Characterisation of postpartum ovarian activities using milk progestrone profiles in dairy cows in arban/peri-urban dairy production systems

Postpartum ovarian activity was investigated in dairy cows in urban/peri urban dairy production systems in and around Addis Ababa using milk progestrone profiles. Nineteen crossbred (friesian x Zebu) dairy cows which calved between March and June 1998 were used for the study. Milk samples were collected twice per week starting two weeks after calving until pregnancy fo determination of progestrone concentrations. the animals were under close supervision for behavioral oestrus manifestation. A sustained rise in progestrone concentration above 3 ng/ml was used as clear cut value of the resumption of postpartum ovarian activity. Oestrous cycles less than 17 days were considered as short, 18-24 days as normal and greater than 24 days as long. The result indicated that 18/19 (95%) cows were cycling. The mean postpartum anoestrus interval was 53.5 plus or minus 32 days. the mean interval between calving and the first behavioural oestrus manifestation was 93.0 plus or minus 52 days. However, the mean interval between calving and the first oestrus as determined from progestrone concentrations was 66 plus or minus 35 days. The mean interval between detected oestrus for repeat breeder was 60 plus or minus 48 days. A total of 78 oestrous cycles were determined on 18 cycling cows. The proportion of short, normal and long oestrus cycles were 41%, 42% and 17%, respectvely. The first postpartum oestrous cycle was of short duration in about 53% of the cows. The mean interval for the first postpartum ovulation to have occurred was 50 plus or minus 33 days. Only 35% of the total ovulations were accompanied by over signs of oestrus, indicating high proportion of silent oestrus of failure in oestrus detection. The mean interval from calving to conception was 116 plus or minus 45 days. the proportion of cows that became pregnant was 55.6% and the number of services per conception was 1.6. It was concluded that delayed resumption of postpartum ovarian activity and first ovulation, delayed calving to first behavioral oestrus, long detected inter-estrus interval, high incidence of short oestrous cycles, high silent oestrus/oestrus not detected and long calving to conception interval are the major problems associated with the low reproductive performance of dairy cows in urban/peri urban dairy production systems. Besides, embryonic mortality/fetal loss (27%) further contributed to reproductive wastage. Therefore, the prevailing management conditions to which cows are exposed should be improved for the enhanced reproductive efficiency.