ABSTRACT 

The rat has been used as the main animal model in several studies involving reproduction because of its short oestrous cycle of 4 to 5 days.  This study evaluated the effects of sire distance on the oestrus rate of female albino rats under the Whitten effect. Sixteen (16) female and 4 male rats were used for this investigation. The males were housed in one rat cage while the females were randomly divided into four caged groups (n = 4). Group A cage was kept side-byside with the male cage, group B was two meters away, group C was 10 meters while group D was kept in the next room away from the males. Then, vaginal smear of each of these mature female albino rats was obtained daily, every 6 pm for 15 days and processed according to standard technique using Methylene Blue. Observations were recorded daily for individual females and groups. Records of vaginal smear cell types were analysed for incidence of cell types for individuals and oestrus synchrony within females in a group. Findings were then compared between groups for the effect of sire distance on oestrus rate and synchrony between groups. The different cellular characteristics of the four phases of the rat oestrous cycle were observed in all the groups in this study. The mean incidence of oestrus (oestrus interval) were within the document normal oestrus interval in rats and did not differ significantly (p > 0.05) between groups (5, 5.5, 5.5 and 4 days for groups A, B, C and D respectively). Synchrony of oestrus was not apparent in any of the groups. It was concluded that the Whitten effect does not influence oestrus rate of albino laboratory rats housed in the Theriogenology laboratory of Michael Okpara University of Agriculture, Umudike. This contradicts previous reports of synchrony of oestrus due to whitten effect possibly because of short duration of this study (15 days only). Further studies with longer duration was suggested.