Fixed-Time Insemination Of Beef Cattle With CIDR-Based Protocols

Results From The New Liskeard Agricultural Research Station

Tom Hamilton, Beef Systems Program Lead

Ontario Ministry of Agriculture, Food and Rural Affairs

New Liskeard, Ontario, Canada

Experiments conducted during 1995-1998 in the Beef Program of the New Liskeard Agricultural Research Station (OMAFRA/University of Guelph) examined various methods of fixed-time, single insemination synchronized breeding. Cattle were either large frame crosses (Char/Lim/Sim) or Ang X large frame crosses.  These trials involved a total of 488 cows and 252 heifers, inseminated in either a spring (May) or fall (Sept) breeding period in each year.  All cattle within a season were A.I.’d once,  on a group basis one day. Two experienced technicians (Gencor, Earlton) provided A.I. services.

Strategies which incorporated a CIDR-B^®  (Controlled Intravaginal Drug Release) device were found to result in pregnancy rates which compared very favourably with other fixed-time methods. The device contains progesterone which is released into the vagina during an insertion period of several days.  In these experiments,  various combinations of other hormones were administered with the CIDRs, with the objective of tightly synchronizing  ovulation.  ^®(CIDR-B , Vetrepharm Canada, InterAg New Zealand)

Table 1 shows pregnancy rates by season and animal age class, for fixed-time artificial insemination with CIDR-based protocols. To give an overall yearly pregnancy rate, results from all protocols within a given season were pooled.  These results were then averaged across years to give an overall outcome.  In addition to the table,  individual protocols within a specific year and season gave fixed-time pregnancy rates which ranged from 60% to 95% for cows, and from 42% to 93% for heifers. 

Table 1: Percent Pregnant To Fixed-time AI CIDR-based

 Protocols,   Four Year Averages and Ranges, NLARS

Based on the results from these trials, the most effective protocol involved handling cattle 4X prior to breeding (Figure 1, Treatment 1).   The injection of progesterone on day 0,  (in addition to that from the CIDR), was found to be beneficial in this research.  An alternative protocol (Treatment 2), which requires handling 3X prior to breeding may give similar results,  but further study is required to confirm this.

Many animal factors affect the success of synchronized breeding programs.  Among these are overall health status;  length of the postpartum period (cows);  % of mature body weight (heifers);  degree of body condition; adequate energy, protein, vitamin and mineral nutrition; and handling stress.  Good handling facilities are needed for efficient processing and to reduce stress on both animals and people. 

In these trials, cow groups averaged 62 – 78 days postpartum at breeding, while  heifer groups averaged 14.1 to 14.6 months of age at breeding.  Overall nutrition was excellent and body condition scores were within the desired range.  As well, animals were familiar with the handling facilities and techniques employed. 

Figure 1.  CIDR - Based Synchronization Protocols

¹Controlled Intravaginal Drug Release device, 1.9 grams progesterone

²Estradiol Benzoate, 1 milligram, intramuscular

³Progesterone, 100 milligrams,  intramuscular

⁴Prostaglandin, 25 milligrams of PGF_{2~   ,}  intramuscular

Notes:

1.   The CIDR device  has Canadian approval for use with prostaglandin to synchronize estrus for breeding on observed heat. CIDRs are available only through Veterinarians. The addition of other drugs to synchronize ovulation for fixed-time breeding must be done under Veterinary prescription.  Consult your veterinarian prior to the breeding season to establish a program suitable for your herd.

2.   Loss of CIDRs after insertion  ranged from 5% to 8% .   To minimize losses from heifers,  the tab may be trimmed to leave about 4 inches protruding from the vulva.

3.   Timing of all procedures is critical.  The optimum window for breeding is 50-52 hours after CIDR removal.  There should be a minimum of 24 hrs between CIDR removal on day 7 and estradiol injection on day 8.

4.   For Day 0, progesterone and estradiol may be combined. This mixture must supply  a total of I milligram (mg)  of estradiol benzoate and 100 milligrams (mg) of progesterone per injection.

5.   With large numbers of cattle (>40hd), separate animals into groups of approximately 20 hd, and process the groups in the same sequence on each treatment day.  This will minimize the variation in timing between procedures for individual animals. A team of two AI technicians will be more efficient than one, especially if multiple sires are used.