Abstract :
The objective of this study was to compare overall pregnancy success achieved using a
combined ovulation synchronization-timed artificial insemination (NCSynch-TAI) protocol
with that obtained using estrus synchronization and artificial insemination (AI). Multiparous
Boer and Boer-cross does (n = 132) were randomly assigned within age (year 1) or
parity (years 2 and 3) to one of two treatments. Control does received 15 mg prostaglandin
F (PGF; Lutalyse®) on days 1 and 10 of treatment. Estrus onset was checked twice daily
with separately penned, intact bucks (year 1) or a vasectomized buck penned with the does
(years 2 and 3). Control does were bred by AI 12 h after estrus onset using frozen semen.
NCSynch-TAI does received 15 mg PGF on day 1 of treatment. Does received 50 g GnRH
(Cystorelin®) on day 8, and 15 mg PGF was given on day 15. On day 18, NCSynch-TAI does
were appointment bred using frozen semen and received 50 g GnRH at breeding. Pregnancy
status was determined using transabdominal ultrasonagraphy with kidding rates
also recorded. In year 1, 13 of 15 control does (87%) were detected in estrus with 8 pregnant
to AI for an overall pregnancy rate of 53%. For NCSynch-TAI, 15 does were bred and
11 (73%) became pregnant. In year 2, 24 of 26 controls (92%) were detected in estrus with
19 pregnant to AI (73% overall pregnancy rate). For NCSynch-TAI, 26 does were bred and
20 (77%) became pregnant. In year 3, 21 of 25 controls (84%) were detected in estrus with
8 pregnant to AI (32% overall pregnancy rate). For NCSynch-TAI, 25 does were bred and 14
(56%) became pregnant. Across all years, the overall pregnancy rate for NCSynch-TAI does
(45/66, 68%) did not differ (P = 0.075) compared to controls (35/66; 53%). Kidding rates for
the two treatments (68% vs. 51%, respectively) also did not differ (P = 0.075). In summary,
pregnancy success following the use of NCSynch-TAI was comparable to that obtained when
does were bred based on detection of estrus.
