Effect of different diluents and storage time on field fertility of cooled ram semen after vaginal insemination

In a field experiment, 206 ewes were inseminated vaginally using liquid semen collected from 7 rams two times with 52 h intervals between sessions. Ejaculates were pooled, split into three equal parts and diluted with a milk-based extender (M), a Tris-glucose (T) and a Tris-glucose containing 0.03125% caproic acid (TC). Ejaculates from the first collection were cooled up to 5 °C over 2 h, incubated for 52 h at 5 °C and inseminated (M52, T52 and TC52), but ejaculates from the second collection were diluted and inseminated immediately (M0, T0 and TC0). The inseminations of ewes were performed after synchronizing estrus. Only ewes in estrus were inseminated. The results of the pair-wise comparison of the lambing rates between the six groups showed significant higher results for TC52 (69.6%) compared with TC0 (46.15%) and also T52 (41.6%; P < 0.05). Consequently, adding caproic acid to Tris-glucose may be useful for ram semen if semen is stored for 52 h at 5 °C.