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Split-timed Artificial Insemination Options for Suckled Beef Cattle
Split-timed Artificial Insemination Options for Suckled Beef Cattle
Wednesday, March 14, 2018: 10:50 AM
210/211 (CenturyLink Convention Center)
Numerous studies have been conducted in suckled beef cows employing timed AI programs using the
recommended CO-Synch + progesterone platform: GnRH-1 + CIDR insert 7 d PGF 2 + CIDR
removal 60 to 66 h AI + GnRH-2. Three experiments were conducted at 12 to 15 locations between
2014 and 2016. Allocating cows (n =1,611) into distinct fixed-time AI sessions based on activated estrus-
detection patches produced 46% of cows in estrus by 60 h and 83% by 75 h. Pregnancy risk (PR)
exceeded 64% for cows detected in estrus. The PR in cows receiving GnRH-2 at 60 or 75 h, and
inseminated at 75 h, did not differ (53 vs. 50%), respectively. In a subsequent study (1,236 cows), PR of
cows inseminated at 65 h did not differ in cows receiving GnRH-2 (62%) compared with those not
receiving GnRH-2 (60%) at AI. In contrast, delaying GnRH-2 and AI to 84 h, GnRH improved PR (41%)
compared with those cows not receiving GnRH-2 (31%). Regardless of AI timing at 65 or 84 h, for cows
detected in estrus by 84 h, GnRH did not affect PR (65%) compared with those not receiving GnRH
(62%). In contrast, if no estrus occurred by 84 h, GnRH-2 doubled the PR for cows receiving GnRH-2 at
AI compared with those not treated (33 vs. 15%), respectively. Two split time combinations of 55-75 vs.
65-85 h were tested in 1,062 cows. Cows detected in estrus by 55 or 65 h (no GnRH-2) were inseminated,
whereas those not in estrus by 55 or 65 h were treated with GnRH-2 and then inseminated at 75 or 85 h,
respectively. The PR for cows inseminated at 55, 65, 75, and 85 h were: 67% a , 69% a , 50% b and 56% b . The
greatest overall PR was detected in the 65-85 h (63%) vs. the 55-75 h (58%) combination. In other
studies, delayed AI has increased pregnancy risk in suckled beef cows receiving sex-sorted semen. Semen
cost (conventional vs. sex-sorted), desired traits of AI sires, BCS, winter nutrition, estrus expression,
anovulation, and age of cows are considerations for applying split-time AI programs. Employing split-
time AI can reduce the risk associated with timed AI when conditions are less than ideal for optimal
fertility because of inadequate facilities, weather conditions, poor BCS, and nutritional status of cows.
Using split-time AI options, however, requires more labor and the expense of estrus-detection patches.
recommended CO-Synch + progesterone platform: GnRH-1 + CIDR insert 7 d PGF 2 + CIDR
removal 60 to 66 h AI + GnRH-2. Three experiments were conducted at 12 to 15 locations between
2014 and 2016. Allocating cows (n =1,611) into distinct fixed-time AI sessions based on activated estrus-
detection patches produced 46% of cows in estrus by 60 h and 83% by 75 h. Pregnancy risk (PR)
exceeded 64% for cows detected in estrus. The PR in cows receiving GnRH-2 at 60 or 75 h, and
inseminated at 75 h, did not differ (53 vs. 50%), respectively. In a subsequent study (1,236 cows), PR of
cows inseminated at 65 h did not differ in cows receiving GnRH-2 (62%) compared with those not
receiving GnRH-2 (60%) at AI. In contrast, delaying GnRH-2 and AI to 84 h, GnRH improved PR (41%)
compared with those cows not receiving GnRH-2 (31%). Regardless of AI timing at 65 or 84 h, for cows
detected in estrus by 84 h, GnRH did not affect PR (65%) compared with those not receiving GnRH
(62%). In contrast, if no estrus occurred by 84 h, GnRH-2 doubled the PR for cows receiving GnRH-2 at
AI compared with those not treated (33 vs. 15%), respectively. Two split time combinations of 55-75 vs.
65-85 h were tested in 1,062 cows. Cows detected in estrus by 55 or 65 h (no GnRH-2) were inseminated,
whereas those not in estrus by 55 or 65 h were treated with GnRH-2 and then inseminated at 75 or 85 h,
respectively. The PR for cows inseminated at 55, 65, 75, and 85 h were: 67% a , 69% a , 50% b and 56% b . The
greatest overall PR was detected in the 65-85 h (63%) vs. the 55-75 h (58%) combination. In other
studies, delayed AI has increased pregnancy risk in suckled beef cows receiving sex-sorted semen. Semen
cost (conventional vs. sex-sorted), desired traits of AI sires, BCS, winter nutrition, estrus expression,
anovulation, and age of cows are considerations for applying split-time AI programs. Employing split-
time AI can reduce the risk associated with timed AI when conditions are less than ideal for optimal
fertility because of inadequate facilities, weather conditions, poor BCS, and nutritional status of cows.
Using split-time AI options, however, requires more labor and the expense of estrus-detection patches.