Growth of the early bovine fetus.

Testing for bovine hereditary syndactyly used artificial insemination, superovulation, and embryo transfer. Thirty-two suspect bulls and 9 suspect cows were mated with 10 syndactyly cows and two syndactylous bulls, respectively. 209 embryos were recovered and one, two, or three embryos was/were transfered into each recipient cow and 56 to 77 days after transfer, 174 fetuses were recovered. There was a significant relationship between amniotic fluid weights from the left uterine horn, fetal weights from right and left uterine horns, and fetal sex, side of corpus luteum, and number of embryo implants. Fetal membrane weights, amniotic fluid weights, fetal weights, and crown-rump lengths increased significantly with fetal age, but recipient cow weight had no significant effect. Survival data from single, double, and triple embryo implants indicated that it was most profitable under these test conditions to implant two embryos per recipient cow, one in each uterine horn.

Hereditary bovine syndactyly: diagnosis in bovine fetuses.

Diagnostic guidelines were established for progeny testing of hereditary bovine syndactyly. Through the use of superovulation and embryo transfer, 139 fetuses were recovered at 50 to 77 days gestation. Normal (+/+, +/sy) and syndactylous (sy/sy) anatomy of Holstein fetuses was defined, and the accuracy of macroscopic versus microscopic limb diagnosis was assessed. Chondrification and ossification differences between normal (+/+, +/sy) and syndactylous (sy/sy) fetuses were only age-related. Normal (+/+, +/sy) fetal limbs differed from normal (+/+, +/sy) adult bovine limbs in two ways. Fetal metacarpal and metatarsal III and IV bones were not fused, and fetal metacarpal and metatarsal II and V bones often extended up to three-fourths the length of metacarpal and metatarsal III and IV bones. In syndactylous (sy/sy) fetuses, synostosis asymmetries occurred within and between fetal limbs, and between fetuses, representing variable gene expressivity. Synostosis pattern within limbs did not correspond with those of the adult bovine; the second phalangeal pair was synostotic most frequently in the fetus, followed by the first, and then the third pair. Synostosis patterns between fetal limbs agreed with those of the adult; there was a right-left and front-rear limb gradient. Partial synostoses occurred sporadically in all three paired phalanges. Those of the first and third pair always involved the tip closest to the second phalangeal pair. A unique example of variable gene expressivity occurred in one syndactylous fetus. Both front limbs were syndactylous, while both rear limbs were normal grossly. Microscopically the right rear limb was normal while the left rear limb consisted of closely apposed phalangeal blastemata without coalescence.(ABSTRACT TRUNCATED AT 250 WORDS)