Breed in a day! And shorten your calving season


Source: Ontario Ministry of Agriculture, Food and Rural Affairs

Do you know what day you will be breeding your cows this year? With the fixed-time insemination protocol developed by the University of Guelph at the New Liskeard Agricultural Research Station, you can plan your breeding day today. A recent farm trial bears out the validity of the research results.

Use of artificial insemination has been touted as a method of improving the genetics in your herd at a lower cost than the cost of buying a high quality bull. But most producers find the job of heat detection time consuming. The commitment may be there, but time pressures generally reduce the impact of artificial insemination in herds across Ontario.

By using the CIDR™ (Controlled Intravaginal Drug Release) approach producers can maximize artificial insemination on a large scale. Using the progesterone releasing CIDRs, with additional hormones, allows producers to plan their breeding season. Each day of the 4 step program can be booked in advance if taking time off work. Extra help can also be hired in advance for rounding up the cows.

What are realistic expectations with a fixed-time A.I. program? Many producers are surprised to hear that a highly effective natural breeding program only achieves about a 70% pregnancy rate in the first cycle of the breeding season. Some producers who do an excellent job of heat detection, and breed on standing heat, achieve a higher percent than this with artificial breeding. But using a fixed-timeinsemination program can still allow you to obtain pregnancy rates similar to using walking bulls. Five years of data with fixed-time insemination in a farm trial situation shows a range of 43 to 80 % pregnancy each year. Over five years the average pregnancy rate for fixed time insemination was66%. This compares favourably with research at the New Liskeard Agricultural Research Station, (NLARS) which consistently has pregnancy rates in the high 60’s to low 70’s on a fixed-time protocol.

Another benefit of synchronizing cows is shortening the overall calving period. Cows which are synchronized but do not become pregnant in the first cycle will cycle usually have cycled again by day 25 of the breeding season, which will shorten the calving season.

Some producers worry that if they synchronize their cows to be bred on one day, all the calves will be born on one day. What actually happens is a bell curve effect, where calving generally commences a week to 10 days earlier than the set calving date, peaks around the “due date”, and continues to a week to ten days after the scheduled date. There will be more concentrated calving, and producers need to be prepared to manage more calves in a shorter period of time. But bunching the calves allows producers to again focus their labour and management skills over a shorter period of time.

Another benefit of bunched calving is a more uniform calf crop at marketing. This should result in higher prices for calves. A recent study showed that at certain sale facilities, for each one hd increase in lot size, the price per lb increased by one cent.

Table 1: A Fixed -Time Insemination Protocol. Consult with your veterinarian 


Day 0 Day 7 Day 8 Day 9
Insert CIDR™ + inject Estradiol Remove CIDR™ +
Inject Prostaglandin
Inject Estradiol Inseminate cows
52 -54 hours after CIDR™ removal


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