LAUSR

The fertility of cows was affected by the diameter of ovulating follicle size of the native cows. The objective of the present study is to determine the ovulating follicle diameter and conception rate of native PESISIR cows. This study used the synchronization program of 29 cows in OVSYNCH protocol and 33 cows in Co-synch protocol of native PESISIR cows in parity-3 with a body condition score of 3.0. Ultrasonography examination was conducted at GnRH1, PGF2α, and GnRH2 of OVSYNCH and co-synch protocols 30 days after the breeding period to determine the follicular size and conception rate of local cows. The result shows that the diameter of the ovulating follicle is a small follicle category ranging from 6 to 11 mm. The proportion of medium category of follicle size (8- 9.5 mm) is 72.41 % for OVSYNCH protocol and 75.75 % for the co-synch protocol (P>0.05). The mean of ovulating follicle is 7.19 ± 1.69 mm for OVSYNCH protocol and 8.57 ± 1.61 mm for the co-synch protocol (P>0.05). The mean of conception rate is 72.00 % for OVSYNCH protocol and 68.44 % for the co-synch protocol (P.>0.05). The mean of progesterone concentration of ovsynch protocol is 6.76 ; 4,92; 5.44 and 9,56 ng/ml at GnRH-1; PGF2 alpha ; GnRH-2 injection and 30 d post- AI, respectively. In cosynch protocol progesterone concentrations are 6.36; 3.36; 1.92 and 7.84 ng/ml, at GnRH-1; PGF2 alpha; GnRH-2 and 30 d post-AI, respectively. This study concludes that follicle size is the key to determining the fertility of cows. The follicle diameter of local cows has a small category. Ovsynch and co-synch protocols have no significant effects (P>0.05)on both the ovulation and conception rates and the progesterone concentration of local PESISIR cows.