142 Effect of three ovulation inducers in alpacas (Vicugna pacos)

Ovulation in alpacas is induced by copulation and the presence of the nerve growth factor in the seminal plasma of the male; in cows, ovulation occurs spontaneously due to the high concentrations of estradiol produced by the dominant follicle. The objective of the present study was to determine if treatment with estradiol had an effect on ovulation and development of the corpus luteum in alpacas. Adult female alpacas aged 6–8 years and weighing 60–70 kg were evaluated by transrectal ultrasonography (EXAPAD MINI ultrasound machine) and a 7.5-MHz linear rectal transducer to determine the presence of a dominant follicle ≥ 7 mm. Five animals were randomly assigned to each of the four treatments on Day 0: T1, 1 mL of phosphate-buffered saline; T2, 1 mL of seminal plasma; T3, 1.6 mg of estradiol benzoate; and T4, 1.6 mg of estradiol benzoate + 1 mL of seminal plasma. Ovulation was evaluated after 48 h (Day 2) by transrectal ultrasonography, considering ovulation in the absence of the previously visualized follicle (Day 0). The follicular diameter and the corpus luteum were evaluated using one-way ANOVA (R Project program). The results indicated that the follicular size was similar among groups (P = 0.0934): 8.9 ± 0.8 mm (T1), 10 ± 2.0 mm (T2), 9.2 ± 0.9 mm (T3), and 9.7 ± 1.3 mm (T4). On Day 2, all T2 and T4 animals ovulated (P = 0.0001) with the consequent formation of a corpus luteum. In the T3 group, the presence of a corpus luteum was observed in three of five animals. The size of the corpus luteum was larger on Day 9 in all treatments: 11.6 ± 1.4 mm (T2), 10.2 ± 1.6 mm (T3), and 10.3 ± 2.0 mm (T4); it was larger in T2 than in T3 and T4, but the difference was not significant (P = 0.325). The presence of the corpus luteum could be observed until Day 15, being larger in T2 (7.4 ± 3.2 mm) than in T3 (4.0 ± 0.01 mm) and T4 (5.3 ± 1.3 mm), although there was no significant difference in treatment means (P = 0.153) The size of the corpus luteum was greater in T2 throughout the entire period of the evaluation. These data suggest that estradiol benzoate has an important role in the mechanism of corpus luteum formation in alpaca; however, further studies are required to determine its specific effect on ovulation in South American camelids.

This study was supported by Project 149-2017 FONDECYT and Project A22081411-VRIP-UNMSM.