author(s)
Vijyakanth N, Anil Kumar R, Ezakial Napolean R and Thavasiappan V

abstract
Negative energy balance in high producing cows reduces insulin and insulin like growth factor-I (IGF-I) and delays onset of estrous cycle. Under Indian conditions the addition of insulin in the co-sync protocol was not studied in detail. Twelve pluriparous crossbred cows were selected and equally divided into two groups I and II. All the cows were treated with 10 µg of GnRH injection on day 0, 500 µg of PGF2α on day 7 and another 10 µg of GnRH 48 h after PGF2α (day 9) and timed artificial insemination (TAI) was done on day 9 and 10. Cows from group II were injected with insulin (0.2 I.U/ kg bwt) subcutaneously on day 0, 1 and 2 of the experiment. Higher intensity and longer duration of estrum was observed in cows from group II. The ovulation rate was higher in group I cows (83.33 vs. 50.00 per cent) however, no significant difference in conception rate was observed. The concentration of progesterone was slightly lower on day 7 after AI in group II. The concentration of estrogen up to estrum was higher in cows which became pregnant and a significant decline on day 7 and 45 after AI. The concentration of IGF-I was lower during estrum in cows which ovulated. (149.21±16.72 vs. 175.99±25.39 ng/ml). Among the cows which became pregnant the concentration of IGF-I was higher during estrum, day 7 and 45 after AI. Ovulatory responses were effectively turned into pregnancy in insulin injected postpartum anestrum cows, the protocol can utilized under field condition.