Accessory corpus luteum regression during pregnancy II: reproductive outcomes

The objective of this study was to evaluate the effect of accessory corpus luteum (CL) induction on fertility in dairy cows. On day 5 after artificial insemination (AI), lactating Holstein cows were assigned unequally to receive gonadotrophin-releasing hormone treatment (GnRH) (n = 641) or no treatment (control; n = 289). Cows had their blood sampled for progesterone (P4), and ovaries were scanned by ultrasound on days 5, 12, 19, 26, 33, 47, and 61 after AI. Pregnancy diagnosis was performed on days 26, 33, 47, and 61. On day 12, cows treated with GnRH were allocated to ipsilateral (n = 239) or contralateral (n = 241) groups based on the side of accessory CL formation relative to previous ovulation. Accessory CL cows had greater P4 than controls. In total, 52.7% (78/148) of pregnant cows in contralateral group had accessory CL regression earlier (<day 33; 30.8%) or later (days 33–61; 69.2%) in pregnancy with coincident decrease in P4. No cows with ipsilateral accessory CL underwent regression. There was no difference in pregnancy/AI among groups. Cows with contralateral accessory CL that underwent early regression had greater pregnancy loss (30%) than controls (10%), or cows with ipsilateral CL (3%) or contralateral CL with either later or no regression (12%). Cows with ipsilateral accessory CL had lower pregnancy loss than controls. In conclusion, elevating circulating P4 by the induction of accessory CL, particularly ipsilateral CL, increases P4 and reduces pregnancy loss. However, contralateral accessory CL that undergoes regression before day 33 of pregnancy has increased pregnancy loss, possibly due to an abrupt decrease in P4 at a pivotal period of pregnancy (days 26–33).

Characteristics of Libido and Testosterone Concentration of Polled and Horned Bali Bulls after GnRH Injection

Bali cattle are one of the original Indonesian germplasm, which in its development were found to be hornless or polled. Polled are Balinese cattle whose horns do not grow naturally, but have the same characteristics as those with horns. However, there are indications that polled have a lower libido. The purpose of this study was to determine the characteristics of libido and testosterone concentration after gonadotrophin releasing hormone (GnRH) injection. In this study each of 7 male polled and horned Bali cattle aged 3.5-6 years were used. Libido characteristics were observed by recording the first time the male fondled the teaser until ejaculation, while the testosterone concentration was measured using blood plasma taken on day 0 or before injection, day 7^th, and day 14^th after GnRH injection. Testosterone analysis used enzyme linked immunosorbent assay (ELISA) method. The results showed that the libido of polled was not different (P&gt;0.05) compared to that of the horned on the 0, 7^th and 14^th days after GnRH injection. However, in polled on the 7^th day after GnRH injection, it was significantly lower than on day 0 and 14, but on day 0 it was not different with day 14. Testosterone concentration on day 7 after injection of GnRH was not different (P&gt;0.05) compared to day 0 both in polled and horned bulls, but on day 14 after injection was significantly higher (P&lt;0.05) in horned than polled. In conclusion, polled and horned Bali bulls had high libido with a score of +1, but on the 7^th day after GnRH injection, polled had lower libido than horns. The testosterone concentrations of polled and horned on day 7 after GnRH injection were not different compared to day 0, while the 14^th day was higher in horned bull.