35 FERTILITY AFTER FIXED-TIME AI OR INSEMINATION AT DETECTED ESTRUS FOLLOWING CIDR SYNCHRONIZATION PROTOCOLS IN FRENCH DAIRY AND BEEF CATTLE

Abstract

The CIDR synchronization protocol was introduced in France since 2008, as a 7-day intravaginal progesterone treatment (1.38 g of progesterone) coupled with AI at detected estrus. The objective of this study was to compare the synchronization, ovulation, and conception rates following fixed-timed AI (FTAI) and AI on observed heat (HAI) following a CIDR synchronization program in dairy and beef cattle under on-farm conditions. A total of 466 females from Holstein, Limousin, and Charolais breeds were synchronized from October 2008 to March 2009, and inseminated by AI technicians from 4 French cooperatives (Amélis, CECNA, COOPELSO, Groupe Altitude) with the following inclusion criteria : heifers from 14 to 28 months old, cows with 1 to 5 calvings, interval from calving from 50 to 150 days, first breeding following calving without any complication. The CIDR device was left for a 7-day period and combined with a PGF_2α injection 1 day before CIDR removal and an eCG injection at the time of CIDR removal. Cows within each herd were allocated to 2 insemination groups. In the FTAI group, a single insemination was performed 56 h after CIDR removal, whereas the females from the HAI group were inseminated once from 6 to 18 h after detected estrus. For each female, cyclicity was assessed before CIDR insertion with 2 progesterone measurements assayed 10 days apart. The CIDR device was lost in 25 females during treatment. In the remaining females, estrus synchronization was estimated from a progesterone measurement 56 h after CIDR removal. Ovulation rate following CIDR programs was determined by progesterone measurements 14 days after AI. Pregnancy was diagnosed by ultrasonography on Day 35 after AI in 417 females (24 missing values). From results of cycling females prior to treatment (n = 369), synchronization rates averaged 95.6% and 94.3% in HAI and FTAI groups, respectively. Ovulation rate, calculated from 399 synchronized or noncycling females, averaged 93.4% and 91.6% in HAI and FTAI groups, respectively. Conception rate at first AI averaged 51.9% (HAI: 52.6% v. FTAI: 47.4%; P > 0.05), and conception rate following induced estrus (i.e. calculated from ovulated females only) averaged 55% (HAI: 55.3% v. FTAI: 52.2%; P > 0.05). Conception rate was mainly influenced by breed and parity, ranging from 34% in Holstein cows to 58.7% in Holstein heifers (Table 1). To conclude, fixed-time insemination can be coupled to CIDR synchronization protocols in beef and dairy cattle and can be used to as a substitute for heat detection under on-farm conditions.

Table 1.  Conception rates depending on breed and parity