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Mating Behavior of the Ram in the Multi-Sire Pen

U. S. Department of Agriculture¹

Abstract

Seven breeding pens, containing varying numbers and combinations of yearling and mature rams each 48 hours, were observed continuously for 8 days.

When a particular combination of rams was placed in a pen, the dominance of one ram was quickly established. Mature rams were always dominant over yearling rams and were more dominant over yearling rams than were yearling rams dominant over other yearlings. Mature rams tended to be less dominant over other mature rams than were yearlings over yearlings. Dominance rating had highly significant effects on number of teases, mountings, matings and matings per mount. The dominant rams largely controlled activity in the pens under most circumstances. However, when more than one ewe was in heat, the dominant ram often found it impossible to completely curtail the mating activity of the subordinate ram or rams. Dominant rams were also more successful in completing copulation than subordinate rams.

The presence of more than one ram in a pen increased only slightly the total number of matings for the pen, thus reducing the average number of matings per ram below that of the pens containing only one ram. The average number of matings per ram for the dominant rams in combination pens was only slightly less than the average number of matings in the single ram pens. The greater the dominance of one ram, for pens containing equal numbers of rams, the less the total mating activity. This was due primarily to the reduced mating activity of the subordinate ram.

All single rams averaged more matings than rams in any of the combination pens. Pens containing single mature rams provided the most efficient use of individual rams. These single mature rams accomplished significantly more matings per ram than all other combinations except those pens containing single yearling rams and combinations of two mature rams. The ram combination composed of two mature rams and one yearling ram provided the most matings per pen followed closely by the combination composed of two mature rams. The two combinations produced significantly more matings per pen than all other combinations except the single mature rams.

The total and average ram effects for the various ram combinations had highly significant effects on number of matings per day, teases per day and matings per mount. Number of mountings was not significantly affected. The total number of teases was in almost direct proportion to the number of rams in the combinations and the proportion of mature rams.

Dominant rams which are sterile or of low fertility or genetically inferior could greatly reduce the lamb crop, extend the lambing season, or affect the average merit of the lamb crop and thus reduce production and genetic gain.

¹ From the U. S. Sheep Experiment Station and Western Sheep Breeding Laboratory, Sheep and Fur Animal Research Branch, Animal Husbandry Research Division, ARS, Dubois, Idaho, in cooperation with the University of Idaho. Published with the approval of the director of the Idaho Agricultural Experiment Station, Moscow, as Research Paper No. 553.