The fertility in dairy cows is a major issue as studies suggest declines in the reproductive performance of dairy cows over the past 20 years. In this paper, the reproductive performance of H (n=128) and J (n=103) heifers and lactating cows are presented. Cows were on kikuyu pasture supplemented with a pasture replacement mixture consisting of lucerne hay, oat hay and soybean meal. All cows received the same concentrate mixture after milking at 7 kg per cow per day. On average (±s.d.), Jersey heifers were inseminated earlier (P<0.05) than H heifers, i.e. 15.4±2.1 and 16.1±2.3 months of age, respectively. The interval traits calving to first service, first service within 80 days post partum, and cows confirmed pregnant within 100 days post partum for H and J cows were 88±26 and 78±29 days (P<0.01), 0.44 and 0.62 (P<0.01) and 0.31 and 0.51 (P<0.05) respectively. The interval from calving to conception differed (P<0.05) between breeds being 119±61 and 138±62 for J and H cows respectively. Results are consistent with other studies showing a higher conception rate in J cows in comparison to H cows. The poorer reproductive performance of H could be attributed to a greater potential for milk production.