Pregnancy Length, Offspring Weight and Birth Outcomes in Alpaca (Vicugna pacos): An International Survey

Alpaca gestation lasts approximately 11.5 months, but significant variation exists, and contributing factors are poorly described. This study aimed to conduct an international survey to assess pregnancy length (PL), based on geographical location. When available, the survey collected data on embryo transfer, dam and sire identity, maternal age, offspring sex, and time of birth. These variables were analyzed for their potential effects on PL, cria weight (CW), and parturition complications such as dystocia. Data from 7049 worldwide pregnancies were analyzed. The global median PL was 346 days (range: 270-428; coefficient of variation: 3.37%), with 50% of pregnancies between 339 and 353 days. Median birth time was 11:30 AM (range 0:30 AM-11:30PM). Northern hemisphere had longer PL (p < 0.0001, 345.9-346.7 vs 344.3-345.1 days, n = 7049), that depended on the country (p < 0.0001). Fetal sex had no impact, but embryo transfer slightly tended to increase PL (p = 0.0918). While effect of the dam had no influence, the sire and the maternal age did (p < 0.0001; p = 0.0039). No correlation was found between PL and CW, though season and maternal age influenced both in the northern hemisphere (p < 0.0001 for both). Maternal age also affected CW (p < 0.0001). Dystocia rates were not affected by CW, but longer PL slightly tended to increase dystocia risk (p = 0.0798). This survey confirms the median pregnancy length of 346 days and suggests explanations for the wide variability in PL and CW, as sire, dam age, season, and location.