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 degrees C over 2 h, incubated for 52 h at 5 degrees C and inseminated (M-52, T-52 and TC52), but ejaculates from the second collection were diluted and inseminated immediately (M-0, T-0 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 T-52 (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 degrees C. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.