Oestrus induction of seasonally anoestrous ewes by nasal application of ram pheromone containing wool fat

The objective of the study was to clarify if a single nasal application of ram pheromone containing wool fat can induce fertile oestrus in anoestrous ewes under field conditions. The investigations were conducted in 251 sheep from April (pheromone application) until September (lambing). In order to determine the ovary status of the ewes ovary diagnosis was carried out by ultrasonography before pheromone application in 111 (44,2%) randomly selected ewes. Afterwards the sheep were divided into two groups (treated, untreated) and kept in separate pens. Ewes of the treatment group received a nasal application of 2 ml wool fat each. Oestrus was detected by crayon-harnessed rams. During the first 14 days of the mating period 15% of the ewes in both groups showed signs of oestrus. In the following four weeks in the treated group 31.2% more ewes came into heat than in the untreated group (71.9 vs. 40.7%) and 29.7% more treated ewes lambed (61.9 vs. 32.2%). The absolute lambing rate increased by 0.32. In contrast to the control group some treated ewes, which had only had follicles with a maximum diameter of 3 mm, showed oestrus signs or lambed later on due to the handling. Because of the use of a species-characteristic active substance and the simple application of a defined quantity of the substrate it can be concluded that the nasal application of wool fat is suitable to replace other procedures for oestrus induction in seasonally anoestrous sheep.