Prenatal growth and estimation of fetal age in the Australian feral goat

Abstract

The prenatal development of the conceptus in the Australian feral goat (Capra hircus) was studied in 47 does containing 89 fetuses of known gestational age. Quantification of the growth of the fetus allowed the development of a number of predictors of fetal age. The effect of age of fetus was highly significant for the variables body weight, crown-rump straight and curved length, vertebral column length, thorax circumference, forelimb length and hindlimb length (P < 0.01). A quadratic response curve using loge of fetal age accounts for most of the variation in the log, of each fetal measurement (R2 = 0.991 to 0.995). The prenatal growth of these fetal parameters was partitioned using the regressions. There was little difference between the relative growth of crown-rump straight and curved length, vertebral column length and the thorax circumference over the trimesters of gestation. Growth of the limbs tended to be greater in the third trimester when compared with the former parameters. As might be expected from work in other species, 79% of the growth in fetal body weight occurred in the last trimester, and this exceeded the relative growth of all other characters during this period. There was marked (P < 0.01) increase in the weight of the empty uterus up to day 95, after which no change occurred.