Abstract
Holstein cows milked twice daily were assigned to be inseminated at their first detected estrus (control) after 42 days in milk or received PGFza (PG) after 42 days, if they had a high milk progesterone (P4) test on any of 3 consecutive Mondays until first inseminated. Milk P4 tests and injections of PG were given on Mondays, and most of the breeding occurred on Thursdays and Fridays. The proportion of cows inseminated within 21 days of the beginning of the breeding period was greater in the milk P4 + PG group (52.8%) than in the control (38.9%). Compared to controls, use of PG reduced days to first service by 12.2 ± 3.1 d, calving intervals by 23.3 ± 8.9 d, rate of reproductive culling, and cost per pregnancy. We concluded that using PG as a management tool in an AI program is warranted and cost effective. However, the milk P4 test would not be justifiable unless its cost were significantly lower than the cost of a weekly injection of PG.; Dairy Day, 1993, Kansas State University, Manhattan, KS, 1993;
Highlights
Inefficient detection of estrus in dairy herds where AI is practiced contributes to a significant reduction in reproductive performance and potential milk yield
Milk P4 tests and injections of PG were given on Mondays, and most of the breeding occurred on Thursdays and Fridays
The proportion of cows inseminated within 21 days of the beginning of the breeding period was greater in the milk P4 + PG group (52.8%) than in the control (38.9%)
Summary
Inefficient detection of estrus in dairy herds where AI is practiced contributes to a significant reduction in reproductive performance and potential milk yield. Prolonged intervals to first service resulting from inadequate detection of estrus contribute significantly to unacceptably long calving intervals. Insemination of dairy cows at first service is enhanced through the use of PGFZCY (PG). Intervals to conception were reduced by as much as 3 wk when cows were treated with PG after detection of a palpable corpus luteum (CL) compared to those cows in which PG was not used. Administering injections of PG on Monday mornings without prior assessment of CL or P4 status was effective in reducing intervals to first service compared to injecting PG based on palpation of a CL. Were more periods of estrus in cows synchronized or grouped together for weekly AI when PG was used, but the efficiency of detected estrus improved because the number of mounts increased when up to four or more cows were in estrus simultaneously
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Kansas Agricultural Experiment Station Research Reports
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
