Body Condition & Pregnancy Rates

When I was running the CSU embryo transfer laboratory our mission  was in  applying  our research results to see if they worked in  the commercial field. There are many examples where a technique works in the laboratory but does not function efficiently when applied commercially. We had over 1,000 recipients which were observed for estrus twice per day. A pregnancy rate of 67% was consistently maintained with fresh embryos graded from 1 to 3.

It was always a problem and expense in locating and preparing suitable potential recipients, so when Holstein heifers became available in a feed lot program we accepted providing they were used as recipients once only, since they were on a  feedlot fattening ration. The pregnant recipients were sold to the owners of the donors and the failed recipients continued in the feedlot program.

In the next 3 months we averaged 71% pregnancy rate transferring fresh embryos graded 1 to 3. Unfortunately we were then asked to use previously failed recipients and the pregnancy rate plunged to 42%. By the time they were ready for a second embryo they were already fat, difficult to palpate and place an embryo accurately in the selected horn.

Over the years we have observed up to 50% of a group of fat recipients do not stand at the time of estrus and  7 days later after predicted heat a lutein cyst is formed instead of a corpus luteum (CL).

Maintaining a resident recipient herd at optimum fertility is a difficult task requiring excellent management. As we have all experienced, there are times when many embryos are collected, and then there are periods when few embryos are collected, resulting in the problem of consistently maintaining sufficient, fertile recipients. 

In conclusion successful embryo transfer programs require excellent management procedures as well as competent embryo transfer practitioners.

Dr. Peter Elsden
http://www.ETschool.com

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