Effect of the reproductive state of female alpacas on embryonic mortality rate

To study the effect of the reproductive state of female alpacas (ie, maiden [never bred before], barren [bred but failed to conceive or maintain pregnancy in previous breeding season], or gave birth and currently lactating) on embryonic mortality rate.

167 female alpacas (54 lactating, 44 barren, and 69 maiden) that ovulated following a single breeding.

During the first 45 days following breeding, female alpacas underwent periodic transrectal ultrasonography to determine the presence or absence of an embryonic vesicle. Serum progesterone concentrations were determined during the same period. Embryonic survival rate was analyzed for each group of females (lactating, barren, and maiden).

The presence of an embryonic vesicle or embryo was positively associated with high serum progesterone concentrations (>2 ng/mL). The embryonic mortality rate in barren females (21/44 [47.7%]) was significantly higher than in maiden (20/69 [29.0%]) and lactating (16/54 [29.6%]) females. In females that underwent embryonic loss (n=57), 3 patterns of events in terms of serum progesterone concentrations were identified: concomitant decrease of serum progesterone concentration and embryonic loss (24/57 [42.1%]), decrease in serum progesterone concentration before embryonic loss (12/57 [21.1%]), and persistent serum progesterone concentrations beyond embryonic loss (21/57 [36.8%]). Patterns of serum progesterone concentration and embryonic loss did not differ significantly among lactating, barren, and maiden female alpacas.

Embryonic loss in alpacas occurred without any discernible pattern in serum progesterone concentrations. Barren female alpacas had the highest embryonic mortality rate.