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used as a reference. Control experiments showed that pigs stayed much longer in a compartment with the possibility of social contact than in a compartment without that possibility - other respects being equal.

A complication was the possible interaction between social attraction and the factors under test. The pigs stayed longer in the compartment with social contact if both compartments possessed bare concrete floors than when the floors were of earth. Tn the experiments, social contact was offered in addi- tion to the factors being tested.

One experiment showed that pigs preferred a compartment with an earth floor without social contact over a bare compartment with social contact.

In some experiments, pigs showed a diurnal rhythm in their preference; in the daytime some pigs preferred one floor-covering (e.g. woodchips) with social contact over another (e.g. straw) without, and in the night preferred the latter.

To solve the methodological difficulty that a minority-choice of a pig may be more important to that pig than the alternative, we used the follow- ing method: pigs continuously had the possibility to change between 2 compartments but they had to work for this. By determining how much work they were prepared to do to change compartment, we measured the strength of their preference.

GENETIC ANALYSIS OF FRUSTRATION RESPONSES IN THE FOWL

A.D. MILLS and D.G.M. WOOD-GUSH

ARC Poultry Research Centre, Roslin, n4idlothian. and School of Agriculture, University of Edinburgh, Edinburgh (Gt. Britain)

ABSTRACT

Hens kept in battery cages may suffer thwarting of many of their normal pre-laying behaviour patterns and may therefore be frustrated in the period before laying. The pre-laying behaviour of 2 strains of domestic fowl kept in individual battery cages was described. One strain, the T-line, a medium hybrid strain originally derived from a Rhode Island Red X Light Sussex cross, tended to sit during the pre-laying period, whereas the other, the S-line, a light hybrid strain derived from White Leghorn stock, typically showed stereotyped escape behaviour. Quantification of these behaviour patterns showed that the r!ifference between the two strains was very highly signifi- cant (P < 0.001). On a day-to-day basis, each animal was extremely consistent in its behaviour, and within strains there was considerable variability between individuals in the amount of pacing or sitting shown. Individual consistency in pre-laying behaviour was interpreted in terms of a “superstitious” ritual (as described by Skinner, 1948) which becomes reinforced as a consequence

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of a form of aversive conditioning associated with the relief from stress which accompanies laying of the egg.

The tendencies to pace and sit during the pre-laying period were shown to have a genetic basis. Directional selection for pacing in the S-line and for sitting in the T-line increased both variables (h’, pacing = 0.21; h2, sitting = 0.3). Results of a reciprocal F1 cross between the 2 strains indicated ten- tatively that the tendencies to pace or to sit during the pre-laying period are inherited as separate characteristics. The tendency to pace appeared to be controlled by a single recessive gene whilst sitting appeared to be determined by a gene or genes with additive effects. Neither character was sex-linked. Further work is in progress to substantiate these conclusions.

Theoretical and practical implications of these findings were discussed. Practical implications relate to the feasibility of breeding domestic animals which are behaviourally better adapted to life in intensive husbandry systems. Theoretical implications relate to Tinbergen’s (1952) hypothesis that many displays have evolved from “irrelevant” behaviour patterns, such as displace- ment activities and intention movements, shown by animals in situations of motivational conflict or frustration.

REFERENCES

Skinner, B.F., 1948. “Superstition” in the pigeon. J. Exp. Psychol., 38: 168-172. Tinbergen, N., 1952. Derived activities; their causation, biological significance, origin,

and emancipation during evolution. Q. Rev. Biol., 27: l-32.

VOLUNTARY REGULATION OF FOOD INTAKE IN POULTRY

C.J. SAVORY, M.J. GENTLE, J.P. HODGKISS and W. KUENZEL

ARC Poultry Research Centre, Roslin, Midlothian (Gt. Britain)

ABSTRACT

The physiological mechanisms involved in regulation of food intake were briefly summarized and research on particular neural and hormonal systems associated with feeding in poultry were described.

With free access to food, poultry concentrate their feeding in discrete meals, but there is evidence that hunger and satiety mechanisms have only loose control over initiation and termination of meals. Hunger and satiety are concerned with neural and humoral feedback processes which involve the brain, eyes, mouth, alimentary tract and liver.

Feeding behaviour in birds can be divided into 5 separate stages, arousal, orientation, prehension, mandibulation and deglutition, which are controlled