes, plastic balls, steel chains and rubber hoses in the whole experimental period *P<0.05. The percentages were computed as the number of scans in which the pigs were involved in the interaction with the object on total number of scans carried out.

Figure 3 Frequency of interaction with the enrichments across eleven weeks (mean percentage of scans ± SE) (N=14). Interaction with objects after 24 h (Time 1), two (Time 2), six (Time 3) and eleven (Time 4) weeks * P<0.05. The percentages were computed as the number of scans in which the pigs were involved in the interaction with the objects on total number of scans carried out.

Table 3 Number of scans (± SE) (%) with pigs in interaction with enrichments.

Enrichment	Time 1	Time 2	Time 3	Time 4
Hemp ropes	5.95±2.03	15.07±3.95	0.00	6.35±2.68
Steel chains	7.93±2.13	11.90±3.62	2.77±1.41	9.92±4.10
Plastic balls	3.96±1.48	4.58±1.29	8.10±2.06	2.38±1.12
Rubber hoses	12.33±2.28	5.95±1.70	4.36±1.05	5.55±1.14

Table 4 Logistic model coefficients for skin injuries and lesions.

	Exp (Coef)		95% lower		95% upper
	Injuries	Lesions	Injuries	Lesions	Injuries	Lesions
Standard	1.460	6.391	0.620	1.082	3.437	37.769
Sex: m	4.277^**	6.387^*	1.755	1.054	10.426	37.522
Time 2 vs 0: yes	2.931	2.718	0.877	2.047	9.794	8.687
Time 3 vs 0: yes	1.477	1.688b	0.432	1.088	5.051	2.574
Time 4 vs 0: yes	1.000	4.553	0.281	4.483	3.556	4.909

** P<0.01;

* P<0.05.

Table 5 Means and significance of the main effect condition and its interaction with time for the immunological, hematologic, oxidative and hormonal parameters.

Item	Standard/Enriched status			Significance
	S	E	Standard/Enriched status	Standard/Enriched status x time	RSD
Immunological parameters
Serum bactericidal activity, %	26.68	27.39	ns	ns	9.88
Hemolytic complement, CH 50/100 µL	90.18	78.68	^**	ns	22.87
Lysozyme, µg/mL	3.83	3.73	ns	ns	0.80
Haptoglobin, mg/mL	0.86	0.82	ns	ns	0.61
Hematologic parameters
WBC, x10^3/L	19.98	17.83	^**	ns	4.12
Neutrophils, %	36.30	42.42	^***	ns	9.50
Lymphocytes, %	57.35	52.82	ns	^**	8.77
Eosinophils, %	3.41	2.42	ns	^**	1.89
Monocytes, %	2.57	1.94	ns	ns	2.03
Basophils, %	0.35	0.37	ns	ns	0.80
HCT, %	33.31	31.03	^**	ns	3.80
RBC, x10/L^6	6.92	6.73	ns	ns	0.70
MCV, fl	48.44	45.57	^**	ns	5.66
HGB, g/ld	10.06	9.42	^**	ns	1.17
MCH, pg	14.62	13.82	ns	ns	1.76
MCHC, %	30.19	29.80	ns	ns	2.64
Platelets, x10/L^3	470.23	421.66	ns	ns	93.72
Oxidative stress parameters
N:L ratio	0.683	0.892	^**	^***	0.140
ROMs, mM	39.89	41.11	ns	ns	5.52
PAO, µ-M	215.10	211.73	ns	ns	23.40
DHEA-S, µg/mL	0.248	0.238	ns	^**	0.12

S, Standard pigs; E, Enriched pigs;

*** P≤0.01;

** P≤0.05;

ns, not significant (P>0.05); RSD, residual standard deviation.

JensenP. 1980 An ethogram of social interaction patterns in group-housed dry sows Appl. Anim. Ethol 6 341 350

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FraserD. BroomD.M. 1990 Farm animal behaviour and welfare 3rd ed Bailliere Tindall Publ. London, UK

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