The Indian Veterinary Journal (July, 2016) 84 Indian Vet. J., July 2016, 93 (07) : 84 - 85 Effect of Delaying Luteolysis During Second Follicular Wave on Subsequent Fertility Following Timed Articial Insemination in the Buffalo A.G. Bilal, S.S. Dhindsa 1 , M. Honparkhe, S.P.S. Ghuman, R. Jindal and P.S. Brar Department of Veterinary Gynaecology and Obstetrics, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, Punjab, India-141001. (Received : 14-07-2015; Accepted : 25-08-2015) Abstract Forty six postpartum buffaloes were adminis- tered PGF2α (Cloprostenol, 500 mcg) on day -2, GnRH analogue (Buserelin) on days 0 (10 mcg) and 7 (20 mcg). All buffaloes were randomly divided into 2 groups on the basis of administra- tion of second dose of PGF2α on day 14 (Group I, n= 20) and 15 (Group II, n= 26). Third dose of GnRH (Buserelin, 10 mcg) was administered on day 16.5 (Evening) and 17 (Morning) in group I and II, respectively, followed by TAI at 12-16 h later and pregnancy diagnosis on days 45 and 60 post AI. The mean P 4 concentrations on different days were comparable in both groups. A larger (P<0.01) preovulatory dominant follicle was observed at the time of AI in group II compared to group I followed by pregnancy in 46 % vs 35 % buffaloes, respectively. In conclusion, delay- ing the luteolysis during second follicular wave may improve post-TAI fertility in buffaloes. Key words: Buffalo, Pregnancy rate, Progester- one, estrus synchronization Applying estrus synchronization regimens in buffaloes may provide a potential alternative for increasing their productive period as these regimens do not warrant estrus detection and buffaloes can be inseminated at xed-time. Despite that, partial success has been achieved with various estrus synchronization regimens till date in buffaloes (Ghuman et al., 2009b). The information regarding prolonged exposure of dominant follicle (DF) to high P 4 environment during second follicular wave and its effect on subsequent fertility following timed AI in buffaloes remain sparse. This study was, therefore, undertaken to investigate the effect of delaying luteolysis during second follicular wave on subsequent fertility following TAI in cyclic postpartum buffaloes. Materials and Methods The study was conducted on 46 post-partum cyclic buffaloes at dairy farm, GADVASU, Ludhiana, Punjab, India. The selected buffa- loes were administered PGF2α (Cloprostenol: 500 mcg) on day -2, gonadotrophin releasing hormone (GnRH) on days 0 (Buserelin: 10 mcg) and 7 (Buserelin: 20 mcg). Thereafter, all buffa- loes were randomly divided into 2 groups on the basis of administration of second dose of PGF2α (Cloprostenol: 500 mcg) on day 14 (Group I, n= 20) and 15 (Group II, n= 26). A third dose of GnRH (Buserelin: 10 mcg) was administered on day 16.5 and 17 in group I and II, respectively, followed by TAI at 12-16 h later. In both groups, examination of ovarian structures was done by on all the days of protocols. Blood sampling and transrectal ultrasonography were carried out on various days of the modied protocols. The pregnancy diagnosis was performed at day 45 and 60 post AI by transrectal ultrasonography. The P 4 estimation was done by liquid phase Radioimmunoassay procedure: Assay sensitiv- ity 0.1 ng/ml; intra- and inter-assay coefcients of variance 6.0 and 9.3 %, respectively (Ghuman et al., 2009a). The P 4 concentrations were compared by Unpaired T-test and One way ANOVA, whereas, “Chi square test” was applied to compare pre-ovulatory DF diameter and pregnancy rate. Results and Discussion In the present study, mean plasma P 4 concentra- tion on different days of protocol in both groups is presented in Table 1. The concentration of P 4 during different stages of the follicular 1 Corresponding author : Email: shahbazdhindsa76@yahoo.co.in