Association between the social rank, body mass, testicular circumference and linear body measures of rams

Abstract

The social rank refers to the relative position of an individual animal within the dominant hierarchy developed in a group. In rams, social rank is mostly associated with body mass, body size and body condition. However, although the body mass is generally considered as one of the main determinants of social rank, only few studies have been carried out for the purpose of associating of the social behavior and body development of these animals. Objective of this research was to determine how the ram body development measures relate to establishment of social hierarchy. Social rank was established using food competition test at the age of animals between 4 and 17 months. Testing was done on total of 20 male animals of which number 12 animals were selected for further testing (6 dominant and 6 submissive animals). Body mass and testicular circumferences were measured at the age of 4, 7, 12 and 18 months, and linear body measures were taken at the age of 12 and 18 months. Dominant males had higher body mass and greater testicular circumference. The social rank had no significant effect on linear body measures of rams, except for chest girth (P (lt) 0.05) in both control periods. Body mass was moderately to highly positively associated with studied body parameters. Significant positive correlations were established between body mass and body length (r=0.58; P (lt) 0.01), chest width (r=0.44; P (lt) 0.05), chest girth (r=0.65; P (lt) 0.01) and testicular circumference (r=0.62; P (lt) 0.01). Results obtained in this study indicate that it is justified to observe the body mass as one of the main determinants of social rank, as well as the possibility of earlier maturation of dominant animals.

Socijalni rang se odnosi na relativnu poziciju individue unutar dominantne hijerarhije koja se razvija u grupi. Kod ovnova, socijalni rang se najviše povezuje sa telesnom masom, veličinom tela i telesnom kondicijom. Međutim, iako se telesna masa generalno smatra jednom od glavnih determinanti socijalnog ranga, malo je istraživanja sprovedeno u cilju povezivanja socijalnog ponašanja i telesne razvijenosti ovih životinja. Cilj ovog istraživanja bio je da se utvrdi na koju način se mere telesne razvijenosti ovnova odnose prema uspostavljanju socijalne hijerarhije. Socijalni rang utvrđen je pomoću testa kompeticije na hranu kada su životinje bile u uzrastu od 4 i 7 meseci. Testiranje je obavljeno na ukupno 20 muških grla od čega je za dalje ispitivanje odabrano 12 grla (6 dominantnih i 6 submisivnih). Telesna masa i obim testisa mereni su u uzrastu od 4, 7, 12 i 18 meseci, a linearne telesne mere su izmerene u uzrastu od 12 i 18 meseci. Dominantna grla su imala veću telesnu masu i veći obim testisa. Socijalni rang nije imao značajan uticaj na linearne telesne mere ovnova, izuzev na meru obima grudi (P (lt) 0,05) u oba kontrolna perioda. Telesna masa bila je umereno do visoko pozitivno povezana sa ispitivanim telesnim parametrima. Značajne pozitivne korelacije utvrđene su između telesne mase i dužine trupa (r=0,58; P (lt) 0,01), širine grudi (r=0,44; P (lt) 0,05), obima grudi (r=0,65; P (lt) 0,01) i obima testisa (r=0,62; P (lt) 0,01). Rezultati koji proizilaze iz ove studije ukazuju na opravdanost posmatranja mase tela kao jedne od glavnih determinanti socijalnog ranga, kao i na mogućnost ranijeg sazrevanja dominantnih jedinki.