Effects of varying doses of β-nerve growth factor on the timing of ovulation, plasma progesterone concentration and corpus luteum size in female alpacas (Vicugna pacos)

Abstract

Ovulation in camelids is induced by the seminal plasma protein ovulation-inducing factor (OIF), recently identified as β-nerve growth factor (β-NGF). The present study measured the total protein concentration in alpaca seminal plasma using a bicinchoninic acid (BCA) protein quantification assay and found it to be 22.2±2.0mgmL(-1). To measure the effects of varying doses of β-NGF on the incidence and timing of ovulation, corpus luteum (CL) size and plasma progesterone concentration, 24 female alpacas were synchronised and treated with either: (1) 1mL 0.9% saline (n=5); (2) 4µg buserelin (n=5); (3) 1mg β-NGF protein (n=5); (4) 0.1mg β-NGF (n=5); or (5) 0.01mg β-NGF (n=4). Females were examined by transrectal ultrasonography at 1-2-h intervals between 20 and 45h after treatment or until ovulation occurred, as well as on Day 8 to observe the size of the CL, at which time blood was collected to measure plasma progesterone concentrations. Ovulation was detected in 0/5, 5/5, 5/5, 3/5 and 0/4 female alpacas treated with saline, buserelin, 1, 0.1 and 0.01mg β-NGF, respectively. Mean ovulation interval (P=0.76), CL diameter (P=0.96) and plasma progesterone concentration (P=0.96) did not differ between treatments. Mean ovulation interval overall was 26.2±1.0h. In conclusion, buserelin and 1mg β-NGF are equally effective at inducing ovulation in female alpacas, but at doses ≤0.1mg, β-NGF is not a reliable method for the induction of ovulation.

Identification of beta-nerve growth factor in dromedary camel seminal plasma and its role in induction of ovulation in females

“…Referring to the 88% rate of purity of the β-NGF in P2, we can assume that the used quantity of this peptide is equal to 880 µg. Comparable results were found using 1 mg of a commercial NGF protein in alpacas (Stuart et al, 2014) and 1mg of purified llamas seminal plasma . The dose 2 mg P2/Cam-β-NGF used in the present study leads to similar results compared to 1 mg dose.…”

“…The variability of protein fractions could be explained by the differences in the purification procedures and the protein concentration in seminal plasma of camelid species. In literature, protein concentration in seminal plasma averages 22 mg/ml in Bactrian camel (Mosaferi et al, 2005), and ranges from 2.0 to 25.9 mg/ml in dromedary camel (El-Manna et al, 1986;Hammadi et al, 2012;Vyas et al, 2014) and from 2.9 to 43.6 mg/ml in alpaca (Stuart et al, 2014).…”

“…In the light of previous studies that reported an ovulatory response above 90% using 1mg of either llama or alpaca β-NGF (Ulloa- Stuart et al, 2014), a dose of 1 mg of P2/Cam-β-NGF was used. Furthermore, we also tested a dose of 2 mg of P2/Cam-β-NGF based on the body weight of female dromedary camel compared to llama and alpaca females.…”

Semen collection methods in alpacas

“…Although the application of some technologies in female SACs has increased in recent years (Table 1), according to Bravo (2014) andrological reports are rare. One reason for this could be the difficulty of collecting, handling and evaluating semen samples (Morton and others 2008, Bravo 2014, Stuart and others 2015). Despite the increase in ARTs, methods for successful embryo freezing are proving elusive.…”

Overview of New Concepts in Induce Ovulation Triggers in Dromedary Camels

“…However, GnRH purified OIF showed a dose-response relationship for the CL diameter and plasma progesterone concentrations. This indicates a possible luteotrophic effect of OIF, which is independent of the mechanisms involved by GnRH (Tanco et al, 2011;Ulloa-Leal et al, 2014;Stuart et al, 2015). The intramuscular or intrauterine administration of seminal plasma in camelids was revealed inducing the pre-ovulatory luteinizing hormone (LH) flow and after ovulation and formation of corpus luteum.…”