Ultrasonographic studies on effects of hCG administration during first follicular wave of estrous cycle on pregnancy rate of repeat breeder cross-bred cow

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Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu (J&K)
The present study was designed to investigate the effects of hCG (Chorulon®, 1500 I.U.) administration on day 4 (Group 2), 5 (Group 3), 6 (Group 4) and 7 (Group 5) of the estrous cycle, inducing formation of accessory corpus luteum, thus preventing early embryonic mortality due to possible luteal insufficiency, monitoring the size of preovulatory follicle (day 0), dominant follicle (day 4/5/6/7), subsequent corpus luteum, formation of accessory corpus luteum vis-à-vis progesterone profile and conception rate in repeat breeder cross-bred cows. Healthy and normal cyclic repeat breeder cross bred cows (n= 30), “White side negative”, BCS between 3 and 4, aging 4-7 years were used in this study. Animals with pre-ovulatory follicle of ≥ 10 mm were bred artificially. The plasma progesterone was estimated using RIA kit. Ultrasonography and blood collection was done on day 0, 4/5/6/7, 14 of estrous cycle. Pregnancy diagnosis was confirmed at day 45 post breeding. Preovulatory follicle had the largest diameter among all the days of estrous cycle. There was no significant difference in diameter of follicle on various days of observation between and within control and treatment groups except in group2 and group 5 where diameter was significantly higher at day 0 in comparison to day 4 and 14 in group 2 and day 7 and 14 in group 5 respectively. Diameter and area of the corpus luteum increased in treatment group. There was no significant difference in diameter of corpus luteum, while area of corpus luteum of only group 3 differed significantly with control group. No accessory corpus luteum was formed in cows of control group. The formation of accessory corpus luteum was found maximum in number in the group 3 and group 5 in which 3 accessory corpora lutea were formed in each group. The diameter and area of accessory corpus luteum was lesser than the diameter and area of corpus luteum present on the same day respectively. Plasma progesterone concentration on day 14 was significantly high in comparison to day 0, 4/5/6/7 of the estrous cycle within treatment and control group. Progesterone concentration was significantly high on day 14 in treatment group in comparison to control group. The conception rate were Nil, 16.66%, 50%, 16.66% and 33.33% in group 1, 2, 3, 4 and 5, respectively. In group 3 the conception rate was highest among all the treatment groups. It was concluded that there was no significant effect of hCG administration on diameter of pre-ovulatory or dominant follicle. The diameter and area of corpus luteum increased post hCG administration. The accessory corpus luteum could be produced more effectively by hCG administration on day 5 and 7 of the estrous cycle, which is lesser in size. After hCG administration there was significant rise in progesterone concentration, may be due to accessory corpus luteum formation or stimulatory effect on existing corpus luteum. The higher conception rate (50%) was obtained in group 3 (hCG administration on day 5) compared to other groups.