Social position of rams
Description
Social position of rams
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Twelve rams were used and the Dominance Index (DI) was calculated by three methods: using the competition for resources (food and estrous female) or using spontaneous AI, in all case assigning an absolute or relative. In food competition test each test lasted for 5 min, testing each ram only once per day. All behavioral interactions were recorded, and the time that each ram acceded to the bucket was recorded. Different dyadic combinations were tested each day, so over 11 days, all rams were tested once with every other ram from the group. The individual DI was calculated using absolute or relative values. In the first one, the ram that ate for a longer period was assigned a value of 1, while those that did not eat or ate for a shorter period received a value of 0. The second calculation considered the proportion of time each ram ate from the total time that both ate. The sum of the values that each ram received divided by 11 (the number of tests) was calculated for each procedure. In estrous female competition each ram participated in only one test per day, totaling 11 days to test each ram with every other individual from the group. In each test, two rams were placed in a known 2 m x 2 m pen with an estrous ewe. As in the food competition test, the individual DI was calculated by assigning a value of 1 to the individual that interacted more time (absolute value) or a proportion of the time each ram interacted with the ewe (relative value). The hierarchy determined by recording the spontaneous agonistic interaction (AI), was conducted approximately 3 h per week from January to July, totaling 102 h of observation. The spontaneous agonistic behavior of all the animals in their daily enclosure was recorded, with the ram that generated physical displacement of another being considered the dominant one and the latter being considered the subordinate. The absolute DI was calculated according to Álvarez et al. (2003) and Mendl et al. (1992) as: Dominance index = number of displaced rams/(number of displaced rams + number of rams that displaced them). The relative value was calculated based on the amount of dominant spontaneous AI in each individual, assigning a proportional value to each individual (Galindo and Broom, 2000): Dominance index = number of AI in which the ram dominated other rams/(number of AI in which the ram dominated other rams + number of AI in which the ram was dominated by other rams).
Institutions
- Universidad de la Republica Uruguay