The arena test and cortisol response of sheep as indirect selection criteria for the improvement of lamb survival

• Published in: Animal reproduction science Vol. 46; no. 1; pp. 97 - 108
• Main Authors: Kilgour, R.J., Szantar-Coddington, M.R.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.1997
• Subjects: Adrenal Glands - drug effects; Adrenal Glands - metabolism; Adrenocorticotropic Hormone - pharmacology; AGNEAU; AMELIORATION DES ANIMAUX; Anestrus - physiology; ANIMAL BREEDING; Animals; Arena test; Behavior, Animal - physiology; BEHAVIOUR; Breeding management; COMPORTAMIENTO; COMPORTEMENT; CORDERO; Cortisol; CRITERE DE SELECTION; CRITERIOS DE SELECCION; Dogs; Estrus - physiology; Female; Fertility - physiology; GLUCOCORTICOIDE; GLUCOCORTICOIDES; GLUCOCORTICOIDS; Hydrocortisone - blood; Hydrocortisone - metabolism; LAMBS; MEJORAMIENTO ANIMAL; OVIN; OVINOS; PERFORMANCE DE REPRODUCTION; Pregnancy; REPRODUCTIVE PERFORMANCE; REPRODUCTIVIDAD; SELECTION CRITERIA; Selection, Genetic; SHEEP; Sheep - genetics; Sheep - physiology; Sheep-reproductive performance; SUPERVIVENCIA; SURVIE; SURVIVAL; Time Factors; Breeding management; Arena test; Cortisol; Sheep-reproductive performance
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/S0378-4320(96)01591-6

As part of a study of possible indirect selection criteria for the genetic improvement of lamb survival in the Australian Merino, two experiments were conducted. These experiments involved ewes from two flocks, one selected for superior lamb survival (Fertility Flock) the other an unselected flock (Random Flock). In the first experiment, the behaviour in an arena test of ewes from the two flocks was measured under two conditions; the ewes were tested either singly or in a group of four and the ewes were tested when in oestrus or not. When the ewes were tested singly, differences were detected between the two flocks in the total distance travelled, the minimum distance from a human operator in the arena and in the number of bleats. When the ewes were tested in a group of four, the differences in distance travelled and number of bleats disappeared; the difference in closest approach was maintained but the order of the two flocks was reversed; a difference appeared in the furthest distance from the operator. The experiment also showed that arena behaviour was not affected by the oestrous state of the ewes. In the second experiment, the cortisol response of the adrenal gland to stimulation by ACTH or by an external influence (barking dog) was examined in ewes from the two flocks. There were no differences between the two flocks in cortisol response to any of the stimuli. The results show that the behaviour of sheep in the two types of test is different, that the single-animal test may be the more appropriate when improvement in lamb survival is the objective and that the response of the adrenal gland shows little promise as an indirect criterion for selection.